[074/111] Btrfs: fix race between allocate and release extent buffer.

[Greg KH]

2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Yan, Zheng <zheng.yan@xxxxxxxxxx>

commit f044ba7835b84e69c68b620ca8fa27e5ef67759d upstream.

Increase extent buffer's reference count while holding the lock.
Otherwise it can race with try_release_extent_buffer.

Signed-off-by: Yan Zheng <zheng.yan@xxxxxxxxxx>
Signed-off-by: Chris Mason <chris.mason@xxxxxxxxxx>
Acked-by: Jeff Mahoney <jeffm@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>


---
 fs/btrfs/extent_io.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3165,10 +3165,9 @@ struct extent_buffer *alloc_extent_buffe
 		spin_unlock(&tree->buffer_lock);
 		goto free_eb;
 	}
-	spin_unlock(&tree->buffer_lock);
-
 	/* add one reference for the tree */
 	atomic_inc(&eb->refs);
+	spin_unlock(&tree->buffer_lock);
 	return eb;
 
 free_eb:


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