Merge branch 'for-3.17/drivers' of git://git.kernel.dk/linux-block

Pull block driver changes from Jens Axboe:
 "Nothing out of the ordinary here, this pull request contains:

   - A big round of fixes for bcache from Kent Overstreet, Slava Pestov,
     and Surbhi Palande.  No new features, just a lot of fixes.

   - The usual round of drbd updates from Andreas Gruenbacher, Lars
     Ellenberg, and Philipp Reisner.

   - virtio_blk was converted to blk-mq back in 3.13, but now Ming Lei
     has taken it one step further and added support for actually using
     more than one queue.

   - Addition of an explicit SG_FLAG_Q_AT_HEAD for block/bsg, to
     compliment the the default behavior of adding to the tail of the
     queue.  From Douglas Gilbert"

* 'for-3.17/drivers' of git://git.kernel.dk/linux-block: (86 commits)
  bcache: Drop unneeded blk_sync_queue() calls
  bcache: add mutex lock for bch_is_open
  bcache: Correct printing of btree_gc_max_duration_ms
  bcache: try to set b->parent properly
  bcache: fix memory corruption in init error path
  bcache: fix crash with incomplete cache set
  bcache: Fix more early shutdown bugs
  bcache: fix use-after-free in btree_gc_coalesce()
  bcache: Fix an infinite loop in journal replay
  bcache: fix crash in bcache_btree_node_alloc_fail tracepoint
  bcache: bcache_write tracepoint was crashing
  bcache: fix typo in bch_bkey_equal_header
  bcache: Allocate bounce buffers with GFP_NOWAIT
  bcache: Make sure to pass GFP_WAIT to mempool_alloc()
  bcache: fix uninterruptible sleep in writeback thread
  bcache: wait for buckets when allocating new btree root
  bcache: fix crash on shutdown in passthrough mode
  bcache: fix lockdep warnings on shutdown
  bcache allocator: send discards with correct size
  bcache: Fix to remove the rcu_sched stalls.
  ...

16 files changed, 2758 insertions, 1218 deletions

diff --git a/drivers/block/drbd/Makefile b/drivers/block/drbd/Makefile
index 8b45033..4464e35 100644
--- a/drivers/block/drbd/Makefile
+++ b/drivers/block/drbd/Makefile
@@ -3,5 +3,6 @@ drbd-y += drbd_worker.o drbd_receiver.o drbd_req.o drbd_actlog.o
 drbd-y += drbd_main.o drbd_strings.o drbd_nl.o
 drbd-y += drbd_interval.o drbd_state.o
 drbd-y += drbd_nla.o
+drbd-$(CONFIG_DEBUG_FS) += drbd_debugfs.o
 
 obj-$(CONFIG_BLK_DEV_DRBD)     += drbd.o
diff --git a/drivers/block/drbd/drbd_actlog.c b/drivers/block/drbd/drbd_actlog.c
index 05a1780..d26a3fa 100644
--- a/drivers/block/drbd/drbd_actlog.c
+++ b/drivers/block/drbd/drbd_actlog.c
@@ -92,34 +92,26 @@ struct __packed al_transaction_on_disk {
 	__be32	context[AL_CONTEXT_PER_TRANSACTION];
 };
 
-struct update_odbm_work {
-	struct drbd_work w;
-	struct drbd_device *device;
-	unsigned int enr;
-};
-
-struct update_al_work {
-	struct drbd_work w;
-	struct drbd_device *device;
-	struct completion event;
-	int err;
-};
-
-
-void *drbd_md_get_buffer(struct drbd_device *device)
+void *drbd_md_get_buffer(struct drbd_device *device, const char *intent)
 {
 	int r;
 
 	wait_event(device->misc_wait,
-		   (r = atomic_cmpxchg(&device->md_io_in_use, 0, 1)) == 0 ||
+		   (r = atomic_cmpxchg(&device->md_io.in_use, 0, 1)) == 0 ||
 		   device->state.disk <= D_FAILED);
 
-	return r ? NULL : page_address(device->md_io_page);
+	if (r)
+		return NULL;
+
+	device->md_io.current_use = intent;
+	device->md_io.start_jif = jiffies;
+	device->md_io.submit_jif = device->md_io.start_jif - 1;
+	return page_address(device->md_io.page);
 }
 
 void drbd_md_put_buffer(struct drbd_device *device)
 {
-	if (atomic_dec_and_test(&device->md_io_in_use))
+	if (atomic_dec_and_test(&device->md_io.in_use))
 		wake_up(&device->misc_wait);
 }
 
@@ -145,10 +137,11 @@ void wait_until_done_or_force_detached(struct drbd_device *device, struct drbd_b
 
 static int _drbd_md_sync_page_io(struct drbd_device *device,
 				 struct drbd_backing_dev *bdev,
-				 struct page *page, sector_t sector,
-				 int rw, int size)
+				 sector_t sector, int rw)
 {
 	struct bio *bio;
+	/* we do all our meta data IO in aligned 4k blocks. */
+	const int size = 4096;
 	int err;
 
 	device->md_io.done = 0;
@@ -156,15 +149,15 @@ static int _drbd_md_sync_page_io(struct drbd_device *device,
 
 	if ((rw & WRITE) && !test_bit(MD_NO_FUA, &device->flags))
 		rw |= REQ_FUA | REQ_FLUSH;
-	rw |= REQ_SYNC;
+	rw |= REQ_SYNC | REQ_NOIDLE;
 
 	bio = bio_alloc_drbd(GFP_NOIO);
 	bio->bi_bdev = bdev->md_bdev;
 	bio->bi_iter.bi_sector = sector;
 	err = -EIO;
-	if (bio_add_page(bio, page, size, 0) != size)
+	if (bio_add_page(bio, device->md_io.page, size, 0) != size)
 		goto out;
-	bio->bi_private = &device->md_io;
+	bio->bi_private = device;
 	bio->bi_end_io = drbd_md_io_complete;
 	bio->bi_rw = rw;
 
@@ -179,7 +172,8 @@ static int _drbd_md_sync_page_io(struct drbd_device *device,
 	}
 
 	bio_get(bio); /* one bio_put() is in the completion handler */
-	atomic_inc(&device->md_io_in_use); /* drbd_md_put_buffer() is in the completion handler */
+	atomic_inc(&device->md_io.in_use); /* drbd_md_put_buffer() is in the completion handler */
+	device->md_io.submit_jif = jiffies;
 	if (drbd_insert_fault(device, (rw & WRITE) ? DRBD_FAULT_MD_WR : DRBD_FAULT_MD_RD))
 		bio_endio(bio, -EIO);
 	else
@@ -197,9 +191,7 @@ int drbd_md_sync_page_io(struct drbd_device *device, struct drbd_backing_dev *bd
 			 sector_t sector, int rw)
 {
 	int err;
-	struct page *iop = device->md_io_page;
-
-	D_ASSERT(device, atomic_read(&device->md_io_in_use) == 1);
+	D_ASSERT(device, atomic_read(&device->md_io.in_use) == 1);
 
 	BUG_ON(!bdev->md_bdev);
 
@@ -214,8 +206,7 @@ int drbd_md_sync_page_io(struct drbd_device *device, struct drbd_backing_dev *bd
 		     current->comm, current->pid, __func__,
 		     (unsigned long long)sector, (rw & WRITE) ? "WRITE" : "READ");
 
-	/* we do all our meta data IO in aligned 4k blocks. */
-	err = _drbd_md_sync_page_io(device, bdev, iop, sector, rw, 4096);
+	err = _drbd_md_sync_page_io(device, bdev, sector, rw);
 	if (err) {
 		drbd_err(device, "drbd_md_sync_page_io(,%llus,%s) failed with error %d\n",
 		    (unsigned long long)sector, (rw & WRITE) ? "WRITE" : "READ", err);
@@ -297,26 +288,12 @@ bool drbd_al_begin_io_prepare(struct drbd_device *device, struct drbd_interval *
 	return need_transaction;
 }
 
-static int al_write_transaction(struct drbd_device *device, bool delegate);
-
-/* When called through generic_make_request(), we must delegate
- * activity log I/O to the worker thread: a further request
- * submitted via generic_make_request() within the same task
- * would be queued on current->bio_list, and would only start
- * after this function returns (see generic_make_request()).
- *
- * However, if we *are* the worker, we must not delegate to ourselves.
- */
+static int al_write_transaction(struct drbd_device *device);
 
-/*
- * @delegate:   delegate activity log I/O to the worker thread
- */
-void drbd_al_begin_io_commit(struct drbd_device *device, bool delegate)
+void drbd_al_begin_io_commit(struct drbd_device *device)
 {
 	bool locked = false;
 
-	BUG_ON(delegate && current == first_peer_device(device)->connection->worker.task);
-
 	/* Serialize multiple transactions.
 	 * This uses test_and_set_bit, memory barrier is implicit.
 	 */
@@ -335,7 +312,7 @@ void drbd_al_begin_io_commit(struct drbd_device *device, bool delegate)
 			rcu_read_unlock();
 
 			if (write_al_updates)
-				al_write_transaction(device, delegate);
+				al_write_transaction(device);
 			spin_lock_irq(&device->al_lock);
 			/* FIXME
 			if (err)
@@ -352,12 +329,10 @@ void drbd_al_begin_io_commit(struct drbd_device *device, bool delegate)
 /*
  * @delegate:   delegate activity log I/O to the worker thread
  */
-void drbd_al_begin_io(struct drbd_device *device, struct drbd_interval *i, bool delegate)
+void drbd_al_begin_io(struct drbd_device *device, struct drbd_interval *i)
 {
-	BUG_ON(delegate && current == first_peer_device(device)->connection->worker.task);
-
 	if (drbd_al_begin_io_prepare(device, i))
-		drbd_al_begin_io_commit(device, delegate);
+		drbd_al_begin_io_commit(device);
 }
 
 int drbd_al_begin_io_nonblock(struct drbd_device *device, struct drbd_interval *i)
@@ -380,8 +355,19 @@ int drbd_al_begin_io_nonblock(struct drbd_device *device, struct drbd_interval *
 	/* We want all necessary updates for a given request within the same transaction
 	 * We could first check how many updates are *actually* needed,
 	 * and use that instead of the worst-case nr_al_extents */
-	if (available_update_slots < nr_al_extents)
-		return -EWOULDBLOCK;
+	if (available_update_slots < nr_al_extents) {
+		/* Too many activity log extents are currently "hot".
+		 *
+		 * If we have accumulated pending changes already,
+		 * we made progress.
+		 *
+		 * If we cannot get even a single pending change through,
+		 * stop the fast path until we made some progress,
+		 * or requests to "cold" extents could be starved. */
+		if (!al->pending_changes)
+			__set_bit(__LC_STARVING, &device->act_log->flags);
+		return -ENOBUFS;
+	}
 
 	/* Is resync active in this area? */
 	for (enr = first; enr <= last; enr++) {
@@ -452,15 +438,6 @@ static unsigned int al_extent_to_bm_page(unsigned int al_enr)
 		 (AL_EXTENT_SHIFT - BM_BLOCK_SHIFT));
 }
 
-static unsigned int rs_extent_to_bm_page(unsigned int rs_enr)
-{
-	return rs_enr >>
-		/* bit to page */
-		((PAGE_SHIFT + 3) -
-		/* resync extent number to bit */
-		 (BM_EXT_SHIFT - BM_BLOCK_SHIFT));
-}
-
 static sector_t al_tr_number_to_on_disk_sector(struct drbd_device *device)
 {
 	const unsigned int stripes = device->ldev->md.al_stripes;
@@ -479,8 +456,7 @@ static sector_t al_tr_number_to_on_disk_sector(struct drbd_device *device)
 	return device->ldev->md.md_offset + device->ldev->md.al_offset + t;
 }
 
-static int
-_al_write_transaction(struct drbd_device *device)
+int al_write_transaction(struct drbd_device *device)
 {
 	struct al_transaction_on_disk *buffer;
 	struct lc_element *e;
@@ -505,7 +481,8 @@ _al_write_transaction(struct drbd_device *device)
 		return -EIO;
 	}
 
-	buffer = drbd_md_get_buffer(device); /* protects md_io_buffer, al_tr_cycle, ... */
+	/* protects md_io_buffer, al_tr_cycle, ... */
+	buffer = drbd_md_get_buffer(device, __func__);
 	if (!buffer) {
 		drbd_err(device, "disk failed while waiting for md_io buffer\n");
 		put_ldev(device);
@@ -590,38 +567,6 @@ _al_write_transaction(struct drbd_device *device)
 	return err;
 }
 
-
-static int w_al_write_transaction(struct drbd_work *w, int unused)
-{
-	struct update_al_work *aw = container_of(w, struct update_al_work, w);
-	struct drbd_device *device = aw->device;
-	int err;
-
-	err = _al_write_transaction(device);
-	aw->err = err;
-	complete(&aw->event);
-
-	return err != -EIO ? err : 0;
-}
-
-/* Calls from worker context (see w_restart_disk_io()) need to write the
-   transaction directly. Others came through generic_make_request(),
-   those need to delegate it to the worker. */
-static int al_write_transaction(struct drbd_device *device, bool delegate)
-{
-	if (delegate) {
-		struct update_al_work al_work;
-		init_completion(&al_work.event);
-		al_work.w.cb = w_al_write_transaction;
-		al_work.device = device;
-		drbd_queue_work_front(&first_peer_device(device)->connection->sender_work,
-				      &al_work.w);
-		wait_for_completion(&al_work.event);
-		return al_work.err;
-	} else
-		return _al_write_transaction(device);
-}
-
 static int _try_lc_del(struct drbd_device *device, struct lc_element *al_ext)
 {
 	int rv;
@@ -682,72 +627,56 @@ int drbd_initialize_al(struct drbd_device *device, void *buffer)
 	return 0;
 }
 
-static int w_update_odbm(struct drbd_work *w, int unused)
-{
-	struct update_odbm_work *udw = container_of(w, struct update_odbm_work, w);
-	struct drbd_device *device = udw->device;
-	struct sib_info sib = { .sib_reason = SIB_SYNC_PROGRESS, };
-
-	if (!get_ldev(device)) {
-		if (__ratelimit(&drbd_ratelimit_state))
-			drbd_warn(device, "Can not update on disk bitmap, local IO disabled.\n");
-		kfree(udw);
-		return 0;
-	}
-
-	drbd_bm_write_page(device, rs_extent_to_bm_page(udw->enr));
-	put_ldev(device);
-
-	kfree(udw);
-
-	if (drbd_bm_total_weight(device) <= device->rs_failed) {
-		switch (device->state.conn) {
-		case C_SYNC_SOURCE:  case C_SYNC_TARGET:
-		case C_PAUSED_SYNC_S: case C_PAUSED_SYNC_T:
-			drbd_resync_finished(device);
-		default:
-			/* nothing to do */
-			break;
-		}
-	}
-	drbd_bcast_event(device, &sib);
-
-	return 0;
-}
-
+static const char *drbd_change_sync_fname[] = {
+	[RECORD_RS_FAILED] = "drbd_rs_failed_io",
+	[SET_IN_SYNC] = "drbd_set_in_sync",
+	[SET_OUT_OF_SYNC] = "drbd_set_out_of_sync"
+};
 
 /* ATTENTION. The AL's extents are 4MB each, while the extents in the
  * resync LRU-cache are 16MB each.
  * The caller of this function has to hold an get_ldev() reference.
  *
+ * Adjusts the caching members ->rs_left (success) or ->rs_failed (!success),
+ * potentially pulling in (and recounting the corresponding bits)
+ * this resync extent into the resync extent lru cache.
+ *
+ * Returns whether all bits have been cleared for this resync extent,
+ * precisely: (rs_left <= rs_failed)
+ *
  * TODO will be obsoleted once we have a caching lru of the on disk bitmap
  */
-static void drbd_try_clear_on_disk_bm(struct drbd_device *device, sector_t sector,
-				      int count, int success)
+static bool update_rs_extent(struct drbd_device *device,
+		unsigned int enr, int count,
+		enum update_sync_bits_mode mode)
 {
 	struct lc_element *e;
-	struct update_odbm_work *udw;
-
-	unsigned int enr;
 
 	D_ASSERT(device, atomic_read(&device->local_cnt));
 
-	/* I simply assume that a sector/size pair never crosses
-	 * a 16 MB extent border. (Currently this is true...) */
-	enr = BM_SECT_TO_EXT(sector);
-
-	e = lc_get(device->resync, enr);
+	/* When setting out-of-sync bits,
+	 * we don't need it cached (lc_find).
+	 * But if it is present in the cache,
+	 * we should update the cached bit count.
+	 * Otherwise, that extent should be in the resync extent lru cache
+	 * already -- or we want to pull it in if necessary -- (lc_get),
+	 * then update and check rs_left and rs_failed. */
+	if (mode == SET_OUT_OF_SYNC)
+		e = lc_find(device->resync, enr);
+	else
+		e = lc_get(device->resync, enr);
 	if (e) {
 		struct bm_extent *ext = lc_entry(e, struct bm_extent, lce);
 		if (ext->lce.lc_number == enr) {
-			if (success)
+			if (mode == SET_IN_SYNC)
 				ext->rs_left -= count;
+			else if (mode == SET_OUT_OF_SYNC)
+				ext->rs_left += count;
 			else
 				ext->rs_failed += count;
 			if (ext->rs_left < ext->rs_failed) {
-				drbd_warn(device, "BAD! sector=%llus enr=%u rs_left=%d "
+				drbd_warn(device, "BAD! enr=%u rs_left=%d "
 				    "rs_failed=%d count=%d cstate=%s\n",
-				     (unsigned long long)sector,
 				     ext->lce.lc_number, ext->rs_left,
 				     ext->rs_failed, count,
 				     drbd_conn_str(device->state.conn));
@@ -781,34 +710,27 @@ static void drbd_try_clear_on_disk_bm(struct drbd_device *device, sector_t secto
 				     ext->lce.lc_number, ext->rs_failed);
 			}
 			ext->rs_left = rs_left;
-			ext->rs_failed = success ? 0 : count;
+			ext->rs_failed = (mode == RECORD_RS_FAILED) ? count : 0;
 			/* we don't keep a persistent log of the resync lru,
 			 * we can commit any change right away. */
 			lc_committed(device->resync);
 		}
-		lc_put(device->resync, &ext->lce);
+		if (mode != SET_OUT_OF_SYNC)
+			lc_put(device->resync, &ext->lce);
 		/* no race, we are within the al_lock! */
 
-		if (ext->rs_left == ext->rs_failed) {
+		if (ext->rs_left <= ext->rs_failed) {
 			ext->rs_failed = 0;
-
-			udw = kmalloc(sizeof(*udw), GFP_ATOMIC);
-			if (udw) {
-				udw->enr = ext->lce.lc_number;
-				udw->w.cb = w_update_odbm;
-				udw->device = device;
-				drbd_queue_work_front(&first_peer_device(device)->connection->sender_work,
-						      &udw->w);
-			} else {
-				drbd_warn(device, "Could not kmalloc an udw\n");
-			}
+			return true;
 		}
-	} else {
+	} else if (mode != SET_OUT_OF_SYNC) {
+		/* be quiet if lc_find() did not find it. */
 		drbd_err(device, "lc_get() failed! locked=%d/%d flags=%lu\n",
 		    device->resync_locked,
 		    device->resync->nr_elements,
 		    device->resync->flags);
 	}
+	return false;
 }
 
 void drbd_advance_rs_marks(struct drbd_device *device, unsigned long still_to_go)
@@ -827,105 +749,105 @@ void drbd_advance_rs_marks(struct drbd_device *device, unsigned long still_to_go
 	}
 }
 
-/* clear the bit corresponding to the piece of storage in question:
- * size byte of data starting from sector.  Only clear a bits of the affected
- * one ore more _aligned_ BM_BLOCK_SIZE blocks.
- *
- * called by worker on C_SYNC_TARGET and receiver on SyncSource.
- *
- */
-void __drbd_set_in_sync(struct drbd_device *device, sector_t sector, int size,
-		       const char *file, const unsigned int line)
+/* It is called lazy update, so don't do write-out too often. */
+static bool lazy_bitmap_update_due(struct drbd_device *device)
 {
-	/* Is called from worker and receiver context _only_ */
-	unsigned long sbnr, ebnr, lbnr;
-	unsigned long count = 0;
-	sector_t esector, nr_sectors;
-	int wake_up = 0;
-	unsigned long flags;
+	return time_after(jiffies, device->rs_last_bcast + 2*HZ);
+}
 
-	if (size <= 0 || !IS_ALIGNED(size, 512) || size > DRBD_MAX_DISCARD_SIZE) {
-		drbd_err(device, "drbd_set_in_sync: sector=%llus size=%d nonsense!\n",
-				(unsigned long long)sector, size);
+static void maybe_schedule_on_disk_bitmap_update(struct drbd_device *device, bool rs_done)
+{
+	if (rs_done)
+		set_bit(RS_DONE, &device->flags);
+		/* and also set RS_PROGRESS below */
+	else if (!lazy_bitmap_update_due(device))
 		return;
-	}
-
-	if (!get_ldev(device))
-		return; /* no disk, no metadata, no bitmap to clear bits in */
-
-	nr_sectors = drbd_get_capacity(device->this_bdev);
-	esector = sector + (size >> 9) - 1;
-
-	if (!expect(sector < nr_sectors))
-		goto out;
-	if (!expect(esector < nr_sectors))
-		esector = nr_sectors - 1;
-
-	lbnr = BM_SECT_TO_BIT(nr_sectors-1);
-
-	/* we clear it (in sync).
-	 * round up start sector, round down end sector.  we make sure we only
-	 * clear full, aligned, BM_BLOCK_SIZE (4K) blocks */
-	if (unlikely(esector < BM_SECT_PER_BIT-1))
-		goto out;
-	if (unlikely(esector == (nr_sectors-1)))
-		ebnr = lbnr;
-	else
-		ebnr = BM_SECT_TO_BIT(esector - (BM_SECT_PER_BIT-1));
-	sbnr = BM_SECT_TO_BIT(sector + BM_SECT_PER_BIT-1);
 
-	if (sbnr > ebnr)
-		goto out;
+	drbd_device_post_work(device, RS_PROGRESS);
+}
 
+static int update_sync_bits(struct drbd_device *device,
+		unsigned long sbnr, unsigned long ebnr,
+		enum update_sync_bits_mode mode)
+{
 	/*
-	 * ok, (capacity & 7) != 0 sometimes, but who cares...
-	 * we count rs_{total,left} in bits, not sectors.
+	 * We keep a count of set bits per resync-extent in the ->rs_left
+	 * caching member, so we need to loop and work within the resync extent
+	 * alignment. Typically this loop will execute exactly once.
 	 */
-	count = drbd_bm_clear_bits(device, sbnr, ebnr);
-	if (count) {
-		drbd_advance_rs_marks(device, drbd_bm_total_weight(device));
-		spin_lock_irqsave(&device->al_lock, flags);
-		drbd_try_clear_on_disk_bm(device, sector, count, true);
-		spin_unlock_irqrestore(&device->al_lock, flags);
-
-		/* just wake_up unconditional now, various lc_chaged(),
-		 * lc_put() in drbd_try_clear_on_disk_bm(). */
-		wake_up = 1;
+	unsigned long flags;
+	unsigned long count = 0;
+	unsigned int cleared = 0;
+	while (sbnr <= ebnr) {
+		/* set temporary boundary bit number to last bit number within
+		 * the resync extent of the current start bit number,
+		 * but cap at provided end bit number */
+		unsigned long tbnr = min(ebnr, sbnr | BM_BLOCKS_PER_BM_EXT_MASK);
+		unsigned long c;
+
+		if (mode == RECORD_RS_FAILED)
+			/* Only called from drbd_rs_failed_io(), bits
+			 * supposedly still set.  Recount, maybe some
+			 * of the bits have been successfully cleared
+			 * by application IO meanwhile.
+			 */
+			c = drbd_bm_count_bits(device, sbnr, tbnr);
+		else if (mode == SET_IN_SYNC)
+			c = drbd_bm_clear_bits(device, sbnr, tbnr);
+		else /* if (mode == SET_OUT_OF_SYNC) */
+			c = drbd_bm_set_bits(device, sbnr, tbnr);
+
+		if (c) {
+			spin_lock_irqsave(&device->al_lock, flags);
+			cleared += update_rs_extent(device, BM_BIT_TO_EXT(sbnr), c, mode);
+			spin_unlock_irqrestore(&device->al_lock, flags);
+			count += c;
+		}
+		sbnr = tbnr + 1;
 	}
-out:
-	put_ldev(device);
-	if (wake_up)
+	if (count) {
+		if (mode == SET_IN_SYNC) {
+			unsigned long still_to_go = drbd_bm_total_weight(device);
+			bool rs_is_done = (still_to_go <= device->rs_failed);
+			drbd_advance_rs_marks(device, still_to_go);
+			if (cleared || rs_is_done)
+				maybe_schedule_on_disk_bitmap_update(device, rs_is_done);
+		} else if (mode == RECORD_RS_FAILED)
+			device->rs_failed += count;
 		wake_up(&device->al_wait);
+	}
+	return count;
 }
 
-/*
- * this is intended to set one request worth of data out of sync.
- * affects at least 1 bit,
- * and at most 1+DRBD_MAX_BIO_SIZE/BM_BLOCK_SIZE bits.
+/* clear the bit corresponding to the piece of storage in question:
+ * size byte of data starting from sector.  Only clear a bits of the affected
+ * one ore more _aligned_ BM_BLOCK_SIZE blocks.
+ *
+ * called by worker on C_SYNC_TARGET and receiver on SyncSource.
  *
- * called by tl_clear and drbd_send_dblock (==drbd_make_request).
- * so this can be _any_ process.
  */
-int __drbd_set_out_of_sync(struct drbd_device *device, sector_t sector, int size,
-			    const char *file, const unsigned int line)
+int __drbd_change_sync(struct drbd_device *device, sector_t sector, int size,
+		enum update_sync_bits_mode mode,
+		const char *file, const unsigned int line)
 {
-	unsigned long sbnr, ebnr, flags;
+	/* Is called from worker and receiver context _only_ */
+	unsigned long sbnr, ebnr, lbnr;
+	unsigned long count = 0;
 	sector_t esector, nr_sectors;
-	unsigned int enr, count = 0;
-	struct lc_element *e;
 
-	/* this should be an empty REQ_FLUSH */
-	if (size == 0)
+	/* This would be an empty REQ_FLUSH, be silent. */
+	if ((mode == SET_OUT_OF_SYNC) && size == 0)
 		return 0;
 
-	if (size < 0 || !IS_ALIGNED(size, 512) || size > DRBD_MAX_DISCARD_SIZE) {
-		drbd_err(device, "sector: %llus, size: %d\n",
-			(unsigned long long)sector, size);
+	if (size <= 0 || !IS_ALIGNED(size, 512) || size > DRBD_MAX_DISCARD_SIZE) {
+		drbd_err(device, "%s: sector=%llus size=%d nonsense!\n",
+				drbd_change_sync_fname[mode],
+				(unsigned long long)sector, size);
 		return 0;
 	}
 
 	if (!get_ldev(device))
-		return 0; /* no disk, no metadata, no bitmap to set bits in */
+		return 0; /* no disk, no metadata, no bitmap to manipulate bits in */
 
 	nr_sectors = drbd_get_capacity(device->this_bdev);
 	esector = sector + (size >> 9) - 1;
@@ -935,25 +857,28 @@ int __drbd_set_out_of_sync(struct drbd_device *device, sector_t sector, int size
 	if (!expect(esector < nr_sectors))
 		esector = nr_sectors - 1;
 
-	/* we set it out of sync,
-	 * we do not need to round anything here */
-	sbnr = BM_SECT_TO_BIT(sector);
-	ebnr = BM_SECT_TO_BIT(esector);
-
-	/* ok, (capacity & 7) != 0 sometimes, but who cares...
-	 * we count rs_{total,left} in bits, not sectors.  */
-	spin_lock_irqsave(&device->al_lock, flags);
-	count = drbd_bm_set_bits(device, sbnr, ebnr);
+	lbnr = BM_SECT_TO_BIT(nr_sectors-1);
 
-	enr = BM_SECT_TO_EXT(sector);
-	e = lc_find(device->resync, enr);
-	if (e)
-		lc_entry(e, struct bm_extent, lce)->rs_left += count;
-	spin_unlock_irqrestore(&device->al_lock, flags);
+	if (mode == SET_IN_SYNC) {
+		/* Round up start sector, round down end sector.  We make sure
+		 * we only clear full, aligned, BM_BLOCK_SIZE blocks. */
+		if (unlikely(esector < BM_SECT_PER_BIT-1))
+			goto out;
+		if (unlikely(esector == (nr_sectors-1)))
+			ebnr = lbnr;
+		else
+			ebnr = BM_SECT_TO_BIT(esector - (BM_SECT_PER_BIT-1));
+		sbnr = BM_SECT_TO_BIT(sector + BM_SECT_PER_BIT-1);
+	} else {
+		/* We set it out of sync, or record resync failure.
+		 * Should not round anything here. */
+		sbnr = BM_SECT_TO_BIT(sector);
+		ebnr = BM_SECT_TO_BIT(esector);
+	}
 
+	count = update_sync_bits(device, sbnr, ebnr, mode);
 out:
 	put_ldev(device);
-
 	return count;
 }
 
@@ -1075,6 +1000,15 @@ int drbd_try_rs_begin_io(struct drbd_device *device, sector_t sector)
 	struct lc_element *e;
 	struct bm_extent *bm_ext;
 	int i;
+	bool throttle = drbd_rs_should_slow_down(device, sector, true);
+
+	/* If we need to throttle, a half-locked (only marked BME_NO_WRITES,
+	 * not yet BME_LOCKED) extent needs to be kicked out explicitly if we
+	 * need to throttle. There is at most one such half-locked extent,
+	 * which is remembered in resync_wenr. */
+
+	if (throttle && device->resync_wenr != enr)
+		return -EAGAIN;
 
 	spin_lock_irq(&device->al_lock);
 	if (device->resync_wenr != LC_FREE && device->resync_wenr != enr) {
@@ -1098,8 +1032,10 @@ int drbd_try_rs_begin_io(struct drbd_device *device, sector_t sector)
 			D_ASSERT(device, test_bit(BME_NO_WRITES, &bm_ext->flags));
 			clear_bit(BME_NO_WRITES, &bm_ext->flags);
 			device->resync_wenr = LC_FREE;
-			if (lc_put(device->resync, &bm_ext->lce) == 0)
+			if (lc_put(device->resync, &bm_ext->lce) == 0) {
+				bm_ext->flags = 0;
 				device->resync_locked--;
+			}
 			wake_up(&device->al_wait);
 		} else {
 			drbd_alert(device, "LOGIC BUG\n");
@@ -1161,8 +1097,20 @@ proceed:
 	return 0;
 
 try_again:
-	if (bm_ext)
-		device->resync_wenr = enr;
+	if (bm_ext) {
+		if (throttle) {
+			D_ASSERT(device, !test_bit(BME_LOCKED, &bm_ext->flags));
+			D_ASSERT(device, test_bit(BME_NO_WRITES, &bm_ext->flags));
+			clear_bit(BME_NO_WRITES, &bm_ext->flags);
+			device->resync_wenr = LC_FREE;
+			if (lc_put(device->resync, &bm_ext->lce) == 0) {
+				bm_ext->flags = 0;
+				device->resync_locked--;
+			}
+			wake_up(&device->al_wait);
+		} else
+			device->resync_wenr = enr;
+	}
 	spin_unlock_irq(&device->al_lock);
 	return -EAGAIN;
 }
@@ -1270,69 +1218,3 @@ int drbd_rs_del_all(struct drbd_device *device)
 
 	return 0;
 }
-
-/**
- * drbd_rs_failed_io() - Record information on a failure to resync the specified blocks
- * @device:	DRBD device.
- * @sector:	The sector number.
- * @size:	Size of failed IO operation, in byte.
- */
-void drbd_rs_failed_io(struct drbd_device *device, sector_t sector, int size)
-{
-	/* Is called from worker and receiver context _only_ */
-	unsigned long sbnr, ebnr, lbnr;
-	unsigned long count;
-	sector_t esector, nr_sectors;
-	int wake_up = 0;
-
-	if (size <= 0 || !IS_ALIGNED(size, 512) || size > DRBD_MAX_DISCARD_SIZE) {
-		drbd_err(device, "drbd_rs_failed_io: sector=%llus size=%d nonsense!\n",
-				(unsigned long long)sector, size);
-		return;
-	}
-	nr_sectors = drbd_get_capacity(device->this_bdev);
-	esector = sector + (size >> 9) - 1;
-
-	if (!expect(sector < nr_sectors))
-		return;
-	if (!expect(esector < nr_sectors))
-		esector = nr_sectors - 1;
-
-	lbnr = BM_SECT_TO_BIT(nr_sectors-1);
-
-	/*
-	 * round up start sector, round down end sector.  we make sure we only
-	 * handle full, aligned, BM_BLOCK_SIZE (4K) blocks */
-	if (unlikely(esector < BM_SECT_PER_BIT-1))
-		return;
-	if (unlikely(esector == (nr_sectors-1)))
-		ebnr = lbnr;
-	else
-		ebnr = BM_SECT_TO_BIT(esector - (BM_SECT_PER_BIT-1));
-	sbnr = BM_SECT_TO_BIT(sector + BM_SECT_PER_BIT-1);
-
-	if (sbnr > ebnr)
-		return;
-
-	/*
-	 * ok, (capacity & 7) != 0 sometimes, but who cares...
-	 * we count rs_{total,left} in bits, not sectors.
-	 */
-	spin_lock_irq(&device->al_lock);
-	count = drbd_bm_count_bits(device, sbnr, ebnr);
-	if (count) {
-		device->rs_failed += count;
-
-		if (get_ldev(device)) {
-			drbd_try_clear_on_disk_bm(device, sector, count, false);
-			put_ldev(device);
-		}
-
-		/* just wake_up unconditional now, various lc_chaged(),
-		 * lc_put() in drbd_try_clear_on_disk_bm(). */
-		wake_up = 1;
-	}
-	spin_unlock_irq(&device->al_lock);
-	if (wake_up)
-		wake_up(&device->al_wait);
-}
diff --git a/drivers/block/drbd/drbd_bitmap.c b/drivers/block/drbd/drbd_bitmap.c
index 1aa29f8..426c97a 100644
--- a/drivers/block/drbd/drbd_bitmap.c
+++ b/drivers/block/drbd/drbd_bitmap.c
@@ -22,6 +22,8 @@
    the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
+
 #include <linux/bitops.h>
 #include <linux/vmalloc.h>
 #include <linux/string.h>
@@ -353,9 +355,8 @@ static void bm_free_pages(struct page **pages, unsigned long number)
 
 	for (i = 0; i < number; i++) {
 		if (!pages[i]) {
-			printk(KERN_ALERT "drbd: bm_free_pages tried to free "
-					  "a NULL pointer; i=%lu n=%lu\n",
-					  i, number);
+			pr_alert("bm_free_pages tried to free a NULL pointer; i=%lu n=%lu\n",
+				 i, number);
 			continue;
 		}
 		__free_page(pages[i]);
@@ -592,7 +593,7 @@ static void bm_memset(struct drbd_bitmap *b, size_t offset, int c, size_t len)
 	end = offset + len;
 
 	if (end > b->bm_words) {
-		printk(KERN_ALERT "drbd: bm_memset end > bm_words\n");
+		pr_alert("bm_memset end > bm_words\n");
 		return;
 	}
 
@@ -602,7 +603,7 @@ static void bm_memset(struct drbd_bitmap *b, size_t offset, int c, size_t len)
 		p_addr = bm_map_pidx(b, idx);
 		bm = p_addr + MLPP(offset);
 		if (bm+do_now > p_addr + LWPP) {
-			printk(KERN_ALERT "drbd: BUG BUG BUG! p_addr:%p bm:%p do_now:%d\n",
+			pr_alert("BUG BUG BUG! p_addr:%p bm:%p do_now:%d\n",
 			       p_addr, bm, (int)do_now);
 		} else
 			memset(bm, c, do_now * sizeof(long));
@@ -927,22 +928,14 @@ void drbd_bm_clear_all(struct drbd_device *device)
 	spin_unlock_irq(&b->bm_lock);
 }
 
-struct bm_aio_ctx {
-	struct drbd_device *device;
-	atomic_t in_flight;
-	unsigned int done;
-	unsigned flags;
-#define BM_AIO_COPY_PAGES	1
-#define BM_AIO_WRITE_HINTED	2
-#define BM_WRITE_ALL_PAGES	4
-	int error;
-	struct kref kref;
-};
-
-static void bm_aio_ctx_destroy(struct kref *kref)
+static void drbd_bm_aio_ctx_destroy(struct kref *kref)
 {
-	struct bm_aio_ctx *ctx = container_of(kref, struct bm_aio_ctx, kref);
+	struct drbd_bm_aio_ctx *ctx = container_of(kref, struct drbd_bm_aio_ctx, kref);
+	unsigned long flags;
 
+	spin_lock_irqsave(&ctx->device->resource->req_lock, flags);
+	list_del(&ctx->list);
+	spin_unlock_irqrestore(&ctx->device->resource->req_lock, flags);
 	put_ldev(ctx->device);
 	kfree(ctx);
 }
@@ -950,7 +943,7 @@ static void bm_aio_ctx_destroy(struct kref *kref)
 /* bv_page may be a copy, or may be the original */
 static void bm_async_io_complete(struct bio *bio, int error)
 {
-	struct bm_aio_ctx *ctx = bio->bi_private;
+	struct drbd_bm_aio_ctx *ctx = bio->bi_private;
 	struct drbd_device *device = ctx->device;
 	struct drbd_bitmap *b = device->bitmap;
 	unsigned int idx = bm_page_to_idx(bio->bi_io_vec[0].bv_page);
@@ -993,17 +986,18 @@ static void bm_async_io_complete(struct bio *bio, int error)
 	if (atomic_dec_and_test(&ctx->in_flight)) {
 		ctx->done = 1;
 		wake_up(&device->misc_wait);
-		kref_put(&ctx->kref, &bm_aio_ctx_destroy);
+		kref_put(&ctx->kref, &drbd_bm_aio_ctx_destroy);
 	}
 }
 
-static void bm_page_io_async(struct bm_aio_ctx *ctx, int page_nr, int rw) __must_hold(local)
+static void bm_page_io_async(struct drbd_bm_aio_ctx *ctx, int page_nr) __must_hold(local)
 {
 	struct bio *bio = bio_alloc_drbd(GFP_NOIO);
 	struct drbd_device *device = ctx->device;
 	struct drbd_bitmap *b = device->bitmap;
 	struct page *page;
 	unsigned int len;
+	unsigned int rw = (ctx->flags & BM_AIO_READ) ? READ : WRITE;
 
 	sector_t on_disk_sector =
 		device->ldev->md.md_offset + device->ldev->md.bm_offset;
@@ -1049,9 +1043,9 @@ static void bm_page_io_async(struct bm_aio_ctx *ctx, int page_nr, int rw) __must
 /*
  * bm_rw: read/write the whole bitmap from/to its on disk location.
  */
-static int bm_rw(struct drbd_device *device, int rw, unsigned flags, unsigned lazy_writeout_upper_idx) __must_hold(local)
+static int bm_rw(struct drbd_device *device, const unsigned int flags, unsigned lazy_writeout_upper_idx) __must_hold(local)
 {
-	struct bm_aio_ctx *ctx;
+	struct drbd_bm_aio_ctx *ctx;
 	struct drbd_bitmap *b = device->bitmap;
 	int num_pages, i, count = 0;
 	unsigned long now;
@@ -1067,12 +1061,13 @@ static int bm_rw(struct drbd_device *device, int rw, unsigned flags, unsigned la
 	 * as we submit copies of pages anyways.
 	 */
 
-	ctx = kmalloc(sizeof(struct bm_aio_ctx), GFP_NOIO);
+	ctx = kmalloc(sizeof(struct drbd_bm_aio_ctx), GFP_NOIO);
 	if (!ctx)
 		return -ENOMEM;
 
-	*ctx = (struct bm_aio_ctx) {
+	*ctx = (struct drbd_bm_aio_ctx) {
 		.device = device,
+		.start_jif = jiffies,
 		.in_flight = ATOMIC_INIT(1),
 		.done = 0,
 		.flags = flags,
@@ -1080,15 +1075,21 @@ static int bm_rw(struct drbd_device *device, int rw, unsigned flags, unsigned la
 		.kref = { ATOMIC_INIT(2) },
 	};
 
-	if (!get_ldev_if_state(device, D_ATTACHING)) {  /* put is in bm_aio_ctx_destroy() */
+	if (!get_ldev_if_state(device, D_ATTACHING)) {  /* put is in drbd_bm_aio_ctx_destroy() */
 		drbd_err(device, "ASSERT FAILED: get_ldev_if_state() == 1 in bm_rw()\n");
 		kfree(ctx);
 		return -ENODEV;
 	}
+	/* Here D_ATTACHING is sufficient since drbd_bm_read() is called only from
+	   drbd_adm_attach(), after device->ldev was assigned. */
 
-	if (!ctx->flags)
+	if (0 == (ctx->flags & ~BM_AIO_READ))
 		WARN_ON(!(BM_LOCKED_MASK & b->bm_flags));
 
+	spin_lock_irq(&device->resource->req_lock);
+	list_add_tail(&ctx->list, &device->pending_bitmap_io);
+	spin_unlock_irq(&device->resource->req_lock);
+
 	num_pages = b->bm_number_of_pages;
 
 	now = jiffies;
@@ -1098,13 +1099,13 @@ static int bm_rw(struct drbd_device *device, int rw, unsigned flags, unsigned la
 		/* ignore completely unchanged pages */
 		if (lazy_writeout_upper_idx && i == lazy_writeout_upper_idx)
 			break;
-		if (rw & WRITE) {
+		if (!(flags & BM_AIO_READ)) {
 			if ((flags & BM_AIO_WRITE_HINTED) &&
 			    !test_and_clear_bit(BM_PAGE_HINT_WRITEOUT,
 				    &page_private(b->bm_pages[i])))
 				continue;
 
-			if (!(flags & BM_WRITE_ALL_PAGES) &&
+			if (!(flags & BM_AIO_WRITE_ALL_PAGES) &&
 			    bm_test_page_unchanged(b->bm_pages[i])) {
 				dynamic_drbd_dbg(device, "skipped bm write for idx %u\n", i);
 				continue;
@@ -1118,7 +1119,7 @@ static int bm_rw(struct drbd_device *device, int rw, unsigned flags, unsigned la
 			}
 		}
 		atomic_inc(&ctx->in_flight);
-		bm_page_io_async(ctx, i, rw);
+		bm_page_io_async(ctx, i);
 		++count;
 		cond_resched();
 	}
@@ -1134,12 +1135,12 @@ static int bm_rw(struct drbd_device *device, int rw, unsigned flags, unsigned la
 	if (!atomic_dec_and_test(&ctx->in_flight))
 		wait_until_done_or_force_detached(device, device->ldev, &ctx->done);
 	else
-		kref_put(&ctx->kref, &bm_aio_ctx_destroy);
+		kref_put(&ctx->kref, &drbd_bm_aio_ctx_destroy);
 
 	/* summary for global bitmap IO */
 	if (flags == 0)
 		drbd_info(device, "bitmap %s of %u pages took %lu jiffies\n",
-			 rw == WRITE ? "WRITE" : "READ",
+			 (flags & BM_AIO_READ) ? "READ" : "WRITE",
 			 count, jiffies - now);
 
 	if (ctx->error) {
@@ -1152,20 +1153,18 @@ static int bm_rw(struct drbd_device *device, int rw, unsigned flags, unsigned la
 		err = -EIO; /* Disk timeout/force-detach during IO... */
 
 	now = jiffies;
-	if (rw == WRITE) {
-		drbd_md_flush(device);
-	} else /* rw == READ */ {
+	if (flags & BM_AIO_READ) {
 		b->bm_set = bm_count_bits(b);
 		drbd_info(device, "recounting of set bits took additional %lu jiffies\n",
 		     jiffies - now);
 	}
 	now = b->bm_set;
 
-	if (flags == 0)
+	if ((flags & ~BM_AIO_READ) == 0)
 		drbd_info(device, "%s (%lu bits) marked out-of-sync by on disk bit-map.\n",
 		     ppsize(ppb, now << (BM_BLOCK_SHIFT-10)), now);
 
-	kref_put(&ctx->kref, &bm_aio_ctx_destroy);
+	kref_put(&ctx->kref, &drbd_bm_aio_ctx_destroy);
 	return err;
 }
 
@@ -1175,7 +1174,7 @@ static int bm_rw(struct drbd_device *device, int rw, unsigned flags, unsigned la
  */
 int drbd_bm_read(struct drbd_device *device) __must_hold(local)
 {
-	return bm_rw(device, READ, 0, 0);
+	return bm_rw(device, BM_AIO_READ, 0);
 }
 
 /**
@@ -1186,7 +1185,7 @@ int drbd_bm_read(struct drbd_device *device) __must_hold(local)
  */
 int drbd_bm_write(struct drbd_device *device) __must_hold(local)
 {
-	return bm_rw(device, WRITE, 0, 0);
+	return bm_rw(device, 0, 0);
 }
 
 /**
@@ -1197,7 +1196,17 @@ int drbd_bm_write(struct drbd_device *device) __must_hold(local)
  */
 int drbd_bm_write_all(struct drbd_device *device) __must_hold(local)
 {
-	return bm_rw(device, WRITE, BM_WRITE_ALL_PAGES, 0);
+	return bm_rw(device, BM_AIO_WRITE_ALL_PAGES, 0);
+}
+
+/**
+ * drbd_bm_write_lazy() - Write bitmap pages 0 to @upper_idx-1, if they have changed.
+ * @device:	DRBD device.
+ * @upper_idx:	0: write all changed pages; +ve: page index to stop scanning for changed pages
+ */
+int drbd_bm_write_lazy(struct drbd_device *device, unsigned upper_idx) __must_hold(local)
+{
+	return bm_rw(device, BM_AIO_COPY_PAGES, upper_idx);
 }
 
 /**
@@ -1213,7 +1222,7 @@ int drbd_bm_write_all(struct drbd_device *device) __must_hold(local)
  */
 int drbd_bm_write_copy_pages(struct drbd_device *device) __must_hold(local)
 {
-	return bm_rw(device, WRITE, BM_AIO_COPY_PAGES, 0);
+	return bm_rw(device, BM_AIO_COPY_PAGES, 0);
 }
 
 /**
@@ -1222,62 +1231,7 @@ int drbd_bm_write_copy_pages(struct drbd_device *device) __must_hold(local)
  */
 int drbd_bm_write_hinted(struct drbd_device *device) __must_hold(local)
 {
-	return bm_rw(device, WRITE, BM_AIO_WRITE_HINTED | BM_AIO_COPY_PAGES, 0);
-}
-
-/**
- * drbd_bm_write_page() - Writes a PAGE_SIZE aligned piece of bitmap
- * @device:	DRBD device.
- * @idx:	bitmap page index
- *
- * We don't want to special case on logical_block_size of the backend device,
- * so we submit PAGE_SIZE aligned pieces.
- * Note that on "most" systems, PAGE_SIZE is 4k.
- *
- * In case this becomes an issue on systems with larger PAGE_SIZE,
- * we may want to change this again to write 4k aligned 4k pieces.
- */
-int drbd_bm_write_page(struct drbd_device *device, unsigned int idx) __must_hold(local)
-{
-	struct bm_aio_ctx *ctx;
-	int err;
-
-	if (bm_test_page_unchanged(device->bitmap->bm_pages[idx])) {
-		dynamic_drbd_dbg(device, "skipped bm page write for idx %u\n", idx);
-		return 0;
-	}
-
-	ctx = kmalloc(sizeof(struct bm_aio_ctx), GFP_NOIO);
-	if (!ctx)
-		return -ENOMEM;
-
-	*ctx = (struct bm_aio_ctx) {
-		.device = device,
-		.in_flight = ATOMIC_INIT(1),
-		.done = 0,
-		.flags = BM_AIO_COPY_PAGES,
-		.error = 0,
-		.kref = { ATOMIC_INIT(2) },
-	};
-
-	if (!get_ldev_if_state(device, D_ATTACHING)) {  /* put is in bm_aio_ctx_destroy() */
-		drbd_err(device, "ASSERT FAILED: get_ldev_if_state() == 1 in drbd_bm_write_page()\n");
-		kfree(ctx);
-		return -ENODEV;
-	}
-
-	bm_page_io_async(ctx, idx, WRITE_SYNC);
-	wait_until_done_or_force_detached(device, device->ldev, &ctx->done);
-
-	if (ctx->error)
-		drbd_chk_io_error(device, 1, DRBD_META_IO_ERROR);
-		/* that causes us to detach, so the in memory bitmap will be
-		 * gone in a moment as well. */
-
-	device->bm_writ_cnt++;
-	err = atomic_read(&ctx->in_flight) ? -EIO : ctx->error;
-	kref_put(&ctx->kref, &bm_aio_ctx_destroy);
-	return err;
+	return bm_rw(device, BM_AIO_WRITE_HINTED | BM_AIO_COPY_PAGES, 0);
 }
 
 /* NOTE
diff --git a/drivers/block/drbd/drbd_debugfs.c b/drivers/block/drbd/drbd_debugfs.c
new file mode 100644
index 0000000..5c20b18
--- /dev/null
+++ b/drivers/block/drbd/drbd_debugfs.c
@@ -0,0 +1,958 @@
+#define pr_fmt(fmt) "drbd debugfs: " fmt
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+#include <linux/stat.h>
+#include <linux/jiffies.h>
+#include <linux/list.h>
+
+#include "drbd_int.h"
+#include "drbd_req.h"
+#include "drbd_debugfs.h"
+
+
+/**********************************************************************
+ * Whenever you change the file format, remember to bump the version. *
+ **********************************************************************/
+
+static struct dentry *drbd_debugfs_root;
+static struct dentry *drbd_debugfs_version;
+static struct dentry *drbd_debugfs_resources;
+static struct dentry *drbd_debugfs_minors;
+
+static void seq_print_age_or_dash(struct seq_file *m, bool valid, unsigned long dt)
+{
+	if (valid)
+		seq_printf(m, "\t%d", jiffies_to_msecs(dt));
+	else
+		seq_printf(m, "\t-");
+}
+
+static void __seq_print_rq_state_bit(struct seq_file *m,
+	bool is_set, char *sep, const char *set_name, const char *unset_name)
+{
+	if (is_set && set_name) {
+		seq_putc(m, *sep);
+		seq_puts(m, set_name);
+		*sep = '|';
+	} else if (!is_set && unset_name) {
+		seq_putc(m, *sep);
+		seq_puts(m, unset_name);
+		*sep = '|';
+	}
+}
+
+static void seq_print_rq_state_bit(struct seq_file *m,
+	bool is_set, char *sep, const char *set_name)
+{
+	__seq_print_rq_state_bit(m, is_set, sep, set_name, NULL);
+}
+
+/* pretty print enum drbd_req_state_bits req->rq_state */
+static void seq_print_request_state(struct seq_file *m, struct drbd_request *req)
+{
+	unsigned int s = req->rq_state;
+	char sep = ' ';
+	seq_printf(m, "\t0x%08x", s);
+	seq_printf(m, "\tmaster: %s", req->master_bio ? "pending" : "completed");
+
+	/* RQ_WRITE ignored, already reported */
+	seq_puts(m, "\tlocal:");
+	seq_print_rq_state_bit(m, s & RQ_IN_ACT_LOG, &sep, "in-AL");
+	seq_print_rq_state_bit(m, s & RQ_POSTPONED, &sep, "postponed");
+	seq_print_rq_state_bit(m, s & RQ_COMPLETION_SUSP, &sep, "suspended");
+	sep = ' ';
+	seq_print_rq_state_bit(m, s & RQ_LOCAL_PENDING, &sep, "pending");
+	seq_print_rq_state_bit(m, s & RQ_LOCAL_COMPLETED, &sep, "completed");
+	seq_print_rq_state_bit(m, s & RQ_LOCAL_ABORTED, &sep, "aborted");
+	seq_print_rq_state_bit(m, s & RQ_LOCAL_OK, &sep, "ok");
+	if (sep == ' ')
+		seq_puts(m, " -");
+
+	/* for_each_connection ... */
+	seq_printf(m, "\tnet:");
+	sep = ' ';
+	seq_print_rq_state_bit(m, s & RQ_NET_PENDING, &sep, "pending");
+	seq_print_rq_state_bit(m, s & RQ_NET_QUEUED, &sep, "queued");
+	seq_print_rq_state_bit(m, s & RQ_NET_SENT, &sep, "sent");
+	seq_print_rq_state_bit(m, s & RQ_NET_DONE, &sep, "done");
+	seq_print_rq_state_bit(m, s & RQ_NET_SIS, &sep, "sis");
+	seq_print_rq_state_bit(m, s & RQ_NET_OK, &sep, "ok");
+	if (sep == ' ')
+		seq_puts(m, " -");
+
+	seq_printf(m, " :");
+	sep = ' ';
+	seq_print_rq_state_bit(m, s & RQ_EXP_RECEIVE_ACK, &sep, "B");
+	seq_print_rq_state_bit(m, s & RQ_EXP_WRITE_ACK, &sep, "C");
+	seq_print_rq_state_bit(m, s & RQ_EXP_BARR_ACK, &sep, "barr");
+	if (sep == ' ')
+		seq_puts(m, " -");
+	seq_printf(m, "\n");
+}
+
+static void seq_print_one_request(struct seq_file *m, struct drbd_request *req, unsigned long now)
+{
+	/* change anything here, fixup header below! */
+	unsigned int s = req->rq_state;
+
+#define RQ_HDR_1 "epoch\tsector\tsize\trw"
+	seq_printf(m, "0x%x\t%llu\t%u\t%s",
+		req->epoch,
+		(unsigned long long)req->i.sector, req->i.size >> 9,
+		(s & RQ_WRITE) ? "W" : "R");
+
+#define RQ_HDR_2 "\tstart\tin AL\tsubmit"
+	seq_printf(m, "\t%d", jiffies_to_msecs(now - req->start_jif));
+	seq_print_age_or_dash(m, s & RQ_IN_ACT_LOG, now - req->in_actlog_jif);
+	seq_print_age_or_dash(m, s & RQ_LOCAL_PENDING, now - req->pre_submit_jif);
+
+#define RQ_HDR_3 "\tsent\tacked\tdone"
+	seq_print_age_or_dash(m, s & RQ_NET_SENT, now - req->pre_send_jif);
+	seq_print_age_or_dash(m, (s & RQ_NET_SENT) && !(s & RQ_NET_PENDING), now - req->acked_jif);
+	seq_print_age_or_dash(m, s & RQ_NET_DONE, now - req->net_done_jif);
+
+#define RQ_HDR_4 "\tstate\n"
+	seq_print_request_state(m, req);
+}
+#define RQ_HDR RQ_HDR_1 RQ_HDR_2 RQ_HDR_3 RQ_HDR_4
+
+static void seq_print_minor_vnr_req(struct seq_file *m, struct drbd_request *req, unsigned long now)
+{
+	seq_printf(m, "%u\t%u\t", req->device->minor, req->device->vnr);
+	seq_print_one_request(m, req, now);
+}
+
+static void seq_print_resource_pending_meta_io(struct seq_file *m, struct drbd_resource *resource, unsigned long now)
+{
+	struct drbd_device *device;
+	unsigned int i;
+
+	seq_puts(m, "minor\tvnr\tstart\tsubmit\tintent\n");
+	rcu_read_lock();
+	idr_for_each_entry(&resource->devices, device, i) {
+		struct drbd_md_io tmp;
+		/* In theory this is racy,
+		 * in the sense that there could have been a
+		 * drbd_md_put_buffer(); drbd_md_get_buffer();
+		 * between accessing these members here.  */
+		tmp = device->md_io;
+		if (atomic_read(&tmp.in_use)) {
+			seq_printf(m, "%u\t%u\t%d\t",
+				device->minor, device->vnr,
+				jiffies_to_msecs(now - tmp.start_jif));
+			if (time_before(tmp.submit_jif, tmp.start_jif))
+				seq_puts(m, "-\t");
+			else
+				seq_printf(m, "%d\t", jiffies_to_msecs(now - tmp.submit_jif));
+			seq_printf(m, "%s\n", tmp.current_use);
+		}
+	}
+	rcu_read_unlock();
+}
+
+static void seq_print_waiting_for_AL(struct seq_file *m, struct drbd_resource *resource, unsigned long now)
+{
+	struct drbd_device *device;
+	unsigned int i;
+
+	seq_puts(m, "minor\tvnr\tage\t#waiting\n");
+	rcu_read_lock();
+	idr_for_each_entry(&resource->devices, device, i) {
+		unsigned long jif;
+		struct drbd_request *req;
+		int n = atomic_read(&device->ap_actlog_cnt);
+		if (n) {
+			spin_lock_irq(&device->resource->req_lock);
+			req = list_first_entry_or_null(&device->pending_master_completion[1],
+				struct drbd_request, req_pending_master_completion);
+			/* if the oldest request does not wait for the activity log
+			 * it is not interesting for us here */
+			if (req && !(req->rq_state & RQ_IN_ACT_LOG))
+				jif = req->start_jif;
+			else
+				req = NULL;
+			spin_unlock_irq(&device->resource->req_lock);
+		}
+		if (n) {
+			seq_printf(m, "%u\t%u\t", device->minor, device->vnr);
+			if (req)
+				seq_printf(m, "%u\t", jiffies_to_msecs(now - jif));
+			else
+				seq_puts(m, "-\t");
+			seq_printf(m, "%u\n", n);
+		}
+	}
+	rcu_read_unlock();
+}
+
+static void seq_print_device_bitmap_io(struct seq_file *m, struct drbd_device *device, unsigned long now)
+{
+	struct drbd_bm_aio_ctx *ctx;
+	unsigned long start_jif;
+	unsigned int in_flight;
+	unsigned int flags;
+	spin_lock_irq(&device->resource->req_lock);
+	ctx = list_first_entry_or_null(&device->pending_bitmap_io, struct drbd_bm_aio_ctx, list);
+	if (ctx && ctx->done)
+		ctx = NULL;
+	if (ctx) {
+		start_jif = ctx->start_jif;
+		in_flight = atomic_read(&ctx->in_flight);
+		flags = ctx->flags;
+	}
+	spin_unlock_irq(&device->resource->req_lock);
+	if (ctx) {
+		seq_printf(m, "%u\t%u\t%c\t%u\t%u\n",
+			device->minor, device->vnr,
+			(flags & BM_AIO_READ) ? 'R' : 'W',
+			jiffies_to_msecs(now - start_jif),
+			in_flight);
+	}
+}
+
+static void seq_print_resource_pending_bitmap_io(struct seq_file *m, struct drbd_resource *resource, unsigned long now)
+{
+	struct drbd_device *device;
+	unsigned int i;
+
+	seq_puts(m, "minor\tvnr\trw\tage\t#in-flight\n");
+	rcu_read_lock();
+	idr_for_each_entry(&resource->devices, device, i) {
+		seq_print_device_bitmap_io(m, device, now);
+	}
+	rcu_read_unlock();
+}
+
+/* pretty print enum peer_req->flags */
+static void seq_print_peer_request_flags(struct seq_file *m, struct drbd_peer_request *peer_req)
+{
+	unsigned long f = peer_req->flags;
+	char sep = ' ';
+
+	__seq_print_rq_state_bit(m, f & EE_SUBMITTED, &sep, "submitted", "preparing");
+	__seq_print_rq_state_bit(m, f & EE_APPLICATION, &sep, "application", "internal");
+	seq_print_rq_state_bit(m, f & EE_CALL_AL_COMPLETE_IO, &sep, "in-AL");
+	seq_print_rq_state_bit(m, f & EE_SEND_WRITE_ACK, &sep, "C");
+	seq_print_rq_state_bit(m, f & EE_MAY_SET_IN_SYNC, &sep, "set-in-sync");
+
+	if (f & EE_IS_TRIM) {
+		seq_putc(m, sep);
+		sep = '|';
+		if (f & EE_IS_TRIM_USE_ZEROOUT)
+			seq_puts(m, "zero-out");
+		else
+			seq_puts(m, "trim");
+	}
+	seq_putc(m, '\n');
+}
+
+static void seq_print_peer_request(struct seq_file *m,
+	struct drbd_device *device, struct list_head *lh,
+	unsigned long now)
+{
+	bool reported_preparing = false;
+	struct drbd_peer_request *peer_req;
+	list_for_each_entry(peer_req, lh, w.list) {
+		if (reported_preparing && !(peer_req->flags & EE_SUBMITTED))
+			continue;
+
+		if (device)
+			seq_printf(m, "%u\t%u\t", device->minor, device->vnr);
+
+		seq_printf(m, "%llu\t%u\t%c\t%u\t",
+			(unsigned long long)peer_req->i.sector, peer_req->i.size >> 9,
+			(peer_req->flags & EE_WRITE) ? 'W' : 'R',
+			jiffies_to_msecs(now - peer_req->submit_jif));
+		seq_print_peer_request_flags(m, peer_req);
+		if (peer_req->flags & EE_SUBMITTED)
+			break;
+		else
+			reported_preparing = true;
+	}
+}
+
+static void seq_print_device_peer_requests(struct seq_file *m,
+	struct drbd_device *device, unsigned long now)
+{
+	seq_puts(m, "minor\tvnr\tsector\tsize\trw\tage\tflags\n");
+	spin_lock_irq(&device->resource->req_lock);
+	seq_print_peer_request(m, device, &device->active_ee, now);
+	seq_print_peer_request(m, device, &device->read_ee, now);
+	seq_print_peer_request(m, device, &device->sync_ee, now);
+	spin_unlock_irq(&device->resource->req_lock);
+	if (test_bit(FLUSH_PENDING, &device->flags)) {
+		seq_printf(m, "%u\t%u\t-\t-\tF\t%u\tflush\n",
+			device->minor, device->vnr,
+			jiffies_to_msecs(now - device->flush_jif));
+	}
+}
+
+static void seq_print_resource_pending_peer_requests(struct seq_file *m,
+	struct drbd_resource *resource, unsigned long now)
+{
+	struct drbd_device *device;
+	unsigned int i;
+
+	rcu_read_lock();
+	idr_for_each_entry(&resource->devices, device, i) {
+		seq_print_device_peer_requests(m, device, now);
+	}
+	rcu_read_unlock();
+}
+
+static void seq_print_resource_transfer_log_summary(struct seq_file *m,
+	struct drbd_resource *resource,
+	struct drbd_connection *connection,
+	unsigned long now)
+{
+	struct drbd_request *req;
+	unsigned int count = 0;
+	unsigned int show_state = 0;
+
+	seq_puts(m, "n\tdevice\tvnr\t" RQ_HDR);
+	spin_lock_irq(&resource->req_lock);
+	list_for_each_entry(req, &connection->transfer_log, tl_requests) {
+		unsigned int tmp = 0;
+		unsigned int s;
+		++count;
+
+		/* don't disable irq "forever" */
+		if (!(count & 0x1ff)) {
+			struct drbd_request *req_next;
+			kref_get(&req->kref);
+			spin_unlock_irq(&resource->req_lock);
+			cond_resched();
+			spin_lock_irq(&resource->req_lock);
+			req_next = list_next_entry(req, tl_requests);
+			if (kref_put(&req->kref, drbd_req_destroy))
+				req = req_next;
+			if (&req->tl_requests == &connection->transfer_log)
+				break;
+		}
+
+		s = req->rq_state;
+
+		/* This is meant to summarize timing issues, to be able to tell
+		 * local disk problems from network problems.
+		 * Skip requests, if we have shown an even older request with
+		 * similar aspects already.  */
+		if (req->master_bio == NULL)
+			tmp |= 1;
+		if ((s & RQ_LOCAL_MASK) && (s & RQ_LOCAL_PENDING))
+			tmp |= 2;
+		if (s & RQ_NET_MASK) {
+			if (!(s & RQ_NET_SENT))
+				tmp |= 4;
+			if (s & RQ_NET_PENDING)
+				tmp |= 8;
+			if (!(s & RQ_NET_DONE))
+				tmp |= 16;
+		}
+		if ((tmp & show_state) == tmp)
+			continue;
+		show_state |= tmp;
+		seq_printf(m, "%u\t", count);
+		seq_print_minor_vnr_req(m, req, now);
+		if (show_state == 0x1f)
+			break;
+	}
+	spin_unlock_irq(&resource->req_lock);
+}
+
+/* TODO: transfer_log and friends should be moved to resource */
+static int in_flight_summary_show(struct seq_file *m, void *pos)
+{
+	struct drbd_resource *resource = m->private;
+	struct drbd_connection *connection;
+	unsigned long jif = jiffies;
+
+	connection = first_connection(resource);
+	/* This does not happen, actually.
+	 * But be robust and prepare for future code changes. */
+	if (!connection || !kref_get_unless_zero(&connection->kref))
+		return -ESTALE;
+
+	/* BUMP me if you change the file format/content/presentation */
+	seq_printf(m, "v: %u\n\n", 0);
+
+	seq_puts(m, "oldest bitmap IO\n");
+	seq_print_resource_pending_bitmap_io(m, resource, jif);
+	seq_putc(m, '\n');
+
+	seq_puts(m, "meta data IO\n");
+	seq_print_resource_pending_meta_io(m, resource, jif);
+	seq_putc(m, '\n');
+
+	seq_puts(m, "socket buffer stats\n");
+	/* for each connection ... once we have more than one */
+	rcu_read_lock();
+	if (connection->data.socket) {
+		/* open coded SIOCINQ, the "relevant" part */
+		struct tcp_sock *tp = tcp_sk(connection->data.socket->sk);
+		int answ = tp->rcv_nxt - tp->copied_seq;
+		seq_printf(m, "unread receive buffer: %u Byte\n", answ);
+		/* open coded SIOCOUTQ, the "relevant" part */
+		answ = tp->write_seq - tp->snd_una;
+		seq_printf(m, "unacked send buffer: %u Byte\n", answ);
+	}
+	rcu_read_unlock();
+	seq_putc(m, '\n');
+
+	seq_puts(m, "oldest peer requests\n");
+	seq_print_resource_pending_peer_requests(m, resource, jif);
+	seq_putc(m, '\n');
+
+	seq_puts(m, "application requests waiting for activity log\n");
+	seq_print_waiting_for_AL(m, resource, jif);
+	seq_putc(m, '\n');
+
+	seq_puts(m, "oldest application requests\n");
+	seq_print_resource_transfer_log_summary(m, resource, connection, jif);
+	seq_putc(m, '\n');
+
+	jif = jiffies - jif;
+	if (jif)
+		seq_printf(m, "generated in %d ms\n", jiffies_to_msecs(jif));
+	kref_put(&connection->kref, drbd_destroy_connection);
+	return 0;
+}
+
+/* simple_positive(file->f_dentry) respectively debugfs_positive(),
+ * but neither is "reachable" from here.
+ * So we have our own inline version of it above.  :-( */
+static inline int debugfs_positive(struct dentry *dentry)
+{
+        return dentry->d_inode && !d_unhashed(dentry);
+}
+
+/* make sure at *open* time that the respective object won't go away. */
+static int drbd_single_open(struct file *file, int (*show)(struct seq_file *, void *),
+		                void *data, struct kref *kref,
+				void (*release)(struct kref *))
+{
+	struct dentry *parent;
+	int ret = -ESTALE;
+
+	/* Are we still linked,
+	 * or has debugfs_remove() already been called? */
+	parent = file->f_dentry->d_parent;
+	/* not sure if this can happen: */
+	if (!parent || !parent->d_inode)
+		goto out;
+	/* serialize with d_delete() */
+	mutex_lock(&parent->d_inode->i_mutex);
+	/* Make sure the object is still alive */
+	if (debugfs_positive(file->f_dentry)
+	&& kref_get_unless_zero(kref))
+		ret = 0;
+	mutex_unlock(&parent->d_inode->i_mutex);
+	if (!ret) {
+		ret = single_open(file, show, data);
+		if (ret)
+			kref_put(kref, release);
+	}
+out:
+	return ret;
+}
+
+static int in_flight_summary_open(struct inode *inode, struct file *file)
+{
+	struct drbd_resource *resource = inode->i_private;
+	return drbd_single_open(file, in_flight_summary_show, resource,
+				&resource->kref, drbd_destroy_resource);
+}
+
+static int in_flight_summary_release(struct inode *inode, struct file *file)
+{
+	struct drbd_resource *resource = inode->i_private;
+	kref_put(&resource->kref, drbd_destroy_resource);
+	return single_release(inode, file);
+}
+
+static const struct file_operations in_flight_summary_fops = {
+	.owner		= THIS_MODULE,
+	.open		= in_flight_summary_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= in_flight_summary_release,
+};
+
+void drbd_debugfs_resource_add(struct drbd_resource *resource)
+{
+	struct dentry *dentry;
+	if (!drbd_debugfs_resources)
+		return;
+
+	dentry = debugfs_create_dir(resource->name, drbd_debugfs_resources);
+	if (IS_ERR_OR_NULL(dentry))
+		goto fail;
+	resource->debugfs_res = dentry;
+
+	dentry = debugfs_create_dir("volumes", resource->debugfs_res);
+	if (IS_ERR_OR_NULL(dentry))
+		goto fail;
+	resource->debugfs_res_volumes = dentry;
+
+	dentry = debugfs_create_dir("connections", resource->debugfs_res);
+	if (IS_ERR_OR_NULL(dentry))
+		goto fail;
+	resource->debugfs_res_connections = dentry;
+
+	dentry = debugfs_create_file("in_flight_summary", S_IRUSR|S_IRGRP,
+			resource->debugfs_res, resource,
+			&in_flight_summary_fops);
+	if (IS_ERR_OR_NULL(dentry))
+		goto fail;
+	resource->debugfs_res_in_flight_summary = dentry;
+	return;
+
+fail:
+	drbd_debugfs_resource_cleanup(resource);
+	drbd_err(resource, "failed to create debugfs dentry\n");
+}
+
+static void drbd_debugfs_remove(struct dentry **dp)
+{
+	debugfs_remove(*dp);
+	*dp = NULL;
+}
+
+void drbd_debugfs_resource_cleanup(struct drbd_resource *resource)
+{
+	/* it is ok to call debugfs_remove(NULL) */
+	drbd_debugfs_remove(&resource->debugfs_res_in_flight_summary);
+	drbd_debugfs_remove(&resource->debugfs_res_connections);
+	drbd_debugfs_remove(&resource->debugfs_res_volumes);
+	drbd_debugfs_remove(&resource->debugfs_res);
+}
+
+static void seq_print_one_timing_detail(struct seq_file *m,
+	const struct drbd_thread_timing_details *tdp,
+	unsigned long now)
+{
+	struct drbd_thread_timing_details td;
+	/* No locking...
+	 * use temporary assignment to get at consistent data. */
+	do {
+		td = *tdp;
+	} while (td.cb_nr != tdp->cb_nr);
+	if (!td.cb_addr)
+		return;
+	seq_printf(m, "%u\t%d\t%s:%u\t%ps\n",
+			td.cb_nr,
+			jiffies_to_msecs(now - td.start_jif),
+			td.caller_fn, td.line,
+			td.cb_addr);
+}
+
+static void seq_print_timing_details(struct seq_file *m,
+		const char *title,
+		unsigned int cb_nr, struct drbd_thread_timing_details *tdp, unsigned long now)
+{
+	unsigned int start_idx;
+	unsigned int i;
+
+	seq_printf(m, "%s\n", title);
+	/* If not much is going on, this will result in natural ordering.
+	 * If it is very busy, we will possibly skip events, or even see wrap
+	 * arounds, which could only be avoided with locking.
+	 */
+	start_idx = cb_nr % DRBD_THREAD_DETAILS_HIST;
+	for (i = start_idx; i < DRBD_THREAD_DETAILS_HIST; i++)
+		seq_print_one_timing_detail(m, tdp+i, now);
+	for (i = 0; i < start_idx; i++)
+		seq_print_one_timing_detail(m, tdp+i, now);
+}
+
+static int callback_history_show(struct seq_file *m, void *ignored)
+{
+	struct drbd_connection *connection = m->private;
+	unsigned long jif = jiffies;
+
+	/* BUMP me if you change the file format/content/presentation */
+	seq_printf(m, "v: %u\n\n", 0);
+
+	seq_puts(m, "n\tage\tcallsite\tfn\n");
+	seq_print_timing_details(m, "worker", connection->w_cb_nr, connection->w_timing_details, jif);
+	seq_print_timing_details(m, "receiver", connection->r_cb_nr, connection->r_timing_details, jif);
+	return 0;
+}
+
+static int callback_history_open(struct inode *inode, struct file *file)
+{
+	struct drbd_connection *connection = inode->i_private;
+	return drbd_single_open(file, callback_history_show, connection,
+				&connection->kref, drbd_destroy_connection);
+}
+
+static int callback_history_release(struct inode *inode, struct file *file)
+{
+	struct drbd_connection *connection = inode->i_private;
+	kref_put(&connection->kref, drbd_destroy_connection);
+	return single_release(inode, file);
+}
+
+static const struct file_operations connection_callback_history_fops = {
+	.owner		= THIS_MODULE,
+	.open		= callback_history_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= callback_history_release,
+};
+
+static int connection_oldest_requests_show(struct seq_file *m, void *ignored)
+{
+	struct drbd_connection *connection = m->private;
+	unsigned long now = jiffies;
+	struct drbd_request *r1, *r2;
+
+	/* BUMP me if you change the file format/content/presentation */
+	seq_printf(m, "v: %u\n\n", 0);
+
+	spin_lock_irq(&connection->resource->req_lock);
+	r1 = connection->req_next;
+	if (r1)
+		seq_print_minor_vnr_req(m, r1, now);
+	r2 = connection->req_ack_pending;
+	if (r2 && r2 != r1) {
+		r1 = r2;
+		seq_print_minor_vnr_req(m, r1, now);
+	}
+	r2 = connection->req_not_net_done;
+	if (r2 && r2 != r1)
+		seq_print_minor_vnr_req(m, r2, now);
+	spin_unlock_irq(&connection->resource->req_lock);
+	return 0;
+}
+
+static int connection_oldest_requests_open(struct inode *inode, struct file *file)
+{
+	struct drbd_connection *connection = inode->i_private;
+	return drbd_single_open(file, connection_oldest_requests_show, connection,
+				&connection->kref, drbd_destroy_connection);
+}
+
+static int connection_oldest_requests_release(struct inode *inode, struct file *file)
+{
+	struct drbd_connection *connection = inode->i_private;
+	kref_put(&connection->kref, drbd_destroy_connection);
+	return single_release(inode, file);
+}
+
+static const struct file_operations connection_oldest_requests_fops = {
+	.owner		= THIS_MODULE,
+	.open		= connection_oldest_requests_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= connection_oldest_requests_release,
+};
+
+void drbd_debugfs_connection_add(struct drbd_connection *connection)
+{
+	struct dentry *conns_dir = connection->resource->debugfs_res_connections;
+	struct dentry *dentry;
+	if (!conns_dir)
+		return;
+
+	/* Once we enable mutliple peers,
+	 * these connections will have descriptive names.
+	 * For now, it is just the one connection to the (only) "peer". */
+	dentry = debugfs_create_dir("peer", conns_dir);
+	if (IS_ERR_OR_NULL(dentry))
+		goto fail;
+	connection->debugfs_conn = dentry;
+
+	dentry = debugfs_create_file("callback_history", S_IRUSR|S_IRGRP,
+			connection->debugfs_conn, connection,
+			&connection_callback_history_fops);
+	if (IS_ERR_OR_NULL(dentry))
+		goto fail;
+	connection->debugfs_conn_callback_history = dentry;
+
+	dentry = debugfs_create_file("oldest_requests", S_IRUSR|S_IRGRP,
+			connection->debugfs_conn, connection,
+			&connection_oldest_requests_fops);
+	if (IS_ERR_OR_NULL(dentry))
+		goto fail;
+	connection->debugfs_conn_oldest_requests = dentry;
+	return;
+
+fail:
+	drbd_debugfs_connection_cleanup(connection);
+	drbd_err(connection, "failed to create debugfs dentry\n");
+}
+
+void drbd_debugfs_connection_cleanup(struct drbd_connection *connection)
+{
+	drbd_debugfs_remove(&connection->debugfs_conn_callback_history);
+	drbd_debugfs_remove(&connection->debugfs_conn_oldest_requests);
+	drbd_debugfs_remove(&connection->debugfs_conn);
+}
+
+static void resync_dump_detail(struct seq_file *m, struct lc_element *e)
+{
+       struct bm_extent *bme = lc_entry(e, struct bm_extent, lce);
+
+       seq_printf(m, "%5d %s %s %s\n", bme->rs_left,
+		  test_bit(BME_NO_WRITES, &bme->flags) ? "NO_WRITES" : "---------",
+		  test_bit(BME_LOCKED, &bme->flags) ? "LOCKED" : "------",
+		  test_bit(BME_PRIORITY, &bme->flags) ? "PRIORITY" : "--------"
+		  );
+}
+
+static int device_resync_extents_show(struct seq_file *m, void *ignored)
+{
+	struct drbd_device *device = m->private;
+
+	/* BUMP me if you change the file format/content/presentation */
+	seq_printf(m, "v: %u\n\n", 0);
+
+	if (get_ldev_if_state(device, D_FAILED)) {
+		lc_seq_printf_stats(m, device->resync);
+		lc_seq_dump_details(m, device->resync, "rs_left flags", resync_dump_detail);
+		put_ldev(device);
+	}
+	return 0;
+}
+
+static int device_act_log_extents_show(struct seq_file *m, void *ignored)
+{
+	struct drbd_device *device = m->private;
+
+	/* BUMP me if you change the file format/content/presentation */
+	seq_printf(m, "v: %u\n\n", 0);
+
+	if (get_ldev_if_state(device, D_FAILED)) {
+		lc_seq_printf_stats(m, device->act_log);
+		lc_seq_dump_details(m, device->act_log, "", NULL);
+		put_ldev(device);
+	}
+	return 0;
+}
+
+static int device_oldest_requests_show(struct seq_file *m, void *ignored)
+{
+	struct drbd_device *device = m->private;
+	struct drbd_resource *resource = device->resource;
+	unsigned long now = jiffies;
+	struct drbd_request *r1, *r2;
+	int i;
+
+	/* BUMP me if you change the file format/content/presentation */
+	seq_printf(m, "v: %u\n\n", 0);
+
+	seq_puts(m, RQ_HDR);
+	spin_lock_irq(&resource->req_lock);
+	/* WRITE, then READ */
+	for (i = 1; i >= 0; --i) {
+		r1 = list_first_entry_or_null(&device->pending_master_completion[i],
+			struct drbd_request, req_pending_master_completion);
+		r2 = list_first_entry_or_null(&device->pending_completion[i],
+			struct drbd_request, req_pending_local);
+		if (r1)
+			seq_print_one_request(m, r1, now);
+		if (r2 && r2 != r1)
+			seq_print_one_request(m, r2, now);
+	}
+	spin_unlock_irq(&resource->req_lock);
+	return 0;
+}
+
+static int device_data_gen_id_show(struct seq_file *m, void *ignored)
+{
+	struct drbd_device *device = m->private;
+	struct drbd_md *md;
+	enum drbd_uuid_index idx;
+
+	if (!get_ldev_if_state(device, D_FAILED))
+		return -ENODEV;
+
+	md = &device->ldev->md;
+	spin_lock_irq(&md->uuid_lock);
+	for (idx = UI_CURRENT; idx <= UI_HISTORY_END; idx++) {
+		seq_printf(m, "0x%016llX\n", md->uuid[idx]);
+	}
+	spin_unlock_irq(&md->uuid_lock);
+	put_ldev(device);
+	return 0;
+}
+
+#define drbd_debugfs_device_attr(name)						\
+static int device_ ## name ## _open(struct inode *inode, struct file *file)	\
+{										\
+	struct drbd_device *device = inode->i_private;				\
+	return drbd_single_open(file, device_ ## name ## _show, device,		\
+				&device->kref, drbd_destroy_device);		\
+}										\
+static int device_ ## name ## _release(struct inode *inode, struct file *file)	\
+{										\
+	struct drbd_device *device = inode->i_private;				\
+	kref_put(&device->kref, drbd_destroy_device);				\
+	return single_release(inode, file);					\
+}										\
+static const struct file_operations device_ ## name ## _fops = {		\
+	.owner		= THIS_MODULE,						\
+	.open		= device_ ## name ## _open,				\
+	.read		= seq_read,						\
+	.llseek		= seq_lseek,						\
+	.release	= device_ ## name ## _release,				\
+};
+
+drbd_debugfs_device_attr(oldest_requests)
+drbd_debugfs_device_attr(act_log_extents)
+drbd_debugfs_device_attr(resync_extents)
+drbd_debugfs_device_attr(data_gen_id)
+
+void drbd_debugfs_device_add(struct drbd_device *device)
+{
+	struct dentry *vols_dir = device->resource->debugfs_res_volumes;
+	char minor_buf[8]; /* MINORMASK, MINORBITS == 20; */
+	char vnr_buf[8];   /* volume number vnr is even 16 bit only; */
+	char *slink_name = NULL;
+
+	struct dentry *dentry;
+	if (!vols_dir || !drbd_debugfs_minors)
+		return;
+
+	snprintf(vnr_buf, sizeof(vnr_buf), "%u", device->vnr);
+	dentry = debugfs_create_dir(vnr_buf, vols_dir);
+	if (IS_ERR_OR_NULL(dentry))
+		goto fail;
+	device->debugfs_vol = dentry;
+
+	snprintf(minor_buf, sizeof(minor_buf), "%u", device->minor);
+	slink_name = kasprintf(GFP_KERNEL, "../resources/%s/volumes/%u",
+			device->resource->name, device->vnr);
+	if (!slink_name)
+		goto fail;
+	dentry = debugfs_create_symlink(minor_buf, drbd_debugfs_minors, slink_name);
+	kfree(slink_name);
+	slink_name = NULL;
+	if (IS_ERR_OR_NULL(dentry))
+		goto fail;
+	device->debugfs_minor = dentry;
+
+#define DCF(name)	do {					\
+	dentry = debugfs_create_file(#name, S_IRUSR|S_IRGRP,	\
+			device->debugfs_vol, device,		\
+			&device_ ## name ## _fops);		\
+	if (IS_ERR_OR_NULL(dentry))				\
+		goto fail;					\
+	device->debugfs_vol_ ## name = dentry;			\
+	} while (0)
+
+	DCF(oldest_requests);
+	DCF(act_log_extents);
+	DCF(resync_extents);
+	DCF(data_gen_id);
+#undef DCF
+	return;
+
+fail:
+	drbd_debugfs_device_cleanup(device);
+	drbd_err(device, "failed to create debugfs entries\n");
+}
+
+void drbd_debugfs_device_cleanup(struct drbd_device *device)
+{
+	drbd_debugfs_remove(&device->debugfs_minor);
+	drbd_debugfs_remove(&device->debugfs_vol_oldest_requests);
+	drbd_debugfs_remove(&device->debugfs_vol_act_log_extents);
+	drbd_debugfs_remove(&device->debugfs_vol_resync_extents);
+	drbd_debugfs_remove(&device->debugfs_vol_data_gen_id);
+	drbd_debugfs_remove(&device->debugfs_vol);
+}
+
+void drbd_debugfs_peer_device_add(struct drbd_peer_device *peer_device)
+{
+	struct dentry *conn_dir = peer_device->connection->debugfs_conn;
+	struct dentry *dentry;
+	char vnr_buf[8];
+
+	if (!conn_dir)
+		return;
+
+	snprintf(vnr_buf, sizeof(vnr_buf), "%u", peer_device->device->vnr);
+	dentry = debugfs_create_dir(vnr_buf, conn_dir);
+	if (IS_ERR_OR_NULL(dentry))
+		goto fail;
+	peer_device->debugfs_peer_dev = dentry;
+	return;
+
+fail:
+	drbd_debugfs_peer_device_cleanup(peer_device);
+	drbd_err(peer_device, "failed to create debugfs entries\n");
+}
+
+void drbd_debugfs_peer_device_cleanup(struct drbd_peer_device *peer_device)
+{
+	drbd_debugfs_remove(&peer_device->debugfs_peer_dev);
+}
+
+static int drbd_version_show(struct seq_file *m, void *ignored)
+{
+	seq_printf(m, "# %s\n", drbd_buildtag());
+	seq_printf(m, "VERSION=%s\n", REL_VERSION);
+	seq_printf(m, "API_VERSION=%u\n", API_VERSION);
+	seq_printf(m, "PRO_VERSION_MIN=%u\n", PRO_VERSION_MIN);
+	seq_printf(m, "PRO_VERSION_MAX=%u\n", PRO_VERSION_MAX);
+	return 0;
+}
+
+static int drbd_version_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, drbd_version_show, NULL);
+}
+
+static struct file_operations drbd_version_fops = {
+	.owner = THIS_MODULE,
+	.open = drbd_version_open,
+	.llseek = seq_lseek,
+	.read = seq_read,
+	.release = single_release,
+};
+
+/* not __exit, may be indirectly called
+ * from the module-load-failure path as well. */
+void drbd_debugfs_cleanup(void)
+{
+	drbd_debugfs_remove(&drbd_debugfs_resources);
+	drbd_debugfs_remove(&drbd_debugfs_minors);
+	drbd_debugfs_remove(&drbd_debugfs_version);
+	drbd_debugfs_remove(&drbd_debugfs_root);
+}
+
+int __init drbd_debugfs_init(void)
+{
+	struct dentry *dentry;
+
+	dentry = debugfs_create_dir("drbd", NULL);
+	if (IS_ERR_OR_NULL(dentry))
+		goto fail;
+	drbd_debugfs_root = dentry;
+
+	dentry = debugfs_create_file("version", 0444, drbd_debugfs_root, NULL, &drbd_version_fops);
+	if (IS_ERR_OR_NULL(dentry))
+		goto fail;
+	drbd_debugfs_version = dentry;
+
+	dentry = debugfs_create_dir("resources", drbd_debugfs_root);
+	if (IS_ERR_OR_NULL(dentry))
+		goto fail;
+	drbd_debugfs_resources = dentry;
+
+	dentry = debugfs_create_dir("minors", drbd_debugfs_root);
+	if (IS_ERR_OR_NULL(dentry))
+		goto fail;
+	drbd_debugfs_minors = dentry;
+	return 0;
+
+fail:
+	drbd_debugfs_cleanup();
+	if (dentry)
+		return PTR_ERR(dentry);
+	else
+		return -EINVAL;
+}
diff --git a/drivers/block/drbd/drbd_debugfs.h b/drivers/block/drbd/drbd_debugfs.h
new file mode 100644
index 0000000..8bee213
--- /dev/null
+++ b/drivers/block/drbd/drbd_debugfs.h
@@ -0,0 +1,39 @@
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/debugfs.h>
+
+#include "drbd_int.h"
+
+#ifdef CONFIG_DEBUG_FS
+int __init drbd_debugfs_init(void);
+void drbd_debugfs_cleanup(void);
+
+void drbd_debugfs_resource_add(struct drbd_resource *resource);
+void drbd_debugfs_resource_cleanup(struct drbd_resource *resource);
+
+void drbd_debugfs_connection_add(struct drbd_connection *connection);
+void drbd_debugfs_connection_cleanup(struct drbd_connection *connection);
+
+void drbd_debugfs_device_add(struct drbd_device *device);
+void drbd_debugfs_device_cleanup(struct drbd_device *device);
+
+void drbd_debugfs_peer_device_add(struct drbd_peer_device *peer_device);
+void drbd_debugfs_peer_device_cleanup(struct drbd_peer_device *peer_device);
+#else
+
+static inline int __init drbd_debugfs_init(void) { return -ENODEV; }
+static inline void drbd_debugfs_cleanup(void) { }
+
+static inline void drbd_debugfs_resource_add(struct drbd_resource *resource) { }
+static inline void drbd_debugfs_resource_cleanup(struct drbd_resource *resource) { }
+
+static inline void drbd_debugfs_connection_add(struct drbd_connection *connection) { }
+static inline void drbd_debugfs_connection_cleanup(struct drbd_connection *connection) { }
+
+static inline void drbd_debugfs_device_add(struct drbd_device *device) { }
+static inline void drbd_debugfs_device_cleanup(struct drbd_device *device) { }
+
+static inline void drbd_debugfs_peer_device_add(struct drbd_peer_device *peer_device) { }
+static inline void drbd_debugfs_peer_device_cleanup(struct drbd_peer_device *peer_device) { }
+
+#endif
diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index a76ceb3..1a00001 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -317,7 +317,63 @@ struct drbd_request {
 
 	struct list_head tl_requests; /* ring list in the transfer log */
 	struct bio *master_bio;       /* master bio pointer */
-	unsigned long start_time;
+
+	/* see struct drbd_device */
+	struct list_head req_pending_master_completion;
+	struct list_head req_pending_local;
+
+	/* for generic IO accounting */
+	unsigned long start_jif;
+
+	/* for DRBD internal statistics */
+
+	/* Minimal set of time stamps to determine if we wait for activity log
+	 * transactions, local disk or peer.  32 bit "jiffies" are good enough,
+	 * we don't expect a DRBD request to be stalled for several month.
+	 */
+
+	/* before actual request processing */
+	unsigned long in_actlog_jif;
+
+	/* local disk */
+	unsigned long pre_submit_jif;
+
+	/* per connection */
+	unsigned long pre_send_jif;
+	unsigned long acked_jif;
+	unsigned long net_done_jif;
+
+	/* Possibly even more detail to track each phase:
+	 *  master_completion_jif
+	 *      how long did it take to complete the master bio
+	 *      (application visible latency)
+	 *  allocated_jif
+	 *      how long the master bio was blocked until we finally allocated
+	 *      a tracking struct
+	 *  in_actlog_jif
+	 *      how long did we wait for activity log transactions
+	 *
+	 *  net_queued_jif
+	 *      when did we finally queue it for sending
+	 *  pre_send_jif
+	 *      when did we start sending it
+	 *  post_send_jif
+	 *      how long did we block in the network stack trying to send it
+	 *  acked_jif
+	 *      when did we receive (or fake, in protocol A) a remote ACK
+	 *  net_done_jif
+	 *      when did we receive final acknowledgement (P_BARRIER_ACK),
+	 *      or decide, e.g. on connection loss, that we do no longer expect
+	 *      anything from this peer for this request.
+	 *
+	 *  pre_submit_jif
+	 *  post_sub_jif
+	 *      when did we start submiting to the lower level device,
+	 *      and how long did we block in that submit function
+	 *  local_completion_jif
+	 *      how long did it take the lower level device to complete this request
+	 */
+
 
 	/* once it hits 0, we may complete the master_bio */
 	atomic_t completion_ref;
@@ -366,6 +422,7 @@ struct drbd_peer_request {
 	struct drbd_interval i;
 	/* see comments on ee flag bits below */
 	unsigned long flags;
+	unsigned long submit_jif;
 	union {
 		u64 block_id;
 		struct digest_info *digest;
@@ -408,6 +465,17 @@ enum {
 
 	/* Is set when net_conf had two_primaries set while creating this peer_req */
 	__EE_IN_INTERVAL_TREE,
+
+	/* for debugfs: */
+	/* has this been submitted, or does it still wait for something else? */
+	__EE_SUBMITTED,
+
+	/* this is/was a write request */
+	__EE_WRITE,
+
+	/* this originates from application on peer
+	 * (not some resync or verify or other DRBD internal request) */
+	__EE_APPLICATION,
 };
 #define EE_CALL_AL_COMPLETE_IO (1<<__EE_CALL_AL_COMPLETE_IO)
 #define EE_MAY_SET_IN_SYNC     (1<<__EE_MAY_SET_IN_SYNC)
@@ -419,6 +487,9 @@ enum {
 #define EE_RESTART_REQUESTS	(1<<__EE_RESTART_REQUESTS)
 #define EE_SEND_WRITE_ACK	(1<<__EE_SEND_WRITE_ACK)
 #define EE_IN_INTERVAL_TREE	(1<<__EE_IN_INTERVAL_TREE)
+#define EE_SUBMITTED		(1<<__EE_SUBMITTED)
+#define EE_WRITE		(1<<__EE_WRITE)
+#define EE_APPLICATION		(1<<__EE_APPLICATION)
 
 /* flag bits per device */
 enum {
@@ -433,11 +504,11 @@ enum {
 	CONSIDER_RESYNC,
 
 	MD_NO_FUA,		/* Users wants us to not use FUA/FLUSH on meta data dev */
+
 	SUSPEND_IO,		/* suspend application io */
 	BITMAP_IO,		/* suspend application io;
 				   once no more io in flight, start bitmap io */
 	BITMAP_IO_QUEUED,       /* Started bitmap IO */
-	GO_DISKLESS,		/* Disk is being detached, on io-error or admin request. */
 	WAS_IO_ERROR,		/* Local disk failed, returned IO error */
 	WAS_READ_ERROR,		/* Local disk READ failed (set additionally to the above) */
 	FORCE_DETACH,		/* Force-detach from local disk, aborting any pending local IO */
@@ -450,6 +521,20 @@ enum {
 	B_RS_H_DONE,		/* Before resync handler done (already executed) */
 	DISCARD_MY_DATA,	/* discard_my_data flag per volume */
 	READ_BALANCE_RR,
+
+	FLUSH_PENDING,		/* if set, device->flush_jif is when we submitted that flush
+				 * from drbd_flush_after_epoch() */
+
+	/* cleared only after backing device related structures have been destroyed. */
+	GOING_DISKLESS,		/* Disk is being detached, because of io-error, or admin request. */
+
+	/* to be used in drbd_device_post_work() */
+	GO_DISKLESS,		/* tell worker to schedule cleanup before detach */
+	DESTROY_DISK,		/* tell worker to close backing devices and destroy related structures. */
+	MD_SYNC,		/* tell worker to call drbd_md_sync() */
+	RS_START,		/* tell worker to start resync/OV */
+	RS_PROGRESS,		/* tell worker that resync made significant progress */
+	RS_DONE,		/* tell worker that resync is done */
 };
 
 struct drbd_bitmap; /* opaque for drbd_device */
@@ -531,6 +616,11 @@ struct drbd_backing_dev {
 };
 
 struct drbd_md_io {
+	struct page *page;
+	unsigned long start_jif;	/* last call to drbd_md_get_buffer */
+	unsigned long submit_jif;	/* last _drbd_md_sync_page_io() submit */
+	const char *current_use;
+	atomic_t in_use;
 	unsigned int done;
 	int error;
 };
@@ -577,10 +667,18 @@ enum {
 				 * and potentially deadlock on, this drbd worker.
 				 */
 	DISCONNECT_SENT,
+
+	DEVICE_WORK_PENDING,	/* tell worker that some device has pending work */
 };
 
 struct drbd_resource {
 	char *name;
+#ifdef CONFIG_DEBUG_FS
+	struct dentry *debugfs_res;
+	struct dentry *debugfs_res_volumes;
+	struct dentry *debugfs_res_connections;
+	struct dentry *debugfs_res_in_flight_summary;
+#endif
 	struct kref kref;
 	struct idr devices;		/* volume number to device mapping */
 	struct list_head connections;
@@ -594,12 +692,28 @@ struct drbd_resource {
 	unsigned susp_nod:1;		/* IO suspended because no data */
 	unsigned susp_fen:1;		/* IO suspended because fence peer handler runs */
 
+	enum write_ordering_e write_ordering;
+
 	cpumask_var_t cpu_mask;
 };
 
+struct drbd_thread_timing_details
+{
+	unsigned long start_jif;
+	void *cb_addr;
+	const char *caller_fn;
+	unsigned int line;
+	unsigned int cb_nr;
+};
+
 struct drbd_connection {
 	struct list_head connections;
 	struct drbd_resource *resource;
+#ifdef CONFIG_DEBUG_FS
+	struct dentry *debugfs_conn;
+	struct dentry *debugfs_conn_callback_history;
+	struct dentry *debugfs_conn_oldest_requests;
+#endif
 	struct kref kref;
 	struct idr peer_devices;	/* volume number to peer device mapping */
 	enum drbd_conns cstate;		/* Only C_STANDALONE to C_WF_REPORT_PARAMS */
@@ -636,7 +750,6 @@ struct drbd_connection {
 	struct drbd_epoch *current_epoch;
 	spinlock_t epoch_lock;
 	unsigned int epochs;
-	enum write_ordering_e write_ordering;
 	atomic_t current_tle_nr;	/* transfer log epoch number */
 	unsigned current_tle_writes;	/* writes seen within this tl epoch */
 
@@ -645,9 +758,22 @@ struct drbd_connection {
 	struct drbd_thread worker;
 	struct drbd_thread asender;
 
+	/* cached pointers,
+	 * so we can look up the oldest pending requests more quickly.
+	 * protected by resource->req_lock */
+	struct drbd_request *req_next; /* DRBD 9: todo.req_next */
+	struct drbd_request *req_ack_pending;
+	struct drbd_request *req_not_net_done;
+
 	/* sender side */
 	struct drbd_work_queue sender_work;
 
+#define DRBD_THREAD_DETAILS_HIST	16
+	unsigned int w_cb_nr; /* keeps counting up */
+	unsigned int r_cb_nr; /* keeps counting up */
+	struct drbd_thread_timing_details w_timing_details[DRBD_THREAD_DETAILS_HIST];
+	struct drbd_thread_timing_details r_timing_details[DRBD_THREAD_DETAILS_HIST];
+
 	struct {
 		/* whether this sender thread
 		 * has processed a single write yet. */
@@ -663,11 +789,22 @@ struct drbd_connection {
 	} send;
 };
 
+void __update_timing_details(
+		struct drbd_thread_timing_details *tdp,
+		unsigned int *cb_nr,
+		void *cb,
+		const char *fn, const unsigned int line);
+
+#define update_worker_timing_details(c, cb) \
+	__update_timing_details(c->w_timing_details, &c->w_cb_nr, cb, __func__ , __LINE__ )
+#define update_receiver_timing_details(c, cb) \
+	__update_timing_details(c->r_timing_details, &c->r_cb_nr, cb, __func__ , __LINE__ )
+
 struct submit_worker {
 	struct workqueue_struct *wq;
 	struct work_struct worker;
 
-	spinlock_t lock;
+	/* protected by ..->resource->req_lock */
 	struct list_head writes;
 };
 
@@ -675,12 +812,29 @@ struct drbd_peer_device {
 	struct list_head peer_devices;
 	struct drbd_device *device;
 	struct drbd_connection *connection;
+#ifdef CONFIG_DEBUG_FS
+	struct dentry *debugfs_peer_dev;
+#endif
 };
 
 struct drbd_device {
 	struct drbd_resource *resource;
 	struct list_head peer_devices;
-	int vnr;			/* volume number within the connection */
+	struct list_head pending_bitmap_io;
+
+	unsigned long flush_jif;
+#ifdef CONFIG_DEBUG_FS
+	struct dentry *debugfs_minor;
+	struct dentry *debugfs_vol;
+	struct dentry *debugfs_vol_oldest_requests;
+	struct dentry *debugfs_vol_act_log_extents;
+	struct dentry *debugfs_vol_resync_extents;
+	struct dentry *debugfs_vol_data_gen_id;
+#endif
+
+	unsigned int vnr;	/* volume number within the connection */
+	unsigned int minor;	/* device minor number */
+
 	struct kref kref;
 
 	/* things that are stored as / read from meta data on disk */
@@ -697,19 +851,10 @@ struct drbd_device {
 	unsigned long last_reattach_jif;
 	struct drbd_work resync_work;
 	struct drbd_work unplug_work;
-	struct drbd_work go_diskless;
-	struct drbd_work md_sync_work;
-	struct drbd_work start_resync_work;
 	struct timer_list resync_timer;
 	struct timer_list md_sync_timer;
 	struct timer_list start_resync_timer;
 	struct timer_list request_timer;
-#ifdef DRBD_DEBUG_MD_SYNC
-	struct {
-		unsigned int line;
-		const char* func;
-	} last_md_mark_dirty;
-#endif
 
 	/* Used after attach while negotiating new disk state. */
 	union drbd_state new_state_tmp;
@@ -724,6 +869,7 @@ struct drbd_device {
 	unsigned int al_writ_cnt;
 	unsigned int bm_writ_cnt;
 	atomic_t ap_bio_cnt;	 /* Requests we need to complete */
+	atomic_t ap_actlog_cnt;  /* Requests waiting for activity log */
 	atomic_t ap_pending_cnt; /* AP data packets on the wire, ack expected */
 	atomic_t rs_pending_cnt; /* RS request/data packets on the wire */
 	atomic_t unacked_cnt;	 /* Need to send replies for */
@@ -733,6 +879,13 @@ struct drbd_device {
 	struct rb_root read_requests;
 	struct rb_root write_requests;
 
+	/* for statistics and timeouts */
+	/* [0] read, [1] write */
+	struct list_head pending_master_completion[2];
+	struct list_head pending_completion[2];
+
+	/* use checksums for *this* resync */
+	bool use_csums;
 	/* blocks to resync in this run [unit BM_BLOCK_SIZE] */
 	unsigned long rs_total;
 	/* number of resync blocks that failed in this run */
@@ -788,9 +941,7 @@ struct drbd_device {
 	atomic_t pp_in_use;		/* allocated from page pool */
 	atomic_t pp_in_use_by_net;	/* sendpage()d, still referenced by tcp */
 	wait_queue_head_t ee_wait;
-	struct page *md_io_page;	/* one page buffer for md_io */
 	struct drbd_md_io md_io;
-	atomic_t md_io_in_use;		/* protects the md_io, md_io_page and md_io_tmpp */
 	spinlock_t al_lock;
 	wait_queue_head_t al_wait;
 	struct lru_cache *act_log;	/* activity log */
@@ -800,7 +951,6 @@ struct drbd_device {
 	atomic_t packet_seq;
 	unsigned int peer_seq;
 	spinlock_t peer_seq_lock;
-	unsigned int minor;
 	unsigned long comm_bm_set; /* communicated number of set bits. */
 	struct bm_io_work bm_io_work;
 	u64 ed_uuid; /* UUID of the exposed data */
@@ -824,6 +974,21 @@ struct drbd_device {
 	struct submit_worker submit;
 };
 
+struct drbd_bm_aio_ctx {
+	struct drbd_device *device;
+	struct list_head list; /* on device->pending_bitmap_io */;
+	unsigned long start_jif;
+	atomic_t in_flight;
+	unsigned int done;
+	unsigned flags;
+#define BM_AIO_COPY_PAGES	1
+#define BM_AIO_WRITE_HINTED	2
+#define BM_AIO_WRITE_ALL_PAGES	4
+#define BM_AIO_READ		8
+	int error;
+	struct kref kref;
+};
+
 struct drbd_config_context {
 	/* assigned from drbd_genlmsghdr */
 	unsigned int minor;
@@ -949,7 +1114,7 @@ extern int drbd_send_ov_request(struct drbd_peer_device *, sector_t sector, int
 extern int drbd_send_bitmap(struct drbd_device *device);
 extern void drbd_send_sr_reply(struct drbd_peer_device *, enum drbd_state_rv retcode);
 extern void conn_send_sr_reply(struct drbd_connection *connection, enum drbd_state_rv retcode);
-extern void drbd_free_bc(struct drbd_backing_dev *ldev);
+extern void drbd_free_ldev(struct drbd_backing_dev *ldev);
 extern void drbd_device_cleanup(struct drbd_device *device);
 void drbd_print_uuids(struct drbd_device *device, const char *text);
 
@@ -966,13 +1131,7 @@ extern void __drbd_uuid_set(struct drbd_device *device, int idx, u64 val) __must
 extern void drbd_md_set_flag(struct drbd_device *device, int flags) __must_hold(local);
 extern void drbd_md_clear_flag(struct drbd_device *device, int flags)__must_hold(local);
 extern int drbd_md_test_flag(struct drbd_backing_dev *, int);
-#ifndef DRBD_DEBUG_MD_SYNC
 extern void drbd_md_mark_dirty(struct drbd_device *device);
-#else
-#define drbd_md_mark_dirty(m)	drbd_md_mark_dirty_(m, __LINE__ , __func__ )
-extern void drbd_md_mark_dirty_(struct drbd_device *device,
-		unsigned int line, const char *func);
-#endif
 extern void drbd_queue_bitmap_io(struct drbd_device *device,
 				 int (*io_fn)(struct drbd_device *),
 				 void (*done)(struct drbd_device *, int),
@@ -983,9 +1142,8 @@ extern int drbd_bitmap_io(struct drbd_device *device,
 extern int drbd_bitmap_io_from_worker(struct drbd_device *device,
 		int (*io_fn)(struct drbd_device *),
 		char *why, enum bm_flag flags);
-extern int drbd_bmio_set_n_write(struct drbd_device *device);
-extern int drbd_bmio_clear_n_write(struct drbd_device *device);
-extern void drbd_ldev_destroy(struct drbd_device *device);
+extern int drbd_bmio_set_n_write(struct drbd_device *device) __must_hold(local);
+extern int drbd_bmio_clear_n_write(struct drbd_device *device) __must_hold(local);
 
 /* Meta data layout
  *
@@ -1105,17 +1263,21 @@ struct bm_extent {
 /* in which _bitmap_ extent (resp. sector) the bit for a certain
  * _storage_ sector is located in */
 #define BM_SECT_TO_EXT(x)   ((x)>>(BM_EXT_SHIFT-9))
+#define BM_BIT_TO_EXT(x)    ((x) >> (BM_EXT_SHIFT - BM_BLOCK_SHIFT))
 
-/* how much _storage_ sectors we have per bitmap sector */
+/* first storage sector a bitmap extent corresponds to */
 #define BM_EXT_TO_SECT(x)   ((sector_t)(x) << (BM_EXT_SHIFT-9))
+/* how much _storage_ sectors we have per bitmap extent */
 #define BM_SECT_PER_EXT     BM_EXT_TO_SECT(1)
+/* how many bits are covered by one bitmap extent (resync extent) */
+#define BM_BITS_PER_EXT     (1UL << (BM_EXT_SHIFT - BM_BLOCK_SHIFT))
+
+#define BM_BLOCKS_PER_BM_EXT_MASK  (BM_BITS_PER_EXT - 1)
+
 
 /* in one sector of the bitmap, we have this many activity_log extents. */
 #define AL_EXT_PER_BM_SECT  (1 << (BM_EXT_SHIFT - AL_EXTENT_SHIFT))
 
-#define BM_BLOCKS_PER_BM_EXT_B (BM_EXT_SHIFT - BM_BLOCK_SHIFT)
-#define BM_BLOCKS_PER_BM_EXT_MASK  ((1<<BM_BLOCKS_PER_BM_EXT_B) - 1)
-
 /* the extent in "PER_EXTENT" below is an activity log extent
  * we need that many (long words/bytes) to store the bitmap
  *		     of one AL_EXTENT_SIZE chunk of storage.
@@ -1195,11 +1357,11 @@ extern void _drbd_bm_set_bits(struct drbd_device *device,
 		const unsigned long s, const unsigned long e);
 extern int  drbd_bm_test_bit(struct drbd_device *device, unsigned long bitnr);
 extern int  drbd_bm_e_weight(struct drbd_device *device, unsigned long enr);
-extern int  drbd_bm_write_page(struct drbd_device *device, unsigned int idx) __must_hold(local);
 extern int  drbd_bm_read(struct drbd_device *device) __must_hold(local);
 extern void drbd_bm_mark_for_writeout(struct drbd_device *device, int page_nr);
 extern int  drbd_bm_write(struct drbd_device *device) __must_hold(local);
 extern int  drbd_bm_write_hinted(struct drbd_device *device) __must_hold(local);
+extern int  drbd_bm_write_lazy(struct drbd_device *device, unsigned upper_idx) __must_hold(local);
 extern int drbd_bm_write_all(struct drbd_device *device) __must_hold(local);
 extern int  drbd_bm_write_copy_pages(struct drbd_device *device) __must_hold(local);
 extern size_t	     drbd_bm_words(struct drbd_device *device);
@@ -1213,7 +1375,6 @@ extern unsigned long _drbd_bm_find_next(struct drbd_device *device, unsigned lon
 extern unsigned long _drbd_bm_find_next_zero(struct drbd_device *device, unsigned long bm_fo);
 extern unsigned long _drbd_bm_total_weight(struct drbd_device *device);
 extern unsigned long drbd_bm_total_weight(struct drbd_device *device);
-extern int drbd_bm_rs_done(struct drbd_device *device);
 /* for receive_bitmap */
 extern void drbd_bm_merge_lel(struct drbd_device *device, size_t offset,
 		size_t number, unsigned long *buffer);
@@ -1312,7 +1473,7 @@ enum determine_dev_size {
 extern enum determine_dev_size
 drbd_determine_dev_size(struct drbd_device *, enum dds_flags, struct resize_parms *) __must_hold(local);
 extern void resync_after_online_grow(struct drbd_device *);
-extern void drbd_reconsider_max_bio_size(struct drbd_device *device);
+extern void drbd_reconsider_max_bio_size(struct drbd_device *device, struct drbd_backing_dev *bdev);
 extern enum drbd_state_rv drbd_set_role(struct drbd_device *device,
 					enum drbd_role new_role,
 					int force);
@@ -1333,7 +1494,7 @@ extern void resume_next_sg(struct drbd_device *device);
 extern void suspend_other_sg(struct drbd_device *device);
 extern int drbd_resync_finished(struct drbd_device *device);
 /* maybe rather drbd_main.c ? */
-extern void *drbd_md_get_buffer(struct drbd_device *device);
+extern void *drbd_md_get_buffer(struct drbd_device *device, const char *intent);
 extern void drbd_md_put_buffer(struct drbd_device *device);
 extern int drbd_md_sync_page_io(struct drbd_device *device,
 		struct drbd_backing_dev *bdev, sector_t sector, int rw);
@@ -1380,7 +1541,8 @@ extern void drbd_endio_write_sec_final(struct drbd_peer_request *peer_req);
 extern int drbd_receiver(struct drbd_thread *thi);
 extern int drbd_asender(struct drbd_thread *thi);
 extern bool drbd_rs_c_min_rate_throttle(struct drbd_device *device);
-extern bool drbd_rs_should_slow_down(struct drbd_device *device, sector_t sector);
+extern bool drbd_rs_should_slow_down(struct drbd_device *device, sector_t sector,
+		bool throttle_if_app_is_waiting);
 extern int drbd_submit_peer_request(struct drbd_device *,
 				    struct drbd_peer_request *, const unsigned,
 				    const int);
@@ -1464,10 +1626,7 @@ static inline void drbd_generic_make_request(struct drbd_device *device,
 {
 	__release(local);
 	if (!bio->bi_bdev) {
-		printk(KERN_ERR "drbd%d: drbd_generic_make_request: "
-				"bio->bi_bdev == NULL\n",
-		       device_to_minor(device));
-		dump_stack();
+		drbd_err(device, "drbd_generic_make_request: bio->bi_bdev == NULL\n");
 		bio_endio(bio, -ENODEV);
 		return;
 	}
@@ -1478,7 +1637,8 @@ static inline void drbd_generic_make_request(struct drbd_device *device,
 		generic_make_request(bio);
 }
 
-void drbd_bump_write_ordering(struct drbd_connection *connection, enum write_ordering_e wo);
+void drbd_bump_write_ordering(struct drbd_resource *resource, struct drbd_backing_dev *bdev,
+			      enum write_ordering_e wo);
 
 /* drbd_proc.c */
 extern struct proc_dir_entry *drbd_proc;
@@ -1489,9 +1649,9 @@ extern const char *drbd_role_str(enum drbd_role s);
 /* drbd_actlog.c */
 extern bool drbd_al_begin_io_prepare(struct drbd_device *device, struct drbd_interval *i);
 extern int drbd_al_begin_io_nonblock(struct drbd_device *device, struct drbd_interval *i);
-extern void drbd_al_begin_io_commit(struct drbd_device *device, bool delegate);
+extern void drbd_al_begin_io_commit(struct drbd_device *device);
 extern bool drbd_al_begin_io_fastpath(struct drbd_device *device, struct drbd_interval *i);
-extern void drbd_al_begin_io(struct drbd_device *device, struct drbd_interval *i, bool delegate);
+extern void drbd_al_begin_io(struct drbd_device *device, struct drbd_interval *i);
 extern void drbd_al_complete_io(struct drbd_device *device, struct drbd_interval *i);
 extern void drbd_rs_complete_io(struct drbd_device *device, sector_t sector);
 extern int drbd_rs_begin_io(struct drbd_device *device, sector_t sector);
@@ -1501,14 +1661,17 @@ extern int drbd_rs_del_all(struct drbd_device *device);
 extern void drbd_rs_failed_io(struct drbd_device *device,
 		sector_t sector, int size);
 extern void drbd_advance_rs_marks(struct drbd_device *device, unsigned long still_to_go);
-extern void __drbd_set_in_sync(struct drbd_device *device, sector_t sector,
-		int size, const char *file, const unsigned int line);
+
+enum update_sync_bits_mode { RECORD_RS_FAILED, SET_OUT_OF_SYNC, SET_IN_SYNC };
+extern int __drbd_change_sync(struct drbd_device *device, sector_t sector, int size,
+		enum update_sync_bits_mode mode,
+		const char *file, const unsigned int line);
 #define drbd_set_in_sync(device, sector, size) \
-	__drbd_set_in_sync(device, sector, size, __FILE__, __LINE__)
-extern int __drbd_set_out_of_sync(struct drbd_device *device, sector_t sector,
-		int size, const char *file, const unsigned int line);
+	__drbd_change_sync(device, sector, size, SET_IN_SYNC, __FILE__, __LINE__)
 #define drbd_set_out_of_sync(device, sector, size) \
-	__drbd_set_out_of_sync(device, sector, size, __FILE__, __LINE__)
+	__drbd_change_sync(device, sector, size, SET_OUT_OF_SYNC, __FILE__, __LINE__)
+#define drbd_rs_failed_io(device, sector, size) \
+	__drbd_change_sync(device, sector, size, RECORD_RS_FAILED, __FILE__, __LINE__)
 extern void drbd_al_shrink(struct drbd_device *device);
 extern int drbd_initialize_al(struct drbd_device *, void *);
 
@@ -1764,25 +1927,38 @@ static inline sector_t drbd_md_ss(struct drbd_backing_dev *bdev)
 }
 
 static inline void
-drbd_queue_work_front(struct drbd_work_queue *q, struct drbd_work *w)
+drbd_queue_work(struct drbd_work_queue *q, struct drbd_work *w)
 {
 	unsigned long flags;
 	spin_lock_irqsave(&q->q_lock, flags);
-	list_add(&w->list, &q->q);
+	list_add_tail(&w->list, &q->q);
 	spin_unlock_irqrestore(&q->q_lock, flags);
 	wake_up(&q->q_wait);
 }
 
 static inline void
-drbd_queue_work(struct drbd_work_queue *q, struct drbd_work *w)
+drbd_queue_work_if_unqueued(struct drbd_work_queue *q, struct drbd_work *w)
 {
 	unsigned long flags;
 	spin_lock_irqsave(&q->q_lock, flags);
-	list_add_tail(&w->list, &q->q);
+	if (list_empty_careful(&w->list))
+		list_add_tail(&w->list, &q->q);
 	spin_unlock_irqrestore(&q->q_lock, flags);
 	wake_up(&q->q_wait);
 }
 
+static inline void
+drbd_device_post_work(struct drbd_device *device, int work_bit)
+{
+	if (!test_and_set_bit(work_bit, &device->flags)) {
+		struct drbd_connection *connection =
+			first_peer_device(device)->connection;
+		struct drbd_work_queue *q = &connection->sender_work;
+		if (!test_and_set_bit(DEVICE_WORK_PENDING, &connection->flags))
+			wake_up(&q->q_wait);
+	}
+}
+
 extern void drbd_flush_workqueue(struct drbd_work_queue *work_queue);
 
 static inline void wake_asender(struct drbd_connection *connection)
@@ -1859,7 +2035,7 @@ static inline void inc_ap_pending(struct drbd_device *device)
 			func, line,					\
 			atomic_read(&device->which))
 
-#define dec_ap_pending(device) _dec_ap_pending(device, __FUNCTION__, __LINE__)
+#define dec_ap_pending(device) _dec_ap_pending(device, __func__, __LINE__)
 static inline void _dec_ap_pending(struct drbd_device *device, const char *func, int line)
 {
 	if (atomic_dec_and_test(&device->ap_pending_cnt))
@@ -1878,7 +2054,7 @@ static inline void inc_rs_pending(struct drbd_device *device)
 	atomic_inc(&device->rs_pending_cnt);
 }
 
-#define dec_rs_pending(device) _dec_rs_pending(device, __FUNCTION__, __LINE__)
+#define dec_rs_pending(device) _dec_rs_pending(device, __func__, __LINE__)
 static inline void _dec_rs_pending(struct drbd_device *device, const char *func, int line)
 {
 	atomic_dec(&device->rs_pending_cnt);
@@ -1899,20 +2075,29 @@ static inline void inc_unacked(struct drbd_device *device)
 	atomic_inc(&device->unacked_cnt);
 }
 
-#define dec_unacked(device) _dec_unacked(device, __FUNCTION__, __LINE__)
+#define dec_unacked(device) _dec_unacked(device, __func__, __LINE__)
 static inline void _dec_unacked(struct drbd_device *device, const char *func, int line)
 {
 	atomic_dec(&device->unacked_cnt);
 	ERR_IF_CNT_IS_NEGATIVE(unacked_cnt, func, line);
 }
 
-#define sub_unacked(device, n) _sub_unacked(device, n, __FUNCTION__, __LINE__)
+#define sub_unacked(device, n) _sub_unacked(device, n, __func__, __LINE__)
 static inline void _sub_unacked(struct drbd_device *device, int n, const char *func, int line)
 {
 	atomic_sub(n, &device->unacked_cnt);
 	ERR_IF_CNT_IS_NEGATIVE(unacked_cnt, func, line);
 }
 
+static inline bool is_sync_state(enum drbd_conns connection_state)
+{
+	return
+	   (connection_state == C_SYNC_SOURCE
+	||  connection_state == C_SYNC_TARGET
+	||  connection_state == C_PAUSED_SYNC_S
+	||  connection_state == C_PAUSED_SYNC_T);
+}
+
 /**
  * get_ldev() - Increase the ref count on device->ldev. Returns 0 if there is no ldev
  * @M:		DRBD device.
@@ -1924,6 +2109,11 @@ static inline void _sub_unacked(struct drbd_device *device, int n, const char *f
 
 static inline void put_ldev(struct drbd_device *device)
 {
+	enum drbd_disk_state ds = device->state.disk;
+	/* We must check the state *before* the atomic_dec becomes visible,
+	 * or we have a theoretical race where someone hitting zero,
+	 * while state still D_FAILED, will then see D_DISKLESS in the
+	 * condition below and calling into destroy, where he must not, yet. */
 	int i = atomic_dec_return(&device->local_cnt);
 
 	/* This may be called from some endio handler,
@@ -1932,15 +2122,13 @@ static inline void put_ldev(struct drbd_device *device)
 	__release(local);
 	D_ASSERT(device, i >= 0);
 	if (i == 0) {
-		if (device->state.disk == D_DISKLESS)
+		if (ds == D_DISKLESS)
 			/* even internal references gone, safe to destroy */
-			drbd_ldev_destroy(device);
-		if (device->state.disk == D_FAILED) {
+			drbd_device_post_work(device, DESTROY_DISK);
+		if (ds == D_FAILED)
 			/* all application IO references gone. */
-			if (!test_and_set_bit(GO_DISKLESS, &device->flags))
-				drbd_queue_work(&first_peer_device(device)->connection->sender_work,
-						&device->go_diskless);
-		}
+			if (!test_and_set_bit(GOING_DISKLESS, &device->flags))
+				drbd_device_post_work(device, GO_DISKLESS);
 		wake_up(&device->misc_wait);
 	}
 }
@@ -1964,54 +2152,6 @@ static inline int _get_ldev_if_state(struct drbd_device *device, enum drbd_disk_
 extern int _get_ldev_if_state(struct drbd_device *device, enum drbd_disk_state mins);
 #endif
 
-/* you must have an "get_ldev" reference */
-static inline void drbd_get_syncer_progress(struct drbd_device *device,
-		unsigned long *bits_left, unsigned int *per_mil_done)
-{
-	/* this is to break it at compile time when we change that, in case we
-	 * want to support more than (1<<32) bits on a 32bit arch. */
-	typecheck(unsigned long, device->rs_total);
-
-	/* note: both rs_total and rs_left are in bits, i.e. in
-	 * units of BM_BLOCK_SIZE.
-	 * for the percentage, we don't care. */
-
-	if (device->state.conn == C_VERIFY_S || device->state.conn == C_VERIFY_T)
-		*bits_left = device->ov_left;
-	else
-		*bits_left = drbd_bm_total_weight(device) - device->rs_failed;
-	/* >> 10 to prevent overflow,
-	 * +1 to prevent division by zero */
-	if (*bits_left > device->rs_total) {
-		/* doh. maybe a logic bug somewhere.
-		 * may also be just a race condition
-		 * between this and a disconnect during sync.
-		 * for now, just prevent in-kernel buffer overflow.
-		 */
-		smp_rmb();
-		drbd_warn(device, "cs:%s rs_left=%lu > rs_total=%lu (rs_failed %lu)\n",
-				drbd_conn_str(device->state.conn),
-				*bits_left, device->rs_total, device->rs_failed);
-		*per_mil_done = 0;
-	} else {
-		/* Make sure the division happens in long context.
-		 * We allow up to one petabyte storage right now,
-		 * at a granularity of 4k per bit that is 2**38 bits.
-		 * After shift right and multiplication by 1000,
-		 * this should still fit easily into a 32bit long,
-		 * so we don't need a 64bit division on 32bit arch.
-		 * Note: currently we don't support such large bitmaps on 32bit
-		 * arch anyways, but no harm done to be prepared for it here.
-		 */
-		unsigned int shift = device->rs_total > UINT_MAX ? 16 : 10;
-		unsigned long left = *bits_left >> shift;
-		unsigned long total = 1UL + (device->rs_total >> shift);
-		unsigned long tmp = 1000UL - left * 1000UL/total;
-		*per_mil_done = tmp;
-	}
-}
-
-
 /* this throttles on-the-fly application requests
  * according to max_buffers settings;
  * maybe re-implement using semaphores? */
@@ -2201,25 +2341,6 @@ static inline int drbd_queue_order_type(struct drbd_device *device)
 	return QUEUE_ORDERED_NONE;
 }
 
-static inline void drbd_md_flush(struct drbd_device *device)
-{
-	int r;
-
-	if (device->ldev == NULL) {
-		drbd_warn(device, "device->ldev == NULL in drbd_md_flush\n");
-		return;
-	}
-
-	if (test_bit(MD_NO_FUA, &device->flags))
-		return;
-
-	r = blkdev_issue_flush(device->ldev->md_bdev, GFP_NOIO, NULL);
-	if (r) {
-		set_bit(MD_NO_FUA, &device->flags);
-		drbd_err(device, "meta data flush failed with status %d, disabling md-flushes\n", r);
-	}
-}
-
 static inline struct drbd_connection *first_connection(struct drbd_resource *resource)
 {
 	return list_first_entry_or_null(&resource->connections,
diff --git a/drivers/block/drbd/drbd_interval.h b/drivers/block/drbd/drbd_interval.h
index f38fcb0..f210543 100644
--- a/drivers/block/drbd/drbd_interval.h
+++ b/drivers/block/drbd/drbd_interval.h
@@ -10,7 +10,9 @@ struct drbd_interval {
 	unsigned int size;	/* size in bytes */
 	sector_t end;		/* highest interval end in subtree */
 	int local:1		/* local or remote request? */;
-	int waiting:1;
+	int waiting:1;		/* someone is waiting for this to complete */
+	int completed:1;	/* this has been completed already;
+				 * ignore for conflict detection */
 };
 
 static inline void drbd_clear_interval(struct drbd_interval *i)
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 960645c..9b465bb 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -26,7 +26,10 @@
 
  */
 
+#define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
+
 #include <linux/module.h>
+#include <linux/jiffies.h>
 #include <linux/drbd.h>
 #include <asm/uaccess.h>
 #include <asm/types.h>
@@ -54,16 +57,14 @@
 #include "drbd_int.h"
 #include "drbd_protocol.h"
 #include "drbd_req.h" /* only for _req_mod in tl_release and tl_clear */
-
 #include "drbd_vli.h"
+#include "drbd_debugfs.h"
 
 static DEFINE_MUTEX(drbd_main_mutex);
 static int drbd_open(struct block_device *bdev, fmode_t mode);
 static void drbd_release(struct gendisk *gd, fmode_t mode);
-static int w_md_sync(struct drbd_work *w, int unused);
 static void md_sync_timer_fn(unsigned long data);
 static int w_bitmap_io(struct drbd_work *w, int unused);
-static int w_go_diskless(struct drbd_work *w, int unused);
 
 MODULE_AUTHOR("Philipp Reisner <phil@linbit.com>, "
 	      "Lars Ellenberg <lars@linbit.com>");
@@ -264,7 +265,7 @@ bail:
 
 /**
  * _tl_restart() - Walks the transfer log, and applies an action to all requests
- * @device:	DRBD device.
+ * @connection:	DRBD connection to operate on.
  * @what:       The action/event to perform with all request objects
  *
  * @what might be one of CONNECTION_LOST_WHILE_PENDING, RESEND, FAIL_FROZEN_DISK_IO,
@@ -662,6 +663,11 @@ static int __send_command(struct drbd_connection *connection, int vnr,
 			    msg_flags);
 	if (data && !err)
 		err = drbd_send_all(connection, sock->socket, data, size, 0);
+	/* DRBD protocol "pings" are latency critical.
+	 * This is supposed to trigger tcp_push_pending_frames() */
+	if (!err && (cmd == P_PING || cmd == P_PING_ACK))
+		drbd_tcp_nodelay(sock->socket);
+
 	return err;
 }
 
@@ -1636,7 +1642,10 @@ int drbd_send_dblock(struct drbd_peer_device *peer_device, struct drbd_request *
 	if (peer_device->connection->agreed_pro_version >= 100) {
 		if (req->rq_state & RQ_EXP_RECEIVE_ACK)
 			dp_flags |= DP_SEND_RECEIVE_ACK;
-		if (req->rq_state & RQ_EXP_WRITE_ACK)
+		/* During resync, request an explicit write ack,
+		 * even in protocol != C */
+		if (req->rq_state & RQ_EXP_WRITE_ACK
+		|| (dp_flags & DP_MAY_SET_IN_SYNC))
 			dp_flags |= DP_SEND_WRITE_ACK;
 	}
 	p->dp_flags = cpu_to_be32(dp_flags);
@@ -1900,6 +1909,7 @@ void drbd_init_set_defaults(struct drbd_device *device)
 	drbd_set_defaults(device);
 
 	atomic_set(&device->ap_bio_cnt, 0);
+	atomic_set(&device->ap_actlog_cnt, 0);
 	atomic_set(&device->ap_pending_cnt, 0);
 	atomic_set(&device->rs_pending_cnt, 0);
 	atomic_set(&device->unacked_cnt, 0);
@@ -1908,7 +1918,7 @@ void drbd_init_set_defaults(struct drbd_device *device)
 	atomic_set(&device->rs_sect_in, 0);
 	atomic_set(&device->rs_sect_ev, 0);
 	atomic_set(&device->ap_in_flight, 0);
-	atomic_set(&device->md_io_in_use, 0);
+	atomic_set(&device->md_io.in_use, 0);
 
 	mutex_init(&device->own_state_mutex);
 	device->state_mutex = &device->own_state_mutex;
@@ -1924,17 +1934,15 @@ void drbd_init_set_defaults(struct drbd_device *device)
 	INIT_LIST_HEAD(&device->resync_reads);
 	INIT_LIST_HEAD(&device->resync_work.list);
 	INIT_LIST_HEAD(&device->unplug_work.list);
-	INIT_LIST_HEAD(&device->go_diskless.list);
-	INIT_LIST_HEAD(&device->md_sync_work.list);
-	INIT_LIST_HEAD(&device->start_resync_work.list);
 	INIT_LIST_HEAD(&device->bm_io_work.w.list);
+	INIT_LIST_HEAD(&device->pending_master_completion[0]);
+	INIT_LIST_HEAD(&device->pending_master_completion[1]);
+	INIT_LIST_HEAD(&device->pending_completion[0]);
+	INIT_LIST_HEAD(&device->pending_completion[1]);
 
 	device->resync_work.cb  = w_resync_timer;
 	device->unplug_work.cb  = w_send_write_hint;
-	device->go_diskless.cb  = w_go_diskless;
-	device->md_sync_work.cb = w_md_sync;
 	device->bm_io_work.w.cb = w_bitmap_io;
-	device->start_resync_work.cb = w_start_resync;
 
 	init_timer(&device->resync_timer);
 	init_timer(&device->md_sync_timer);
@@ -1992,7 +2000,7 @@ void drbd_device_cleanup(struct drbd_device *device)
 		drbd_bm_cleanup(device);
 	}
 
-	drbd_free_bc(device->ldev);
+	drbd_free_ldev(device->ldev);
 	device->ldev = NULL;
 
 	clear_bit(AL_SUSPENDED, &device->flags);
@@ -2006,7 +2014,6 @@ void drbd_device_cleanup(struct drbd_device *device)
 	D_ASSERT(device, list_empty(&first_peer_device(device)->connection->sender_work.q));
 	D_ASSERT(device, list_empty(&device->resync_work.list));
 	D_ASSERT(device, list_empty(&device->unplug_work.list));
-	D_ASSERT(device, list_empty(&device->go_diskless.list));
 
 	drbd_set_defaults(device);
 }
@@ -2129,20 +2136,6 @@ Enomem:
 	return -ENOMEM;
 }
 
-static int drbd_notify_sys(struct notifier_block *this, unsigned long code,
-	void *unused)
-{
-	/* just so we have it.  you never know what interesting things we
-	 * might want to do here some day...
-	 */
-
-	return NOTIFY_DONE;
-}
-
-static struct notifier_block drbd_notifier = {
-	.notifier_call = drbd_notify_sys,
-};
-
 static void drbd_release_all_peer_reqs(struct drbd_device *device)
 {
 	int rr;
@@ -2173,7 +2166,7 @@ void drbd_destroy_device(struct kref *kref)
 {
 	struct drbd_device *device = container_of(kref, struct drbd_device, kref);
 	struct drbd_resource *resource = device->resource;
-	struct drbd_connection *connection;
+	struct drbd_peer_device *peer_device, *tmp_peer_device;
 
 	del_timer_sync(&device->request_timer);
 
@@ -2187,7 +2180,7 @@ void drbd_destroy_device(struct kref *kref)
 	if (device->this_bdev)
 		bdput(device->this_bdev);
 
-	drbd_free_bc(device->ldev);
+	drbd_free_ldev(device->ldev);
 	device->ldev = NULL;
 
 	drbd_release_all_peer_reqs(device);
@@ -2200,15 +2193,20 @@ void drbd_destroy_device(struct kref *kref)
 
 	if (device->bitmap) /* should no longer be there. */
 		drbd_bm_cleanup(device);
-	__free_page(device->md_io_page);
+	__free_page(device->md_io.page);
 	put_disk(device->vdisk);
 	blk_cleanup_queue(device->rq_queue);
 	kfree(device->rs_plan_s);
-	kfree(first_peer_device(device));
-	kfree(device);
 
-	for_each_connection(connection, resource)
-		kref_put(&connection->kref, drbd_destroy_connection);
+	/* not for_each_connection(connection, resource):
+	 * those may have been cleaned up and disassociated already.
+	 */
+	for_each_peer_device_safe(peer_device, tmp_peer_device, device) {
+		kref_put(&peer_device->connection->kref, drbd_destroy_connection);
+		kfree(peer_device);
+	}
+	memset(device, 0xfd, sizeof(*device));
+	kfree(device);
 	kref_put(&resource->kref, drbd_destroy_resource);
 }
 
@@ -2236,7 +2234,7 @@ static void do_retry(struct work_struct *ws)
 	list_for_each_entry_safe(req, tmp, &writes, tl_requests) {
 		struct drbd_device *device = req->device;
 		struct bio *bio = req->master_bio;
-		unsigned long start_time = req->start_time;
+		unsigned long start_jif = req->start_jif;
 		bool expected;
 
 		expected =
@@ -2271,10 +2269,12 @@ static void do_retry(struct work_struct *ws)
 		/* We are not just doing generic_make_request(),
 		 * as we want to keep the start_time information. */
 		inc_ap_bio(device);
-		__drbd_make_request(device, bio, start_time);
+		__drbd_make_request(device, bio, start_jif);
 	}
 }
 
+/* called via drbd_req_put_completion_ref(),
+ * holds resource->req_lock */
 void drbd_restart_request(struct drbd_request *req)
 {
 	unsigned long flags;
@@ -2298,6 +2298,7 @@ void drbd_destroy_resource(struct kref *kref)
 	idr_destroy(&resource->devices);
 	free_cpumask_var(resource->cpu_mask);
 	kfree(resource->name);
+	memset(resource, 0xf2, sizeof(*resource));
 	kfree(resource);
 }
 
@@ -2307,8 +2308,10 @@ void drbd_free_resource(struct drbd_resource *resource)
 
 	for_each_connection_safe(connection, tmp, resource) {
 		list_del(&connection->connections);
+		drbd_debugfs_connection_cleanup(connection);
 		kref_put(&connection->kref, drbd_destroy_connection);
 	}
+	drbd_debugfs_resource_cleanup(resource);
 	kref_put(&resource->kref, drbd_destroy_resource);
 }
 
@@ -2318,8 +2321,6 @@ static void drbd_cleanup(void)
 	struct drbd_device *device;
 	struct drbd_resource *resource, *tmp;
 
-	unregister_reboot_notifier(&drbd_notifier);
-
 	/* first remove proc,
 	 * drbdsetup uses it's presence to detect
 	 * whether DRBD is loaded.
@@ -2335,6 +2336,7 @@ static void drbd_cleanup(void)
 		destroy_workqueue(retry.wq);
 
 	drbd_genl_unregister();
+	drbd_debugfs_cleanup();
 
 	idr_for_each_entry(&drbd_devices, device, i)
 		drbd_delete_device(device);
@@ -2350,7 +2352,7 @@ static void drbd_cleanup(void)
 
 	idr_destroy(&drbd_devices);
 
-	printk(KERN_INFO "drbd: module cleanup done.\n");
+	pr_info("module cleanup done.\n");
 }
 
 /**
@@ -2539,6 +2541,20 @@ int set_resource_options(struct drbd_resource *resource, struct res_opts *res_op
 	if (nr_cpu_ids > 1 && res_opts->cpu_mask[0] != 0) {
 		err = bitmap_parse(res_opts->cpu_mask, DRBD_CPU_MASK_SIZE,
 				   cpumask_bits(new_cpu_mask), nr_cpu_ids);
+		if (err == -EOVERFLOW) {
+			/* So what. mask it out. */
+			cpumask_var_t tmp_cpu_mask;
+			if (zalloc_cpumask_var(&tmp_cpu_mask, GFP_KERNEL)) {
+				cpumask_setall(tmp_cpu_mask);
+				cpumask_and(new_cpu_mask, new_cpu_mask, tmp_cpu_mask);
+				drbd_warn(resource, "Overflow in bitmap_parse(%.12s%s), truncating to %u bits\n",
+					res_opts->cpu_mask,
+					strlen(res_opts->cpu_mask) > 12 ? "..." : "",
+					nr_cpu_ids);
+				free_cpumask_var(tmp_cpu_mask);
+				err = 0;
+			}
+		}
 		if (err) {
 			drbd_warn(resource, "bitmap_parse() failed with %d\n", err);
 			/* retcode = ERR_CPU_MASK_PARSE; */
@@ -2579,10 +2595,12 @@ struct drbd_resource *drbd_create_resource(const char *name)
 	kref_init(&resource->kref);
 	idr_init(&resource->devices);
 	INIT_LIST_HEAD(&resource->connections);
+	resource->write_ordering = WO_bdev_flush;
 	list_add_tail_rcu(&resource->resources, &drbd_resources);
 	mutex_init(&resource->conf_update);
 	mutex_init(&resource->adm_mutex);
 	spin_lock_init(&resource->req_lock);
+	drbd_debugfs_resource_add(resource);
 	return resource;
 
 fail_free_name:
@@ -2593,7 +2611,7 @@ fail:
 	return NULL;
 }
 
-/* caller must be under genl_lock() */
+/* caller must be under adm_mutex */
 struct drbd_connection *conn_create(const char *name, struct res_opts *res_opts)
 {
 	struct drbd_resource *resource;
@@ -2617,7 +2635,6 @@ struct drbd_connection *conn_create(const char *name, struct res_opts *res_opts)
 	INIT_LIST_HEAD(&connection->current_epoch->list);
 	connection->epochs = 1;
 	spin_lock_init(&connection->epoch_lock);
-	connection->write_ordering = WO_bdev_flush;
 
 	connection->send.seen_any_write_yet = false;
 	connection->send.current_epoch_nr = 0;
@@ -2652,6 +2669,7 @@ struct drbd_connection *conn_create(const char *name, struct res_opts *res_opts)
 
 	kref_get(&resource->kref);
 	list_add_tail_rcu(&connection->connections, &resource->connections);
+	drbd_debugfs_connection_add(connection);
 	return connection;
 
 fail_resource:
@@ -2680,6 +2698,7 @@ void drbd_destroy_connection(struct kref *kref)
 	drbd_free_socket(&connection->data);
 	kfree(connection->int_dig_in);
 	kfree(connection->int_dig_vv);
+	memset(connection, 0xfc, sizeof(*connection));
 	kfree(connection);
 	kref_put(&resource->kref, drbd_destroy_resource);
 }
@@ -2694,7 +2713,6 @@ static int init_submitter(struct drbd_device *device)
 		return -ENOMEM;
 
 	INIT_WORK(&device->submit.worker, do_submit);
-	spin_lock_init(&device->submit.lock);
 	INIT_LIST_HEAD(&device->submit.writes);
 	return 0;
 }
@@ -2764,8 +2782,8 @@ enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsig
 	blk_queue_merge_bvec(q, drbd_merge_bvec);
 	q->queue_lock = &resource->req_lock;
 
-	device->md_io_page = alloc_page(GFP_KERNEL);
-	if (!device->md_io_page)
+	device->md_io.page = alloc_page(GFP_KERNEL);
+	if (!device->md_io.page)
 		goto out_no_io_page;
 
 	if (drbd_bm_init(device))
@@ -2794,6 +2812,7 @@ enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsig
 	kref_get(&device->kref);
 
 	INIT_LIST_HEAD(&device->peer_devices);
+	INIT_LIST_HEAD(&device->pending_bitmap_io);
 	for_each_connection(connection, resource) {
 		peer_device = kzalloc(sizeof(struct drbd_peer_device), GFP_KERNEL);
 		if (!peer_device)
@@ -2829,7 +2848,10 @@ enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsig
 		for_each_peer_device(peer_device, device)
 			drbd_connected(peer_device);
 	}
-
+	/* move to create_peer_device() */
+	for_each_peer_device(peer_device, device)
+		drbd_debugfs_peer_device_add(peer_device);
+	drbd_debugfs_device_add(device);
 	return NO_ERROR;
 
 out_idr_remove_vol:
@@ -2853,7 +2875,7 @@ out_idr_remove_minor:
 out_no_minor_idr:
 	drbd_bm_cleanup(device);
 out_no_bitmap:
-	__free_page(device->md_io_page);
+	__free_page(device->md_io.page);
 out_no_io_page:
 	put_disk(disk);
 out_no_disk:
@@ -2868,8 +2890,13 @@ void drbd_delete_device(struct drbd_device *device)
 {
 	struct drbd_resource *resource = device->resource;
 	struct drbd_connection *connection;
+	struct drbd_peer_device *peer_device;
 	int refs = 3;
 
+	/* move to free_peer_device() */
+	for_each_peer_device(peer_device, device)
+		drbd_debugfs_peer_device_cleanup(peer_device);
+	drbd_debugfs_device_cleanup(device);
 	for_each_connection(connection, resource) {
 		idr_remove(&connection->peer_devices, device->vnr);
 		refs++;
@@ -2881,13 +2908,12 @@ void drbd_delete_device(struct drbd_device *device)
 	kref_sub(&device->kref, refs, drbd_destroy_device);
 }
 
-int __init drbd_init(void)
+static int __init drbd_init(void)
 {
 	int err;
 
 	if (minor_count < DRBD_MINOR_COUNT_MIN || minor_count > DRBD_MINOR_COUNT_MAX) {
-		printk(KERN_ERR
-		       "drbd: invalid minor_count (%d)\n", minor_count);
+		pr_err("invalid minor_count (%d)\n", minor_count);
 #ifdef MODULE
 		return -EINVAL;
 #else
@@ -2897,14 +2923,11 @@ int __init drbd_init(void)
 
 	err = register_blkdev(DRBD_MAJOR, "drbd");
 	if (err) {
-		printk(KERN_ERR
-		       "drbd: unable to register block device major %d\n",
+		pr_err("unable to register block device major %d\n",
 		       DRBD_MAJOR);
 		return err;
 	}
 
-	register_reboot_notifier(&drbd_notifier);
-
 	/*
 	 * allocate all necessary structs
 	 */
@@ -2918,7 +2941,7 @@ int __init drbd_init(void)
 
 	err = drbd_genl_register();
 	if (err) {
-		printk(KERN_ERR "drbd: unable to register generic netlink family\n");
+		pr_err("unable to register generic netlink family\n");
 		goto fail;
 	}
 
@@ -2929,38 +2952,39 @@ int __init drbd_init(void)
 	err = -ENOMEM;
 	drbd_proc = proc_create_data("drbd", S_IFREG | S_IRUGO , NULL, &drbd_proc_fops, NULL);
 	if (!drbd_proc)	{
-		printk(KERN_ERR "drbd: unable to register proc file\n");
+		pr_err("unable to register proc file\n");
 		goto fail;
 	}
 
 	retry.wq = create_singlethread_workqueue("drbd-reissue");
 	if (!retry.wq) {
-		printk(KERN_ERR "drbd: unable to create retry workqueue\n");
+		pr_err("unable to create retry workqueue\n");
 		goto fail;
 	}
 	INIT_WORK(&retry.worker, do_retry);
 	spin_lock_init(&retry.lock);
 	INIT_LIST_HEAD(&retry.writes);
 
-	printk(KERN_INFO "drbd: initialized. "
+	if (drbd_debugfs_init())
+		pr_notice("failed to initialize debugfs -- will not be available\n");
+
+	pr_info("initialized. "
 	       "Version: " REL_VERSION " (api:%d/proto:%d-%d)\n",
 	       API_VERSION, PRO_VERSION_MIN, PRO_VERSION_MAX);
-	printk(KERN_INFO "drbd: %s\n", drbd_buildtag());
-	printk(KERN_INFO "drbd: registered as block device major %d\n",
-		DRBD_MAJOR);
-
+	pr_info("%s\n", drbd_buildtag());
+	pr_info("registered as block device major %d\n", DRBD_MAJOR);
 	return 0; /* Success! */
 
 fail:
 	drbd_cleanup();
 	if (err == -ENOMEM)
-		printk(KERN_ERR "drbd: ran out of memory\n");
+		pr_err("ran out of memory\n");
 	else
-		printk(KERN_ERR "drbd: initialization failure\n");
+		pr_err("initialization failure\n");
 	return err;
 }
 
-void drbd_free_bc(struct drbd_backing_dev *ldev)
+void drbd_free_ldev(struct drbd_backing_dev *ldev)
 {
 	if (ldev == NULL)
 		return;
@@ -2972,24 +2996,29 @@ void drbd_free_bc(struct drbd_backing_dev *ldev)
 	kfree(ldev);
 }
 
-void drbd_free_sock(struct drbd_connection *connection)
+static void drbd_free_one_sock(struct drbd_socket *ds)
 {
-	if (connection->data.socket) {
-		mutex_lock(&connection->data.mutex);
-		kernel_sock_shutdown(connection->data.socket, SHUT_RDWR);
-		sock_release(connection->data.socket);
-		connection->data.socket = NULL;
-		mutex_unlock(&connection->data.mutex);
-	}
-	if (connection->meta.socket) {
-		mutex_lock(&connection->meta.mutex);
-		kernel_sock_shutdown(connection->meta.socket, SHUT_RDWR);
-		sock_release(connection->meta.socket);
-		connection->meta.socket = NULL;
-		mutex_unlock(&connection->meta.mutex);
+	struct socket *s;
+	mutex_lock(&ds->mutex);
+	s = ds->socket;
+	ds->socket = NULL;
+	mutex_unlock(&ds->mutex);
+	if (s) {
+		/* so debugfs does not need to mutex_lock() */
+		synchronize_rcu();
+		kernel_sock_shutdown(s, SHUT_RDWR);
+		sock_release(s);
 	}
 }
 
+void drbd_free_sock(struct drbd_connection *connection)
+{
+	if (connection->data.socket)
+		drbd_free_one_sock(&connection->data);
+	if (connection->meta.socket)
+		drbd_free_one_sock(&connection->meta);
+}
+
 /* meta data management */
 
 void conn_md_sync(struct drbd_connection *connection)
@@ -3093,7 +3122,7 @@ void drbd_md_sync(struct drbd_device *device)
 	if (!get_ldev_if_state(device, D_FAILED))
 		return;
 
-	buffer = drbd_md_get_buffer(device);
+	buffer = drbd_md_get_buffer(device, __func__);
 	if (!buffer)
 		goto out;
 
@@ -3253,7 +3282,7 @@ int drbd_md_read(struct drbd_device *device, struct drbd_backing_dev *bdev)
 	if (device->state.disk != D_DISKLESS)
 		return ERR_DISK_CONFIGURED;
 
-	buffer = drbd_md_get_buffer(device);
+	buffer = drbd_md_get_buffer(device, __func__);
 	if (!buffer)
 		return ERR_NOMEM;
 
@@ -3466,23 +3495,19 @@ void drbd_uuid_set_bm(struct drbd_device *device, u64 val) __must_hold(local)
  *
  * Sets all bits in the bitmap and writes the whole bitmap to stable storage.
  */
-int drbd_bmio_set_n_write(struct drbd_device *device)
+int drbd_bmio_set_n_write(struct drbd_device *device) __must_hold(local)
 {
 	int rv = -EIO;
 
-	if (get_ldev_if_state(device, D_ATTACHING)) {
-		drbd_md_set_flag(device, MDF_FULL_SYNC);
-		drbd_md_sync(device);
-		drbd_bm_set_all(device);
-
-		rv = drbd_bm_write(device);
+	drbd_md_set_flag(device, MDF_FULL_SYNC);
+	drbd_md_sync(device);
+	drbd_bm_set_all(device);
 
-		if (!rv) {
-			drbd_md_clear_flag(device, MDF_FULL_SYNC);
-			drbd_md_sync(device);
-		}
+	rv = drbd_bm_write(device);
 
-		put_ldev(device);
+	if (!rv) {
+		drbd_md_clear_flag(device, MDF_FULL_SYNC);
+		drbd_md_sync(device);
 	}
 
 	return rv;
@@ -3494,18 +3519,11 @@ int drbd_bmio_set_n_write(struct drbd_device *device)
  *
  * Clears all bits in the bitmap and writes the whole bitmap to stable storage.
  */
-int drbd_bmio_clear_n_write(struct drbd_device *device)
+int drbd_bmio_clear_n_write(struct drbd_device *device) __must_hold(local)
 {
-	int rv = -EIO;
-
 	drbd_resume_al(device);
-	if (get_ldev_if_state(device, D_ATTACHING)) {
-		drbd_bm_clear_all(device);
-		rv = drbd_bm_write(device);
-		put_ldev(device);
-	}
-
-	return rv;
+	drbd_bm_clear_all(device);
+	return drbd_bm_write(device);
 }
 
 static int w_bitmap_io(struct drbd_work *w, int unused)
@@ -3537,61 +3555,6 @@ static int w_bitmap_io(struct drbd_work *w, int unused)
 	return 0;
 }
 
-void drbd_ldev_destroy(struct drbd_device *device)
-{
-	lc_destroy(device->resync);
-	device->resync = NULL;
-	lc_destroy(device->act_log);
-	device->act_log = NULL;
-	__no_warn(local,
-		drbd_free_bc(device->ldev);
-		device->ldev = NULL;);
-
-	clear_bit(GO_DISKLESS, &device->flags);
-}
-
-static int w_go_diskless(struct drbd_work *w, int unused)
-{
-	struct drbd_device *device =
-		container_of(w, struct drbd_device, go_diskless);
-
-	D_ASSERT(device, device->state.disk == D_FAILED);
-	/* we cannot assert local_cnt == 0 here, as get_ldev_if_state will
-	 * inc/dec it frequently. Once we are D_DISKLESS, no one will touch
-	 * the protected members anymore, though, so once put_ldev reaches zero
-	 * again, it will be safe to free them. */
-
-	/* Try to write changed bitmap pages, read errors may have just
-	 * set some bits outside the area covered by the activity log.
-	 *
-	 * If we have an IO error during the bitmap writeout,
-	 * we will want a full sync next time, just in case.
-	 * (Do we want a specific meta data flag for this?)
-	 *
-	 * If that does not make it to stable storage either,
-	 * we cannot do anything about that anymore.
-	 *
-	 * We still need to check if both bitmap and ldev are present, we may
-	 * end up here after a failed attach, before ldev was even assigned.
-	 */
-	if (device->bitmap && device->ldev) {
-		/* An interrupted resync or similar is allowed to recounts bits
-		 * while we detach.
-		 * Any modifications would not be expected anymore, though.
-		 */
-		if (drbd_bitmap_io_from_worker(device, drbd_bm_write,
-					"detach", BM_LOCKED_TEST_ALLOWED)) {
-			if (test_bit(WAS_READ_ERROR, &device->flags)) {
-				drbd_md_set_flag(device, MDF_FULL_SYNC);
-				drbd_md_sync(device);
-			}
-		}
-	}
-
-	drbd_force_state(device, NS(disk, D_DISKLESS));
-	return 0;
-}
-
 /**
  * drbd_queue_bitmap_io() - Queues an IO operation on the whole bitmap
  * @device:	DRBD device.
@@ -3603,6 +3566,9 @@ static int w_go_diskless(struct drbd_work *w, int unused)
  * that drbd_set_out_of_sync() can not be called. This function MAY ONLY be
  * called from worker context. It MUST NOT be used while a previous such
  * work is still pending!
+ *
+ * Its worker function encloses the call of io_fn() by get_ldev() and
+ * put_ldev().
  */
 void drbd_queue_bitmap_io(struct drbd_device *device,
 			  int (*io_fn)(struct drbd_device *),
@@ -3685,25 +3651,7 @@ int drbd_md_test_flag(struct drbd_backing_dev *bdev, int flag)
 static void md_sync_timer_fn(unsigned long data)
 {
 	struct drbd_device *device = (struct drbd_device *) data;
-
-	/* must not double-queue! */
-	if (list_empty(&device->md_sync_work.list))
-		drbd_queue_work_front(&first_peer_device(device)->connection->sender_work,
-				      &device->md_sync_work);
-}
-
-static int w_md_sync(struct drbd_work *w, int unused)
-{
-	struct drbd_device *device =
-		container_of(w, struct drbd_device, md_sync_work);
-
-	drbd_warn(device, "md_sync_timer expired! Worker calls drbd_md_sync().\n");
-#ifdef DEBUG
-	drbd_warn(device, "last md_mark_dirty: %s:%u\n",
-		device->last_md_mark_dirty.func, device->last_md_mark_dirty.line);
-#endif
-	drbd_md_sync(device);
-	return 0;
+	drbd_device_post_work(device, MD_SYNC);
 }
 
 const char *cmdname(enum drbd_packet cmd)
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 3f2e167..1cd47df 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -23,6 +23,8 @@
 
  */
 
+#define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
+
 #include <linux/module.h>
 #include <linux/drbd.h>
 #include <linux/in.h>
@@ -85,7 +87,7 @@ static void drbd_adm_send_reply(struct sk_buff *skb, struct genl_info *info)
 {
 	genlmsg_end(skb, genlmsg_data(nlmsg_data(nlmsg_hdr(skb))));
 	if (genlmsg_reply(skb, info))
-		printk(KERN_ERR "drbd: error sending genl reply\n");
+		pr_err("error sending genl reply\n");
 }
 
 /* Used on a fresh "drbd_adm_prepare"d reply_skb, this cannot fail: The only
@@ -558,8 +560,10 @@ void conn_try_outdate_peer_async(struct drbd_connection *connection)
 }
 
 enum drbd_state_rv
-drbd_set_role(struct drbd_device *device, enum drbd_role new_role, int force)
+drbd_set_role(struct drbd_device *const device, enum drbd_role new_role, int force)
 {
+	struct drbd_peer_device *const peer_device = first_peer_device(device);
+	struct drbd_connection *const connection = peer_device ? peer_device->connection : NULL;
 	const int max_tries = 4;
 	enum drbd_state_rv rv = SS_UNKNOWN_ERROR;
 	struct net_conf *nc;
@@ -607,7 +611,7 @@ drbd_set_role(struct drbd_device *device, enum drbd_role new_role, int force)
 		    device->state.disk == D_CONSISTENT && mask.pdsk == 0) {
 			D_ASSERT(device, device->state.pdsk == D_UNKNOWN);
 
-			if (conn_try_outdate_peer(first_peer_device(device)->connection)) {
+			if (conn_try_outdate_peer(connection)) {
 				val.disk = D_UP_TO_DATE;
 				mask.disk = D_MASK;
 			}
@@ -617,7 +621,7 @@ drbd_set_role(struct drbd_device *device, enum drbd_role new_role, int force)
 		if (rv == SS_NOTHING_TO_DO)
 			goto out;
 		if (rv == SS_PRIMARY_NOP && mask.pdsk == 0) {
-			if (!conn_try_outdate_peer(first_peer_device(device)->connection) && force) {
+			if (!conn_try_outdate_peer(connection) && force) {
 				drbd_warn(device, "Forced into split brain situation!\n");
 				mask.pdsk = D_MASK;
 				val.pdsk  = D_OUTDATED;
@@ -630,7 +634,7 @@ drbd_set_role(struct drbd_device *device, enum drbd_role new_role, int force)
 			   retry at most once more in this case. */
 			int timeo;
 			rcu_read_lock();
-			nc = rcu_dereference(first_peer_device(device)->connection->net_conf);
+			nc = rcu_dereference(connection->net_conf);
 			timeo = nc ? (nc->ping_timeo + 1) * HZ / 10 : 1;
 			rcu_read_unlock();
 			schedule_timeout_interruptible(timeo);
@@ -659,19 +663,17 @@ drbd_set_role(struct drbd_device *device, enum drbd_role new_role, int force)
 	/* FIXME also wait for all pending P_BARRIER_ACK? */
 
 	if (new_role == R_SECONDARY) {
-		set_disk_ro(device->vdisk, true);
 		if (get_ldev(device)) {
 			device->ldev->md.uuid[UI_CURRENT] &= ~(u64)1;
 			put_ldev(device);
 		}
 	} else {
-		/* Called from drbd_adm_set_role only.
-		 * We are still holding the conf_update mutex. */
-		nc = first_peer_device(device)->connection->net_conf;
+		mutex_lock(&device->resource->conf_update);
+		nc = connection->net_conf;
 		if (nc)
 			nc->discard_my_data = 0; /* without copy; single bit op is atomic */
+		mutex_unlock(&device->resource->conf_update);
 
-		set_disk_ro(device->vdisk, false);
 		if (get_ldev(device)) {
 			if (((device->state.conn < C_CONNECTED ||
 			       device->state.pdsk <= D_FAILED)
@@ -689,12 +691,12 @@ drbd_set_role(struct drbd_device *device, enum drbd_role new_role, int force)
 	if (device->state.conn >= C_WF_REPORT_PARAMS) {
 		/* if this was forced, we should consider sync */
 		if (forced)
-			drbd_send_uuids(first_peer_device(device));
-		drbd_send_current_state(first_peer_device(device));
+			drbd_send_uuids(peer_device);
+		drbd_send_current_state(peer_device);
 	}
 
 	drbd_md_sync(device);
-
+	set_disk_ro(device->vdisk, new_role == R_SECONDARY);
 	kobject_uevent(&disk_to_dev(device->vdisk)->kobj, KOBJ_CHANGE);
 out:
 	mutex_unlock(device->state_mutex);
@@ -891,7 +893,7 @@ drbd_determine_dev_size(struct drbd_device *device, enum dds_flags flags, struct
 	 * still lock the act_log to not trigger ASSERTs there.
 	 */
 	drbd_suspend_io(device);
-	buffer = drbd_md_get_buffer(device); /* Lock meta-data IO */
+	buffer = drbd_md_get_buffer(device, __func__); /* Lock meta-data IO */
 	if (!buffer) {
 		drbd_resume_io(device);
 		return DS_ERROR;
@@ -971,6 +973,10 @@ drbd_determine_dev_size(struct drbd_device *device, enum dds_flags flags, struct
 	if (la_size_changed || md_moved || rs) {
 		u32 prev_flags;
 
+		/* We do some synchronous IO below, which may take some time.
+		 * Clear the timer, to avoid scary "timer expired!" messages,
+		 * "Superblock" is written out at least twice below, anyways. */
+		del_timer(&device->md_sync_timer);
 		drbd_al_shrink(device); /* All extents inactive. */
 
 		prev_flags = md->flags;
@@ -1116,15 +1122,16 @@ static int drbd_check_al_size(struct drbd_device *device, struct disk_conf *dc)
 	return 0;
 }
 
-static void drbd_setup_queue_param(struct drbd_device *device, unsigned int max_bio_size)
+static void drbd_setup_queue_param(struct drbd_device *device, struct drbd_backing_dev *bdev,
+				   unsigned int max_bio_size)
 {
 	struct request_queue * const q = device->rq_queue;
 	unsigned int max_hw_sectors = max_bio_size >> 9;
 	unsigned int max_segments = 0;
 	struct request_queue *b = NULL;
 
-	if (get_ldev_if_state(device, D_ATTACHING)) {
-		b = device->ldev->backing_bdev->bd_disk->queue;
+	if (bdev) {
+		b = bdev->backing_bdev->bd_disk->queue;
 
 		max_hw_sectors = min(queue_max_hw_sectors(b), max_bio_size >> 9);
 		rcu_read_lock();
@@ -1169,11 +1176,10 @@ static void drbd_setup_queue_param(struct drbd_device *device, unsigned int max_
 				 b->backing_dev_info.ra_pages);
 			q->backing_dev_info.ra_pages = b->backing_dev_info.ra_pages;
 		}
-		put_ldev(device);
 	}
 }
 
-void drbd_reconsider_max_bio_size(struct drbd_device *device)
+void drbd_reconsider_max_bio_size(struct drbd_device *device, struct drbd_backing_dev *bdev)
 {
 	unsigned int now, new, local, peer;
 
@@ -1181,10 +1187,9 @@ void drbd_reconsider_max_bio_size(struct drbd_device *device)
 	local = device->local_max_bio_size; /* Eventually last known value, from volatile memory */
 	peer = device->peer_max_bio_size; /* Eventually last known value, from meta data */
 
-	if (get_ldev_if_state(device, D_ATTACHING)) {
-		local = queue_max_hw_sectors(device->ldev->backing_bdev->bd_disk->queue) << 9;
+	if (bdev) {
+		local = queue_max_hw_sectors(bdev->backing_bdev->bd_disk->queue) << 9;
 		device->local_max_bio_size = local;
-		put_ldev(device);
 	}
 	local = min(local, DRBD_MAX_BIO_SIZE);
 
@@ -1217,7 +1222,7 @@ void drbd_reconsider_max_bio_size(struct drbd_device *device)
 	if (new != now)
 		drbd_info(device, "max BIO size = %u\n", new);
 
-	drbd_setup_queue_param(device, new);
+	drbd_setup_queue_param(device, bdev, new);
 }
 
 /* Starts the worker thread */
@@ -1299,6 +1304,13 @@ static unsigned int drbd_al_extents_max(struct drbd_backing_dev *bdev)
 	return (al_size_4k - 1) * AL_CONTEXT_PER_TRANSACTION;
 }
 
+static bool write_ordering_changed(struct disk_conf *a, struct disk_conf *b)
+{
+	return	a->disk_barrier != b->disk_barrier ||
+		a->disk_flushes != b->disk_flushes ||
+		a->disk_drain != b->disk_drain;
+}
+
 int drbd_adm_disk_opts(struct sk_buff *skb, struct genl_info *info)
 {
 	struct drbd_config_context adm_ctx;
@@ -1405,7 +1417,8 @@ int drbd_adm_disk_opts(struct sk_buff *skb, struct genl_info *info)
 	else
 		set_bit(MD_NO_FUA, &device->flags);
 
-	drbd_bump_write_ordering(first_peer_device(device)->connection, WO_bdev_flush);
+	if (write_ordering_changed(old_disk_conf, new_disk_conf))
+		drbd_bump_write_ordering(device->resource, NULL, WO_bdev_flush);
 
 	drbd_md_sync(device);
 
@@ -1440,6 +1453,8 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
 {
 	struct drbd_config_context adm_ctx;
 	struct drbd_device *device;
+	struct drbd_peer_device *peer_device;
+	struct drbd_connection *connection;
 	int err;
 	enum drbd_ret_code retcode;
 	enum determine_dev_size dd;
@@ -1462,7 +1477,9 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
 
 	device = adm_ctx.device;
 	mutex_lock(&adm_ctx.resource->adm_mutex);
-	conn_reconfig_start(first_peer_device(device)->connection);
+	peer_device = first_peer_device(device);
+	connection = peer_device ? peer_device->connection : NULL;
+	conn_reconfig_start(connection);
 
 	/* if you want to reconfigure, please tear down first */
 	if (device->state.disk > D_DISKLESS) {
@@ -1473,7 +1490,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
 	 * drbd_ldev_destroy is done already, we may end up here very fast,
 	 * e.g. if someone calls attach from the on-io-error handler,
 	 * to realize a "hot spare" feature (not that I'd recommend that) */
-	wait_event(device->misc_wait, !atomic_read(&device->local_cnt));
+	wait_event(device->misc_wait, !test_bit(GOING_DISKLESS, &device->flags));
 
 	/* make sure there is no leftover from previous force-detach attempts */
 	clear_bit(FORCE_DETACH, &device->flags);
@@ -1529,7 +1546,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
 		goto fail;
 
 	rcu_read_lock();
-	nc = rcu_dereference(first_peer_device(device)->connection->net_conf);
+	nc = rcu_dereference(connection->net_conf);
 	if (nc) {
 		if (new_disk_conf->fencing == FP_STONITH && nc->wire_protocol == DRBD_PROT_A) {
 			rcu_read_unlock();
@@ -1649,7 +1666,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
 	 */
 	wait_event(device->misc_wait, !atomic_read(&device->ap_pending_cnt) || drbd_suspended(device));
 	/* and for any other previously queued work */
-	drbd_flush_workqueue(&first_peer_device(device)->connection->sender_work);
+	drbd_flush_workqueue(&connection->sender_work);
 
 	rv = _drbd_request_state(device, NS(disk, D_ATTACHING), CS_VERBOSE);
 	retcode = rv;  /* FIXME: Type mismatch. */
@@ -1710,7 +1727,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
 	new_disk_conf = NULL;
 	new_plan = NULL;
 
-	drbd_bump_write_ordering(first_peer_device(device)->connection, WO_bdev_flush);
+	drbd_bump_write_ordering(device->resource, device->ldev, WO_bdev_flush);
 
 	if (drbd_md_test_flag(device->ldev, MDF_CRASHED_PRIMARY))
 		set_bit(CRASHED_PRIMARY, &device->flags);
@@ -1726,7 +1743,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
 	device->read_cnt = 0;
 	device->writ_cnt = 0;
 
-	drbd_reconsider_max_bio_size(device);
+	drbd_reconsider_max_bio_size(device, device->ldev);
 
 	/* If I am currently not R_PRIMARY,
 	 * but meta data primary indicator is set,
@@ -1845,7 +1862,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
 
 	kobject_uevent(&disk_to_dev(device->vdisk)->kobj, KOBJ_CHANGE);
 	put_ldev(device);
-	conn_reconfig_done(first_peer_device(device)->connection);
+	conn_reconfig_done(connection);
 	mutex_unlock(&adm_ctx.resource->adm_mutex);
 	drbd_adm_finish(&adm_ctx, info, retcode);
 	return 0;
@@ -1856,7 +1873,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
 	drbd_force_state(device, NS(disk, D_DISKLESS));
 	drbd_md_sync(device);
  fail:
-	conn_reconfig_done(first_peer_device(device)->connection);
+	conn_reconfig_done(connection);
 	if (nbc) {
 		if (nbc->backing_bdev)
 			blkdev_put(nbc->backing_bdev,
@@ -1888,7 +1905,7 @@ static int adm_detach(struct drbd_device *device, int force)
 	}
 
 	drbd_suspend_io(device); /* so no-one is stuck in drbd_al_begin_io */
-	drbd_md_get_buffer(device); /* make sure there is no in-flight meta-data IO */
+	drbd_md_get_buffer(device, __func__); /* make sure there is no in-flight meta-data IO */
 	retcode = drbd_request_state(device, NS(disk, D_FAILED));
 	drbd_md_put_buffer(device);
 	/* D_FAILED will transition to DISKLESS. */
@@ -2654,8 +2671,13 @@ int drbd_adm_invalidate(struct sk_buff *skb, struct genl_info *info)
 	if (retcode != NO_ERROR)
 		goto out;
 
-	mutex_lock(&adm_ctx.resource->adm_mutex);
 	device = adm_ctx.device;
+	if (!get_ldev(device)) {
+		retcode = ERR_NO_DISK;
+		goto out;
+	}
+
+	mutex_lock(&adm_ctx.resource->adm_mutex);
 
 	/* If there is still bitmap IO pending, probably because of a previous
 	 * resync just being finished, wait for it before requesting a new resync.
@@ -2679,6 +2701,7 @@ int drbd_adm_invalidate(struct sk_buff *skb, struct genl_info *info)
 		retcode = drbd_request_state(device, NS(conn, C_STARTING_SYNC_T));
 	drbd_resume_io(device);
 	mutex_unlock(&adm_ctx.resource->adm_mutex);
+	put_ldev(device);
 out:
 	drbd_adm_finish(&adm_ctx, info, retcode);
 	return 0;
@@ -2704,7 +2727,7 @@ out:
 	return 0;
 }
 
-static int drbd_bmio_set_susp_al(struct drbd_device *device)
+static int drbd_bmio_set_susp_al(struct drbd_device *device) __must_hold(local)
 {
 	int rv;
 
@@ -2725,8 +2748,13 @@ int drbd_adm_invalidate_peer(struct sk_buff *skb, struct genl_info *info)
 	if (retcode != NO_ERROR)
 		goto out;
 
-	mutex_lock(&adm_ctx.resource->adm_mutex);
 	device = adm_ctx.device;
+	if (!get_ldev(device)) {
+		retcode = ERR_NO_DISK;
+		goto out;
+	}
+
+	mutex_lock(&adm_ctx.resource->adm_mutex);
 
 	/* If there is still bitmap IO pending, probably because of a previous
 	 * resync just being finished, wait for it before requesting a new resync.
@@ -2753,6 +2781,7 @@ int drbd_adm_invalidate_peer(struct sk_buff *skb, struct genl_info *info)
 		retcode = drbd_request_state(device, NS(conn, C_STARTING_SYNC_S));
 	drbd_resume_io(device);
 	mutex_unlock(&adm_ctx.resource->adm_mutex);
+	put_ldev(device);
 out:
 	drbd_adm_finish(&adm_ctx, info, retcode);
 	return 0;
@@ -2892,7 +2921,7 @@ static struct drbd_connection *the_only_connection(struct drbd_resource *resourc
 	return list_first_entry(&resource->connections, struct drbd_connection, connections);
 }
 
-int nla_put_status_info(struct sk_buff *skb, struct drbd_device *device,
+static int nla_put_status_info(struct sk_buff *skb, struct drbd_device *device,
 		const struct sib_info *sib)
 {
 	struct drbd_resource *resource = device->resource;
@@ -3622,13 +3651,6 @@ void drbd_bcast_event(struct drbd_device *device, const struct sib_info *sib)
 	unsigned seq;
 	int err = -ENOMEM;
 
-	if (sib->sib_reason == SIB_SYNC_PROGRESS) {
-		if (time_after(jiffies, device->rs_last_bcast + HZ))
-			device->rs_last_bcast = jiffies;
-		else
-			return;
-	}
-
 	seq = atomic_inc_return(&drbd_genl_seq);
 	msg = genlmsg_new(NLMSG_GOODSIZE, GFP_NOIO);
 	if (!msg)
diff --git a/drivers/block/drbd/drbd_proc.c b/drivers/block/drbd/drbd_proc.c
index 89736bd..06e6147 100644
--- a/drivers/block/drbd/drbd_proc.c
+++ b/drivers/block/drbd/drbd_proc.c
@@ -60,20 +60,65 @@ static void seq_printf_with_thousands_grouping(struct seq_file *seq, long v)
 		seq_printf(seq, "%ld", v);
 }
 
+static void drbd_get_syncer_progress(struct drbd_device *device,
+		union drbd_dev_state state, unsigned long *rs_total,
+		unsigned long *bits_left, unsigned int *per_mil_done)
+{
+	/* this is to break it at compile time when we change that, in case we
+	 * want to support more than (1<<32) bits on a 32bit arch. */
+	typecheck(unsigned long, device->rs_total);
+	*rs_total = device->rs_total;
+
+	/* note: both rs_total and rs_left are in bits, i.e. in
+	 * units of BM_BLOCK_SIZE.
+	 * for the percentage, we don't care. */
+
+	if (state.conn == C_VERIFY_S || state.conn == C_VERIFY_T)
+		*bits_left = device->ov_left;
+	else
+		*bits_left = drbd_bm_total_weight(device) - device->rs_failed;
+	/* >> 10 to prevent overflow,
+	 * +1 to prevent division by zero */
+	if (*bits_left > *rs_total) {
+		/* D'oh. Maybe a logic bug somewhere.  More likely just a race
+		 * between state change and reset of rs_total.
+		 */
+		*bits_left = *rs_total;
+		*per_mil_done = *rs_total ? 0 : 1000;
+	} else {
+		/* Make sure the division happens in long context.
+		 * We allow up to one petabyte storage right now,
+		 * at a granularity of 4k per bit that is 2**38 bits.
+		 * After shift right and multiplication by 1000,
+		 * this should still fit easily into a 32bit long,
+		 * so we don't need a 64bit division on 32bit arch.
+		 * Note: currently we don't support such large bitmaps on 32bit
+		 * arch anyways, but no harm done to be prepared for it here.
+		 */
+		unsigned int shift = *rs_total > UINT_MAX ? 16 : 10;
+		unsigned long left = *bits_left >> shift;
+		unsigned long total = 1UL + (*rs_total >> shift);
+		unsigned long tmp = 1000UL - left * 1000UL/total;
+		*per_mil_done = tmp;
+	}
+}
+
+
 /*lge
  * progress bars shamelessly adapted from driver/md/md.c
  * output looks like
  *	[=====>..............] 33.5% (23456/123456)
  *	finish: 2:20:20 speed: 6,345 (6,456) K/sec
  */
-static void drbd_syncer_progress(struct drbd_device *device, struct seq_file *seq)
+static void drbd_syncer_progress(struct drbd_device *device, struct seq_file *seq,
+		union drbd_dev_state state)
 {
-	unsigned long db, dt, dbdt, rt, rs_left;
+	unsigned long db, dt, dbdt, rt, rs_total, rs_left;
 	unsigned int res;
 	int i, x, y;
 	int stalled = 0;
 
-	drbd_get_syncer_progress(device, &rs_left, &res);
+	drbd_get_syncer_progress(device, state, &rs_total, &rs_left, &res);
 
 	x = res/50;
 	y = 20-x;
@@ -85,21 +130,21 @@ static void drbd_syncer_progress(struct drbd_device *device, struct seq_file *se
 		seq_printf(seq, ".");
 	seq_printf(seq, "] ");
 
-	if (device->state.conn == C_VERIFY_S || device->state.conn == C_VERIFY_T)
+	if (state.conn == C_VERIFY_S || state.conn == C_VERIFY_T)
 		seq_printf(seq, "verified:");
 	else
 		seq_printf(seq, "sync'ed:");
 	seq_printf(seq, "%3u.%u%% ", res / 10, res % 10);
 
 	/* if more than a few GB, display in MB */
-	if (device->rs_total > (4UL << (30 - BM_BLOCK_SHIFT)))
+	if (rs_total > (4UL << (30 - BM_BLOCK_SHIFT)))
 		seq_printf(seq, "(%lu/%lu)M",
 			    (unsigned long) Bit2KB(rs_left >> 10),
-			    (unsigned long) Bit2KB(device->rs_total >> 10));
+			    (unsigned long) Bit2KB(rs_total >> 10));
 	else
 		seq_printf(seq, "(%lu/%lu)K\n\t",
 			    (unsigned long) Bit2KB(rs_left),
-			    (unsigned long) Bit2KB(device->rs_total));
+			    (unsigned long) Bit2KB(rs_total));
 
 	/* see drivers/md/md.c
 	 * We do not want to overflow, so the order of operands and
@@ -150,13 +195,13 @@ static void drbd_syncer_progress(struct drbd_device *device, struct seq_file *se
 	dt = (jiffies - device->rs_start - device->rs_paused) / HZ;
 	if (dt == 0)
 		dt = 1;
-	db = device->rs_total - rs_left;
+	db = rs_total - rs_left;
 	dbdt = Bit2KB(db/dt);
 	seq_printf_with_thousands_grouping(seq, dbdt);
 	seq_printf(seq, ")");
 
-	if (device->state.conn == C_SYNC_TARGET ||
-	    device->state.conn == C_VERIFY_S) {
+	if (state.conn == C_SYNC_TARGET ||
+	    state.conn == C_VERIFY_S) {
 		seq_printf(seq, " want: ");
 		seq_printf_with_thousands_grouping(seq, device->c_sync_rate);
 	}
@@ -168,8 +213,8 @@ static void drbd_syncer_progress(struct drbd_device *device, struct seq_file *se
 		unsigned long bm_bits = drbd_bm_bits(device);
 		unsigned long bit_pos;
 		unsigned long long stop_sector = 0;
-		if (device->state.conn == C_VERIFY_S ||
-		    device->state.conn == C_VERIFY_T) {
+		if (state.conn == C_VERIFY_S ||
+		    state.conn == C_VERIFY_T) {
 			bit_pos = bm_bits - device->ov_left;
 			if (verify_can_do_stop_sector(device))
 				stop_sector = device->ov_stop_sector;
@@ -188,22 +233,13 @@ static void drbd_syncer_progress(struct drbd_device *device, struct seq_file *se
 	}
 }
 
-static void resync_dump_detail(struct seq_file *seq, struct lc_element *e)
-{
-	struct bm_extent *bme = lc_entry(e, struct bm_extent, lce);
-
-	seq_printf(seq, "%5d %s %s\n", bme->rs_left,
-		   bme->flags & BME_NO_WRITES ? "NO_WRITES" : "---------",
-		   bme->flags & BME_LOCKED ? "LOCKED" : "------"
-		   );
-}
-
 static int drbd_seq_show(struct seq_file *seq, void *v)
 {
 	int i, prev_i = -1;
 	const char *sn;
 	struct drbd_device *device;
 	struct net_conf *nc;
+	union drbd_dev_state state;
 	char wp;
 
 	static char write_ordering_chars[] = {
@@ -241,11 +277,12 @@ static int drbd_seq_show(struct seq_file *seq, void *v)
 			seq_printf(seq, "\n");
 		prev_i = i;
 
-		sn = drbd_conn_str(device->state.conn);
+		state = device->state;
+		sn = drbd_conn_str(state.conn);
 
-		if (device->state.conn == C_STANDALONE &&
-		    device->state.disk == D_DISKLESS &&
-		    device->state.role == R_SECONDARY) {
+		if (state.conn == C_STANDALONE &&
+		    state.disk == D_DISKLESS &&
+		    state.role == R_SECONDARY) {
 			seq_printf(seq, "%2d: cs:Unconfigured\n", i);
 		} else {
 			/* reset device->congestion_reason */
@@ -258,15 +295,15 @@ static int drbd_seq_show(struct seq_file *seq, void *v)
 			   "    ns:%u nr:%u dw:%u dr:%u al:%u bm:%u "
 			   "lo:%d pe:%d ua:%d ap:%d ep:%d wo:%c",
 			   i, sn,
-			   drbd_role_str(device->state.role),
-			   drbd_role_str(device->state.peer),
-			   drbd_disk_str(device->state.disk),
-			   drbd_disk_str(device->state.pdsk),
+			   drbd_role_str(state.role),
+			   drbd_role_str(state.peer),
+			   drbd_disk_str(state.disk),
+			   drbd_disk_str(state.pdsk),
 			   wp,
 			   drbd_suspended(device) ? 's' : 'r',
-			   device->state.aftr_isp ? 'a' : '-',
-			   device->state.peer_isp ? 'p' : '-',
-			   device->state.user_isp ? 'u' : '-',
+			   state.aftr_isp ? 'a' : '-',
+			   state.peer_isp ? 'p' : '-',
+			   state.user_isp ? 'u' : '-',
 			   device->congestion_reason ?: '-',
 			   test_bit(AL_SUSPENDED, &device->flags) ? 's' : '-',
 			   device->send_cnt/2,
@@ -281,17 +318,17 @@ static int drbd_seq_show(struct seq_file *seq, void *v)
 			   atomic_read(&device->unacked_cnt),
 			   atomic_read(&device->ap_bio_cnt),
 			   first_peer_device(device)->connection->epochs,
-			   write_ordering_chars[first_peer_device(device)->connection->write_ordering]
+			   write_ordering_chars[device->resource->write_ordering]
 			);
 			seq_printf(seq, " oos:%llu\n",
 				   Bit2KB((unsigned long long)
 					   drbd_bm_total_weight(device)));
 		}
-		if (device->state.conn == C_SYNC_SOURCE ||
-		    device->state.conn == C_SYNC_TARGET ||
-		    device->state.conn == C_VERIFY_S ||
-		    device->state.conn == C_VERIFY_T)
-			drbd_syncer_progress(device, seq);
+		if (state.conn == C_SYNC_SOURCE ||
+		    state.conn == C_SYNC_TARGET ||
+		    state.conn == C_VERIFY_S ||
+		    state.conn == C_VERIFY_T)
+			drbd_syncer_progress(device, seq, state);
 
 		if (proc_details >= 1 && get_ldev_if_state(device, D_FAILED)) {
 			lc_seq_printf_stats(seq, device->resync);
@@ -299,12 +336,8 @@ static int drbd_seq_show(struct seq_file *seq, void *v)
 			put_ldev(device);
 		}
 
-		if (proc_details >= 2) {
-			if (device->resync) {
-				lc_seq_dump_details(seq, device->resync, "rs_left",
-					resync_dump_detail);
-			}
-		}
+		if (proc_details >= 2)
+			seq_printf(seq, "\tblocked on activity log: %d\n", atomic_read(&device->ap_actlog_cnt));
 	}
 	rcu_read_unlock();
 
@@ -316,7 +349,7 @@ static int drbd_proc_open(struct inode *inode, struct file *file)
 	int err;
 
 	if (try_module_get(THIS_MODULE)) {
-		err = single_open(file, drbd_seq_show, PDE_DATA(inode));
+		err = single_open(file, drbd_seq_show, NULL);
 		if (err)
 			module_put(THIS_MODULE);
 		return err;
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 5b17ec8..9342b8d 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -362,17 +362,14 @@ drbd_alloc_peer_req(struct drbd_peer_device *peer_device, u64 id, sector_t secto
 			goto fail;
 	}
 
+	memset(peer_req, 0, sizeof(*peer_req));
+	INIT_LIST_HEAD(&peer_req->w.list);
 	drbd_clear_interval(&peer_req->i);
 	peer_req->i.size = data_size;
 	peer_req->i.sector = sector;
-	peer_req->i.local = false;
-	peer_req->i.waiting = false;
-
-	peer_req->epoch = NULL;
+	peer_req->submit_jif = jiffies;
 	peer_req->peer_device = peer_device;
 	peer_req->pages = page;
-	atomic_set(&peer_req->pending_bios, 0);
-	peer_req->flags = 0;
 	/*
 	 * The block_id is opaque to the receiver.  It is not endianness
 	 * converted, and sent back to the sender unchanged.
@@ -389,11 +386,16 @@ drbd_alloc_peer_req(struct drbd_peer_device *peer_device, u64 id, sector_t secto
 void __drbd_free_peer_req(struct drbd_device *device, struct drbd_peer_request *peer_req,
 		       int is_net)
 {
+	might_sleep();
 	if (peer_req->flags & EE_HAS_DIGEST)
 		kfree(peer_req->digest);
 	drbd_free_pages(device, peer_req->pages, is_net);
 	D_ASSERT(device, atomic_read(&peer_req->pending_bios) == 0);
 	D_ASSERT(device, drbd_interval_empty(&peer_req->i));
+	if (!expect(!(peer_req->flags & EE_CALL_AL_COMPLETE_IO))) {
+		peer_req->flags &= ~EE_CALL_AL_COMPLETE_IO;
+		drbd_al_complete_io(device, &peer_req->i);
+	}
 	mempool_free(peer_req, drbd_ee_mempool);
 }
 
@@ -791,8 +793,18 @@ static int receive_first_packet(struct drbd_connection *connection, struct socke
 {
 	unsigned int header_size = drbd_header_size(connection);
 	struct packet_info pi;
+	struct net_conf *nc;
 	int err;
 
+	rcu_read_lock();
+	nc = rcu_dereference(connection->net_conf);
+	if (!nc) {
+		rcu_read_unlock();
+		return -EIO;
+	}
+	sock->sk->sk_rcvtimeo = nc->ping_timeo * 4 * HZ / 10;
+	rcu_read_unlock();
+
 	err = drbd_recv_short(sock, connection->data.rbuf, header_size, 0);
 	if (err != header_size) {
 		if (err >= 0)
@@ -809,7 +821,7 @@ static int receive_first_packet(struct drbd_connection *connection, struct socke
  * drbd_socket_okay() - Free the socket if its connection is not okay
  * @sock:	pointer to the pointer to the socket.
  */
-static int drbd_socket_okay(struct socket **sock)
+static bool drbd_socket_okay(struct socket **sock)
 {
 	int rr;
 	char tb[4];
@@ -827,6 +839,30 @@ static int drbd_socket_okay(struct socket **sock)
 		return false;
 	}
 }
+
+static bool connection_established(struct drbd_connection *connection,
+				   struct socket **sock1,
+				   struct socket **sock2)
+{
+	struct net_conf *nc;
+	int timeout;
+	bool ok;
+
+	if (!*sock1 || !*sock2)
+		return false;
+
+	rcu_read_lock();
+	nc = rcu_dereference(connection->net_conf);
+	timeout = (nc->sock_check_timeo ?: nc->ping_timeo) * HZ / 10;
+	rcu_read_unlock();
+	schedule_timeout_interruptible(timeout);
+
+	ok = drbd_socket_okay(sock1);
+	ok = drbd_socket_okay(sock2) && ok;
+
+	return ok;
+}
+
 /* Gets called if a connection is established, or if a new minor gets created
    in a connection */
 int drbd_connected(struct drbd_peer_device *peer_device)
@@ -868,8 +904,8 @@ static int conn_connect(struct drbd_connection *connection)
 	struct drbd_socket sock, msock;
 	struct drbd_peer_device *peer_device;
 	struct net_conf *nc;
-	int vnr, timeout, h, ok;
-	bool discard_my_data;
+	int vnr, timeout, h;
+	bool discard_my_data, ok;
 	enum drbd_state_rv rv;
 	struct accept_wait_data ad = {
 		.connection = connection,
@@ -913,17 +949,8 @@ static int conn_connect(struct drbd_connection *connection)
 			}
 		}
 
-		if (sock.socket && msock.socket) {
-			rcu_read_lock();
-			nc = rcu_dereference(connection->net_conf);
-			timeout = nc->ping_timeo * HZ / 10;
-			rcu_read_unlock();
-			schedule_timeout_interruptible(timeout);
-			ok = drbd_socket_okay(&sock.socket);
-			ok = drbd_socket_okay(&msock.socket) && ok;
-			if (ok)
-				break;
-		}
+		if (connection_established(connection, &sock.socket, &msock.socket))
+			break;
 
 retry:
 		s = drbd_wait_for_connect(connection, &ad);
@@ -969,8 +996,7 @@ randomize:
 				goto out_release_sockets;
 		}
 
-		ok = drbd_socket_okay(&sock.socket);
-		ok = drbd_socket_okay(&msock.socket) && ok;
+		ok = connection_established(connection, &sock.socket, &msock.socket);
 	} while (!ok);
 
 	if (ad.s_listen)
@@ -1151,7 +1177,7 @@ static void drbd_flush(struct drbd_connection *connection)
 	struct drbd_peer_device *peer_device;
 	int vnr;
 
-	if (connection->write_ordering >= WO_bdev_flush) {
+	if (connection->resource->write_ordering >= WO_bdev_flush) {
 		rcu_read_lock();
 		idr_for_each_entry(&connection->peer_devices, peer_device, vnr) {
 			struct drbd_device *device = peer_device->device;
@@ -1161,14 +1187,22 @@ static void drbd_flush(struct drbd_connection *connection)
 			kref_get(&device->kref);
 			rcu_read_unlock();
 
+			/* Right now, we have only this one synchronous code path
+			 * for flushes between request epochs.
+			 * We may want to make those asynchronous,
+			 * or at least parallelize the flushes to the volume devices.
+			 */
+			device->flush_jif = jiffies;
+			set_bit(FLUSH_PENDING, &device->flags);
 			rv = blkdev_issue_flush(device->ldev->backing_bdev,
 					GFP_NOIO, NULL);
+			clear_bit(FLUSH_PENDING, &device->flags);
 			if (rv) {
 				drbd_info(device, "local disk flush failed with status %d\n", rv);
 				/* would rather check on EOPNOTSUPP, but that is not reliable.
 				 * don't try again for ANY return value != 0
 				 * if (rv == -EOPNOTSUPP) */
-				drbd_bump_write_ordering(connection, WO_drain_io);
+				drbd_bump_write_ordering(connection->resource, NULL, WO_drain_io);
 			}
 			put_ldev(device);
 			kref_put(&device->kref, drbd_destroy_device);
@@ -1257,15 +1291,30 @@ static enum finish_epoch drbd_may_finish_epoch(struct drbd_connection *connectio
 	return rv;
 }
 
+static enum write_ordering_e
+max_allowed_wo(struct drbd_backing_dev *bdev, enum write_ordering_e wo)
+{
+	struct disk_conf *dc;
+
+	dc = rcu_dereference(bdev->disk_conf);
+
+	if (wo == WO_bdev_flush && !dc->disk_flushes)
+		wo = WO_drain_io;
+	if (wo == WO_drain_io && !dc->disk_drain)
+		wo = WO_none;
+
+	return wo;
+}
+
 /**
  * drbd_bump_write_ordering() - Fall back to an other write ordering method
  * @connection:	DRBD connection.
  * @wo:		Write ordering method to try.
  */
-void drbd_bump_write_ordering(struct drbd_connection *connection, enum write_ordering_e wo)
+void drbd_bump_write_ordering(struct drbd_resource *resource, struct drbd_backing_dev *bdev,
+			      enum write_ordering_e wo)
 {
-	struct disk_conf *dc;
-	struct drbd_peer_device *peer_device;
+	struct drbd_device *device;
 	enum write_ordering_e pwo;
 	int vnr;
 	static char *write_ordering_str[] = {
@@ -1274,26 +1323,27 @@ void drbd_bump_write_ordering(struct drbd_connection *connection, enum write_ord
 		[WO_bdev_flush] = "flush",
 	};
 
-	pwo = connection->write_ordering;
-	wo = min(pwo, wo);
+	pwo = resource->write_ordering;
+	if (wo != WO_bdev_flush)
+		wo = min(pwo, wo);
 	rcu_read_lock();
-	idr_for_each_entry(&connection->peer_devices, peer_device, vnr) {
-		struct drbd_device *device = peer_device->device;
+	idr_for_each_entry(&resource->devices, device, vnr) {
+		if (get_ldev(device)) {
+			wo = max_allowed_wo(device->ldev, wo);
+			if (device->ldev == bdev)
+				bdev = NULL;
+			put_ldev(device);
+		}
+	}
 
-		if (!get_ldev_if_state(device, D_ATTACHING))
-			continue;
-		dc = rcu_dereference(device->ldev->disk_conf);
+	if (bdev)
+		wo = max_allowed_wo(bdev, wo);
 
-		if (wo == WO_bdev_flush && !dc->disk_flushes)
-			wo = WO_drain_io;
-		if (wo == WO_drain_io && !dc->disk_drain)
-			wo = WO_none;
-		put_ldev(device);
-	}
 	rcu_read_unlock();
-	connection->write_ordering = wo;
-	if (pwo != connection->write_ordering || wo == WO_bdev_flush)
-		drbd_info(connection, "Method to ensure write ordering: %s\n", write_ordering_str[connection->write_ordering]);
+
+	resource->write_ordering = wo;
+	if (pwo != resource->write_ordering || wo == WO_bdev_flush)
+		drbd_info(resource, "Method to ensure write ordering: %s\n", write_ordering_str[resource->write_ordering]);
 }
 
 /**
@@ -1330,6 +1380,13 @@ int drbd_submit_peer_request(struct drbd_device *device,
 		/* wait for all pending IO completions, before we start
 		 * zeroing things out. */
 		conn_wait_active_ee_empty(first_peer_device(device)->connection);
+		/* add it to the active list now,
+		 * so we can find it to present it in debugfs */
+		peer_req->submit_jif = jiffies;
+		peer_req->flags |= EE_SUBMITTED;
+		spin_lock_irq(&device->resource->req_lock);
+		list_add_tail(&peer_req->w.list, &device->active_ee);
+		spin_unlock_irq(&device->resource->req_lock);
 		if (blkdev_issue_zeroout(device->ldev->backing_bdev,
 			sector, ds >> 9, GFP_NOIO))
 			peer_req->flags |= EE_WAS_ERROR;
@@ -1398,6 +1455,9 @@ submit:
 	D_ASSERT(device, page == NULL);
 
 	atomic_set(&peer_req->pending_bios, n_bios);
+	/* for debugfs: update timestamp, mark as submitted */
+	peer_req->submit_jif = jiffies;
+	peer_req->flags |= EE_SUBMITTED;
 	do {
 		bio = bios;
 		bios = bios->bi_next;
@@ -1471,7 +1531,7 @@ static int receive_Barrier(struct drbd_connection *connection, struct packet_inf
 	 * R_PRIMARY crashes now.
 	 * Therefore we must send the barrier_ack after the barrier request was
 	 * completed. */
-	switch (connection->write_ordering) {
+	switch (connection->resource->write_ordering) {
 	case WO_none:
 		if (rv == FE_RECYCLED)
 			return 0;
@@ -1498,7 +1558,8 @@ static int receive_Barrier(struct drbd_connection *connection, struct packet_inf
 
 		return 0;
 	default:
-		drbd_err(connection, "Strangeness in connection->write_ordering %d\n", connection->write_ordering);
+		drbd_err(connection, "Strangeness in connection->write_ordering %d\n",
+			 connection->resource->write_ordering);
 		return -EIO;
 	}
 
@@ -1531,7 +1592,7 @@ read_in_block(struct drbd_peer_device *peer_device, u64 id, sector_t sector,
 	struct drbd_peer_request *peer_req;
 	struct page *page;
 	int dgs, ds, err;
-	int data_size = pi->size;
+	unsigned int data_size = pi->size;
 	void *dig_in = peer_device->connection->int_dig_in;
 	void *dig_vv = peer_device->connection->int_dig_vv;
 	unsigned long *data;
@@ -1578,6 +1639,7 @@ read_in_block(struct drbd_peer_device *peer_device, u64 id, sector_t sector,
 	if (!peer_req)
 		return NULL;
 
+	peer_req->flags |= EE_WRITE;
 	if (trim)
 		return peer_req;
 
@@ -1734,9 +1796,10 @@ static int recv_resync_read(struct drbd_peer_device *peer_device, sector_t secto
 	 * respective _drbd_clear_done_ee */
 
 	peer_req->w.cb = e_end_resync_block;
+	peer_req->submit_jif = jiffies;
 
 	spin_lock_irq(&device->resource->req_lock);
-	list_add(&peer_req->w.list, &device->sync_ee);
+	list_add_tail(&peer_req->w.list, &device->sync_ee);
 	spin_unlock_irq(&device->resource->req_lock);
 
 	atomic_add(pi->size >> 9, &device->rs_sect_ev);
@@ -1889,6 +1952,7 @@ static int e_end_block(struct drbd_work *w, int cancel)
 		}
 		dec_unacked(device);
 	}
+
 	/* we delete from the conflict detection hash _after_ we sent out the
 	 * P_WRITE_ACK / P_NEG_ACK, to get the sequence number right.  */
 	if (peer_req->flags & EE_IN_INTERVAL_TREE) {
@@ -2115,6 +2179,8 @@ static int handle_write_conflicts(struct drbd_device *device,
 	drbd_for_each_overlap(i, &device->write_requests, sector, size) {
 		if (i == &peer_req->i)
 			continue;
+		if (i->completed)
+			continue;
 
 		if (!i->local) {
 			/*
@@ -2147,7 +2213,6 @@ static int handle_write_conflicts(struct drbd_device *device,
 					  (unsigned long long)sector, size,
 					  superseded ? "local" : "remote");
 
-			inc_unacked(device);
 			peer_req->w.cb = superseded ? e_send_superseded :
 						   e_send_retry_write;
 			list_add_tail(&peer_req->w.list, &device->done_ee);
@@ -2206,6 +2271,7 @@ static int receive_Data(struct drbd_connection *connection, struct packet_info *
 {
 	struct drbd_peer_device *peer_device;
 	struct drbd_device *device;
+	struct net_conf *nc;
 	sector_t sector;
 	struct drbd_peer_request *peer_req;
 	struct p_data *p = pi->data;
@@ -2245,6 +2311,8 @@ static int receive_Data(struct drbd_connection *connection, struct packet_info *
 	}
 
 	peer_req->w.cb = e_end_block;
+	peer_req->submit_jif = jiffies;
+	peer_req->flags |= EE_APPLICATION;
 
 	dp_flags = be32_to_cpu(p->dp_flags);
 	rw |= wire_flags_to_bio(dp_flags);
@@ -2271,9 +2339,36 @@ static int receive_Data(struct drbd_connection *connection, struct packet_info *
 	spin_unlock(&connection->epoch_lock);
 
 	rcu_read_lock();
-	tp = rcu_dereference(peer_device->connection->net_conf)->two_primaries;
+	nc = rcu_dereference(peer_device->connection->net_conf);
+	tp = nc->two_primaries;
+	if (peer_device->connection->agreed_pro_version < 100) {
+		switch (nc->wire_protocol) {
+		case DRBD_PROT_C:
+			dp_flags |= DP_SEND_WRITE_ACK;
+			break;
+		case DRBD_PROT_B:
+			dp_flags |= DP_SEND_RECEIVE_ACK;
+			break;
+		}
+	}
 	rcu_read_unlock();
+
+	if (dp_flags & DP_SEND_WRITE_ACK) {
+		peer_req->flags |= EE_SEND_WRITE_ACK;
+		inc_unacked(device);
+		/* corresponding dec_unacked() in e_end_block()
+		 * respective _drbd_clear_done_ee */
+	}
+
+	if (dp_flags & DP_SEND_RECEIVE_ACK) {
+		/* I really don't like it that the receiver thread
+		 * sends on the msock, but anyways */
+		drbd_send_ack(first_peer_device(device), P_RECV_ACK, peer_req);
+	}
+
 	if (tp) {
+		/* two primaries implies protocol C */
+		D_ASSERT(device, dp_flags & DP_SEND_WRITE_ACK);
 		peer_req->flags |= EE_IN_INTERVAL_TREE;
 		err = wait_for_and_update_peer_seq(peer_device, peer_seq);
 		if (err)
@@ -2297,44 +2392,18 @@ static int receive_Data(struct drbd_connection *connection, struct packet_info *
 	 * active_ee to become empty in drbd_submit_peer_request();
 	 * better not add ourselves here. */
 	if ((peer_req->flags & EE_IS_TRIM_USE_ZEROOUT) == 0)
-		list_add(&peer_req->w.list, &device->active_ee);
+		list_add_tail(&peer_req->w.list, &device->active_ee);
 	spin_unlock_irq(&device->resource->req_lock);
 
 	if (device->state.conn == C_SYNC_TARGET)
 		wait_event(device->ee_wait, !overlapping_resync_write(device, peer_req));
 
-	if (peer_device->connection->agreed_pro_version < 100) {
-		rcu_read_lock();
-		switch (rcu_dereference(peer_device->connection->net_conf)->wire_protocol) {
-		case DRBD_PROT_C:
-			dp_flags |= DP_SEND_WRITE_ACK;
-			break;
-		case DRBD_PROT_B:
-			dp_flags |= DP_SEND_RECEIVE_ACK;
-			break;
-		}
-		rcu_read_unlock();
-	}
-
-	if (dp_flags & DP_SEND_WRITE_ACK) {
-		peer_req->flags |= EE_SEND_WRITE_ACK;
-		inc_unacked(device);
-		/* corresponding dec_unacked() in e_end_block()
-		 * respective _drbd_clear_done_ee */
-	}
-
-	if (dp_flags & DP_SEND_RECEIVE_ACK) {
-		/* I really don't like it that the receiver thread
-		 * sends on the msock, but anyways */
-		drbd_send_ack(first_peer_device(device), P_RECV_ACK, peer_req);
-	}
-
 	if (device->state.pdsk < D_INCONSISTENT) {
 		/* In case we have the only disk of the cluster, */
 		drbd_set_out_of_sync(device, peer_req->i.sector, peer_req->i.size);
-		peer_req->flags |= EE_CALL_AL_COMPLETE_IO;
 		peer_req->flags &= ~EE_MAY_SET_IN_SYNC;
-		drbd_al_begin_io(device, &peer_req->i, true);
+		drbd_al_begin_io(device, &peer_req->i);
+		peer_req->flags |= EE_CALL_AL_COMPLETE_IO;
 	}
 
 	err = drbd_submit_peer_request(device, peer_req, rw, DRBD_FAULT_DT_WR);
@@ -2347,8 +2416,10 @@ static int receive_Data(struct drbd_connection *connection, struct packet_info *
 	list_del(&peer_req->w.list);
 	drbd_remove_epoch_entry_interval(device, peer_req);
 	spin_unlock_irq(&device->resource->req_lock);
-	if (peer_req->flags & EE_CALL_AL_COMPLETE_IO)
+	if (peer_req->flags & EE_CALL_AL_COMPLETE_IO) {
+		peer_req->flags &= ~EE_CALL_AL_COMPLETE_IO;
 		drbd_al_complete_io(device, &peer_req->i);
+	}
 
 out_interrupted:
 	drbd_may_finish_epoch(connection, peer_req->epoch, EV_PUT + EV_CLEANUP);
@@ -2368,13 +2439,14 @@ out_interrupted:
  * The current sync rate used here uses only the most recent two step marks,
  * to have a short time average so we can react faster.
  */
-bool drbd_rs_should_slow_down(struct drbd_device *device, sector_t sector)
+bool drbd_rs_should_slow_down(struct drbd_device *device, sector_t sector,
+		bool throttle_if_app_is_waiting)
 {
 	struct lc_element *tmp;
-	bool throttle = true;
+	bool throttle = drbd_rs_c_min_rate_throttle(device);
 
-	if (!drbd_rs_c_min_rate_throttle(device))
-		return false;
+	if (!throttle || throttle_if_app_is_waiting)
+		return throttle;
 
 	spin_lock_irq(&device->al_lock);
 	tmp = lc_find(device->resync, BM_SECT_TO_EXT(sector));
@@ -2382,7 +2454,8 @@ bool drbd_rs_should_slow_down(struct drbd_device *device, sector_t sector)
 		struct bm_extent *bm_ext = lc_entry(tmp, struct bm_extent, lce);
 		if (test_bit(BME_PRIORITY, &bm_ext->flags))
 			throttle = false;
-		/* Do not slow down if app IO is already waiting for this extent */
+		/* Do not slow down if app IO is already waiting for this extent,
+		 * and our progress is necessary for application IO to complete. */
 	}
 	spin_unlock_irq(&device->al_lock);
 
@@ -2407,7 +2480,9 @@ bool drbd_rs_c_min_rate_throttle(struct drbd_device *device)
 	curr_events = (int)part_stat_read(&disk->part0, sectors[0]) +
 		      (int)part_stat_read(&disk->part0, sectors[1]) -
 			atomic_read(&device->rs_sect_ev);
-	if (!device->rs_last_events || curr_events - device->rs_last_events > 64) {
+
+	if (atomic_read(&device->ap_actlog_cnt)
+	    || !device->rs_last_events || curr_events - device->rs_last_events > 64) {
 		unsigned long rs_left;
 		int i;
 
@@ -2508,6 +2583,7 @@ static int receive_DataRequest(struct drbd_connection *connection, struct packet
 		peer_req->w.cb = w_e_end_data_req;
 		fault_type = DRBD_FAULT_DT_RD;
 		/* application IO, don't drbd_rs_begin_io */
+		peer_req->flags |= EE_APPLICATION;
 		goto submit;
 
 	case P_RS_DATA_REQUEST:
@@ -2538,6 +2614,8 @@ static int receive_DataRequest(struct drbd_connection *connection, struct packet
 			peer_req->w.cb = w_e_end_csum_rs_req;
 			/* used in the sector offset progress display */
 			device->bm_resync_fo = BM_SECT_TO_BIT(sector);
+			/* remember to report stats in drbd_resync_finished */
+			device->use_csums = true;
 		} else if (pi->cmd == P_OV_REPLY) {
 			/* track progress, we may need to throttle */
 			atomic_add(size >> 9, &device->rs_sect_in);
@@ -2595,8 +2673,20 @@ static int receive_DataRequest(struct drbd_connection *connection, struct packet
 	 * we would also throttle its application reads.
 	 * In that case, throttling is done on the SyncTarget only.
 	 */
-	if (device->state.peer != R_PRIMARY && drbd_rs_should_slow_down(device, sector))
+
+	/* Even though this may be a resync request, we do add to "read_ee";
+	 * "sync_ee" is only used for resync WRITEs.
+	 * Add to list early, so debugfs can find this request
+	 * even if we have to sleep below. */
+	spin_lock_irq(&device->resource->req_lock);
+	list_add_tail(&peer_req->w.list, &device->read_ee);
+	spin_unlock_irq(&device->resource->req_lock);
+
+	update_receiver_timing_details(connection, drbd_rs_should_slow_down);
+	if (device->state.peer != R_PRIMARY
+	&& drbd_rs_should_slow_down(device, sector, false))
 		schedule_timeout_uninterruptible(HZ/10);
+	update_receiver_timing_details(connection, drbd_rs_begin_io);
 	if (drbd_rs_begin_io(device, sector))
 		goto out_free_e;
 
@@ -2604,22 +2694,20 @@ submit_for_resync:
 	atomic_add(size >> 9, &device->rs_sect_ev);
 
 submit:
+	update_receiver_timing_details(connection, drbd_submit_peer_request);
 	inc_unacked(device);
-	spin_lock_irq(&device->resource->req_lock);
-	list_add_tail(&peer_req->w.list, &device->read_ee);
-	spin_unlock_irq(&device->resource->req_lock);
-
 	if (drbd_submit_peer_request(device, peer_req, READ, fault_type) == 0)
 		return 0;
 
 	/* don't care for the reason here */
 	drbd_err(device, "submit failed, triggering re-connect\n");
+
+out_free_e:
 	spin_lock_irq(&device->resource->req_lock);
 	list_del(&peer_req->w.list);
 	spin_unlock_irq(&device->resource->req_lock);
 	/* no drbd_rs_complete_io(), we are dropping the connection anyways */
 
-out_free_e:
 	put_ldev(device);
 	drbd_free_peer_req(device, peer_req);
 	return -EIO;
@@ -2842,8 +2930,10 @@ static void drbd_uuid_dump(struct drbd_device *device, char *text, u64 *uuid,
 -1091   requires proto 91
 -1096   requires proto 96
  */
-static int drbd_uuid_compare(struct drbd_device *device, int *rule_nr) __must_hold(local)
+static int drbd_uuid_compare(struct drbd_device *const device, int *rule_nr) __must_hold(local)
 {
+	struct drbd_peer_device *const peer_device = first_peer_device(device);
+	struct drbd_connection *const connection = peer_device ? peer_device->connection : NULL;
 	u64 self, peer;
 	int i, j;
 
@@ -2869,7 +2959,7 @@ static int drbd_uuid_compare(struct drbd_device *device, int *rule_nr) __must_ho
 
 		if (device->p_uuid[UI_BITMAP] == (u64)0 && device->ldev->md.uuid[UI_BITMAP] != (u64)0) {
 
-			if (first_peer_device(device)->connection->agreed_pro_version < 91)
+			if (connection->agreed_pro_version < 91)
 				return -1091;
 
 			if ((device->ldev->md.uuid[UI_BITMAP] & ~((u64)1)) == (device->p_uuid[UI_HISTORY_START] & ~((u64)1)) &&
@@ -2892,7 +2982,7 @@ static int drbd_uuid_compare(struct drbd_device *device, int *rule_nr) __must_ho
 
 		if (device->ldev->md.uuid[UI_BITMAP] == (u64)0 && device->p_uuid[UI_BITMAP] != (u64)0) {
 
-			if (first_peer_device(device)->connection->agreed_pro_version < 91)
+			if (connection->agreed_pro_version < 91)
 				return -1091;
 
 			if ((device->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1)) == (device->p_uuid[UI_BITMAP] & ~((u64)1)) &&
@@ -2925,7 +3015,7 @@ static int drbd_uuid_compare(struct drbd_device *device, int *rule_nr) __must_ho
 		case 1: /*  self_pri && !peer_pri */ return 1;
 		case 2: /* !self_pri &&  peer_pri */ return -1;
 		case 3: /*  self_pri &&  peer_pri */
-			dc = test_bit(RESOLVE_CONFLICTS, &first_peer_device(device)->connection->flags);
+			dc = test_bit(RESOLVE_CONFLICTS, &connection->flags);
 			return dc ? -1 : 1;
 		}
 	}
@@ -2938,14 +3028,14 @@ static int drbd_uuid_compare(struct drbd_device *device, int *rule_nr) __must_ho
 	*rule_nr = 51;
 	peer = device->p_uuid[UI_HISTORY_START] & ~((u64)1);
 	if (self == peer) {
-		if (first_peer_device(device)->connection->agreed_pro_version < 96 ?
+		if (connection->agreed_pro_version < 96 ?
 		    (device->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1)) ==
 		    (device->p_uuid[UI_HISTORY_START + 1] & ~((u64)1)) :
 		    peer + UUID_NEW_BM_OFFSET == (device->p_uuid[UI_BITMAP] & ~((u64)1))) {
 			/* The last P_SYNC_UUID did not get though. Undo the last start of
 			   resync as sync source modifications of the peer's UUIDs. */
 
-			if (first_peer_device(device)->connection->agreed_pro_version < 91)
+			if (connection->agreed_pro_version < 91)
 				return -1091;
 
 			device->p_uuid[UI_BITMAP] = device->p_uuid[UI_HISTORY_START];
@@ -2975,14 +3065,14 @@ static int drbd_uuid_compare(struct drbd_device *device, int *rule_nr) __must_ho
 	*rule_nr = 71;
 	self = device->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1);
 	if (self == peer) {
-		if (first_peer_device(device)->connection->agreed_pro_version < 96 ?
+		if (connection->agreed_pro_version < 96 ?
 		    (device->ldev->md.uuid[UI_HISTORY_START + 1] & ~((u64)1)) ==
 		    (device->p_uuid[UI_HISTORY_START] & ~((u64)1)) :
 		    self + UUID_NEW_BM_OFFSET == (device->ldev->md.uuid[UI_BITMAP] & ~((u64)1))) {
 			/* The last P_SYNC_UUID did not get though. Undo the last start of
 			   resync as sync source modifications of our UUIDs. */
 
-			if (first_peer_device(device)->connection->agreed_pro_version < 91)
+			if (connection->agreed_pro_version < 91)
 				return -1091;
 
 			__drbd_uuid_set(device, UI_BITMAP, device->ldev->md.uuid[UI_HISTORY_START]);
@@ -3352,8 +3442,7 @@ disconnect:
  * return: NULL (alg name was "")
  *         ERR_PTR(error) if something goes wrong
  *         or the crypto hash ptr, if it worked out ok. */
-static
-struct crypto_hash *drbd_crypto_alloc_digest_safe(const struct drbd_device *device,
+static struct crypto_hash *drbd_crypto_alloc_digest_safe(const struct drbd_device *device,
 		const char *alg, const char *name)
 {
 	struct crypto_hash *tfm;
@@ -3639,7 +3728,7 @@ static int receive_sizes(struct drbd_connection *connection, struct packet_info
 	struct drbd_device *device;
 	struct p_sizes *p = pi->data;
 	enum determine_dev_size dd = DS_UNCHANGED;
-	sector_t p_size, p_usize, my_usize;
+	sector_t p_size, p_usize, p_csize, my_usize;
 	int ldsc = 0; /* local disk size changed */
 	enum dds_flags ddsf;
 
@@ -3650,6 +3739,7 @@ static int receive_sizes(struct drbd_connection *connection, struct packet_info
 
 	p_size = be64_to_cpu(p->d_size);
 	p_usize = be64_to_cpu(p->u_size);
+	p_csize = be64_to_cpu(p->c_size);
 
 	/* just store the peer's disk size for now.
 	 * we still need to figure out whether we accept that. */
@@ -3710,7 +3800,6 @@ static int receive_sizes(struct drbd_connection *connection, struct packet_info
 	}
 
 	device->peer_max_bio_size = be32_to_cpu(p->max_bio_size);
-	drbd_reconsider_max_bio_size(device);
 	/* Leave drbd_reconsider_max_bio_size() before drbd_determine_dev_size().
 	   In case we cleared the QUEUE_FLAG_DISCARD from our queue in
 	   drbd_reconsider_max_bio_size(), we can be sure that after
@@ -3718,14 +3807,28 @@ static int receive_sizes(struct drbd_connection *connection, struct packet_info
 
 	ddsf = be16_to_cpu(p->dds_flags);
 	if (get_ldev(device)) {
+		drbd_reconsider_max_bio_size(device, device->ldev);
 		dd = drbd_determine_dev_size(device, ddsf, NULL);
 		put_ldev(device);
 		if (dd == DS_ERROR)
 			return -EIO;
 		drbd_md_sync(device);
 	} else {
-		/* I am diskless, need to accept the peer's size. */
-		drbd_set_my_capacity(device, p_size);
+		/*
+		 * I am diskless, need to accept the peer's *current* size.
+		 * I must NOT accept the peers backing disk size,
+		 * it may have been larger than mine all along...
+		 *
+		 * At this point, the peer knows more about my disk, or at
+		 * least about what we last agreed upon, than myself.
+		 * So if his c_size is less than his d_size, the most likely
+		 * reason is that *my* d_size was smaller last time we checked.
+		 *
+		 * However, if he sends a zero current size,
+		 * take his (user-capped or) backing disk size anyways.
+		 */
+		drbd_reconsider_max_bio_size(device, NULL);
+		drbd_set_my_capacity(device, p_csize ?: p_usize ?: p_size);
 	}
 
 	if (get_ldev(device)) {
@@ -4501,6 +4604,7 @@ static void drbdd(struct drbd_connection *connection)
 		struct data_cmd *cmd;
 
 		drbd_thread_current_set_cpu(&connection->receiver);
+		update_receiver_timing_details(connection, drbd_recv_header);
 		if (drbd_recv_header(connection, &pi))
 			goto err_out;
 
@@ -4519,12 +4623,14 @@ static void drbdd(struct drbd_connection *connection)
 		}
 
 		if (shs) {
+			update_receiver_timing_details(connection, drbd_recv_all_warn);
 			err = drbd_recv_all_warn(connection, pi.data, shs);
 			if (err)
 				goto err_out;
 			pi.size -= shs;
 		}
 
+		update_receiver_timing_details(connection, cmd->fn);
 		err = cmd->fn(connection, &pi);
 		if (err) {
 			drbd_err(connection, "error receiving %s, e: %d l: %d!\n",
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 09803d0..c67717d 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -52,7 +52,7 @@ static void _drbd_start_io_acct(struct drbd_device *device, struct drbd_request
 static void _drbd_end_io_acct(struct drbd_device *device, struct drbd_request *req)
 {
 	int rw = bio_data_dir(req->master_bio);
-	unsigned long duration = jiffies - req->start_time;
+	unsigned long duration = jiffies - req->start_jif;
 	int cpu;
 	cpu = part_stat_lock();
 	part_stat_add(cpu, &device->vdisk->part0, ticks[rw], duration);
@@ -66,7 +66,7 @@ static struct drbd_request *drbd_req_new(struct drbd_device *device,
 {
 	struct drbd_request *req;
 
-	req = mempool_alloc(drbd_request_mempool, GFP_NOIO);
+	req = mempool_alloc(drbd_request_mempool, GFP_NOIO | __GFP_ZERO);
 	if (!req)
 		return NULL;
 
@@ -84,6 +84,8 @@ static struct drbd_request *drbd_req_new(struct drbd_device *device,
 
 	INIT_LIST_HEAD(&req->tl_requests);
 	INIT_LIST_HEAD(&req->w.list);
+	INIT_LIST_HEAD(&req->req_pending_master_completion);
+	INIT_LIST_HEAD(&req->req_pending_local);
 
 	/* one reference to be put by __drbd_make_request */
 	atomic_set(&req->completion_ref, 1);
@@ -92,6 +94,19 @@ static struct drbd_request *drbd_req_new(struct drbd_device *device,
 	return req;
 }
 
+static void drbd_remove_request_interval(struct rb_root *root,
+					 struct drbd_request *req)
+{
+	struct drbd_device *device = req->device;
+	struct drbd_interval *i = &req->i;
+
+	drbd_remove_interval(root, i);
+
+	/* Wake up any processes waiting for this request to complete.  */
+	if (i->waiting)
+		wake_up(&device->misc_wait);
+}
+
 void drbd_req_destroy(struct kref *kref)
 {
 	struct drbd_request *req = container_of(kref, struct drbd_request, kref);
@@ -107,14 +122,30 @@ void drbd_req_destroy(struct kref *kref)
 		return;
 	}
 
-	/* remove it from the transfer log.
-	 * well, only if it had been there in the first
-	 * place... if it had not (local only or conflicting
-	 * and never sent), it should still be "empty" as
-	 * initialized in drbd_req_new(), so we can list_del() it
-	 * here unconditionally */
+	/* If called from mod_rq_state (expected normal case) or
+	 * drbd_send_and_submit (the less likely normal path), this holds the
+	 * req_lock, and req->tl_requests will typicaly be on ->transfer_log,
+	 * though it may be still empty (never added to the transfer log).
+	 *
+	 * If called from do_retry(), we do NOT hold the req_lock, but we are
+	 * still allowed to unconditionally list_del(&req->tl_requests),
+	 * because it will be on a local on-stack list only. */
 	list_del_init(&req->tl_requests);
 
+	/* finally remove the request from the conflict detection
+	 * respective block_id verification interval tree. */
+	if (!drbd_interval_empty(&req->i)) {
+		struct rb_root *root;
+
+		if (s & RQ_WRITE)
+			root = &device->write_requests;
+		else
+			root = &device->read_requests;
+		drbd_remove_request_interval(root, req);
+	} else if (s & (RQ_NET_MASK & ~RQ_NET_DONE) && req->i.size != 0)
+		drbd_err(device, "drbd_req_destroy: Logic BUG: interval empty, but: rq_state=0x%x, sect=%llu, size=%u\n",
+			s, (unsigned long long)req->i.sector, req->i.size);
+
 	/* if it was a write, we may have to set the corresponding
 	 * bit(s) out-of-sync first. If it had a local part, we need to
 	 * release the reference to the activity log. */
@@ -188,19 +219,6 @@ void complete_master_bio(struct drbd_device *device,
 }
 
 
-static void drbd_remove_request_interval(struct rb_root *root,
-					 struct drbd_request *req)
-{
-	struct drbd_device *device = req->device;
-	struct drbd_interval *i = &req->i;
-
-	drbd_remove_interval(root, i);
-
-	/* Wake up any processes waiting for this request to complete.  */
-	if (i->waiting)
-		wake_up(&device->misc_wait);
-}
-
 /* Helper for __req_mod().
  * Set m->bio to the master bio, if it is fit to be completed,
  * or leave it alone (it is initialized to NULL in __req_mod),
@@ -254,18 +272,6 @@ void drbd_req_complete(struct drbd_request *req, struct bio_and_error *m)
 	ok = (s & RQ_LOCAL_OK) || (s & RQ_NET_OK);
 	error = PTR_ERR(req->private_bio);
 
-	/* remove the request from the conflict detection
-	 * respective block_id verification hash */
-	if (!drbd_interval_empty(&req->i)) {
-		struct rb_root *root;
-
-		if (rw == WRITE)
-			root = &device->write_requests;
-		else
-			root = &device->read_requests;
-		drbd_remove_request_interval(root, req);
-	}
-
 	/* Before we can signal completion to the upper layers,
 	 * we may need to close the current transfer log epoch.
 	 * We are within the request lock, so we can simply compare
@@ -301,9 +307,24 @@ void drbd_req_complete(struct drbd_request *req, struct bio_and_error *m)
 		m->error = ok ? 0 : (error ?: -EIO);
 		m->bio = req->master_bio;
 		req->master_bio = NULL;
+		/* We leave it in the tree, to be able to verify later
+		 * write-acks in protocol != C during resync.
+		 * But we mark it as "complete", so it won't be counted as
+		 * conflict in a multi-primary setup. */
+		req->i.completed = true;
 	}
+
+	if (req->i.waiting)
+		wake_up(&device->misc_wait);
+
+	/* Either we are about to complete to upper layers,
+	 * or we will restart this request.
+	 * In either case, the request object will be destroyed soon,
+	 * so better remove it from all lists. */
+	list_del_init(&req->req_pending_master_completion);
 }
 
+/* still holds resource->req_lock */
 static int drbd_req_put_completion_ref(struct drbd_request *req, struct bio_and_error *m, int put)
 {
 	struct drbd_device *device = req->device;
@@ -324,12 +345,91 @@ static int drbd_req_put_completion_ref(struct drbd_request *req, struct bio_and_
 	return 1;
 }
 
+static void set_if_null_req_next(struct drbd_peer_device *peer_device, struct drbd_request *req)
+{
+	struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
+	if (!connection)
+		return;
+	if (connection->req_next == NULL)
+		connection->req_next = req;
+}
+
+static void advance_conn_req_next(struct drbd_peer_device *peer_device, struct drbd_request *req)
+{
+	struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
+	if (!connection)
+		return;
+	if (connection->req_next != req)
+		return;
+	list_for_each_entry_continue(req, &connection->transfer_log, tl_requests) {
+		const unsigned s = req->rq_state;
+		if (s & RQ_NET_QUEUED)
+			break;
+	}
+	if (&req->tl_requests == &connection->transfer_log)
+		req = NULL;
+	connection->req_next = req;
+}
+
+static void set_if_null_req_ack_pending(struct drbd_peer_device *peer_device, struct drbd_request *req)
+{
+	struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
+	if (!connection)
+		return;
+	if (connection->req_ack_pending == NULL)
+		connection->req_ack_pending = req;
+}
+
+static void advance_conn_req_ack_pending(struct drbd_peer_device *peer_device, struct drbd_request *req)
+{
+	struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
+	if (!connection)
+		return;
+	if (connection->req_ack_pending != req)
+		return;
+	list_for_each_entry_continue(req, &connection->transfer_log, tl_requests) {
+		const unsigned s = req->rq_state;
+		if ((s & RQ_NET_SENT) && (s & RQ_NET_PENDING))
+			break;
+	}
+	if (&req->tl_requests == &connection->transfer_log)
+		req = NULL;
+	connection->req_ack_pending = req;
+}
+
+static void set_if_null_req_not_net_done(struct drbd_peer_device *peer_device, struct drbd_request *req)
+{
+	struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
+	if (!connection)
+		return;
+	if (connection->req_not_net_done == NULL)
+		connection->req_not_net_done = req;
+}
+
+static void advance_conn_req_not_net_done(struct drbd_peer_device *peer_device, struct drbd_request *req)
+{
+	struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
+	if (!connection)
+		return;
+	if (connection->req_not_net_done != req)
+		return;
+	list_for_each_entry_continue(req, &connection->transfer_log, tl_requests) {
+		const unsigned s = req->rq_state;
+		if ((s & RQ_NET_SENT) && !(s & RQ_NET_DONE))
+			break;
+	}
+	if (&req->tl_requests == &connection->transfer_log)
+		req = NULL;
+	connection->req_not_net_done = req;
+}
+
 /* I'd like this to be the only place that manipulates
  * req->completion_ref and req->kref. */
 static void mod_rq_state(struct drbd_request *req, struct bio_and_error *m,
 		int clear, int set)
 {
 	struct drbd_device *device = req->device;
+	struct drbd_peer_device *peer_device = first_peer_device(device);
 	unsigned s = req->rq_state;
 	int c_put = 0;
 	int k_put = 0;
@@ -356,14 +456,23 @@ static void mod_rq_state(struct drbd_request *req, struct bio_and_error *m,
 		atomic_inc(&req->completion_ref);
 	}
 
-	if (!(s & RQ_NET_QUEUED) && (set & RQ_NET_QUEUED))
+	if (!(s & RQ_NET_QUEUED) && (set & RQ_NET_QUEUED)) {
 		atomic_inc(&req->completion_ref);
+		set_if_null_req_next(peer_device, req);
+	}
 
 	if (!(s & RQ_EXP_BARR_ACK) && (set & RQ_EXP_BARR_ACK))
 		kref_get(&req->kref); /* wait for the DONE */
 
-	if (!(s & RQ_NET_SENT) && (set & RQ_NET_SENT))
-		atomic_add(req->i.size >> 9, &device->ap_in_flight);
+	if (!(s & RQ_NET_SENT) && (set & RQ_NET_SENT)) {
+		/* potentially already completed in the asender thread */
+		if (!(s & RQ_NET_DONE)) {
+			atomic_add(req->i.size >> 9, &device->ap_in_flight);
+			set_if_null_req_not_net_done(peer_device, req);
+		}
+		if (s & RQ_NET_PENDING)
+			set_if_null_req_ack_pending(peer_device, req);
+	}
 
 	if (!(s & RQ_COMPLETION_SUSP) && (set & RQ_COMPLETION_SUSP))
 		atomic_inc(&req->completion_ref);
@@ -386,20 +495,34 @@ static void mod_rq_state(struct drbd_request *req, struct bio_and_error *m,
 			++k_put;
 		else
 			++c_put;
+		list_del_init(&req->req_pending_local);
 	}
 
 	if ((s & RQ_NET_PENDING) && (clear & RQ_NET_PENDING)) {
 		dec_ap_pending(device);
 		++c_put;
+		req->acked_jif = jiffies;
+		advance_conn_req_ack_pending(peer_device, req);
 	}
 
-	if ((s & RQ_NET_QUEUED) && (clear & RQ_NET_QUEUED))
+	if ((s & RQ_NET_QUEUED) && (clear & RQ_NET_QUEUED)) {
 		++c_put;
+		advance_conn_req_next(peer_device, req);
+	}
 
-	if ((s & RQ_EXP_BARR_ACK) && !(s & RQ_NET_DONE) && (set & RQ_NET_DONE)) {
-		if (req->rq_state & RQ_NET_SENT)
+	if (!(s & RQ_NET_DONE) && (set & RQ_NET_DONE)) {
+		if (s & RQ_NET_SENT)
 			atomic_sub(req->i.size >> 9, &device->ap_in_flight);
-		++k_put;
+		if (s & RQ_EXP_BARR_ACK)
+			++k_put;
+		req->net_done_jif = jiffies;
+
+		/* in ahead/behind mode, or just in case,
+		 * before we finally destroy this request,
+		 * the caching pointers must not reference it anymore */
+		advance_conn_req_next(peer_device, req);
+		advance_conn_req_ack_pending(peer_device, req);
+		advance_conn_req_not_net_done(peer_device, req);
 	}
 
 	/* potentially complete and destroy */
@@ -439,6 +562,19 @@ static void drbd_report_io_error(struct drbd_device *device, struct drbd_request
 			bdevname(device->ldev->backing_bdev, b));
 }
 
+/* Helper for HANDED_OVER_TO_NETWORK.
+ * Is this a protocol A write (neither WRITE_ACK nor RECEIVE_ACK expected)?
+ * Is it also still "PENDING"?
+ * --> If so, clear PENDING and set NET_OK below.
+ * If it is a protocol A write, but not RQ_PENDING anymore, neg-ack was faster
+ * (and we must not set RQ_NET_OK) */
+static inline bool is_pending_write_protocol_A(struct drbd_request *req)
+{
+	return (req->rq_state &
+		   (RQ_WRITE|RQ_NET_PENDING|RQ_EXP_WRITE_ACK|RQ_EXP_RECEIVE_ACK))
+		== (RQ_WRITE|RQ_NET_PENDING);
+}
+
 /* obviously this could be coded as many single functions
  * instead of one huge switch,
  * or by putting the code directly in the respective locations
@@ -454,7 +590,9 @@ static void drbd_report_io_error(struct drbd_device *device, struct drbd_request
 int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 		struct bio_and_error *m)
 {
-	struct drbd_device *device = req->device;
+	struct drbd_device *const device = req->device;
+	struct drbd_peer_device *const peer_device = first_peer_device(device);
+	struct drbd_connection *const connection = peer_device ? peer_device->connection : NULL;
 	struct net_conf *nc;
 	int p, rv = 0;
 
@@ -477,7 +615,7 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 		 * and from w_read_retry_remote */
 		D_ASSERT(device, !(req->rq_state & RQ_NET_MASK));
 		rcu_read_lock();
-		nc = rcu_dereference(first_peer_device(device)->connection->net_conf);
+		nc = rcu_dereference(connection->net_conf);
 		p = nc->wire_protocol;
 		rcu_read_unlock();
 		req->rq_state |=
@@ -549,7 +687,7 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 		D_ASSERT(device, (req->rq_state & RQ_LOCAL_MASK) == 0);
 		mod_rq_state(req, m, 0, RQ_NET_QUEUED);
 		req->w.cb = w_send_read_req;
-		drbd_queue_work(&first_peer_device(device)->connection->sender_work,
+		drbd_queue_work(&connection->sender_work,
 				&req->w);
 		break;
 
@@ -585,23 +723,23 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 		D_ASSERT(device, req->rq_state & RQ_NET_PENDING);
 		mod_rq_state(req, m, 0, RQ_NET_QUEUED|RQ_EXP_BARR_ACK);
 		req->w.cb =  w_send_dblock;
-		drbd_queue_work(&first_peer_device(device)->connection->sender_work,
+		drbd_queue_work(&connection->sender_work,
 				&req->w);
 
 		/* close the epoch, in case it outgrew the limit */
 		rcu_read_lock();
-		nc = rcu_dereference(first_peer_device(device)->connection->net_conf);
+		nc = rcu_dereference(connection->net_conf);
 		p = nc->max_epoch_size;
 		rcu_read_unlock();
-		if (first_peer_device(device)->connection->current_tle_writes >= p)
-			start_new_tl_epoch(first_peer_device(device)->connection);
+		if (connection->current_tle_writes >= p)
+			start_new_tl_epoch(connection);
 
 		break;
 
 	case QUEUE_FOR_SEND_OOS:
 		mod_rq_state(req, m, 0, RQ_NET_QUEUED);
 		req->w.cb =  w_send_out_of_sync;
-		drbd_queue_work(&first_peer_device(device)->connection->sender_work,
+		drbd_queue_work(&connection->sender_work,
 				&req->w);
 		break;
 
@@ -615,18 +753,16 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 
 	case HANDED_OVER_TO_NETWORK:
 		/* assert something? */
-		if (bio_data_dir(req->master_bio) == WRITE &&
-		    !(req->rq_state & (RQ_EXP_RECEIVE_ACK | RQ_EXP_WRITE_ACK))) {
+		if (is_pending_write_protocol_A(req))
 			/* this is what is dangerous about protocol A:
 			 * pretend it was successfully written on the peer. */
-			if (req->rq_state & RQ_NET_PENDING)
-				mod_rq_state(req, m, RQ_NET_PENDING, RQ_NET_OK);
-			/* else: neg-ack was faster... */
-			/* it is still not yet RQ_NET_DONE until the
-			 * corresponding epoch barrier got acked as well,
-			 * so we know what to dirty on connection loss */
-		}
-		mod_rq_state(req, m, RQ_NET_QUEUED, RQ_NET_SENT);
+			mod_rq_state(req, m, RQ_NET_QUEUED|RQ_NET_PENDING,
+						RQ_NET_SENT|RQ_NET_OK);
+		else
+			mod_rq_state(req, m, RQ_NET_QUEUED, RQ_NET_SENT);
+		/* It is still not yet RQ_NET_DONE until the
+		 * corresponding epoch barrier got acked as well,
+		 * so we know what to dirty on connection loss. */
 		break;
 
 	case OOS_HANDED_TO_NETWORK:
@@ -658,12 +794,13 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 	case WRITE_ACKED_BY_PEER_AND_SIS:
 		req->rq_state |= RQ_NET_SIS;
 	case WRITE_ACKED_BY_PEER:
-		D_ASSERT(device, req->rq_state & RQ_EXP_WRITE_ACK);
-		/* protocol C; successfully written on peer.
+		/* Normal operation protocol C: successfully written on peer.
+		 * During resync, even in protocol != C,
+		 * we requested an explicit write ack anyways.
+		 * Which means we cannot even assert anything here.
 		 * Nothing more to do here.
 		 * We want to keep the tl in place for all protocols, to cater
 		 * for volatile write-back caches on lower level devices. */
-
 		goto ack_common;
 	case RECV_ACKED_BY_PEER:
 		D_ASSERT(device, req->rq_state & RQ_EXP_RECEIVE_ACK);
@@ -671,7 +808,6 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 		 * see also notes above in HANDED_OVER_TO_NETWORK about
 		 * protocol != C */
 	ack_common:
-		D_ASSERT(device, req->rq_state & RQ_NET_PENDING);
 		mod_rq_state(req, m, RQ_NET_PENDING, RQ_NET_OK);
 		break;
 
@@ -714,7 +850,7 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 
 		get_ldev(device); /* always succeeds in this call path */
 		req->w.cb = w_restart_disk_io;
-		drbd_queue_work(&first_peer_device(device)->connection->sender_work,
+		drbd_queue_work(&connection->sender_work,
 				&req->w);
 		break;
 
@@ -736,7 +872,8 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 
 			mod_rq_state(req, m, RQ_COMPLETION_SUSP, RQ_NET_QUEUED|RQ_NET_PENDING);
 			if (req->w.cb) {
-				drbd_queue_work(&first_peer_device(device)->connection->sender_work,
+				/* w.cb expected to be w_send_dblock, or w_send_read_req */
+				drbd_queue_work(&connection->sender_work,
 						&req->w);
 				rv = req->rq_state & RQ_WRITE ? MR_WRITE : MR_READ;
 			} /* else: FIXME can this happen? */
@@ -769,7 +906,7 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 		break;
 
 	case QUEUE_AS_DRBD_BARRIER:
-		start_new_tl_epoch(first_peer_device(device)->connection);
+		start_new_tl_epoch(connection);
 		mod_rq_state(req, m, 0, RQ_NET_OK|RQ_NET_DONE);
 		break;
 	};
@@ -886,6 +1023,9 @@ static void maybe_pull_ahead(struct drbd_device *device)
 	    connection->agreed_pro_version < 96)
 		return;
 
+	if (on_congestion == OC_PULL_AHEAD && device->state.conn == C_AHEAD)
+		return; /* nothing to do ... */
+
 	/* If I don't even have good local storage, we can not reasonably try
 	 * to pull ahead of the peer. We also need the local reference to make
 	 * sure device->act_log is there.
@@ -1021,6 +1161,7 @@ drbd_submit_req_private_bio(struct drbd_request *req)
 	 * stable storage, and this is a WRITE, we may not even submit
 	 * this bio. */
 	if (get_ldev(device)) {
+		req->pre_submit_jif = jiffies;
 		if (drbd_insert_fault(device,
 				      rw == WRITE ? DRBD_FAULT_DT_WR
 				    : rw == READ  ? DRBD_FAULT_DT_RD
@@ -1035,10 +1176,14 @@ drbd_submit_req_private_bio(struct drbd_request *req)
 
 static void drbd_queue_write(struct drbd_device *device, struct drbd_request *req)
 {
-	spin_lock(&device->submit.lock);
+	spin_lock_irq(&device->resource->req_lock);
 	list_add_tail(&req->tl_requests, &device->submit.writes);
-	spin_unlock(&device->submit.lock);
+	list_add_tail(&req->req_pending_master_completion,
+			&device->pending_master_completion[1 /* WRITE */]);
+	spin_unlock_irq(&device->resource->req_lock);
 	queue_work(device->submit.wq, &device->submit.worker);
+	/* do_submit() may sleep internally on al_wait, too */
+	wake_up(&device->al_wait);
 }
 
 /* returns the new drbd_request pointer, if the caller is expected to
@@ -1047,7 +1192,7 @@ static void drbd_queue_write(struct drbd_device *device, struct drbd_request *re
  * Returns ERR_PTR(-ENOMEM) if we cannot allocate a drbd_request.
  */
 static struct drbd_request *
-drbd_request_prepare(struct drbd_device *device, struct bio *bio, unsigned long start_time)
+drbd_request_prepare(struct drbd_device *device, struct bio *bio, unsigned long start_jif)
 {
 	const int rw = bio_data_dir(bio);
 	struct drbd_request *req;
@@ -1062,7 +1207,7 @@ drbd_request_prepare(struct drbd_device *device, struct bio *bio, unsigned long
 		bio_endio(bio, -ENOMEM);
 		return ERR_PTR(-ENOMEM);
 	}
-	req->start_time = start_time;
+	req->start_jif = start_jif;
 
 	if (!get_ldev(device)) {
 		bio_put(req->private_bio);
@@ -1075,10 +1220,12 @@ drbd_request_prepare(struct drbd_device *device, struct bio *bio, unsigned long
 	if (rw == WRITE && req->private_bio && req->i.size
 	&& !test_bit(AL_SUSPENDED, &device->flags)) {
 		if (!drbd_al_begin_io_fastpath(device, &req->i)) {
+			atomic_inc(&device->ap_actlog_cnt);
 			drbd_queue_write(device, req);
 			return NULL;
 		}
 		req->rq_state |= RQ_IN_ACT_LOG;
+		req->in_actlog_jif = jiffies;
 	}
 
 	return req;
@@ -1086,11 +1233,13 @@ drbd_request_prepare(struct drbd_device *device, struct bio *bio, unsigned long
 
 static void drbd_send_and_submit(struct drbd_device *device, struct drbd_request *req)
 {
+	struct drbd_resource *resource = device->resource;
 	const int rw = bio_rw(req->master_bio);
 	struct bio_and_error m = { NULL, };
 	bool no_remote = false;
+	bool submit_private_bio = false;
 
-	spin_lock_irq(&device->resource->req_lock);
+	spin_lock_irq(&resource->req_lock);
 	if (rw == WRITE) {
 		/* This may temporarily give up the req_lock,
 		 * but will re-aquire it before it returns here.
@@ -1148,13 +1297,18 @@ static void drbd_send_and_submit(struct drbd_device *device, struct drbd_request
 			no_remote = true;
 	}
 
+	/* If it took the fast path in drbd_request_prepare, add it here.
+	 * The slow path has added it already. */
+	if (list_empty(&req->req_pending_master_completion))
+		list_add_tail(&req->req_pending_master_completion,
+			&device->pending_master_completion[rw == WRITE]);
 	if (req->private_bio) {
 		/* needs to be marked within the same spinlock */
+		list_add_tail(&req->req_pending_local,
+			&device->pending_completion[rw == WRITE]);
 		_req_mod(req, TO_BE_SUBMITTED);
 		/* but we need to give up the spinlock to submit */
-		spin_unlock_irq(&device->resource->req_lock);
-		drbd_submit_req_private_bio(req);
-		spin_lock_irq(&device->resource->req_lock);
+		submit_private_bio = true;
 	} else if (no_remote) {
 nodata:
 		if (__ratelimit(&drbd_ratelimit_state))
@@ -1167,15 +1321,23 @@ nodata:
 out:
 	if (drbd_req_put_completion_ref(req, &m, 1))
 		kref_put(&req->kref, drbd_req_destroy);
-	spin_unlock_irq(&device->resource->req_lock);
-
+	spin_unlock_irq(&resource->req_lock);
+
+	/* Even though above is a kref_put(), this is safe.
+	 * As long as we still need to submit our private bio,
+	 * we hold a completion ref, and the request cannot disappear.
+	 * If however this request did not even have a private bio to submit
+	 * (e.g. remote read), req may already be invalid now.
+	 * That's why we cannot check on req->private_bio. */
+	if (submit_private_bio)
+		drbd_submit_req_private_bio(req);
 	if (m.bio)
 		complete_master_bio(device, &m);
 }
 
-void __drbd_make_request(struct drbd_device *device, struct bio *bio, unsigned long start_time)
+void __drbd_make_request(struct drbd_device *device, struct bio *bio, unsigned long start_jif)
 {
-	struct drbd_request *req = drbd_request_prepare(device, bio, start_time);
+	struct drbd_request *req = drbd_request_prepare(device, bio, start_jif);
 	if (IS_ERR_OR_NULL(req))
 		return;
 	drbd_send_and_submit(device, req);
@@ -1194,6 +1356,8 @@ static void submit_fast_path(struct drbd_device *device, struct list_head *incom
 				continue;
 
 			req->rq_state |= RQ_IN_ACT_LOG;
+			req->in_actlog_jif = jiffies;
+			atomic_dec(&device->ap_actlog_cnt);
 		}
 
 		list_del_init(&req->tl_requests);
@@ -1203,7 +1367,8 @@ static void submit_fast_path(struct drbd_device *device, struct list_head *incom
 
 static bool prepare_al_transaction_nonblock(struct drbd_device *device,
 					    struct list_head *incoming,
-					    struct list_head *pending)
+					    struct list_head *pending,
+					    struct list_head *later)
 {
 	struct drbd_request *req, *tmp;
 	int wake = 0;
@@ -1212,45 +1377,105 @@ static bool prepare_al_transaction_nonblock(struct drbd_device *device,
 	spin_lock_irq(&device->al_lock);
 	list_for_each_entry_safe(req, tmp, incoming, tl_requests) {
 		err = drbd_al_begin_io_nonblock(device, &req->i);
+		if (err == -ENOBUFS)
+			break;
 		if (err == -EBUSY)
 			wake = 1;
 		if (err)
-			continue;
-		req->rq_state |= RQ_IN_ACT_LOG;
-		list_move_tail(&req->tl_requests, pending);
+			list_move_tail(&req->tl_requests, later);
+		else
+			list_move_tail(&req->tl_requests, pending);
 	}
 	spin_unlock_irq(&device->al_lock);
 	if (wake)
 		wake_up(&device->al_wait);
-
 	return !list_empty(pending);
 }
 
+void send_and_submit_pending(struct drbd_device *device, struct list_head *pending)
+{
+	struct drbd_request *req, *tmp;
+
+	list_for_each_entry_safe(req, tmp, pending, tl_requests) {
+		req->rq_state |= RQ_IN_ACT_LOG;
+		req->in_actlog_jif = jiffies;
+		atomic_dec(&device->ap_actlog_cnt);
+		list_del_init(&req->tl_requests);
+		drbd_send_and_submit(device, req);
+	}
+}
+
 void do_submit(struct work_struct *ws)
 {
 	struct drbd_device *device = container_of(ws, struct drbd_device, submit.worker);
-	LIST_HEAD(incoming);
-	LIST_HEAD(pending);
-	struct drbd_request *req, *tmp;
+	LIST_HEAD(incoming);	/* from drbd_make_request() */
+	LIST_HEAD(pending);	/* to be submitted after next AL-transaction commit */
+	LIST_HEAD(busy);	/* blocked by resync requests */
+
+	/* grab new incoming requests */
+	spin_lock_irq(&device->resource->req_lock);
+	list_splice_tail_init(&device->submit.writes, &incoming);
+	spin_unlock_irq(&device->resource->req_lock);
 
 	for (;;) {
-		spin_lock(&device->submit.lock);
-		list_splice_tail_init(&device->submit.writes, &incoming);
-		spin_unlock(&device->submit.lock);
+		DEFINE_WAIT(wait);
 
+		/* move used-to-be-busy back to front of incoming */
+		list_splice_init(&busy, &incoming);
 		submit_fast_path(device, &incoming);
 		if (list_empty(&incoming))
 			break;
 
-skip_fast_path:
-		wait_event(device->al_wait, prepare_al_transaction_nonblock(device, &incoming, &pending));
-		/* Maybe more was queued, while we prepared the transaction?
-		 * Try to stuff them into this transaction as well.
-		 * Be strictly non-blocking here, no wait_event, we already
-		 * have something to commit.
-		 * Stop if we don't make any more progres.
-		 */
 		for (;;) {
+			prepare_to_wait(&device->al_wait, &wait, TASK_UNINTERRUPTIBLE);
+
+			list_splice_init(&busy, &incoming);
+			prepare_al_transaction_nonblock(device, &incoming, &pending, &busy);
+			if (!list_empty(&pending))
+				break;
+
+			schedule();
+
+			/* If all currently "hot" activity log extents are kept busy by
+			 * incoming requests, we still must not totally starve new
+			 * requests to "cold" extents.
+			 * Something left on &incoming means there had not been
+			 * enough update slots available, and the activity log
+			 * has been marked as "starving".
+			 *
+			 * Try again now, without looking for new requests,
+			 * effectively blocking all new requests until we made
+			 * at least _some_ progress with what we currently have.
+			 */
+			if (!list_empty(&incoming))
+				continue;
+
+			/* Nothing moved to pending, but nothing left
+			 * on incoming: all moved to busy!
+			 * Grab new and iterate. */
+			spin_lock_irq(&device->resource->req_lock);
+			list_splice_tail_init(&device->submit.writes, &incoming);
+			spin_unlock_irq(&device->resource->req_lock);
+		}
+		finish_wait(&device->al_wait, &wait);
+
+		/* If the transaction was full, before all incoming requests
+		 * had been processed, skip ahead to commit, and iterate
+		 * without splicing in more incoming requests from upper layers.
+		 *
+		 * Else, if all incoming have been processed,
+		 * they have become either "pending" (to be submitted after
+		 * next transaction commit) or "busy" (blocked by resync).
+		 *
+		 * Maybe more was queued, while we prepared the transaction?
+		 * Try to stuff those into this transaction as well.
+		 * Be strictly non-blocking here,
+		 * we already have something to commit.
+		 *
+		 * Commit if we don't make any more progres.
+		 */
+
+		while (list_empty(&incoming)) {
 			LIST_HEAD(more_pending);
 			LIST_HEAD(more_incoming);
 			bool made_progress;
@@ -1260,55 +1485,32 @@ skip_fast_path:
 			if (list_empty(&device->submit.writes))
 				break;
 
-			spin_lock(&device->submit.lock);
+			spin_lock_irq(&device->resource->req_lock);
 			list_splice_tail_init(&device->submit.writes, &more_incoming);
-			spin_unlock(&device->submit.lock);
+			spin_unlock_irq(&device->resource->req_lock);
 
 			if (list_empty(&more_incoming))
 				break;
 
-			made_progress = prepare_al_transaction_nonblock(device, &more_incoming, &more_pending);
+			made_progress = prepare_al_transaction_nonblock(device, &more_incoming, &more_pending, &busy);
 
 			list_splice_tail_init(&more_pending, &pending);
 			list_splice_tail_init(&more_incoming, &incoming);
-
 			if (!made_progress)
 				break;
 		}
-		drbd_al_begin_io_commit(device, false);
-
-		list_for_each_entry_safe(req, tmp, &pending, tl_requests) {
-			list_del_init(&req->tl_requests);
-			drbd_send_and_submit(device, req);
-		}
 
-		/* If all currently hot activity log extents are kept busy by
-		 * incoming requests, we still must not totally starve new
-		 * requests to cold extents. In that case, prepare one request
-		 * in blocking mode. */
-		list_for_each_entry_safe(req, tmp, &incoming, tl_requests) {
-			list_del_init(&req->tl_requests);
-			req->rq_state |= RQ_IN_ACT_LOG;
-			if (!drbd_al_begin_io_prepare(device, &req->i)) {
-				/* Corresponding extent was hot after all? */
-				drbd_send_and_submit(device, req);
-			} else {
-				/* Found a request to a cold extent.
-				 * Put on "pending" list,
-				 * and try to cumulate with more. */
-				list_add(&req->tl_requests, &pending);
-				goto skip_fast_path;
-			}
-		}
+		drbd_al_begin_io_commit(device);
+		send_and_submit_pending(device, &pending);
 	}
 }
 
 void drbd_make_request(struct request_queue *q, struct bio *bio)
 {
 	struct drbd_device *device = (struct drbd_device *) q->queuedata;
-	unsigned long start_time;
+	unsigned long start_jif;
 
-	start_time = jiffies;
+	start_jif = jiffies;
 
 	/*
 	 * what we "blindly" assume:
@@ -1316,7 +1518,7 @@ void drbd_make_request(struct request_queue *q, struct bio *bio)
 	D_ASSERT(device, IS_ALIGNED(bio->bi_iter.bi_size, 512));
 
 	inc_ap_bio(device);
-	__drbd_make_request(device, bio, start_time);
+	__drbd_make_request(device, bio, start_jif);
 }
 
 /* This is called by bio_add_page().
@@ -1353,36 +1555,13 @@ int drbd_merge_bvec(struct request_queue *q, struct bvec_merge_data *bvm, struct
 	return limit;
 }
 
-static void find_oldest_requests(
-		struct drbd_connection *connection,
-		struct drbd_device *device,
-		struct drbd_request **oldest_req_waiting_for_peer,
-		struct drbd_request **oldest_req_waiting_for_disk)
-{
-	struct drbd_request *r;
-	*oldest_req_waiting_for_peer = NULL;
-	*oldest_req_waiting_for_disk = NULL;
-	list_for_each_entry(r, &connection->transfer_log, tl_requests) {
-		const unsigned s = r->rq_state;
-		if (!*oldest_req_waiting_for_peer
-		&& ((s & RQ_NET_MASK) && !(s & RQ_NET_DONE)))
-			*oldest_req_waiting_for_peer = r;
-
-		if (!*oldest_req_waiting_for_disk
-		&& (s & RQ_LOCAL_PENDING) && r->device == device)
-			*oldest_req_waiting_for_disk = r;
-
-		if (*oldest_req_waiting_for_peer && *oldest_req_waiting_for_disk)
-			break;
-	}
-}
-
 void request_timer_fn(unsigned long data)
 {
 	struct drbd_device *device = (struct drbd_device *) data;
 	struct drbd_connection *connection = first_peer_device(device)->connection;
-	struct drbd_request *req_disk, *req_peer; /* oldest request */
+	struct drbd_request *req_read, *req_write, *req_peer; /* oldest request */
 	struct net_conf *nc;
+	unsigned long oldest_submit_jif;
 	unsigned long ent = 0, dt = 0, et, nt; /* effective timeout = ko_count * timeout */
 	unsigned long now;
 
@@ -1403,14 +1582,31 @@ void request_timer_fn(unsigned long data)
 		return; /* Recurring timer stopped */
 
 	now = jiffies;
+	nt = now + et;
 
 	spin_lock_irq(&device->resource->req_lock);
-	find_oldest_requests(connection, device, &req_peer, &req_disk);
-	if (req_peer == NULL && req_disk == NULL) {
-		spin_unlock_irq(&device->resource->req_lock);
-		mod_timer(&device->request_timer, now + et);
-		return;
-	}
+	req_read = list_first_entry_or_null(&device->pending_completion[0], struct drbd_request, req_pending_local);
+	req_write = list_first_entry_or_null(&device->pending_completion[1], struct drbd_request, req_pending_local);
+	req_peer = connection->req_not_net_done;
+	/* maybe the oldest request waiting for the peer is in fact still
+	 * blocking in tcp sendmsg */
+	if (!req_peer && connection->req_next && connection->req_next->pre_send_jif)
+		req_peer = connection->req_next;
+
+	/* evaluate the oldest peer request only in one timer! */
+	if (req_peer && req_peer->device != device)
+		req_peer = NULL;
+
+	/* do we have something to evaluate? */
+	if (req_peer == NULL && req_write == NULL && req_read == NULL)
+		goto out;
+
+	oldest_submit_jif =
+		(req_write && req_read)
+		? ( time_before(req_write->pre_submit_jif, req_read->pre_submit_jif)
+		  ? req_write->pre_submit_jif : req_read->pre_submit_jif )
+		: req_write ? req_write->pre_submit_jif
+		: req_read ? req_read->pre_submit_jif : now;
 
 	/* The request is considered timed out, if
 	 * - we have some effective timeout from the configuration,
@@ -1429,13 +1625,13 @@ void request_timer_fn(unsigned long data)
 	 * to expire twice (worst case) to become effective. Good enough.
 	 */
 	if (ent && req_peer &&
-		 time_after(now, req_peer->start_time + ent) &&
+		 time_after(now, req_peer->pre_send_jif + ent) &&
 		!time_in_range(now, connection->last_reconnect_jif, connection->last_reconnect_jif + ent)) {
 		drbd_warn(device, "Remote failed to finish a request within ko-count * timeout\n");
 		_drbd_set_state(_NS(device, conn, C_TIMEOUT), CS_VERBOSE | CS_HARD, NULL);
 	}
-	if (dt && req_disk &&
-		 time_after(now, req_disk->start_time + dt) &&
+	if (dt && oldest_submit_jif != now &&
+		 time_after(now, oldest_submit_jif + dt) &&
 		!time_in_range(now, device->last_reattach_jif, device->last_reattach_jif + dt)) {
 		drbd_warn(device, "Local backing device failed to meet the disk-timeout\n");
 		__drbd_chk_io_error(device, DRBD_FORCE_DETACH);
@@ -1443,11 +1639,12 @@ void request_timer_fn(unsigned long data)
 
 	/* Reschedule timer for the nearest not already expired timeout.
 	 * Fallback to now + min(effective network timeout, disk timeout). */
-	ent = (ent && req_peer && time_before(now, req_peer->start_time + ent))
-		? req_peer->start_time + ent : now + et;
-	dt = (dt && req_disk && time_before(now, req_disk->start_time + dt))
-		? req_disk->start_time + dt : now + et;
+	ent = (ent && req_peer && time_before(now, req_peer->pre_send_jif + ent))
+		? req_peer->pre_send_jif + ent : now + et;
+	dt = (dt && oldest_submit_jif != now && time_before(now, oldest_submit_jif + dt))
+		? oldest_submit_jif + dt : now + et;
 	nt = time_before(ent, dt) ? ent : dt;
+out:
 	spin_unlock_irq(&connection->resource->req_lock);
 	mod_timer(&device->request_timer, nt);
 }
diff --git a/drivers/block/drbd/drbd_req.h b/drivers/block/drbd/drbd_req.h
index 8566cd5..9f6a040 100644
--- a/drivers/block/drbd/drbd_req.h
+++ b/drivers/block/drbd/drbd_req.h
@@ -288,6 +288,7 @@ extern void complete_master_bio(struct drbd_device *device,
 extern void request_timer_fn(unsigned long data);
 extern void tl_restart(struct drbd_connection *connection, enum drbd_req_event what);
 extern void _tl_restart(struct drbd_connection *connection, enum drbd_req_event what);
+extern void tl_abort_disk_io(struct drbd_device *device);
 
 /* this is in drbd_main.c */
 extern void drbd_restart_request(struct drbd_request *req);
diff --git a/drivers/block/drbd/drbd_state.c b/drivers/block/drbd/drbd_state.c
index a5d8aae..c35c0f0 100644
--- a/drivers/block/drbd/drbd_state.c
+++ b/drivers/block/drbd/drbd_state.c
@@ -410,7 +410,7 @@ _drbd_request_state(struct drbd_device *device, union drbd_state mask,
 	return rv;
 }
 
-static void print_st(struct drbd_device *device, char *name, union drbd_state ns)
+static void print_st(struct drbd_device *device, const char *name, union drbd_state ns)
 {
 	drbd_err(device, " %s = { cs:%s ro:%s/%s ds:%s/%s %c%c%c%c%c%c }\n",
 	    name,
@@ -952,11 +952,12 @@ enum drbd_state_rv
 __drbd_set_state(struct drbd_device *device, union drbd_state ns,
 	         enum chg_state_flags flags, struct completion *done)
 {
+	struct drbd_peer_device *peer_device = first_peer_device(device);
+	struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
 	union drbd_state os;
 	enum drbd_state_rv rv = SS_SUCCESS;
 	enum sanitize_state_warnings ssw;
 	struct after_state_chg_work *ascw;
-	bool did_remote, should_do_remote;
 
 	os = drbd_read_state(device);
 
@@ -978,9 +979,9 @@ __drbd_set_state(struct drbd_device *device, union drbd_state ns,
 			   this happen...*/
 
 			if (is_valid_state(device, os) == rv)
-				rv = is_valid_soft_transition(os, ns, first_peer_device(device)->connection);
+				rv = is_valid_soft_transition(os, ns, connection);
 		} else
-			rv = is_valid_soft_transition(os, ns, first_peer_device(device)->connection);
+			rv = is_valid_soft_transition(os, ns, connection);
 	}
 
 	if (rv < SS_SUCCESS) {
@@ -997,7 +998,7 @@ __drbd_set_state(struct drbd_device *device, union drbd_state ns,
 	   sanitize_state(). Only display it here if we where not called from
 	   _conn_request_state() */
 	if (!(flags & CS_DC_SUSP))
-		conn_pr_state_change(first_peer_device(device)->connection, os, ns,
+		conn_pr_state_change(connection, os, ns,
 				     (flags & ~CS_DC_MASK) | CS_DC_SUSP);
 
 	/* if we are going -> D_FAILED or D_DISKLESS, grab one extra reference
@@ -1008,28 +1009,35 @@ __drbd_set_state(struct drbd_device *device, union drbd_state ns,
 	    (os.disk != D_DISKLESS && ns.disk == D_DISKLESS))
 		atomic_inc(&device->local_cnt);
 
-	did_remote = drbd_should_do_remote(device->state);
+	if (!is_sync_state(os.conn) && is_sync_state(ns.conn))
+		clear_bit(RS_DONE, &device->flags);
+
+	/* changes to local_cnt and device flags should be visible before
+	 * changes to state, which again should be visible before anything else
+	 * depending on that change happens. */
+	smp_wmb();
 	device->state.i = ns.i;
-	should_do_remote = drbd_should_do_remote(device->state);
 	device->resource->susp = ns.susp;
 	device->resource->susp_nod = ns.susp_nod;
 	device->resource->susp_fen = ns.susp_fen;
+	smp_wmb();
 
 	/* put replicated vs not-replicated requests in seperate epochs */
-	if (did_remote != should_do_remote)
-		start_new_tl_epoch(first_peer_device(device)->connection);
+	if (drbd_should_do_remote((union drbd_dev_state)os.i) !=
+	    drbd_should_do_remote((union drbd_dev_state)ns.i))
+		start_new_tl_epoch(connection);
 
 	if (os.disk == D_ATTACHING && ns.disk >= D_NEGOTIATING)
 		drbd_print_uuids(device, "attached to UUIDs");
 
 	/* Wake up role changes, that were delayed because of connection establishing */
 	if (os.conn == C_WF_REPORT_PARAMS && ns.conn != C_WF_REPORT_PARAMS &&
-	    no_peer_wf_report_params(first_peer_device(device)->connection))
-		clear_bit(STATE_SENT, &first_peer_device(device)->connection->flags);
+	    no_peer_wf_report_params(connection))
+		clear_bit(STATE_SENT, &connection->flags);
 
 	wake_up(&device->misc_wait);
 	wake_up(&device->state_wait);
-	wake_up(&first_peer_device(device)->connection->ping_wait);
+	wake_up(&connection->ping_wait);
 
 	/* Aborted verify run, or we reached the stop sector.
 	 * Log the last position, unless end-of-device. */
@@ -1118,21 +1126,21 @@ __drbd_set_state(struct drbd_device *device, union drbd_state ns,
 
 	/* Receiver should clean up itself */
 	if (os.conn != C_DISCONNECTING && ns.conn == C_DISCONNECTING)
-		drbd_thread_stop_nowait(&first_peer_device(device)->connection->receiver);
+		drbd_thread_stop_nowait(&connection->receiver);
 
 	/* Now the receiver finished cleaning up itself, it should die */
 	if (os.conn != C_STANDALONE && ns.conn == C_STANDALONE)
-		drbd_thread_stop_nowait(&first_peer_device(device)->connection->receiver);
+		drbd_thread_stop_nowait(&connection->receiver);
 
 	/* Upon network failure, we need to restart the receiver. */
 	if (os.conn > C_WF_CONNECTION &&
 	    ns.conn <= C_TEAR_DOWN && ns.conn >= C_TIMEOUT)
-		drbd_thread_restart_nowait(&first_peer_device(device)->connection->receiver);
+		drbd_thread_restart_nowait(&connection->receiver);
 
 	/* Resume AL writing if we get a connection */
 	if (os.conn < C_CONNECTED && ns.conn >= C_CONNECTED) {
 		drbd_resume_al(device);
-		first_peer_device(device)->connection->connect_cnt++;
+		connection->connect_cnt++;
 	}
 
 	/* remember last attach time so request_timer_fn() won't
@@ -1150,7 +1158,7 @@ __drbd_set_state(struct drbd_device *device, union drbd_state ns,
 		ascw->w.cb = w_after_state_ch;
 		ascw->device = device;
 		ascw->done = done;
-		drbd_queue_work(&first_peer_device(device)->connection->sender_work,
+		drbd_queue_work(&connection->sender_work,
 				&ascw->w);
 	} else {
 		drbd_err(device, "Could not kmalloc an ascw\n");
@@ -1222,13 +1230,16 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
 			   union drbd_state ns, enum chg_state_flags flags)
 {
 	struct drbd_resource *resource = device->resource;
+	struct drbd_peer_device *peer_device = first_peer_device(device);
+	struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
 	struct sib_info sib;
 
 	sib.sib_reason = SIB_STATE_CHANGE;
 	sib.os = os;
 	sib.ns = ns;
 
-	if (os.conn != C_CONNECTED && ns.conn == C_CONNECTED) {
+	if ((os.disk != D_UP_TO_DATE || os.pdsk != D_UP_TO_DATE)
+	&&  (ns.disk == D_UP_TO_DATE && ns.pdsk == D_UP_TO_DATE)) {
 		clear_bit(CRASHED_PRIMARY, &device->flags);
 		if (device->p_uuid)
 			device->p_uuid[UI_FLAGS] &= ~((u64)2);
@@ -1245,7 +1256,6 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
 	   state change. This function might sleep */
 
 	if (ns.susp_nod) {
-		struct drbd_connection *connection = first_peer_device(device)->connection;
 		enum drbd_req_event what = NOTHING;
 
 		spin_lock_irq(&device->resource->req_lock);
@@ -1267,8 +1277,6 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
 	}
 
 	if (ns.susp_fen) {
-		struct drbd_connection *connection = first_peer_device(device)->connection;
-
 		spin_lock_irq(&device->resource->req_lock);
 		if (resource->susp_fen && conn_lowest_conn(connection) >= C_CONNECTED) {
 			/* case2: The connection was established again: */
@@ -1294,8 +1302,8 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
 	 * which is unexpected. */
 	if ((os.conn != C_SYNC_SOURCE && os.conn != C_PAUSED_SYNC_S) &&
 	    (ns.conn == C_SYNC_SOURCE || ns.conn == C_PAUSED_SYNC_S) &&
-	    first_peer_device(device)->connection->agreed_pro_version >= 96 && get_ldev(device)) {
-		drbd_gen_and_send_sync_uuid(first_peer_device(device));
+	    connection->agreed_pro_version >= 96 && get_ldev(device)) {
+		drbd_gen_and_send_sync_uuid(peer_device);
 		put_ldev(device);
 	}
 
@@ -1309,8 +1317,8 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
 		atomic_set(&device->rs_pending_cnt, 0);
 		drbd_rs_cancel_all(device);
 
-		drbd_send_uuids(first_peer_device(device));
-		drbd_send_state(first_peer_device(device), ns);
+		drbd_send_uuids(peer_device);
+		drbd_send_state(peer_device, ns);
 	}
 	/* No point in queuing send_bitmap if we don't have a connection
 	 * anymore, so check also the _current_ state, not only the new state
@@ -1335,7 +1343,7 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
 					set_bit(NEW_CUR_UUID, &device->flags);
 				} else {
 					drbd_uuid_new_current(device);
-					drbd_send_uuids(first_peer_device(device));
+					drbd_send_uuids(peer_device);
 				}
 			}
 			put_ldev(device);
@@ -1346,7 +1354,7 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
 		if (os.peer == R_SECONDARY && ns.peer == R_PRIMARY &&
 		    device->ldev->md.uuid[UI_BITMAP] == 0 && ns.disk >= D_UP_TO_DATE) {
 			drbd_uuid_new_current(device);
-			drbd_send_uuids(first_peer_device(device));
+			drbd_send_uuids(peer_device);
 		}
 		/* D_DISKLESS Peer becomes secondary */
 		if (os.peer == R_PRIMARY && ns.peer == R_SECONDARY)
@@ -1373,16 +1381,16 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
 	/* Last part of the attaching process ... */
 	if (ns.conn >= C_CONNECTED &&
 	    os.disk == D_ATTACHING && ns.disk == D_NEGOTIATING) {
-		drbd_send_sizes(first_peer_device(device), 0, 0);  /* to start sync... */
-		drbd_send_uuids(first_peer_device(device));
-		drbd_send_state(first_peer_device(device), ns);
+		drbd_send_sizes(peer_device, 0, 0);  /* to start sync... */
+		drbd_send_uuids(peer_device);
+		drbd_send_state(peer_device, ns);
 	}
 
 	/* We want to pause/continue resync, tell peer. */
 	if (ns.conn >= C_CONNECTED &&
 	     ((os.aftr_isp != ns.aftr_isp) ||
 	      (os.user_isp != ns.user_isp)))
-		drbd_send_state(first_peer_device(device), ns);
+		drbd_send_state(peer_device, ns);
 
 	/* In case one of the isp bits got set, suspend other devices. */
 	if ((!os.aftr_isp && !os.peer_isp && !os.user_isp) &&
@@ -1392,10 +1400,10 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
 	/* Make sure the peer gets informed about eventual state
 	   changes (ISP bits) while we were in WFReportParams. */
 	if (os.conn == C_WF_REPORT_PARAMS && ns.conn >= C_CONNECTED)
-		drbd_send_state(first_peer_device(device), ns);
+		drbd_send_state(peer_device, ns);
 
 	if (os.conn != C_AHEAD && ns.conn == C_AHEAD)
-		drbd_send_state(first_peer_device(device), ns);
+		drbd_send_state(peer_device, ns);
 
 	/* We are in the progress to start a full sync... */
 	if ((os.conn != C_STARTING_SYNC_T && ns.conn == C_STARTING_SYNC_T) ||
@@ -1449,7 +1457,7 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
 					drbd_disk_str(device->state.disk));
 
 			if (ns.conn >= C_CONNECTED)
-				drbd_send_state(first_peer_device(device), ns);
+				drbd_send_state(peer_device, ns);
 
 			drbd_rs_cancel_all(device);
 
@@ -1473,7 +1481,7 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
 				 drbd_disk_str(device->state.disk));
 
 		if (ns.conn >= C_CONNECTED)
-			drbd_send_state(first_peer_device(device), ns);
+			drbd_send_state(peer_device, ns);
 		/* corresponding get_ldev in __drbd_set_state
 		 * this may finally trigger drbd_ldev_destroy. */
 		put_ldev(device);
@@ -1481,7 +1489,7 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
 
 	/* Notify peer that I had a local IO error, and did not detached.. */
 	if (os.disk == D_UP_TO_DATE && ns.disk == D_INCONSISTENT && ns.conn >= C_CONNECTED)
-		drbd_send_state(first_peer_device(device), ns);
+		drbd_send_state(peer_device, ns);
 
 	/* Disks got bigger while they were detached */
 	if (ns.disk > D_NEGOTIATING && ns.pdsk > D_NEGOTIATING &&
@@ -1499,14 +1507,14 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
 	/* sync target done with resync.  Explicitly notify peer, even though
 	 * it should (at least for non-empty resyncs) already know itself. */
 	if (os.disk < D_UP_TO_DATE && os.conn >= C_SYNC_SOURCE && ns.conn == C_CONNECTED)
-		drbd_send_state(first_peer_device(device), ns);
+		drbd_send_state(peer_device, ns);
 
 	/* Verify finished, or reached stop sector.  Peer did not know about
 	 * the stop sector, and we may even have changed the stop sector during
 	 * verify to interrupt/stop early.  Send the new state. */
 	if (os.conn == C_VERIFY_S && ns.conn == C_CONNECTED
 	&& verify_can_do_stop_sector(device))
-		drbd_send_state(first_peer_device(device), ns);
+		drbd_send_state(peer_device, ns);
 
 	/* This triggers bitmap writeout of potentially still unwritten pages
 	 * if the resync finished cleanly, or aborted because of peer disk
@@ -1563,7 +1571,7 @@ static int w_after_conn_state_ch(struct drbd_work *w, int unused)
 		old_conf = connection->net_conf;
 		connection->my_addr_len = 0;
 		connection->peer_addr_len = 0;
-		rcu_assign_pointer(connection->net_conf, NULL);
+		RCU_INIT_POINTER(connection->net_conf, NULL);
 		conn_free_crypto(connection);
 		mutex_unlock(&connection->resource->conf_update);
 
@@ -1599,7 +1607,7 @@ static int w_after_conn_state_ch(struct drbd_work *w, int unused)
 	return 0;
 }
 
-void conn_old_common_state(struct drbd_connection *connection, union drbd_state *pcs, enum chg_state_flags *pf)
+static void conn_old_common_state(struct drbd_connection *connection, union drbd_state *pcs, enum chg_state_flags *pf)
 {
 	enum chg_state_flags flags = ~0;
 	struct drbd_peer_device *peer_device;
@@ -1688,7 +1696,7 @@ conn_is_valid_transition(struct drbd_connection *connection, union drbd_state ma
 	return rv;
 }
 
-void
+static void
 conn_set_state(struct drbd_connection *connection, union drbd_state mask, union drbd_state val,
 	       union drbd_state *pns_min, union drbd_state *pns_max, enum chg_state_flags flags)
 {
diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index d8f57b6..50776b3 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -67,13 +67,10 @@ rwlock_t global_state_lock;
  */
 void drbd_md_io_complete(struct bio *bio, int error)
 {
-	struct drbd_md_io *md_io;
 	struct drbd_device *device;
 
-	md_io = (struct drbd_md_io *)bio->bi_private;
-	device = container_of(md_io, struct drbd_device, md_io);
-
-	md_io->error = error;
+	device = bio->bi_private;
+	device->md_io.error = error;
 
 	/* We grabbed an extra reference in _drbd_md_sync_page_io() to be able
 	 * to timeout on the lower level device, and eventually detach from it.
@@ -87,7 +84,7 @@ void drbd_md_io_complete(struct bio *bio, int error)
 	 * ASSERT(atomic_read(&device->md_io_in_use) == 1) there.
 	 */
 	drbd_md_put_buffer(device);
-	md_io->done = 1;
+	device->md_io.done = 1;
 	wake_up(&device->misc_wait);
 	bio_put(bio);
 	if (device->ldev) /* special case: drbd_md_read() during drbd_adm_attach() */
@@ -135,6 +132,7 @@ void drbd_endio_write_sec_final(struct drbd_peer_request *peer_req) __releases(l
 	i = peer_req->i;
 	do_al_complete_io = peer_req->flags & EE_CALL_AL_COMPLETE_IO;
 	block_id = peer_req->block_id;
+	peer_req->flags &= ~EE_CALL_AL_COMPLETE_IO;
 
 	spin_lock_irqsave(&device->resource->req_lock, flags);
 	device->writ_cnt += peer_req->i.size >> 9;
@@ -398,9 +396,6 @@ static int read_for_csum(struct drbd_peer_device *peer_device, sector_t sector,
 	if (!get_ldev(device))
 		return -EIO;
 
-	if (drbd_rs_should_slow_down(device, sector))
-		goto defer;
-
 	/* GFP_TRY, because if there is no memory available right now, this may
 	 * be rescheduled for later. It is "only" background resync, after all. */
 	peer_req = drbd_alloc_peer_req(peer_device, ID_SYNCER /* unused */, sector,
@@ -410,7 +405,7 @@ static int read_for_csum(struct drbd_peer_device *peer_device, sector_t sector,
 
 	peer_req->w.cb = w_e_send_csum;
 	spin_lock_irq(&device->resource->req_lock);
-	list_add(&peer_req->w.list, &device->read_ee);
+	list_add_tail(&peer_req->w.list, &device->read_ee);
 	spin_unlock_irq(&device->resource->req_lock);
 
 	atomic_add(size >> 9, &device->rs_sect_ev);
@@ -452,9 +447,9 @@ void resync_timer_fn(unsigned long data)
 {
 	struct drbd_device *device = (struct drbd_device *) data;
 
-	if (list_empty(&device->resync_work.list))
-		drbd_queue_work(&first_peer_device(device)->connection->sender_work,
-				&device->resync_work);
+	drbd_queue_work_if_unqueued(
+		&first_peer_device(device)->connection->sender_work,
+		&device->resync_work);
 }
 
 static void fifo_set(struct fifo_buffer *fb, int value)
@@ -504,9 +499,9 @@ struct fifo_buffer *fifo_alloc(int fifo_size)
 static int drbd_rs_controller(struct drbd_device *device, unsigned int sect_in)
 {
 	struct disk_conf *dc;
-	unsigned int want;     /* The number of sectors we want in the proxy */
+	unsigned int want;     /* The number of sectors we want in-flight */
 	int req_sect; /* Number of sectors to request in this turn */
-	int correction; /* Number of sectors more we need in the proxy*/
+	int correction; /* Number of sectors more we need in-flight */
 	int cps; /* correction per invocation of drbd_rs_controller() */
 	int steps; /* Number of time steps to plan ahead */
 	int curr_corr;
@@ -577,20 +572,27 @@ static int drbd_rs_number_requests(struct drbd_device *device)
 	 * potentially causing a distributed deadlock on congestion during
 	 * online-verify or (checksum-based) resync, if max-buffers,
 	 * socket buffer sizes and resync rate settings are mis-configured. */
-	if (mxb - device->rs_in_flight < number)
-		number = mxb - device->rs_in_flight;
+
+	/* note that "number" is in units of "BM_BLOCK_SIZE" (which is 4k),
+	 * mxb (as used here, and in drbd_alloc_pages on the peer) is
+	 * "number of pages" (typically also 4k),
+	 * but "rs_in_flight" is in "sectors" (512 Byte). */
+	if (mxb - device->rs_in_flight/8 < number)
+		number = mxb - device->rs_in_flight/8;
 
 	return number;
 }
 
-static int make_resync_request(struct drbd_device *device, int cancel)
+static int make_resync_request(struct drbd_device *const device, int cancel)
 {
+	struct drbd_peer_device *const peer_device = first_peer_device(device);
+	struct drbd_connection *const connection = peer_device ? peer_device->connection : NULL;
 	unsigned long bit;
 	sector_t sector;
 	const sector_t capacity = drbd_get_capacity(device->this_bdev);
 	int max_bio_size;
 	int number, rollback_i, size;
-	int align, queued, sndbuf;
+	int align, requeue = 0;
 	int i = 0;
 
 	if (unlikely(cancel))
@@ -617,17 +619,22 @@ static int make_resync_request(struct drbd_device *device, int cancel)
 		goto requeue;
 
 	for (i = 0; i < number; i++) {
-		/* Stop generating RS requests, when half of the send buffer is filled */
-		mutex_lock(&first_peer_device(device)->connection->data.mutex);
-		if (first_peer_device(device)->connection->data.socket) {
-			queued = first_peer_device(device)->connection->data.socket->sk->sk_wmem_queued;
-			sndbuf = first_peer_device(device)->connection->data.socket->sk->sk_sndbuf;
-		} else {
-			queued = 1;
-			sndbuf = 0;
-		}
-		mutex_unlock(&first_peer_device(device)->connection->data.mutex);
-		if (queued > sndbuf / 2)
+		/* Stop generating RS requests when half of the send buffer is filled,
+		 * but notify TCP that we'd like to have more space. */
+		mutex_lock(&connection->data.mutex);
+		if (connection->data.socket) {
+			struct sock *sk = connection->data.socket->sk;
+			int queued = sk->sk_wmem_queued;
+			int sndbuf = sk->sk_sndbuf;
+			if (queued > sndbuf / 2) {
+				requeue = 1;
+				if (sk->sk_socket)
+					set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
+			}
+		} else
+			requeue = 1;
+		mutex_unlock(&connection->data.mutex);
+		if (requeue)
 			goto requeue;
 
 next_sector:
@@ -642,8 +649,7 @@ next_sector:
 
 		sector = BM_BIT_TO_SECT(bit);
 
-		if (drbd_rs_should_slow_down(device, sector) ||
-		    drbd_try_rs_begin_io(device, sector)) {
+		if (drbd_try_rs_begin_io(device, sector)) {
 			device->bm_resync_fo = bit;
 			goto requeue;
 		}
@@ -696,9 +702,9 @@ next_sector:
 		/* adjust very last sectors, in case we are oddly sized */
 		if (sector + (size>>9) > capacity)
 			size = (capacity-sector)<<9;
-		if (first_peer_device(device)->connection->agreed_pro_version >= 89 &&
-		    first_peer_device(device)->connection->csums_tfm) {
-			switch (read_for_csum(first_peer_device(device), sector, size)) {
+
+		if (device->use_csums) {
+			switch (read_for_csum(peer_device, sector, size)) {
 			case -EIO: /* Disk failure */
 				put_ldev(device);
 				return -EIO;
@@ -717,7 +723,7 @@ next_sector:
 			int err;
 
 			inc_rs_pending(device);
-			err = drbd_send_drequest(first_peer_device(device), P_RS_DATA_REQUEST,
+			err = drbd_send_drequest(peer_device, P_RS_DATA_REQUEST,
 						 sector, size, ID_SYNCER);
 			if (err) {
 				drbd_err(device, "drbd_send_drequest() failed, aborting...\n");
@@ -774,8 +780,7 @@ static int make_ov_request(struct drbd_device *device, int cancel)
 
 		size = BM_BLOCK_SIZE;
 
-		if (drbd_rs_should_slow_down(device, sector) ||
-		    drbd_try_rs_begin_io(device, sector)) {
+		if (drbd_try_rs_begin_io(device, sector)) {
 			device->ov_position = sector;
 			goto requeue;
 		}
@@ -911,7 +916,7 @@ int drbd_resync_finished(struct drbd_device *device)
 		if (os.conn == C_SYNC_TARGET || os.conn == C_PAUSED_SYNC_T)
 			khelper_cmd = "after-resync-target";
 
-		if (first_peer_device(device)->connection->csums_tfm && device->rs_total) {
+		if (device->use_csums && device->rs_total) {
 			const unsigned long s = device->rs_same_csum;
 			const unsigned long t = device->rs_total;
 			const int ratio =
@@ -1351,13 +1356,15 @@ int w_send_out_of_sync(struct drbd_work *w, int cancel)
 {
 	struct drbd_request *req = container_of(w, struct drbd_request, w);
 	struct drbd_device *device = req->device;
-	struct drbd_connection *connection = first_peer_device(device)->connection;
+	struct drbd_peer_device *const peer_device = first_peer_device(device);
+	struct drbd_connection *const connection = peer_device->connection;
 	int err;
 
 	if (unlikely(cancel)) {
 		req_mod(req, SEND_CANCELED);
 		return 0;
 	}
+	req->pre_send_jif = jiffies;
 
 	/* this time, no connection->send.current_epoch_writes++;
 	 * If it was sent, it was the closing barrier for the last
@@ -1365,7 +1372,7 @@ int w_send_out_of_sync(struct drbd_work *w, int cancel)
 	 * No more barriers will be sent, until we leave AHEAD mode again. */
 	maybe_send_barrier(connection, req->epoch);
 
-	err = drbd_send_out_of_sync(first_peer_device(device), req);
+	err = drbd_send_out_of_sync(peer_device, req);
 	req_mod(req, OOS_HANDED_TO_NETWORK);
 
 	return err;
@@ -1380,19 +1387,21 @@ int w_send_dblock(struct drbd_work *w, int cancel)
 {
 	struct drbd_request *req = container_of(w, struct drbd_request, w);
 	struct drbd_device *device = req->device;
-	struct drbd_connection *connection = first_peer_device(device)->connection;
+	struct drbd_peer_device *const peer_device = first_peer_device(device);
+	struct drbd_connection *connection = peer_device->connection;
 	int err;
 
 	if (unlikely(cancel)) {
 		req_mod(req, SEND_CANCELED);
 		return 0;
 	}
+	req->pre_send_jif = jiffies;
 
 	re_init_if_first_write(connection, req->epoch);
 	maybe_send_barrier(connection, req->epoch);
 	connection->send.current_epoch_writes++;
 
-	err = drbd_send_dblock(first_peer_device(device), req);
+	err = drbd_send_dblock(peer_device, req);
 	req_mod(req, err ? SEND_FAILED : HANDED_OVER_TO_NETWORK);
 
 	return err;
@@ -1407,19 +1416,21 @@ int w_send_read_req(struct drbd_work *w, int cancel)
 {
 	struct drbd_request *req = container_of(w, struct drbd_request, w);
 	struct drbd_device *device = req->device;
-	struct drbd_connection *connection = first_peer_device(device)->connection;
+	struct drbd_peer_device *const peer_device = first_peer_device(device);
+	struct drbd_connection *connection = peer_device->connection;
 	int err;
 
 	if (unlikely(cancel)) {
 		req_mod(req, SEND_CANCELED);
 		return 0;
 	}
+	req->pre_send_jif = jiffies;
 
 	/* Even read requests may close a write epoch,
 	 * if there was any yet. */
 	maybe_send_barrier(connection, req->epoch);
 
-	err = drbd_send_drequest(first_peer_device(device), P_DATA_REQUEST, req->i.sector, req->i.size,
+	err = drbd_send_drequest(peer_device, P_DATA_REQUEST, req->i.sector, req->i.size,
 				 (unsigned long)req);
 
 	req_mod(req, err ? SEND_FAILED : HANDED_OVER_TO_NETWORK);
@@ -1433,7 +1444,7 @@ int w_restart_disk_io(struct drbd_work *w, int cancel)
 	struct drbd_device *device = req->device;
 
 	if (bio_data_dir(req->master_bio) == WRITE && req->rq_state & RQ_IN_ACT_LOG)
-		drbd_al_begin_io(device, &req->i, false);
+		drbd_al_begin_io(device, &req->i);
 
 	drbd_req_make_private_bio(req, req->master_bio);
 	req->private_bio->bi_bdev = device->ldev->backing_bdev;
@@ -1601,26 +1612,32 @@ void drbd_rs_controller_reset(struct drbd_device *device)
 void start_resync_timer_fn(unsigned long data)
 {
 	struct drbd_device *device = (struct drbd_device *) data;
-
-	drbd_queue_work(&first_peer_device(device)->connection->sender_work,
-			&device->start_resync_work);
+	drbd_device_post_work(device, RS_START);
 }
 
-int w_start_resync(struct drbd_work *w, int cancel)
+static void do_start_resync(struct drbd_device *device)
 {
-	struct drbd_device *device =
-		container_of(w, struct drbd_device, start_resync_work);
-
 	if (atomic_read(&device->unacked_cnt) || atomic_read(&device->rs_pending_cnt)) {
-		drbd_warn(device, "w_start_resync later...\n");
+		drbd_warn(device, "postponing start_resync ...\n");
 		device->start_resync_timer.expires = jiffies + HZ/10;
 		add_timer(&device->start_resync_timer);
-		return 0;
+		return;
 	}
 
 	drbd_start_resync(device, C_SYNC_SOURCE);
 	clear_bit(AHEAD_TO_SYNC_SOURCE, &device->flags);
-	return 0;
+}
+
+static bool use_checksum_based_resync(struct drbd_connection *connection, struct drbd_device *device)
+{
+	bool csums_after_crash_only;
+	rcu_read_lock();
+	csums_after_crash_only = rcu_dereference(connection->net_conf)->csums_after_crash_only;
+	rcu_read_unlock();
+	return connection->agreed_pro_version >= 89 &&		/* supported? */
+		connection->csums_tfm &&			/* configured? */
+		(csums_after_crash_only == 0			/* use for each resync? */
+		 || test_bit(CRASHED_PRIMARY, &device->flags));	/* or only after Primary crash? */
 }
 
 /**
@@ -1633,6 +1650,8 @@ int w_start_resync(struct drbd_work *w, int cancel)
  */
 void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
 {
+	struct drbd_peer_device *peer_device = first_peer_device(device);
+	struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
 	union drbd_state ns;
 	int r;
 
@@ -1651,7 +1670,7 @@ void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
 			if (r > 0) {
 				drbd_info(device, "before-resync-target handler returned %d, "
 					 "dropping connection.\n", r);
-				conn_request_state(first_peer_device(device)->connection, NS(conn, C_DISCONNECTING), CS_HARD);
+				conn_request_state(connection, NS(conn, C_DISCONNECTING), CS_HARD);
 				return;
 			}
 		} else /* C_SYNC_SOURCE */ {
@@ -1664,7 +1683,7 @@ void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
 				} else {
 					drbd_info(device, "before-resync-source handler returned %d, "
 						 "dropping connection.\n", r);
-					conn_request_state(first_peer_device(device)->connection,
+					conn_request_state(connection,
 							   NS(conn, C_DISCONNECTING), CS_HARD);
 					return;
 				}
@@ -1672,7 +1691,7 @@ void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
 		}
 	}
 
-	if (current == first_peer_device(device)->connection->worker.task) {
+	if (current == connection->worker.task) {
 		/* The worker should not sleep waiting for state_mutex,
 		   that can take long */
 		if (!mutex_trylock(device->state_mutex)) {
@@ -1733,11 +1752,20 @@ void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
 			device->rs_mark_time[i] = now;
 		}
 		_drbd_pause_after(device);
+		/* Forget potentially stale cached per resync extent bit-counts.
+		 * Open coded drbd_rs_cancel_all(device), we already have IRQs
+		 * disabled, and know the disk state is ok. */
+		spin_lock(&device->al_lock);
+		lc_reset(device->resync);
+		device->resync_locked = 0;
+		device->resync_wenr = LC_FREE;
+		spin_unlock(&device->al_lock);
 	}
 	write_unlock(&global_state_lock);
 	spin_unlock_irq(&device->resource->req_lock);
 
 	if (r == SS_SUCCESS) {
+		wake_up(&device->al_wait); /* for lc_reset() above */
 		/* reset rs_last_bcast when a resync or verify is started,
 		 * to deal with potential jiffies wrap. */
 		device->rs_last_bcast = jiffies - HZ;
@@ -1746,8 +1774,12 @@ void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
 		     drbd_conn_str(ns.conn),
 		     (unsigned long) device->rs_total << (BM_BLOCK_SHIFT-10),
 		     (unsigned long) device->rs_total);
-		if (side == C_SYNC_TARGET)
+		if (side == C_SYNC_TARGET) {
 			device->bm_resync_fo = 0;
+			device->use_csums = use_checksum_based_resync(connection, device);
+		} else {
+			device->use_csums = 0;
+		}
 
 		/* Since protocol 96, we must serialize drbd_gen_and_send_sync_uuid
 		 * with w_send_oos, or the sync target will get confused as to
@@ -1756,12 +1788,10 @@ void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
 		 * drbd_resync_finished from here in that case.
 		 * We drbd_gen_and_send_sync_uuid here for protocol < 96,
 		 * and from after_state_ch otherwise. */
-		if (side == C_SYNC_SOURCE &&
-		    first_peer_device(device)->connection->agreed_pro_version < 96)
-			drbd_gen_and_send_sync_uuid(first_peer_device(device));
+		if (side == C_SYNC_SOURCE && connection->agreed_pro_version < 96)
+			drbd_gen_and_send_sync_uuid(peer_device);
 
-		if (first_peer_device(device)->connection->agreed_pro_version < 95 &&
-		    device->rs_total == 0) {
+		if (connection->agreed_pro_version < 95 && device->rs_total == 0) {
 			/* This still has a race (about when exactly the peers
 			 * detect connection loss) that can lead to a full sync
 			 * on next handshake. In 8.3.9 we fixed this with explicit
@@ -1777,7 +1807,7 @@ void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
 				int timeo;
 
 				rcu_read_lock();
-				nc = rcu_dereference(first_peer_device(device)->connection->net_conf);
+				nc = rcu_dereference(connection->net_conf);
 				timeo = nc->ping_int * HZ + nc->ping_timeo * HZ / 9;
 				rcu_read_unlock();
 				schedule_timeout_interruptible(timeo);
@@ -1799,10 +1829,165 @@ void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
 	mutex_unlock(device->state_mutex);
 }
 
+static void update_on_disk_bitmap(struct drbd_device *device, bool resync_done)
+{
+	struct sib_info sib = { .sib_reason = SIB_SYNC_PROGRESS, };
+	device->rs_last_bcast = jiffies;
+
+	if (!get_ldev(device))
+		return;
+
+	drbd_bm_write_lazy(device, 0);
+	if (resync_done && is_sync_state(device->state.conn))
+		drbd_resync_finished(device);
+
+	drbd_bcast_event(device, &sib);
+	/* update timestamp, in case it took a while to write out stuff */
+	device->rs_last_bcast = jiffies;
+	put_ldev(device);
+}
+
+static void drbd_ldev_destroy(struct drbd_device *device)
+{
+	lc_destroy(device->resync);
+	device->resync = NULL;
+	lc_destroy(device->act_log);
+	device->act_log = NULL;
+	__no_warn(local,
+		drbd_free_ldev(device->ldev);
+		device->ldev = NULL;);
+	clear_bit(GOING_DISKLESS, &device->flags);
+	wake_up(&device->misc_wait);
+}
+
+static void go_diskless(struct drbd_device *device)
+{
+	D_ASSERT(device, device->state.disk == D_FAILED);
+	/* we cannot assert local_cnt == 0 here, as get_ldev_if_state will
+	 * inc/dec it frequently. Once we are D_DISKLESS, no one will touch
+	 * the protected members anymore, though, so once put_ldev reaches zero
+	 * again, it will be safe to free them. */
+
+	/* Try to write changed bitmap pages, read errors may have just
+	 * set some bits outside the area covered by the activity log.
+	 *
+	 * If we have an IO error during the bitmap writeout,
+	 * we will want a full sync next time, just in case.
+	 * (Do we want a specific meta data flag for this?)
+	 *
+	 * If that does not make it to stable storage either,
+	 * we cannot do anything about that anymore.
+	 *
+	 * We still need to check if both bitmap and ldev are present, we may
+	 * end up here after a failed attach, before ldev was even assigned.
+	 */
+	if (device->bitmap && device->ldev) {
+		/* An interrupted resync or similar is allowed to recounts bits
+		 * while we detach.
+		 * Any modifications would not be expected anymore, though.
+		 */
+		if (drbd_bitmap_io_from_worker(device, drbd_bm_write,
+					"detach", BM_LOCKED_TEST_ALLOWED)) {
+			if (test_bit(WAS_READ_ERROR, &device->flags)) {
+				drbd_md_set_flag(device, MDF_FULL_SYNC);
+				drbd_md_sync(device);
+			}
+		}
+	}
+
+	drbd_force_state(device, NS(disk, D_DISKLESS));
+}
+
+static int do_md_sync(struct drbd_device *device)
+{
+	drbd_warn(device, "md_sync_timer expired! Worker calls drbd_md_sync().\n");
+	drbd_md_sync(device);
+	return 0;
+}
+
+/* only called from drbd_worker thread, no locking */
+void __update_timing_details(
+		struct drbd_thread_timing_details *tdp,
+		unsigned int *cb_nr,
+		void *cb,
+		const char *fn, const unsigned int line)
+{
+	unsigned int i = *cb_nr % DRBD_THREAD_DETAILS_HIST;
+	struct drbd_thread_timing_details *td = tdp + i;
+
+	td->start_jif = jiffies;
+	td->cb_addr = cb;
+	td->caller_fn = fn;
+	td->line = line;
+	td->cb_nr = *cb_nr;
+
+	i = (i+1) % DRBD_THREAD_DETAILS_HIST;
+	td = tdp + i;
+	memset(td, 0, sizeof(*td));
+
+	++(*cb_nr);
+}
+
+#define WORK_PENDING(work_bit, todo)	(todo & (1UL << work_bit))
+static void do_device_work(struct drbd_device *device, const unsigned long todo)
+{
+	if (WORK_PENDING(MD_SYNC, todo))
+		do_md_sync(device);
+	if (WORK_PENDING(RS_DONE, todo) ||
+	    WORK_PENDING(RS_PROGRESS, todo))
+		update_on_disk_bitmap(device, WORK_PENDING(RS_DONE, todo));
+	if (WORK_PENDING(GO_DISKLESS, todo))
+		go_diskless(device);
+	if (WORK_PENDING(DESTROY_DISK, todo))
+		drbd_ldev_destroy(device);
+	if (WORK_PENDING(RS_START, todo))
+		do_start_resync(device);
+}
+
+#define DRBD_DEVICE_WORK_MASK	\
+	((1UL << GO_DISKLESS)	\
+	|(1UL << DESTROY_DISK)	\
+	|(1UL << MD_SYNC)	\
+	|(1UL << RS_START)	\
+	|(1UL << RS_PROGRESS)	\
+	|(1UL << RS_DONE)	\
+	)
+
+static unsigned long get_work_bits(unsigned long *flags)
+{
+	unsigned long old, new;
+	do {
+		old = *flags;
+		new = old & ~DRBD_DEVICE_WORK_MASK;
+	} while (cmpxchg(flags, old, new) != old);
+	return old & DRBD_DEVICE_WORK_MASK;
+}
+
+static void do_unqueued_work(struct drbd_connection *connection)
+{
+	struct drbd_peer_device *peer_device;
+	int vnr;
+
+	rcu_read_lock();
+	idr_for_each_entry(&connection->peer_devices, peer_device, vnr) {
+		struct drbd_device *device = peer_device->device;
+		unsigned long todo = get_work_bits(&device->flags);
+		if (!todo)
+			continue;
+
+		kref_get(&device->kref);
+		rcu_read_unlock();
+		do_device_work(device, todo);
+		kref_put(&device->kref, drbd_destroy_device);
+		rcu_read_lock();
+	}
+	rcu_read_unlock();
+}
+
 static bool dequeue_work_batch(struct drbd_work_queue *queue, struct list_head *work_list)
 {
 	spin_lock_irq(&queue->q_lock);
-	list_splice_init(&queue->q, work_list);
+	list_splice_tail_init(&queue->q, work_list);
 	spin_unlock_irq(&queue->q_lock);
 	return !list_empty(work_list);
 }
@@ -1851,7 +2036,7 @@ static void wait_for_work(struct drbd_connection *connection, struct list_head *
 		/* dequeue single item only,
 		 * we still use drbd_queue_work_front() in some places */
 		if (!list_empty(&connection->sender_work.q))
-			list_move(connection->sender_work.q.next, work_list);
+			list_splice_tail_init(&connection->sender_work.q, work_list);
 		spin_unlock(&connection->sender_work.q_lock);	/* FIXME get rid of this one? */
 		if (!list_empty(work_list) || signal_pending(current)) {
 			spin_unlock_irq(&connection->resource->req_lock);
@@ -1873,6 +2058,14 @@ static void wait_for_work(struct drbd_connection *connection, struct list_head *
 		if (send_barrier)
 			maybe_send_barrier(connection,
 					connection->send.current_epoch_nr + 1);
+
+		if (test_bit(DEVICE_WORK_PENDING, &connection->flags))
+			break;
+
+		/* drbd_send() may have called flush_signals() */
+		if (get_t_state(&connection->worker) != RUNNING)
+			break;
+
 		schedule();
 		/* may be woken up for other things but new work, too,
 		 * e.g. if the current epoch got closed.
@@ -1906,10 +2099,15 @@ int drbd_worker(struct drbd_thread *thi)
 	while (get_t_state(thi) == RUNNING) {
 		drbd_thread_current_set_cpu(thi);
 
-		/* as long as we use drbd_queue_work_front(),
-		 * we may only dequeue single work items here, not batches. */
-		if (list_empty(&work_list))
+		if (list_empty(&work_list)) {
+			update_worker_timing_details(connection, wait_for_work);
 			wait_for_work(connection, &work_list);
+		}
+
+		if (test_and_clear_bit(DEVICE_WORK_PENDING, &connection->flags)) {
+			update_worker_timing_details(connection, do_unqueued_work);
+			do_unqueued_work(connection);
+		}
 
 		if (signal_pending(current)) {
 			flush_signals(current);
@@ -1926,6 +2124,7 @@ int drbd_worker(struct drbd_thread *thi)
 		while (!list_empty(&work_list)) {
 			w = list_first_entry(&work_list, struct drbd_work, list);
 			list_del_init(&w->list);
+			update_worker_timing_details(connection, w->cb);
 			if (w->cb(w, connection->cstate < C_WF_REPORT_PARAMS) == 0)
 				continue;
 			if (connection->cstate >= C_WF_REPORT_PARAMS)
@@ -1934,13 +2133,18 @@ int drbd_worker(struct drbd_thread *thi)
 	}
 
 	do {
+		if (test_and_clear_bit(DEVICE_WORK_PENDING, &connection->flags)) {
+			update_worker_timing_details(connection, do_unqueued_work);
+			do_unqueued_work(connection);
+		}
 		while (!list_empty(&work_list)) {
 			w = list_first_entry(&work_list, struct drbd_work, list);
 			list_del_init(&w->list);
+			update_worker_timing_details(connection, w->cb);
 			w->cb(w, 1);
 		}
 		dequeue_work_batch(&connection->sender_work, &work_list);
-	} while (!list_empty(&work_list));
+	} while (!list_empty(&work_list) || test_bit(DEVICE_WORK_PENDING, &connection->flags));
 
 	rcu_read_lock();
 	idr_for_each_entry(&connection->peer_devices, peer_device, vnr) {
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index f63d358..0a58140 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -15,17 +15,22 @@
 #include <linux/numa.h>
 
 #define PART_BITS 4
+#define VQ_NAME_LEN 16
 
 static int major;
 static DEFINE_IDA(vd_index_ida);
 
 static struct workqueue_struct *virtblk_wq;
 
+struct virtio_blk_vq {
+	struct virtqueue *vq;
+	spinlock_t lock;
+	char name[VQ_NAME_LEN];
+} ____cacheline_aligned_in_smp;
+
 struct virtio_blk
 {
 	struct virtio_device *vdev;
-	struct virtqueue *vq;
-	spinlock_t vq_lock;
 
 	/* The disk structure for the kernel. */
 	struct gendisk *disk;
@@ -47,6 +52,10 @@ struct virtio_blk
 
 	/* Ida index - used to track minor number allocations. */
 	int index;
+
+	/* num of vqs */
+	int num_vqs;
+	struct virtio_blk_vq *vqs;
 };
 
 struct virtblk_req
@@ -133,14 +142,15 @@ static void virtblk_done(struct virtqueue *vq)
 {
 	struct virtio_blk *vblk = vq->vdev->priv;
 	bool req_done = false;
+	int qid = vq->index;
 	struct virtblk_req *vbr;
 	unsigned long flags;
 	unsigned int len;
 
-	spin_lock_irqsave(&vblk->vq_lock, flags);
+	spin_lock_irqsave(&vblk->vqs[qid].lock, flags);
 	do {
 		virtqueue_disable_cb(vq);
-		while ((vbr = virtqueue_get_buf(vblk->vq, &len)) != NULL) {
+		while ((vbr = virtqueue_get_buf(vblk->vqs[qid].vq, &len)) != NULL) {
 			blk_mq_complete_request(vbr->req);
 			req_done = true;
 		}
@@ -151,7 +161,7 @@ static void virtblk_done(struct virtqueue *vq)
 	/* In case queue is stopped waiting for more buffers. */
 	if (req_done)
 		blk_mq_start_stopped_hw_queues(vblk->disk->queue, true);
-	spin_unlock_irqrestore(&vblk->vq_lock, flags);
+	spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags);
 }
 
 static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
@@ -160,6 +170,7 @@ static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
 	struct virtblk_req *vbr = blk_mq_rq_to_pdu(req);
 	unsigned long flags;
 	unsigned int num;
+	int qid = hctx->queue_num;
 	const bool last = (req->cmd_flags & REQ_END) != 0;
 	int err;
 	bool notify = false;
@@ -202,12 +213,12 @@ static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
 			vbr->out_hdr.type |= VIRTIO_BLK_T_IN;
 	}
 
-	spin_lock_irqsave(&vblk->vq_lock, flags);
-	err = __virtblk_add_req(vblk->vq, vbr, vbr->sg, num);
+	spin_lock_irqsave(&vblk->vqs[qid].lock, flags);
+	err = __virtblk_add_req(vblk->vqs[qid].vq, vbr, vbr->sg, num);
 	if (err) {
-		virtqueue_kick(vblk->vq);
+		virtqueue_kick(vblk->vqs[qid].vq);
 		blk_mq_stop_hw_queue(hctx);
-		spin_unlock_irqrestore(&vblk->vq_lock, flags);
+		spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags);
 		/* Out of mem doesn't actually happen, since we fall back
 		 * to direct descriptors */
 		if (err == -ENOMEM || err == -ENOSPC)
@@ -215,12 +226,12 @@ static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
 		return BLK_MQ_RQ_QUEUE_ERROR;
 	}
 
-	if (last && virtqueue_kick_prepare(vblk->vq))
+	if (last && virtqueue_kick_prepare(vblk->vqs[qid].vq))
 		notify = true;
-	spin_unlock_irqrestore(&vblk->vq_lock, flags);
+	spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags);
 
 	if (notify)
-		virtqueue_notify(vblk->vq);
+		virtqueue_notify(vblk->vqs[qid].vq);
 	return BLK_MQ_RQ_QUEUE_OK;
 }
 
@@ -377,12 +388,64 @@ static void virtblk_config_changed(struct virtio_device *vdev)
 static int init_vq(struct virtio_blk *vblk)
 {
 	int err = 0;
+	int i;
+	vq_callback_t **callbacks;
+	const char **names;
+	struct virtqueue **vqs;
+	unsigned short num_vqs;
+	struct virtio_device *vdev = vblk->vdev;
+
+	err = virtio_cread_feature(vdev, VIRTIO_BLK_F_MQ,
+				   struct virtio_blk_config, num_queues,
+				   &num_vqs);
+	if (err)
+		num_vqs = 1;
+
+	vblk->vqs = kmalloc(sizeof(*vblk->vqs) * num_vqs, GFP_KERNEL);
+	if (!vblk->vqs) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	names = kmalloc(sizeof(*names) * num_vqs, GFP_KERNEL);
+	if (!names)
+		goto err_names;
+
+	callbacks = kmalloc(sizeof(*callbacks) * num_vqs, GFP_KERNEL);
+	if (!callbacks)
+		goto err_callbacks;
+
+	vqs = kmalloc(sizeof(*vqs) * num_vqs, GFP_KERNEL);
+	if (!vqs)
+		goto err_vqs;
 
-	/* We expect one virtqueue, for output. */
-	vblk->vq = virtio_find_single_vq(vblk->vdev, virtblk_done, "requests");
-	if (IS_ERR(vblk->vq))
-		err = PTR_ERR(vblk->vq);
+	for (i = 0; i < num_vqs; i++) {
+		callbacks[i] = virtblk_done;
+		snprintf(vblk->vqs[i].name, VQ_NAME_LEN, "req.%d", i);
+		names[i] = vblk->vqs[i].name;
+	}
+
+	/* Discover virtqueues and write information to configuration.  */
+	err = vdev->config->find_vqs(vdev, num_vqs, vqs, callbacks, names);
+	if (err)
+		goto err_find_vqs;
 
+	for (i = 0; i < num_vqs; i++) {
+		spin_lock_init(&vblk->vqs[i].lock);
+		vblk->vqs[i].vq = vqs[i];
+	}
+	vblk->num_vqs = num_vqs;
+
+ err_find_vqs:
+	kfree(vqs);
+ err_vqs:
+	kfree(callbacks);
+ err_callbacks:
+	kfree(names);
+ err_names:
+	if (err)
+		kfree(vblk->vqs);
+ out:
 	return err;
 }
 
@@ -551,7 +614,6 @@ static int virtblk_probe(struct virtio_device *vdev)
 	err = init_vq(vblk);
 	if (err)
 		goto out_free_vblk;
-	spin_lock_init(&vblk->vq_lock);
 
 	/* FIXME: How many partitions?  How long is a piece of string? */
 	vblk->disk = alloc_disk(1 << PART_BITS);
@@ -562,7 +624,7 @@ static int virtblk_probe(struct virtio_device *vdev)
 
 	/* Default queue sizing is to fill the ring. */
 	if (!virtblk_queue_depth) {
-		virtblk_queue_depth = vblk->vq->num_free;
+		virtblk_queue_depth = vblk->vqs[0].vq->num_free;
 		/* ... but without indirect descs, we use 2 descs per req */
 		if (!virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC))
 			virtblk_queue_depth /= 2;
@@ -570,7 +632,6 @@ static int virtblk_probe(struct virtio_device *vdev)
 
 	memset(&vblk->tag_set, 0, sizeof(vblk->tag_set));
 	vblk->tag_set.ops = &virtio_mq_ops;
-	vblk->tag_set.nr_hw_queues = 1;
 	vblk->tag_set.queue_depth = virtblk_queue_depth;
 	vblk->tag_set.numa_node = NUMA_NO_NODE;
 	vblk->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
@@ -578,6 +639,7 @@ static int virtblk_probe(struct virtio_device *vdev)
 		sizeof(struct virtblk_req) +
 		sizeof(struct scatterlist) * sg_elems;
 	vblk->tag_set.driver_data = vblk;
+	vblk->tag_set.nr_hw_queues = vblk->num_vqs;
 
 	err = blk_mq_alloc_tag_set(&vblk->tag_set);
 	if (err)
@@ -727,6 +789,7 @@ static void virtblk_remove(struct virtio_device *vdev)
 	refc = atomic_read(&disk_to_dev(vblk->disk)->kobj.kref.refcount);
 	put_disk(vblk->disk);
 	vdev->config->del_vqs(vdev);
+	kfree(vblk->vqs);
 	kfree(vblk);
 
 	/* Only free device id if we don't have any users */
@@ -777,7 +840,8 @@ static const struct virtio_device_id id_table[] = {
 static unsigned int features[] = {
 	VIRTIO_BLK_F_SEG_MAX, VIRTIO_BLK_F_SIZE_MAX, VIRTIO_BLK_F_GEOMETRY,
 	VIRTIO_BLK_F_RO, VIRTIO_BLK_F_BLK_SIZE, VIRTIO_BLK_F_SCSI,
-	VIRTIO_BLK_F_WCE, VIRTIO_BLK_F_TOPOLOGY, VIRTIO_BLK_F_CONFIG_WCE
+	VIRTIO_BLK_F_WCE, VIRTIO_BLK_F_TOPOLOGY, VIRTIO_BLK_F_CONFIG_WCE,
+	VIRTIO_BLK_F_MQ,
 };
 
 static struct virtio_driver virtio_blk = {