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From: Liu Bo <bo.li.liu@oracle.com>
To: linux-btrfs@vger.kernel.org
Cc: David Sterba <dsterba@suse.cz>
Subject: [PATCH] Btrfs: use down_read_nested to make lockdep silent
Date: Thu,  1 Dec 2016 13:44:19 -0800	[thread overview]
Message-ID: <1480628659-17731-1-git-send-email-bo.li.liu@oracle.com> (raw)

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.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
---
 fs/btrfs/extent-tree.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 210c94a..cdb082a 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -7394,7 +7394,8 @@ btrfs_lock_cluster(struct btrfs_block_group_cache *block_group,
 
 		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, 1);
 
 		spin_lock(&cluster->refill_lock);
 		if (used_bg == cluster->block_group)
-- 
2.5.5


             reply	other threads:[~2016-12-01 21:36 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-01 21:44 Liu Bo [this message]
2016-12-12 13:15 ` [PATCH] Btrfs: use down_read_nested to make lockdep silent David Sterba
2016-12-13 23:58 ` [PATCH v2] " Liu Bo

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