Merge tag 'gfs2-4.13.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux-gfs2

Pull GFS2 updates from Bob Peterson:
 "We've got eight GFS2 patches for this merge window:

   - Andreas Gruenbacher has four patches related to cleaning up the
     GFS2 inode evict process. This is about half of his patches
     designed to fix a long-standing GFS2 hang related to the inode
     shrinker: Shrinker calls gfs2 evict, evict calls DLM, DLM requires
     memory and blocks on the shrinker.

     These four patches have been well tested. His second set of patches
     are still being tested, so I plan to hold them until the next merge
     window, after we have more weeks of testing. The first patch
     eliminates the flush_delayed_work, which can block.

   - Andreas's second patch protects setting of gl_object for rgrps with
     a spin_lock to prevent proven races.

   - His third patch introduces a centralized mechanism for queueing
     glock work with better reference counting, to prevent more races.

    -His fourth patch retains a reference to inode glocks when an error
     occurs while creating an inode. This keeps the subsequent evict
     from needing to reacquire the glock, which might call into DLM and
     block in low memory conditions.

   - Arvind Yadav has a patch to add const to attribute_group
     structures.

   - I have a patch to detect directory entry inconsistencies and
     withdraw the file system if any are found. Better that than silent
     corruption.

   - I have a patch to remove a vestigial variable from glock
     structures, saving some slab space.

   - I have another patch to remove a vestigial variable from the GFS2
     in-core superblock structure"

* tag 'gfs2-4.13.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux-gfs2:
  GFS2: constify attribute_group structures.
  gfs2: gfs2_create_inode: Keep glock across iput
  gfs2: Clean up glock work enqueuing
  gfs2: Protect gl->gl_object by spin lock
  gfs2: Get rid of flush_delayed_work in gfs2_evict_inode
  GFS2: Eliminate vestigial sd_log_flush_wrapped
  GFS2: Remove gl_list from glock structure
  GFS2: Withdraw when directory entry inconsistencies are detected

1 files changed, 74 insertions, 50 deletions

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 959a19c..6cd71c5 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -152,20 +152,34 @@ static void gfs2_glock_remove_from_lru(struct gfs2_glock *gl)
 	spin_unlock(&lru_lock);
 }
 
-/**
- * gfs2_glock_put() - Decrement reference count on glock
- * @gl: The glock to put
- *
+/*
+ * Enqueue the glock on the work queue.  Passes one glock reference on to the
+ * work queue.
  */
+static void __gfs2_glock_queue_work(struct gfs2_glock *gl, unsigned long delay) {
+	if (!queue_delayed_work(glock_workqueue, &gl->gl_work, delay)) {
+		/*
+		 * We are holding the lockref spinlock, and the work was still
+		 * queued above.  The queued work (glock_work_func) takes that
+		 * spinlock before dropping its glock reference(s), so it
+		 * cannot have dropped them in the meantime.
+		 */
+		GLOCK_BUG_ON(gl, gl->gl_lockref.count < 2);
+		gl->gl_lockref.count--;
+	}
+}
 
-void gfs2_glock_put(struct gfs2_glock *gl)
+static void gfs2_glock_queue_work(struct gfs2_glock *gl, unsigned long delay) {
+	spin_lock(&gl->gl_lockref.lock);
+	__gfs2_glock_queue_work(gl, delay);
+	spin_unlock(&gl->gl_lockref.lock);
+}
+
+static void __gfs2_glock_put(struct gfs2_glock *gl)
 {
 	struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
 	struct address_space *mapping = gfs2_glock2aspace(gl);
 
-	if (lockref_put_or_lock(&gl->gl_lockref))
-		return;
-
 	lockref_mark_dead(&gl->gl_lockref);
 
 	gfs2_glock_remove_from_lru(gl);
@@ -178,6 +192,20 @@ void gfs2_glock_put(struct gfs2_glock *gl)
 }
 
 /**
+ * gfs2_glock_put() - Decrement reference count on glock
+ * @gl: The glock to put
+ *
+ */
+
+void gfs2_glock_put(struct gfs2_glock *gl)
+{
+	if (lockref_put_or_lock(&gl->gl_lockref))
+		return;
+
+	__gfs2_glock_put(gl);
+}
+
+/**
  * may_grant - check if its ok to grant a new lock
  * @gl: The glock
  * @gh: The lock request which we wish to grant
@@ -482,8 +510,7 @@ __acquires(&gl->gl_lockref.lock)
 		    target == LM_ST_UNLOCKED &&
 		    test_bit(SDF_SKIP_DLM_UNLOCK, &sdp->sd_flags)) {
 			finish_xmote(gl, target);
-			if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0)
-				gfs2_glock_put(gl);
+			gfs2_glock_queue_work(gl, 0);
 		}
 		else if (ret) {
 			pr_err("lm_lock ret %d\n", ret);
@@ -492,8 +519,7 @@ __acquires(&gl->gl_lockref.lock)
 		}
 	} else { /* lock_nolock */
 		finish_xmote(gl, target);
-		if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0)
-			gfs2_glock_put(gl);
+		gfs2_glock_queue_work(gl, 0);
 	}
 
 	spin_lock(&gl->gl_lockref.lock);
@@ -565,8 +591,7 @@ out_sched:
 	clear_bit(GLF_LOCK, &gl->gl_flags);
 	smp_mb__after_atomic();
 	gl->gl_lockref.count++;
-	if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0)
-		gl->gl_lockref.count--;
+	__gfs2_glock_queue_work(gl, 0);
 	return;
 
 out_unlock:
@@ -601,11 +626,11 @@ static void glock_work_func(struct work_struct *work)
 {
 	unsigned long delay = 0;
 	struct gfs2_glock *gl = container_of(work, struct gfs2_glock, gl_work.work);
-	int drop_ref = 0;
+	unsigned int drop_refs = 1;
 
 	if (test_and_clear_bit(GLF_REPLY_PENDING, &gl->gl_flags)) {
 		finish_xmote(gl, gl->gl_reply);
-		drop_ref = 1;
+		drop_refs++;
 	}
 	spin_lock(&gl->gl_lockref.lock);
 	if (test_bit(GLF_PENDING_DEMOTE, &gl->gl_flags) &&
@@ -623,17 +648,25 @@ static void glock_work_func(struct work_struct *work)
 		}
 	}
 	run_queue(gl, 0);
-	spin_unlock(&gl->gl_lockref.lock);
-	if (!delay)
-		gfs2_glock_put(gl);
-	else {
+	if (delay) {
+		/* Keep one glock reference for the work we requeue. */
+		drop_refs--;
 		if (gl->gl_name.ln_type != LM_TYPE_INODE)
 			delay = 0;
-		if (queue_delayed_work(glock_workqueue, &gl->gl_work, delay) == 0)
-			gfs2_glock_put(gl);
+		__gfs2_glock_queue_work(gl, delay);
 	}
-	if (drop_ref)
-		gfs2_glock_put(gl);
+
+	/*
+	 * Drop the remaining glock references manually here. (Mind that
+	 * __gfs2_glock_queue_work depends on the lockref spinlock begin held
+	 * here as well.)
+	 */
+	gl->gl_lockref.count -= drop_refs;
+	if (!gl->gl_lockref.count) {
+		__gfs2_glock_put(gl);
+		return;
+	}
+	spin_unlock(&gl->gl_lockref.lock);
 }
 
 /**
@@ -986,8 +1019,7 @@ int gfs2_glock_nq(struct gfs2_holder *gh)
 		     test_and_clear_bit(GLF_FROZEN, &gl->gl_flags))) {
 		set_bit(GLF_REPLY_PENDING, &gl->gl_flags);
 		gl->gl_lockref.count++;
-		if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0)
-			gl->gl_lockref.count--;
+		__gfs2_glock_queue_work(gl, 0);
 	}
 	run_queue(gl, 1);
 	spin_unlock(&gl->gl_lockref.lock);
@@ -1047,17 +1079,15 @@ void gfs2_glock_dq(struct gfs2_holder *gh)
 		gfs2_glock_add_to_lru(gl);
 
 	trace_gfs2_glock_queue(gh, 0);
+	if (unlikely(!fast_path)) {
+		gl->gl_lockref.count++;
+		if (test_bit(GLF_PENDING_DEMOTE, &gl->gl_flags) &&
+		    !test_bit(GLF_DEMOTE, &gl->gl_flags) &&
+		    gl->gl_name.ln_type == LM_TYPE_INODE)
+			delay = gl->gl_hold_time;
+		__gfs2_glock_queue_work(gl, delay);
+	}
 	spin_unlock(&gl->gl_lockref.lock);
-	if (likely(fast_path))
-		return;
-
-	gfs2_glock_hold(gl);
-	if (test_bit(GLF_PENDING_DEMOTE, &gl->gl_flags) &&
-	    !test_bit(GLF_DEMOTE, &gl->gl_flags) &&
-	    gl->gl_name.ln_type == LM_TYPE_INODE)
-		delay = gl->gl_hold_time;
-	if (queue_delayed_work(glock_workqueue, &gl->gl_work, delay) == 0)
-		gfs2_glock_put(gl);
 }
 
 void gfs2_glock_dq_wait(struct gfs2_holder *gh)
@@ -1233,9 +1263,8 @@ void gfs2_glock_cb(struct gfs2_glock *gl, unsigned int state)
 
 	spin_lock(&gl->gl_lockref.lock);
 	handle_callback(gl, state, delay, true);
+	__gfs2_glock_queue_work(gl, delay);
 	spin_unlock(&gl->gl_lockref.lock);
-	if (queue_delayed_work(glock_workqueue, &gl->gl_work, delay) == 0)
-		gfs2_glock_put(gl);
 }
 
 /**
@@ -1294,10 +1323,8 @@ void gfs2_glock_complete(struct gfs2_glock *gl, int ret)
 
 	gl->gl_lockref.count++;
 	set_bit(GLF_REPLY_PENDING, &gl->gl_flags);
+	__gfs2_glock_queue_work(gl, 0);
 	spin_unlock(&gl->gl_lockref.lock);
-
-	if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0)
-		gfs2_glock_put(gl);
 }
 
 static int glock_cmp(void *priv, struct list_head *a, struct list_head *b)
@@ -1355,8 +1382,7 @@ add_back_to_lru:
 		if (demote_ok(gl))
 			handle_callback(gl, LM_ST_UNLOCKED, 0, false);
 		WARN_ON(!test_and_clear_bit(GLF_LOCK, &gl->gl_flags));
-		if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0)
-			gl->gl_lockref.count--;
+		__gfs2_glock_queue_work(gl, 0);
 		spin_unlock(&gl->gl_lockref.lock);
 		cond_resched_lock(&lru_lock);
 	}
@@ -1462,13 +1488,12 @@ static void glock_hash_walk(glock_examiner examiner, const struct gfs2_sbd *sdp)
 
 static void thaw_glock(struct gfs2_glock *gl)
 {
-	if (!test_and_clear_bit(GLF_FROZEN, &gl->gl_flags))
-		goto out;
-	set_bit(GLF_REPLY_PENDING, &gl->gl_flags);
-	if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0) {
-out:
+	if (!test_and_clear_bit(GLF_FROZEN, &gl->gl_flags)) {
 		gfs2_glock_put(gl);
+		return;
 	}
+	set_bit(GLF_REPLY_PENDING, &gl->gl_flags);
+	gfs2_glock_queue_work(gl, 0);
 }
 
 /**
@@ -1484,9 +1509,8 @@ static void clear_glock(struct gfs2_glock *gl)
 	spin_lock(&gl->gl_lockref.lock);
 	if (gl->gl_state != LM_ST_UNLOCKED)
 		handle_callback(gl, LM_ST_UNLOCKED, 0, false);
+	__gfs2_glock_queue_work(gl, 0);
 	spin_unlock(&gl->gl_lockref.lock);
-	if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0)
-		gfs2_glock_put(gl);
 }
 
 /**