diff options
author | Christoph Hellwig <hch@infradead.org> | 2011-12-07 01:58:19 +0400 |
---|---|---|
committer | Ben Myers <bpm@sgi.com> | 2011-12-15 07:15:42 +0400 |
commit | bf72de3194e73fa210a904b0bd951135286bb385 (patch) | |
tree | 408ead179da91befd82e0cc23ed66830ead2fa59 /fs/xfs/xfs_dquot.c | |
parent | 92678554abfc2a2f2727ad168da87d8d434ac904 (diff) | |
download | linux-bf72de3194e73fa210a904b0bd951135286bb385.tar.xz |
xfs: nest qm_dqfrlist_lock inside the dquot qlock
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.
Document our new lock order now that it has settled.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
Diffstat (limited to 'fs/xfs/xfs_dquot.c')
-rw-r--r-- | fs/xfs/xfs_dquot.c | 97 |
1 files changed, 38 insertions, 59 deletions
diff --git a/fs/xfs/xfs_dquot.c b/fs/xfs/xfs_dquot.c index d06d2a61e31b..f1d3ccb2980e 100644 --- a/fs/xfs/xfs_dquot.c +++ b/fs/xfs/xfs_dquot.c @@ -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 (xfs_dqlock() and friends) + * dquot->q_flush (xfs_dqflock() and friends) + * 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. + */ #ifdef DEBUG xfs_buftarg_t *xfs_dqerror_target; @@ -984,69 +983,49 @@ restart: */ void xfs_qm_dqput( - xfs_dquot_t *dqp) + struct xfs_dquot *dqp) { - xfs_dquot_t *gdqp; + struct xfs_dquot *gdqp; ASSERT(dqp->q_nrefs > 0); ASSERT(XFS_DQ_IS_LOCKED(dqp)); trace_xfs_dqput(dqp); - if (dqp->q_nrefs != 1) { - dqp->q_nrefs--; +recurse: + if (--dqp->q_nrefs > 0) { xfs_dqunlock(dqp); return; } + trace_xfs_dqput_free(dqp); + + mutex_lock(&xfs_Gqm->qm_dqfrlist_lock); + if (list_empty(&dqp->q_freelist)) { + list_add_tail(&dqp->q_freelist, &xfs_Gqm->qm_dqfrlist); + xfs_Gqm->qm_dqfrlist_cnt++; + } + mutex_unlock(&xfs_Gqm->qm_dqfrlist_lock); + /* - * drop the dqlock and acquire the freelist and dqlock - * in the right order; but try to get it out-of-order first + * If we just added a udquot to the freelist, then we want to release + * the gdquot reference that it (probably) has. Otherwise it'll keep + * the gdquot from getting reclaimed. */ - if (!mutex_trylock(&xfs_Gqm->qm_dqfrlist_lock)) { - trace_xfs_dqput_wait(dqp); - xfs_dqunlock(dqp); - mutex_lock(&xfs_Gqm->qm_dqfrlist_lock); - xfs_dqlock(dqp); + gdqp = dqp->q_gdquot; + if (gdqp) { + xfs_dqlock(gdqp); + dqp->q_gdquot = NULL; } + xfs_dqunlock(dqp); - while (1) { - gdqp = NULL; - - /* We can't depend on nrefs being == 1 here */ - if (--dqp->q_nrefs == 0) { - trace_xfs_dqput_free(dqp); - - if (list_empty(&dqp->q_freelist)) { - list_add_tail(&dqp->q_freelist, &xfs_Gqm->qm_dqfrlist); - xfs_Gqm->qm_dqfrlist_cnt++; - } - - /* - * If we just added a udquot to the freelist, then - * we want to release the gdquot reference that - * it (probably) has. Otherwise it'll keep the - * gdquot from getting reclaimed. - */ - if ((gdqp = dqp->q_gdquot)) { - /* - * Avoid a recursive dqput call - */ - xfs_dqlock(gdqp); - dqp->q_gdquot = NULL; - } - } - xfs_dqunlock(dqp); - - /* - * If we had a group quota inside the user quota as a hint, - * release it now. - */ - if (! gdqp) - break; + /* + * If we had a group quota hint, release it now. + */ + if (gdqp) { dqp = gdqp; + goto recurse; } - mutex_unlock(&xfs_Gqm->qm_dqfrlist_lock); } /* |