Patch "Btrfs: use down_read_nested to make lockdep silent" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

Btrfs: use down_read_nested to make lockdep silent

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
btrfs-use-down_read_nested-to-make-lockdep-silent.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Liu Bo <[email protected]>
Date: Wed, 30 Nov 2016 16:11:04 -0800
Subject: Btrfs: use down_read_nested to make lockdep silent

From: Liu Bo <[email protected]>

[ Upstream commit e321f8a801d7b4c40da8005257b05b9c2b51b072 ]

If @block_group is not @used_bg, it'll try to get @used_bg's lock without droping @block_group 's lock and lockdep has throwed a scary deadlock warning about it.
Fix it by using down_read_nested.

---
 fs/btrfs/extent-tree.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

@@ -7401,7 +7401,8 @@ btrfs_lock_cluster(struct btrfs_block_gr
 
 		spin_unlock(&cluster->refill_lock);
 
-		down_read(&used_bg->data_rwsem);
+		/* We should only have one-level nested. */
+		down_read_nested(&used_bg->data_rwsem, SINGLE_DEPTH_NESTING);
 
 		spin_lock(&cluster->refill_lock);
 		if (used_bg == cluster->block_group)

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/btrfs-fix-lockdep-warning-about-log_mutex.patch queue-4.9/btrfs-adjust-outstanding_extents-counter-properly-when-dio-write-is-split.patch queue-4.9/btrfs-use-down_read_nested-to-make-lockdep-silent.patch