Btrfs: Optimize compressed writeback and reads

When reading compressed extents, try to put pages into the page cache
for any pages covered by the compressed extent that readpages didn't already
preload.

Add an async work queue to handle transformations at delayed allocation processing
time.  Right now this is just compression.  The workflow is:

1) Find offsets in the file marked for delayed allocation
2) Lock the pages
3) Lock the state bits
4) Call the async delalloc code

The async delalloc code clears the state lock bits and delalloc bits.  It is
important this happens before the range goes into the work queue because
otherwise it might deadlock with other work queue items that try to lock
those extent bits.

The file pages are compressed, and if the compression doesn't work the
pages are written back directly.

An ordered work queue is used to make sure the inodes are written in the same
order that pdflush or writepages sent them down.

This changes extent_write_cache_pages to let the writepage function
update the wbc nr_written count.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 500 insertions, 143 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 3df0ffa..e01c0d0 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -86,6 +86,10 @@ static unsigned char btrfs_type_by_mode[S_IFMT >> S_SHIFT] = {
 
 static void btrfs_truncate(struct inode *inode);
 static int btrfs_finish_ordered_io(struct inode *inode, u64 start, u64 end);
+static noinline int cow_file_range(struct inode *inode,
+				   struct page *locked_page,
+				   u64 start, u64 end, int *page_started,
+				   unsigned long *nr_written, int unlock);
 
 /*
  * a very lame attempt at stopping writes when the FS is 85% full.  There
@@ -262,35 +266,72 @@ static int cow_file_range_inline(struct btrfs_trans_handle *trans,
 	return 0;
 }
 
+struct async_extent {
+	u64 start;
+	u64 ram_size;
+	u64 compressed_size;
+	struct page **pages;
+	unsigned long nr_pages;
+	struct list_head list;
+};
+
+struct async_cow {
+	struct inode *inode;
+	struct btrfs_root *root;
+	struct page *locked_page;
+	u64 start;
+	u64 end;
+	struct list_head extents;
+	struct btrfs_work work;
+};
+
+static noinline int add_async_extent(struct async_cow *cow,
+				     u64 start, u64 ram_size,
+				     u64 compressed_size,
+				     struct page **pages,
+				     unsigned long nr_pages)
+{
+	struct async_extent *async_extent;
+
+	async_extent = kmalloc(sizeof(*async_extent), GFP_NOFS);
+	async_extent->start = start;
+	async_extent->ram_size = ram_size;
+	async_extent->compressed_size = compressed_size;
+	async_extent->pages = pages;
+	async_extent->nr_pages = nr_pages;
+	list_add_tail(&async_extent->list, &cow->extents);
+	return 0;
+}
+
 /*
- * when extent_io.c finds a delayed allocation range in the file,
- * the call backs end up in this code.  The basic idea is to
- * allocate extents on disk for the range, and create ordered data structs
- * in ram to track those extents.
+ * we create compressed extents in two phases.  The first
+ * phase compresses a range of pages that have already been
+ * locked (both pages and state bits are locked).
  *
- * locked_page is the page that writepage had locked already.  We use
- * it to make sure we don't do extra locks or unlocks.
+ * This is done inside an ordered work queue, and the compression
+ * is spread across many cpus.  The actual IO submission is step
+ * two, and the ordered work queue takes care of making sure that
+ * happens in the same order things were put onto the queue by
+ * writepages and friends.
  *
- * *page_started is set to one if we unlock locked_page and do everything
- * required to start IO on it.  It may be clean and already done with
- * IO when we return.
+ * If this code finds it can't get good compression, it puts an
+ * entry onto the work queue to write the uncompressed bytes.  This
+ * makes sure that both compressed inodes and uncompressed inodes
+ * are written in the same order that pdflush sent them down.
  */
-static int cow_file_range(struct inode *inode, struct page *locked_page,
-			  u64 start, u64 end, int *page_started)
+static noinline int compress_file_range(struct inode *inode,
+					struct page *locked_page,
+					u64 start, u64 end,
+					struct async_cow *async_cow,
+					int *num_added)
 {
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	struct btrfs_trans_handle *trans;
-	u64 alloc_hint = 0;
 	u64 num_bytes;
-	unsigned long ram_size;
 	u64 orig_start;
 	u64 disk_num_bytes;
-	u64 cur_alloc_size;
 	u64 blocksize = root->sectorsize;
 	u64 actual_end;
-	struct btrfs_key ins;
-	struct extent_map *em;
-	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
 	int ret = 0;
 	struct page **pages = NULL;
 	unsigned long nr_pages;
@@ -298,22 +339,12 @@ static int cow_file_range(struct inode *inode, struct page *locked_page,
 	unsigned long total_compressed = 0;
 	unsigned long total_in = 0;
 	unsigned long max_compressed = 128 * 1024;
-	unsigned long max_uncompressed = 256 * 1024;
+	unsigned long max_uncompressed = 128 * 1024;
 	int i;
-	int ordered_type;
 	int will_compress;
 
-	trans = btrfs_join_transaction(root, 1);
-	BUG_ON(!trans);
-	btrfs_set_trans_block_group(trans, inode);
 	orig_start = start;
 
-	/*
-	 * compression made this loop a bit ugly, but the basic idea is to
-	 * compress some pages but keep the total size of the compressed
-	 * extent relatively small.  If compression is off, this goto target
-	 * is never used.
-	 */
 again:
 	will_compress = 0;
 	nr_pages = (end >> PAGE_CACHE_SHIFT) - (start >> PAGE_CACHE_SHIFT) + 1;
@@ -324,7 +355,13 @@ again:
 
 	/* we want to make sure that amount of ram required to uncompress
 	 * an extent is reasonable, so we limit the total size in ram
-	 * of a compressed extent to 256k
+	 * of a compressed extent to 128k.  This is a crucial number
+	 * because it also controls how easily we can spread reads across
+	 * cpus for decompression.
+	 *
+	 * We also want to make sure the amount of IO required to do
+	 * a random read is reasonably small, so we limit the size of
+	 * a compressed extent to 128k.
 	 */
 	total_compressed = min(total_compressed, max_uncompressed);
 	num_bytes = (end - start + blocksize) & ~(blocksize - 1);
@@ -333,18 +370,16 @@ again:
 	total_in = 0;
 	ret = 0;
 
-	/* we do compression for mount -o compress and when the
-	 * inode has not been flagged as nocompress
+	/*
+	 * we do compression for mount -o compress and when the
+	 * inode has not been flagged as nocompress.  This flag can
+	 * change at any time if we discover bad compression ratios.
 	 */
 	if (!btrfs_test_flag(inode, NOCOMPRESS) &&
 	    btrfs_test_opt(root, COMPRESS)) {
 		WARN_ON(pages);
 		pages = kzalloc(sizeof(struct page *) * nr_pages, GFP_NOFS);
 
-		/* we want to make sure the amount of IO required to satisfy
-		 * a random read is reasonably small, so we limit the size
-		 * of a compressed extent to 128k
-		 */
 		ret = btrfs_zlib_compress_pages(inode->i_mapping, start,
 						total_compressed, pages,
 						nr_pages, &nr_pages_ret,
@@ -371,26 +406,34 @@ again:
 		}
 	}
 	if (start == 0) {
+		trans = btrfs_join_transaction(root, 1);
+		BUG_ON(!trans);
+		btrfs_set_trans_block_group(trans, inode);
+
 		/* lets try to make an inline extent */
-		if (ret || total_in < (end - start + 1)) {
+		if (ret || total_in < (actual_end - start)) {
 			/* we didn't compress the entire range, try
-			 * to make an uncompressed inline extent.  This
-			 * is almost sure to fail, but maybe inline sizes
-			 * will get bigger later
+			 * to make an uncompressed inline extent.
 			 */
 			ret = cow_file_range_inline(trans, root, inode,
 						    start, end, 0, NULL);
 		} else {
+			/* try making a compressed inline extent */
 			ret = cow_file_range_inline(trans, root, inode,
 						    start, end,
 						    total_compressed, pages);
 		}
+		btrfs_end_transaction(trans, root);
 		if (ret == 0) {
+			/*
+			 * inline extent creation worked, we don't need
+			 * to create any more async work items.  Unlock
+			 * and free up our temp pages.
+			 */
 			extent_clear_unlock_delalloc(inode,
 						     &BTRFS_I(inode)->io_tree,
-						     start, end, NULL,
-						     1, 1, 1);
-			*page_started = 1;
+						     start, end, NULL, 1, 0,
+						     0, 1, 1, 1);
 			ret = 0;
 			goto free_pages_out;
 		}
@@ -435,53 +478,280 @@ again:
 		/* flag the file so we don't compress in the future */
 		btrfs_set_flag(inode, NOCOMPRESS);
 	}
+	if (will_compress) {
+		*num_added += 1;
 
-	BUG_ON(disk_num_bytes >
-	       btrfs_super_total_bytes(&root->fs_info->super_copy));
+		/* the async work queues will take care of doing actual
+		 * allocation on disk for these compressed pages,
+		 * and will submit them to the elevator.
+		 */
+		add_async_extent(async_cow, start, num_bytes,
+				 total_compressed, pages, nr_pages_ret);
 
-	btrfs_drop_extent_cache(inode, start, start + num_bytes - 1, 0);
+		if (start + num_bytes < end) {
+			start += num_bytes;
+			pages = NULL;
+			cond_resched();
+			goto again;
+		}
+	} else {
+		/*
+		 * No compression, but we still need to write the pages in
+		 * the file we've been given so far.  redirty the locked
+		 * page if it corresponds to our extent and set things up
+		 * for the async work queue to run cow_file_range to do
+		 * the normal delalloc dance
+		 */
+		if (page_offset(locked_page) >= start &&
+		    page_offset(locked_page) <= end) {
+			__set_page_dirty_nobuffers(locked_page);
+			/* unlocked later on in the async handlers */
+		}
+		add_async_extent(async_cow, start, end - start + 1, 0, NULL, 0);
+		*num_added += 1;
+	}
 
-	while(disk_num_bytes > 0) {
-		unsigned long min_bytes;
+out:
+	return 0;
+
+free_pages_out:
+	for (i = 0; i < nr_pages_ret; i++) {
+		WARN_ON(pages[i]->mapping);
+		page_cache_release(pages[i]);
+	}
+	if (pages)
+		kfree(pages);
+
+	goto out;
+}
+
+/*
+ * phase two of compressed writeback.  This is the ordered portion
+ * of the code, which only gets called in the order the work was
+ * queued.  We walk all the async extents created by compress_file_range
+ * and send them down to the disk.
+ */
+static noinline int submit_compressed_extents(struct inode *inode,
+					      struct async_cow *async_cow)
+{
+	struct async_extent *async_extent;
+	u64 alloc_hint = 0;
+	struct btrfs_trans_handle *trans;
+	struct btrfs_key ins;
+	struct extent_map *em;
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
+	struct extent_io_tree *io_tree;
+	int ret;
+
+	if (list_empty(&async_cow->extents))
+		return 0;
+
+	trans = btrfs_join_transaction(root, 1);
+
+	while(!list_empty(&async_cow->extents)) {
+		async_extent = list_entry(async_cow->extents.next,
+					  struct async_extent, list);
+		list_del(&async_extent->list);
 
+		io_tree = &BTRFS_I(inode)->io_tree;
+
+		/* did the compression code fall back to uncompressed IO? */
+		if (!async_extent->pages) {
+			int page_started = 0;
+			unsigned long nr_written = 0;
+
+			lock_extent(io_tree, async_extent->start,
+				    async_extent->start + async_extent->ram_size - 1,
+				    GFP_NOFS);
+
+			/* allocate blocks */
+			cow_file_range(inode, async_cow->locked_page,
+				       async_extent->start,
+				       async_extent->start +
+				       async_extent->ram_size - 1,
+				       &page_started, &nr_written, 0);
+
+			/*
+			 * if page_started, cow_file_range inserted an
+			 * inline extent and took care of all the unlocking
+			 * and IO for us.  Otherwise, we need to submit
+			 * all those pages down to the drive.
+			 */
+			if (!page_started)
+				extent_write_locked_range(io_tree,
+						  inode, async_extent->start,
+					          async_extent->start +
+						  async_extent->ram_size - 1,
+						  btrfs_get_extent,
+						  WB_SYNC_ALL);
+			kfree(async_extent);
+			cond_resched();
+			continue;
+		}
+
+		lock_extent(io_tree, async_extent->start,
+			    async_extent->start + async_extent->ram_size - 1,
+			    GFP_NOFS);
 		/*
-		 * the max size of a compressed extent is pretty small,
-		 * make the code a little less complex by forcing
-		 * the allocator to find a whole compressed extent at once
+		 * here we're doing allocation and writeback of the
+		 * compressed pages
 		 */
-		if (will_compress)
-			min_bytes = disk_num_bytes;
-		else
-			min_bytes = root->sectorsize;
+		btrfs_drop_extent_cache(inode, async_extent->start,
+					async_extent->start +
+					async_extent->ram_size - 1, 0);
+
+		ret = btrfs_reserve_extent(trans, root,
+					   async_extent->compressed_size,
+					   async_extent->compressed_size,
+					   0, alloc_hint,
+					   (u64)-1, &ins, 1);
+		BUG_ON(ret);
+		em = alloc_extent_map(GFP_NOFS);
+		em->start = async_extent->start;
+		em->len = async_extent->ram_size;
+
+		em->block_start = ins.objectid;
+		em->block_len = ins.offset;
+		em->bdev = root->fs_info->fs_devices->latest_bdev;
+		set_bit(EXTENT_FLAG_PINNED, &em->flags);
+		set_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
+
+		while(1) {
+			spin_lock(&em_tree->lock);
+			ret = add_extent_mapping(em_tree, em);
+			spin_unlock(&em_tree->lock);
+			if (ret != -EEXIST) {
+				free_extent_map(em);
+				break;
+			}
+			btrfs_drop_extent_cache(inode, async_extent->start,
+						async_extent->start +
+						async_extent->ram_size - 1, 0);
+		}
+
+		ret = btrfs_add_ordered_extent(inode, async_extent->start,
+					       ins.objectid,
+					       async_extent->ram_size,
+					       ins.offset,
+					       BTRFS_ORDERED_COMPRESSED);
+		BUG_ON(ret);
+
+		btrfs_end_transaction(trans, root);
+
+		/*
+		 * clear dirty, set writeback and unlock the pages.
+		 */
+		extent_clear_unlock_delalloc(inode,
+					     &BTRFS_I(inode)->io_tree,
+					     async_extent->start,
+					     async_extent->start +
+					     async_extent->ram_size - 1,
+					     NULL, 1, 1, 0, 1, 1, 0);
+
+		ret = btrfs_submit_compressed_write(inode,
+				         async_extent->start,
+					 async_extent->ram_size,
+					 ins.objectid,
+					 ins.offset, async_extent->pages,
+					 async_extent->nr_pages);
+
+		BUG_ON(ret);
+		trans = btrfs_join_transaction(root, 1);
+		alloc_hint = ins.objectid + ins.offset;
+		kfree(async_extent);
+		cond_resched();
+	}
+
+	btrfs_end_transaction(trans, root);
+	return 0;
+}
+
+/*
+ * when extent_io.c finds a delayed allocation range in the file,
+ * the call backs end up in this code.  The basic idea is to
+ * allocate extents on disk for the range, and create ordered data structs
+ * in ram to track those extents.
+ *
+ * locked_page is the page that writepage had locked already.  We use
+ * it to make sure we don't do extra locks or unlocks.
+ *
+ * *page_started is set to one if we unlock locked_page and do everything
+ * required to start IO on it.  It may be clean and already done with
+ * IO when we return.
+ */
+static noinline int cow_file_range(struct inode *inode,
+				   struct page *locked_page,
+				   u64 start, u64 end, int *page_started,
+				   unsigned long *nr_written,
+				   int unlock)
+{
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct btrfs_trans_handle *trans;
+	u64 alloc_hint = 0;
+	u64 num_bytes;
+	unsigned long ram_size;
+	u64 disk_num_bytes;
+	u64 cur_alloc_size;
+	u64 blocksize = root->sectorsize;
+	u64 actual_end;
+	struct btrfs_key ins;
+	struct extent_map *em;
+	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
+	int ret = 0;
+
+	trans = btrfs_join_transaction(root, 1);
+	BUG_ON(!trans);
+	btrfs_set_trans_block_group(trans, inode);
 
+	actual_end = min_t(u64, i_size_read(inode), end + 1);
+
+	num_bytes = (end - start + blocksize) & ~(blocksize - 1);
+	num_bytes = max(blocksize,  num_bytes);
+	disk_num_bytes = num_bytes;
+	ret = 0;
+
+	if (start == 0) {
+		/* lets try to make an inline extent */
+		ret = cow_file_range_inline(trans, root, inode,
+					    start, end, 0, NULL);
+		if (ret == 0) {
+			extent_clear_unlock_delalloc(inode,
+						     &BTRFS_I(inode)->io_tree,
+						     start, end, NULL, 1, 1,
+						     1, 1, 1, 1);
+			*nr_written = *nr_written +
+			     (end - start + PAGE_CACHE_SIZE) / PAGE_CACHE_SIZE;
+			*page_started = 1;
+			ret = 0;
+			goto out;
+		}
+	}
+
+	BUG_ON(disk_num_bytes >
+	       btrfs_super_total_bytes(&root->fs_info->super_copy));
+
+	btrfs_drop_extent_cache(inode, start, start + num_bytes - 1, 0);
+
+	while(disk_num_bytes > 0) {
 		cur_alloc_size = min(disk_num_bytes, root->fs_info->max_extent);
 		ret = btrfs_reserve_extent(trans, root, cur_alloc_size,
-					   min_bytes, 0, alloc_hint,
+					   root->sectorsize, 0, alloc_hint,
 					   (u64)-1, &ins, 1);
 		if (ret) {
-			WARN_ON(1);
-			goto free_pages_out_fail;
+			BUG();
 		}
 		em = alloc_extent_map(GFP_NOFS);
 		em->start = start;
 
-		if (will_compress) {
-			ram_size = num_bytes;
-			em->len = num_bytes;
-		} else {
-			/* ramsize == disk size */
-			ram_size = ins.offset;
-			em->len = ins.offset;
-		}
+		ram_size = ins.offset;
+		em->len = ins.offset;
 
 		em->block_start = ins.objectid;
 		em->block_len = ins.offset;
 		em->bdev = root->fs_info->fs_devices->latest_bdev;
 		set_bit(EXTENT_FLAG_PINNED, &em->flags);
 
-		if (will_compress)
-			set_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
-
 		while(1) {
 			spin_lock(&em_tree->lock);
 			ret = add_extent_mapping(em_tree, em);
@@ -495,10 +765,8 @@ again:
 		}
 
 		cur_alloc_size = ins.offset;
-		ordered_type = will_compress ? BTRFS_ORDERED_COMPRESSED : 0;
 		ret = btrfs_add_ordered_extent(inode, start, ins.objectid,
-					       ram_size, cur_alloc_size,
-					       ordered_type);
+					       ram_size, cur_alloc_size, 0);
 		BUG_ON(ret);
 
 		if (disk_num_bytes < cur_alloc_size) {
@@ -506,82 +774,145 @@ again:
 			       cur_alloc_size);
 			break;
 		}
-
-		if (will_compress) {
-			/*
-			 * we're doing compression, we and we need to
-			 * submit the compressed extents down to the device.
-			 *
-			 * We lock down all the file pages, clearing their
-			 * dirty bits and setting them writeback.  Everyone
-			 * that wants to modify the page will wait on the
-			 * ordered extent above.
-			 *
-			 * The writeback bits on the file pages are
-			 * cleared when the compressed pages are on disk
-			 */
-			btrfs_end_transaction(trans, root);
-
-			if (start <= page_offset(locked_page) &&
-			    page_offset(locked_page) < start + ram_size) {
-				*page_started = 1;
-			}
-
-			extent_clear_unlock_delalloc(inode,
-						     &BTRFS_I(inode)->io_tree,
-						     start,
-						     start + ram_size - 1,
-						     NULL, 1, 1, 0);
-
-			ret = btrfs_submit_compressed_write(inode, start,
-						 ram_size, ins.objectid,
-						 cur_alloc_size, pages,
-						 nr_pages_ret);
-
-			BUG_ON(ret);
-			trans = btrfs_join_transaction(root, 1);
-			if (start + ram_size < end) {
-				start += ram_size;
-				alloc_hint = ins.objectid + ins.offset;
-				/* pages will be freed at end_bio time */
-				pages = NULL;
-				goto again;
-			} else {
-				/* we've written everything, time to go */
-				break;
-			}
-		}
 		/* we're not doing compressed IO, don't unlock the first
 		 * page (which the caller expects to stay locked), don't
 		 * clear any dirty bits and don't set any writeback bits
 		 */
 		extent_clear_unlock_delalloc(inode, &BTRFS_I(inode)->io_tree,
 					     start, start + ram_size - 1,
-					     locked_page, 0, 0, 0);
+					     locked_page, unlock, 1,
+					     1, 0, 0, 0);
 		disk_num_bytes -= cur_alloc_size;
 		num_bytes -= cur_alloc_size;
 		alloc_hint = ins.objectid + ins.offset;
 		start += cur_alloc_size;
 	}
-
-	ret = 0;
 out:
+	ret = 0;
 	btrfs_end_transaction(trans, root);
 
 	return ret;
+}
 
-free_pages_out_fail:
-	extent_clear_unlock_delalloc(inode, &BTRFS_I(inode)->io_tree,
-				     start, end, locked_page, 0, 0, 0);
-free_pages_out:
-	for (i = 0; i < nr_pages_ret; i++) {
-		WARN_ON(pages[i]->mapping);
-		page_cache_release(pages[i]);
+/*
+ * work queue call back to started compression on a file and pages
+ */
+static noinline void async_cow_start(struct btrfs_work *work)
+{
+	struct async_cow *async_cow;
+	int num_added = 0;
+	async_cow = container_of(work, struct async_cow, work);
+
+	compress_file_range(async_cow->inode, async_cow->locked_page,
+			    async_cow->start, async_cow->end, async_cow,
+			    &num_added);
+	if (num_added == 0)
+		async_cow->inode = NULL;
+}
+
+/*
+ * work queue call back to submit previously compressed pages
+ */
+static noinline void async_cow_submit(struct btrfs_work *work)
+{
+	struct async_cow *async_cow;
+	struct btrfs_root *root;
+	unsigned long nr_pages;
+
+	async_cow = container_of(work, struct async_cow, work);
+
+	root = async_cow->root;
+	nr_pages = (async_cow->end - async_cow->start + PAGE_CACHE_SIZE) >>
+		PAGE_CACHE_SHIFT;
+
+	atomic_sub(nr_pages, &root->fs_info->async_delalloc_pages);
+
+	if (atomic_read(&root->fs_info->async_delalloc_pages) <
+	    5 * 1042 * 1024 &&
+	    waitqueue_active(&root->fs_info->async_submit_wait))
+		wake_up(&root->fs_info->async_submit_wait);
+
+	if (async_cow->inode) {
+		submit_compressed_extents(async_cow->inode, async_cow);
 	}
-	if (pages)
-		kfree(pages);
+}
 
-	goto out;
+static noinline void async_cow_free(struct btrfs_work *work)
+{
+	struct async_cow *async_cow;
+	async_cow = container_of(work, struct async_cow, work);
+	kfree(async_cow);
+}
+
+static int cow_file_range_async(struct inode *inode, struct page *locked_page,
+				u64 start, u64 end, int *page_started,
+				unsigned long *nr_written)
+{
+	struct async_cow *async_cow;
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	unsigned long nr_pages;
+	u64 cur_end;
+	int limit = 10 * 1024 * 1042;
+
+	if (!btrfs_test_opt(root, COMPRESS)) {
+		return cow_file_range(inode, locked_page, start, end,
+				      page_started, nr_written, 1);
+	}
+
+	clear_extent_bit(&BTRFS_I(inode)->io_tree, start, end, EXTENT_LOCKED |
+			 EXTENT_DELALLOC, 1, 0, GFP_NOFS);
+	while(start < end) {
+		async_cow = kmalloc(sizeof(*async_cow), GFP_NOFS);
+		async_cow->inode = inode;
+		async_cow->root = root;
+		async_cow->locked_page = locked_page;
+		async_cow->start = start;
+
+		if (btrfs_test_flag(inode, NOCOMPRESS))
+			cur_end = end;
+		else
+			cur_end = min(end, start + 512 * 1024 - 1);
+
+		async_cow->end = cur_end;
+		INIT_LIST_HEAD(&async_cow->extents);
+
+		async_cow->work.func = async_cow_start;
+		async_cow->work.ordered_func = async_cow_submit;
+		async_cow->work.ordered_free = async_cow_free;
+		async_cow->work.flags = 0;
+
+		while(atomic_read(&root->fs_info->async_submit_draining) &&
+		      atomic_read(&root->fs_info->async_delalloc_pages)) {
+			wait_event(root->fs_info->async_submit_wait,
+			     (atomic_read(&root->fs_info->async_delalloc_pages)
+			      == 0));
+		}
+
+		nr_pages = (cur_end - start + PAGE_CACHE_SIZE) >>
+			PAGE_CACHE_SHIFT;
+		atomic_add(nr_pages, &root->fs_info->async_delalloc_pages);
+
+		btrfs_queue_worker(&root->fs_info->delalloc_workers,
+				   &async_cow->work);
+
+		if (atomic_read(&root->fs_info->async_delalloc_pages) > limit) {
+			wait_event(root->fs_info->async_submit_wait,
+			   (atomic_read(&root->fs_info->async_delalloc_pages) <
+			    limit));
+		}
+
+		while(atomic_read(&root->fs_info->async_submit_draining) &&
+		      atomic_read(&root->fs_info->async_delalloc_pages)) {
+			wait_event(root->fs_info->async_submit_wait,
+			  (atomic_read(&root->fs_info->async_delalloc_pages) ==
+			   0));
+		}
+
+		*nr_written += nr_pages;
+		start = cur_end + 1;
+	}
+	*page_started = 1;
+	return 0;
 }
 
 /*
@@ -592,7 +923,8 @@ free_pages_out:
  * blocks on disk
  */
 static int run_delalloc_nocow(struct inode *inode, struct page *locked_page,
-			      u64 start, u64 end, int *page_started, int force)
+			      u64 start, u64 end, int *page_started, int force,
+			      unsigned long *nr_written)
 {
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	struct btrfs_trans_handle *trans;
@@ -711,7 +1043,8 @@ out_check:
 		btrfs_release_path(root, path);
 		if (cow_start != (u64)-1) {
 			ret = cow_file_range(inode, locked_page, cow_start,
-					found_key.offset - 1, page_started);
+					found_key.offset - 1, page_started,
+					nr_written, 1);
 			BUG_ON(ret);
 			cow_start = (u64)-1;
 		}
@@ -748,9 +1081,10 @@ out_check:
 		ret = btrfs_add_ordered_extent(inode, cur_offset, disk_bytenr,
 					       num_bytes, num_bytes, type);
 		BUG_ON(ret);
+
 		extent_clear_unlock_delalloc(inode, &BTRFS_I(inode)->io_tree,
 					cur_offset, cur_offset + num_bytes - 1,
-					locked_page, 0, 0, 0);
+					locked_page, 1, 1, 1, 0, 0, 0);
 		cur_offset = extent_end;
 		if (cur_offset > end)
 			break;
@@ -761,7 +1095,7 @@ out_check:
 		cow_start = cur_offset;
 	if (cow_start != (u64)-1) {
 		ret = cow_file_range(inode, locked_page, cow_start, end,
-				     page_started);
+				     page_started, nr_written, 1);
 		BUG_ON(ret);
 	}
 
@@ -775,7 +1109,8 @@ out_check:
  * extent_io.c call back to do delayed allocation processing
  */
 static int run_delalloc_range(struct inode *inode, struct page *locked_page,
-			      u64 start, u64 end, int *page_started)
+			      u64 start, u64 end, int *page_started,
+			      unsigned long *nr_written)
 {
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	int ret;
@@ -783,13 +1118,13 @@ static int run_delalloc_range(struct inode *inode, struct page *locked_page,
 	if (btrfs_test_opt(root, NODATACOW) ||
 	    btrfs_test_flag(inode, NODATACOW))
 		ret = run_delalloc_nocow(inode, locked_page, start, end,
-					 page_started, 0);
+					 page_started, 0, nr_written);
 	else if (btrfs_test_flag(inode, PREALLOC))
 		ret = run_delalloc_nocow(inode, locked_page, start, end,
-					 page_started, 1);
+					 page_started, 1, nr_written);
 	else
-		ret = cow_file_range(inode, locked_page, start, end,
-				     page_started);
+		ret = cow_file_range_async(inode, locked_page, start, end,
+				     page_started, nr_written);
 
 	return ret;
 }
@@ -861,6 +1196,9 @@ int btrfs_merge_bio_hook(struct page *page, unsigned long offset,
 	u64 map_length;
 	int ret;
 
+	if (bio_flags & EXTENT_BIO_COMPRESSED)
+		return 0;
+
 	length = bio->bi_size;
 	map_tree = &root->fs_info->mapping_tree;
 	map_length = length;
@@ -925,12 +1263,12 @@ int btrfs_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
 		btrfs_test_flag(inode, NODATASUM);
 
 	if (!(rw & (1 << BIO_RW))) {
-		if (!skip_sum)
-			btrfs_lookup_bio_sums(root, inode, bio);
 
 		if (bio_flags & EXTENT_BIO_COMPRESSED)
 			return btrfs_submit_compressed_read(inode, bio,
 						    mirror_num, bio_flags);
+		else if (!skip_sum)
+			btrfs_lookup_bio_sums(root, inode, bio);
 		goto mapit;
 	} else if (!skip_sum) {
 		/* we're doing a write, do the async checksumming */
@@ -966,6 +1304,9 @@ static noinline int add_pending_csums(struct btrfs_trans_handle *trans,
 
 int btrfs_set_extent_delalloc(struct inode *inode, u64 start, u64 end)
 {
+	if ((end & (PAGE_CACHE_SIZE - 1)) == 0) {
+		WARN_ON(1);
+	}
 	return set_extent_delalloc(&BTRFS_I(inode)->io_tree, start, end,
 				   GFP_NOFS);
 }
@@ -2105,6 +2446,7 @@ noinline int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
 	int pending_del_nr = 0;
 	int pending_del_slot = 0;
 	int extent_type = -1;
+	int encoding;
 	u64 mask = root->sectorsize - 1;
 
 	if (root->ref_cows)
@@ -2144,6 +2486,7 @@ search_again:
 		leaf = path->nodes[0];
 		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 		found_type = btrfs_key_type(&found_key);
+		encoding = 0;
 
 		if (found_key.objectid != inode->i_ino)
 			break;
@@ -2156,6 +2499,10 @@ search_again:
 			fi = btrfs_item_ptr(leaf, path->slots[0],
 					    struct btrfs_file_extent_item);
 			extent_type = btrfs_file_extent_type(leaf, fi);
+			encoding = btrfs_file_extent_compression(leaf, fi);
+			encoding |= btrfs_file_extent_encryption(leaf, fi);
+			encoding |= btrfs_file_extent_other_encoding(leaf, fi);
+
 			if (extent_type != BTRFS_FILE_EXTENT_INLINE) {
 				item_end +=
 				    btrfs_file_extent_num_bytes(leaf, fi);
@@ -2200,7 +2547,7 @@ search_again:
 		if (extent_type != BTRFS_FILE_EXTENT_INLINE) {
 			u64 num_dec;
 			extent_start = btrfs_file_extent_disk_bytenr(leaf, fi);
-			if (!del_item) {
+			if (!del_item && !encoding) {
 				u64 orig_num_bytes =
 					btrfs_file_extent_num_bytes(leaf, fi);
 				extent_num_bytes = new_size -
@@ -2436,7 +2783,14 @@ int btrfs_cont_expand(struct inode *inode, loff_t size)
 		last_byte = min(extent_map_end(em), block_end);
 		last_byte = (last_byte + mask) & ~mask;
 		if (test_bit(EXTENT_FLAG_VACANCY, &em->flags)) {
+			u64 hint_byte = 0;
 			hole_size = last_byte - cur_offset;
+			err = btrfs_drop_extents(trans, root, inode,
+						 cur_offset,
+						 cur_offset + hole_size,
+						 cur_offset, &hint_byte);
+			if (err)
+				break;
 			err = btrfs_insert_file_extent(trans, root,
 					inode->i_ino, cur_offset, 0,
 					0, hole_size, 0, hole_size,
@@ -3785,6 +4139,7 @@ int btrfs_writepages(struct address_space *mapping,
 		     struct writeback_control *wbc)
 {
 	struct extent_io_tree *tree;
+
 	tree = &BTRFS_I(mapping->host)->io_tree;
 	return extent_writepages(tree, mapping, btrfs_get_extent, wbc);
 }
@@ -4285,9 +4640,11 @@ int btrfs_start_delalloc_inodes(struct btrfs_root *root)
 	 * ordered extents get created before we return
 	 */
 	atomic_inc(&root->fs_info->async_submit_draining);
-	while(atomic_read(&root->fs_info->nr_async_submits)) {
+	while(atomic_read(&root->fs_info->nr_async_submits) ||
+	      atomic_read(&root->fs_info->async_delalloc_pages)) {
 		wait_event(root->fs_info->async_submit_wait,
-		   (atomic_read(&root->fs_info->nr_async_submits) == 0));
+		   (atomic_read(&root->fs_info->nr_async_submits) == 0 &&
+		    atomic_read(&root->fs_info->async_delalloc_pages) == 0));
 	}
 	atomic_dec(&root->fs_info->async_submit_draining);
 	return 0;