Messages in this thread | | | Date | Mon, 25 Aug 2008 13:55:42 +1000 | From | Dave Chinner <> | Subject | Re: [2.6.27-rc4] XFS i_lock vs i_iolock... |
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On Mon, Aug 25, 2008 at 12:12:23PM +1000, Lachlan McIlroy wrote: > Dave Chinner wrote: >> On Fri, Aug 22, 2008 at 10:12:59PM +0100, Daniel J Blueman wrote: >>> On 2.6.27-rc4 with various debug options enabled, lockdep claims lock >>> ordering issues with XFS [1] - easiest reproducer is just running >>> xfs_fsr. Mount options I was using were >>> 'nobarrier,noatime,nodiratime'. >>> >>> Thanks, >>> Daniel >>> >>> --- [1] >>> >>> ======================================================= >>> [ INFO: possible circular locking dependency detected ] >>> 2.6.27-rc4-224c #1 >>> ------------------------------------------------------- >>> xfs_fsr/5763 is trying to acquire lock: >>> (&(&ip->i_lock)->mr_lock/2){--..}, at: [<ffffffff803ad8fc>] xfs_ilock+0x8c/0xb0 >>> >>> but task is already holding lock: >>> (&(&ip->i_iolock)->mr_lock/3){--..}, at: [<ffffffff803ad915>] >>> xfs_ilock+0xa5/0xb0 >> >> False positive. We do: >> >> xfs_lock_two_inodes(ip, tip, XFS_IOLOCK_EXCL | XFS_ILOCK_EXCL); > > Why not just change the above line to two lines: > xfs_lock_two_inodes(ip, tip, XFS_IOLOCK_EXCL); > xfs_lock_two_inodes(ip, tip, XFS_ILOCK_EXCL);
Yeah, that'd work, but it implllies that we no longer allow xfs_lock_two_inodes() to take both inode locks at once. It would need a comment blaming^Wexplaining why lockdep requires us to do this, and then debug code in xfs_lock_two_inodes() to catch this when someone makes this mistake again in the future.
Cheers,
Dave. -- Dave Chinner david@fromorbit.com
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