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ext4: fix possible recursive locking warning in EXT4_IOC_MOVE_EXT 

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@xyzw.org>
Signed-off-by: Akira Fujita <a-fujita@rs.jp.nec.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Akira Fujita 2009-11-23 07:24:41 -05:00 committed by Theodore Ts'o
parent fc04cb49a8
commit 49bd22bc4d
1 changed files with 1 additions and 1 deletions
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2
fs/ext4/move_extent.c
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@ -189,7 +189,7 @@ double_down_write_data_sem(struct inode *orig_inode, struct inode *donor_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);
}
/**