[61/90] ext4: fix possible recursive locking warning in EXT4_IOC_MOVE_EXT

[Greg KH]

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

------------------
(cherry picked from commit 49bd22bc4d603a2a4fc2a6a60e156cbea52eb494)

If CONFIG_PROVE_LOCKING is enabled, the double_down_write_data_sem()
will trigger a false-positive warning of a recursive lock.  Since we
take i_data_sem for the two inodes ordered by their inode numbers,
this isn't a problem.  Use of down_write_nested() will notify the lock
dependency checker machinery that there is no problem here.

This problem was reported by Brian Rogers:

	http://marc.info/?l=linux-ext4&m=125115356928011&w=1

Reported-by: Brian Rogers <brian@xxxxxxxx>
Signed-off-by: Akira Fujita <a-fujita@xxxxxxxxxxxxx>
Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
---
 fs/ext4/move_extent.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -189,7 +189,7 @@ double_down_write_data_sem(struct inode
 	}
 
 	down_write(&EXT4_I(first)->i_data_sem);
-	down_write(&EXT4_I(second)->i_data_sem);
+	down_write_nested(&EXT4_I(second)->i_data_sem, SINGLE_DEPTH_NESTING);
 }
 
 /**


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/