On Mon, Nov 28, 2011 at 03:27:32AM -0500, Christoph Hellwig wrote: > Allow xfs_qm_dqput to work without trylock loops by nesting the freelist lock > inside the dquot qlock. In turn that requires trylocks in the reclaim path > instead, but given it's a classic tradeoff between fast and slow path, and > we follow the model of the inode and dentry caches. Funny how that keeps coming up ;) > Document our new lock order now that it has settled. Excellent. > Signed-off-by: Christoph Hellwig <hch@xxxxxx> Subject line has a type (insise). > > --- > fs/xfs/xfs_dquot.c | 98 +++++++++++++++++++++-------------------------------- > fs/xfs/xfs_qm.c | 4 +- > 2 files changed, 42 insertions(+), 60 deletions(-) > > Index: xfs/fs/xfs/xfs_dquot.c > =================================================================== > --- xfs.orig/fs/xfs/xfs_dquot.c 2011-11-25 11:45:53.348630228 +0100 > +++ xfs/fs/xfs/xfs_dquot.c 2011-11-25 11:56:08.655296826 +0100 > @@ -39,20 +39,19 @@ > #include "xfs_qm.h" > #include "xfs_trace.h" > > - > /* > - LOCK ORDER > - > - inode lock (ilock) > - dquot hash-chain lock (hashlock) > - xqm dquot freelist lock (freelistlock > - mount's dquot list lock (mplistlock) > - user dquot lock - lock ordering among dquots is based on the uid or gid > - group dquot lock - similar to udquots. Between the two dquots, the udquot > - has to be locked first. > - pin lock - the dquot lock must be held to take this lock. > - flush lock - ditto. > -*/ > + * Lock order: > + * > + * ip->i_lock > + * qh->qh_lock > + * qi->qi_dqlist_lock > + * dquot->q_qlock > + * dquot->q_flush > + * xfs_Gqm->qm_dqfrlist_lock > + * > + * If two dquots need to be locked the order is user before group/project, > + * otherwise by the lowest id first, see xfs_dqlock2. For the dquot->q_* locks, it might be worth adding the name of the locking functions here so it is obvious when reading the code as q_qlock and q_flush aren't used anywhere outside the locking wrappers... Otherwise looks sane. Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx> -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
