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btrfs: Add WARN_ON() for double lock in btrfs_tree_lock()

Message ID 68cb57b7e339dd1270037d8f6694a5dccf340688.1438871972.git.zhaolei@cn.fujitsu.com (mailing list archive)
State Accepted
Headers show

Commit Message

Zhaolei Aug. 6, 2015, 2:39 p.m. UTC 
When a task trying to double lock a extent buffer, there are no
lockdep warning about it because this lock may be in "blocking_lock"
state, and make us hard to debug.

This patch add a WARN_ON() for above condition, it can not report
all deadlock cases(as lock between tasks), but at least helps us
some.

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
---
 fs/btrfs/locking.c | 1 +
 1 file changed, 1 insertion(+)
diff mbox

Patch

diff --git a/fs/btrfs/locking.c b/fs/btrfs/locking.c
index f8229ef..d7e6baf 100644
--- a/fs/btrfs/locking.c
+++ b/fs/btrfs/locking.c
@@ -241,6 +241,7 @@  void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb)
  */
 void btrfs_tree_lock(struct extent_buffer *eb)
 {
+	WARN_ON(eb->lock_owner == current->pid);
 again:
 	wait_event(eb->read_lock_wq, atomic_read(&eb->blocking_readers) == 0);
 	wait_event(eb->write_lock_wq, atomic_read(&eb->blocking_writers) == 0);