From 92678554abfc2a2f2727ad168da87d8d434ac904 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 6 Dec 2011 21:58:18 +0000 Subject: [PATCH] xfs: flatten the dquot lock ordering Introduce a new XFS_DQ_FREEING flag that tells lookup and mplist walks to skip a dquot that is beeing freed, and use this avoid the trylock on the hash and mplist locks in xfs_qm_dqreclaim_one. Also simplify xfs_dqpurge by moving the inodes to a dispose list after marking them XFS_DQ_FREEING and avoid the locker ordering constraints. Signed-off-by: Christoph Hellwig Reviewed-by: Dave Chinner Signed-off-by: Ben Myers --- fs/xfs/xfs_dquot.c | 113 +++++++++++++++++--------------------- fs/xfs/xfs_dquot.h | 2 +- fs/xfs/xfs_qm.c | 134 +++++++++++++++++---------------------------- fs/xfs/xfs_quota.h | 4 +- 4 files changed, 103 insertions(+), 150 deletions(-) diff --git a/fs/xfs/xfs_dquot.c b/fs/xfs/xfs_dquot.c index 35d2b8aad0f9..d06d2a61e31b 100644 --- a/fs/xfs/xfs_dquot.c +++ b/fs/xfs/xfs_dquot.c @@ -728,6 +728,12 @@ xfs_qm_dqlookup( trace_xfs_dqlookup_found(dqp); xfs_dqlock(dqp); + if (dqp->dq_flags & XFS_DQ_FREEING) { + *O_dqpp = NULL; + xfs_dqunlock(dqp); + return -1; + } + XFS_DQHOLD(dqp); /* @@ -781,11 +787,7 @@ xfs_qm_dqget( return (EIO); } } -#endif - again: - -#ifdef DEBUG ASSERT(type == XFS_DQ_USER || type == XFS_DQ_PROJ || type == XFS_DQ_GROUP); @@ -797,13 +799,21 @@ xfs_qm_dqget( ASSERT(ip->i_gdquot == NULL); } #endif + +restart: mutex_lock(&h->qh_lock); /* * Look in the cache (hashtable). * The chain is kept locked during lookup. */ - if (xfs_qm_dqlookup(mp, id, h, O_dqpp) == 0) { + switch (xfs_qm_dqlookup(mp, id, h, O_dqpp)) { + case -1: + XQM_STATS_INC(xqmstats.xs_qm_dquot_dups); + mutex_unlock(&h->qh_lock); + delay(1); + goto restart; + case 0: XQM_STATS_INC(xqmstats.xs_qm_dqcachehits); /* * The dquot was found, moved to the front of the chain, @@ -814,9 +824,11 @@ xfs_qm_dqget( ASSERT(XFS_DQ_IS_LOCKED(*O_dqpp)); mutex_unlock(&h->qh_lock); trace_xfs_dqget_hit(*O_dqpp); - return (0); /* success */ + return 0; /* success */ + default: + XQM_STATS_INC(xqmstats.xs_qm_dqcachemisses); + break; } - XQM_STATS_INC(xqmstats.xs_qm_dqcachemisses); /* * Dquot cache miss. We don't want to keep the inode lock across @@ -913,16 +925,21 @@ xfs_qm_dqget( * lock order between the two dquots here since dqp isn't * on any findable lists yet. */ - if (xfs_qm_dqlookup(mp, id, h, &tmpdqp) == 0) { + switch (xfs_qm_dqlookup(mp, id, h, &tmpdqp)) { + case 0: + case -1: /* - * Duplicate found. Just throw away the new dquot - * and start over. + * Duplicate found, either in cache or on its way out. + * Just throw away the new dquot and start over. */ - xfs_qm_dqput(tmpdqp); + if (tmpdqp) + xfs_qm_dqput(tmpdqp); mutex_unlock(&h->qh_lock); xfs_qm_dqdestroy(dqp); XQM_STATS_INC(xqmstats.xs_qm_dquot_dups); - goto again; + goto restart; + default: + break; } } @@ -1250,51 +1267,18 @@ xfs_dqlock2( } } - /* - * Take a dquot out of the mount's dqlist as well as the hashlist. - * This is called via unmount as well as quotaoff, and the purge - * will always succeed unless there are soft (temp) references - * outstanding. - * - * This returns 0 if it was purged, 1 if it wasn't. It's not an error code - * that we're returning! XXXsup - not cool. + * Take a dquot out of the mount's dqlist as well as the hashlist. This is + * called via unmount as well as quotaoff, and the purge will always succeed. */ -/* ARGSUSED */ -int +void xfs_qm_dqpurge( - xfs_dquot_t *dqp) + struct xfs_dquot *dqp) { - xfs_dqhash_t *qh = dqp->q_hash; - xfs_mount_t *mp = dqp->q_mount; - - ASSERT(mutex_is_locked(&mp->m_quotainfo->qi_dqlist_lock)); - ASSERT(mutex_is_locked(&dqp->q_hash->qh_lock)); - - /* - * XXX(hch): horrible locking order, will get cleaned up ASAP. - */ - if (!mutex_trylock(&xfs_Gqm->qm_dqfrlist_lock)) { - mutex_unlock(&dqp->q_hash->qh_lock); - return 1; - } + struct xfs_mount *mp = dqp->q_mount; + struct xfs_dqhash *qh = dqp->q_hash; xfs_dqlock(dqp); - /* - * We really can't afford to purge a dquot that is - * referenced, because these are hard refs. - * It shouldn't happen in general because we went thru _all_ inodes in - * dqrele_all_inodes before calling this and didn't let the mountlock go. - * However it is possible that we have dquots with temporary - * references that are not attached to an inode. e.g. see xfs_setattr(). - */ - if (dqp->q_nrefs != 0) { - xfs_dqunlock(dqp); - mutex_unlock(&dqp->q_hash->qh_lock); - return (1); - } - - ASSERT(!list_empty(&dqp->q_freelist)); /* * If we're turning off quotas, we have to make sure that, for @@ -1313,19 +1297,14 @@ xfs_qm_dqpurge( } /* - * XXXIf we're turning this type of quotas off, we don't care + * If we are turning this type of quotas off, we don't care * about the dirty metadata sitting in this dquot. OTOH, if * we're unmounting, we do care, so we flush it and wait. */ if (XFS_DQ_IS_DIRTY(dqp)) { int error; - /* dqflush unlocks dqflock */ /* - * Given that dqpurge is a very rare occurrence, it is OK - * that we're holding the hashlist and mplist locks - * across the disk write. But, ... XXXsup - * * We don't care about getting disk errors here. We need * to purge this dquot anyway, so we go ahead regardless. */ @@ -1335,28 +1314,36 @@ xfs_qm_dqpurge( __func__, dqp); xfs_dqflock(dqp); } + ASSERT(atomic_read(&dqp->q_pincount) == 0); ASSERT(XFS_FORCED_SHUTDOWN(mp) || !(dqp->q_logitem.qli_item.li_flags & XFS_LI_IN_AIL)); + xfs_dqfunlock(dqp); + xfs_dqunlock(dqp); + + mutex_lock(&qh->qh_lock); list_del_init(&dqp->q_hashlist); qh->qh_version++; + mutex_unlock(&qh->qh_lock); + mutex_lock(&mp->m_quotainfo->qi_dqlist_lock); list_del_init(&dqp->q_mplist); mp->m_quotainfo->qi_dqreclaims++; mp->m_quotainfo->qi_dquots--; + mutex_unlock(&mp->m_quotainfo->qi_dqlist_lock); + /* + * We move dquots to the freelist as soon as their reference count + * hits zero, so it really should be on the freelist here. + */ + mutex_lock(&xfs_Gqm->qm_dqfrlist_lock); + ASSERT(!list_empty(&dqp->q_freelist)); list_del_init(&dqp->q_freelist); xfs_Gqm->qm_dqfrlist_cnt--; - - xfs_dqfunlock(dqp); - xfs_dqunlock(dqp); - mutex_unlock(&xfs_Gqm->qm_dqfrlist_lock); - mutex_unlock(&qh->qh_lock); xfs_qm_dqdestroy(dqp); - return 0; } /* diff --git a/fs/xfs/xfs_dquot.h b/fs/xfs/xfs_dquot.h index 0b5d2ae92028..98488dfe442f 100644 --- a/fs/xfs/xfs_dquot.h +++ b/fs/xfs/xfs_dquot.h @@ -133,7 +133,7 @@ static inline void xfs_dqunlock_nonotify(struct xfs_dquot *dqp) extern void xfs_qm_dqdestroy(xfs_dquot_t *); extern int xfs_qm_dqflush(xfs_dquot_t *, uint); -extern int xfs_qm_dqpurge(xfs_dquot_t *); +extern void xfs_qm_dqpurge(xfs_dquot_t *); extern void xfs_qm_dqunpin_wait(xfs_dquot_t *); extern void xfs_qm_adjust_dqtimers(xfs_mount_t *, xfs_disk_dquot_t *); diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c index 6a0c4f0d9306..f418731e90f4 100644 --- a/fs/xfs/xfs_qm.c +++ b/fs/xfs/xfs_qm.c @@ -398,7 +398,8 @@ xfs_qm_dqflush_all( mutex_lock(&q->qi_dqlist_lock); list_for_each_entry(dqp, &q->qi_dqlist, q_mplist) { xfs_dqlock(dqp); - if (! XFS_DQ_IS_DIRTY(dqp)) { + if ((dqp->dq_flags & XFS_DQ_FREEING) || + !XFS_DQ_IS_DIRTY(dqp)) { xfs_dqunlock(dqp); continue; } @@ -437,6 +438,7 @@ xfs_qm_dqflush_all( /* return ! busy */ return 0; } + /* * Release the group dquot pointers the user dquots may be * carrying around as a hint. mplist is locked on entry and exit. @@ -453,6 +455,13 @@ xfs_qm_detach_gdquots( ASSERT(mutex_is_locked(&q->qi_dqlist_lock)); list_for_each_entry(dqp, &q->qi_dqlist, q_mplist) { xfs_dqlock(dqp); + if (dqp->dq_flags & XFS_DQ_FREEING) { + xfs_dqunlock(dqp); + mutex_unlock(&q->qi_dqlist_lock); + delay(1); + mutex_lock(&q->qi_dqlist_lock); + goto again; + } if ((gdqp = dqp->q_gdquot)) { xfs_dqlock(gdqp); dqp->q_gdquot = NULL; @@ -489,8 +498,8 @@ xfs_qm_dqpurge_int( struct xfs_quotainfo *q = mp->m_quotainfo; struct xfs_dquot *dqp, *n; uint dqtype; - int nrecl; - int nmisses; + int nmisses = 0; + LIST_HEAD (dispose_list); if (!q) return 0; @@ -509,46 +518,26 @@ xfs_qm_dqpurge_int( */ xfs_qm_detach_gdquots(mp); - again: - nmisses = 0; - ASSERT(mutex_is_locked(&q->qi_dqlist_lock)); /* - * Try to get rid of all of the unwanted dquots. The idea is to - * get them off mplist and hashlist, but leave them on freelist. + * Try to get rid of all of the unwanted dquots. */ list_for_each_entry_safe(dqp, n, &q->qi_dqlist, q_mplist) { xfs_dqlock(dqp); - if ((dqp->dq_flags & dqtype) == 0) { - xfs_dqunlock(dqp); - continue; + if ((dqp->dq_flags & dqtype) != 0 && + !(dqp->dq_flags & XFS_DQ_FREEING)) { + if (dqp->q_nrefs == 0) { + dqp->dq_flags |= XFS_DQ_FREEING; + list_move_tail(&dqp->q_mplist, &dispose_list); + } else + nmisses++; } xfs_dqunlock(dqp); - - if (!mutex_trylock(&dqp->q_hash->qh_lock)) { - nrecl = q->qi_dqreclaims; - mutex_unlock(&q->qi_dqlist_lock); - mutex_lock(&dqp->q_hash->qh_lock); - mutex_lock(&q->qi_dqlist_lock); - - /* - * XXXTheoretically, we can get into a very long - * ping pong game here. - * No one can be adding dquots to the mplist at - * this point, but somebody might be taking things off. - */ - if (nrecl != q->qi_dqreclaims) { - mutex_unlock(&dqp->q_hash->qh_lock); - goto again; - } - } - - /* - * Take the dquot off the mplist and hashlist. It may remain on - * freelist in INACTIVE state. - */ - nmisses += xfs_qm_dqpurge(dqp); } mutex_unlock(&q->qi_dqlist_lock); + + list_for_each_entry_safe(dqp, n, &dispose_list, q_mplist) + xfs_qm_dqpurge(dqp); + return nmisses; } @@ -1667,25 +1656,16 @@ xfs_qm_init_quotainos( /* - * Just pop the least recently used dquot off the freelist and - * recycle it. The returned dquot is locked. + * Pop the least recently used dquot off the freelist and recycle it. */ -STATIC xfs_dquot_t * +STATIC struct xfs_dquot * xfs_qm_dqreclaim_one(void) { - xfs_dquot_t *dqpout; - xfs_dquot_t *dqp; - int restarts; - int startagain; - - restarts = 0; - dqpout = NULL; + struct xfs_dquot *dqp; + int restarts = 0; - /* lockorder: hashchainlock, freelistlock, mplistlock, dqlock, dqflock */ -again: - startagain = 0; mutex_lock(&xfs_Gqm->qm_dqfrlist_lock); - +restart: list_for_each_entry(dqp, &xfs_Gqm->qm_dqfrlist, q_freelist) { struct xfs_mount *mp = dqp->q_mount; xfs_dqlock(dqp); @@ -1701,7 +1681,6 @@ xfs_qm_dqreclaim_one(void) list_del_init(&dqp->q_freelist); xfs_Gqm->qm_dqfrlist_cnt--; restarts++; - startagain = 1; goto dqunlock; } @@ -1737,57 +1716,42 @@ xfs_qm_dqreclaim_one(void) } goto dqunlock; } + xfs_dqfunlock(dqp); /* - * We're trying to get the hashlock out of order. This races - * with dqlookup; so, we giveup and goto the next dquot if - * we couldn't get the hashlock. This way, we won't starve - * a dqlookup process that holds the hashlock that is - * waiting for the freelist lock. + * Prevent lookup now that we are going to reclaim the dquot. + * Once XFS_DQ_FREEING is set lookup won't touch the dquot, + * thus we can drop the lock now. */ - if (!mutex_trylock(&dqp->q_hash->qh_lock)) { - restarts++; - goto dqfunlock; - } + dqp->dq_flags |= XFS_DQ_FREEING; + xfs_dqunlock(dqp); - /* - * This races with dquot allocation code as well as dqflush_all - * and reclaim code. So, if we failed to grab the mplist lock, - * giveup everything and start over. - */ - if (!mutex_trylock(&mp->m_quotainfo->qi_dqlist_lock)) { - restarts++; - startagain = 1; - goto qhunlock; - } + mutex_lock(&dqp->q_hash->qh_lock); + list_del_init(&dqp->q_hashlist); + dqp->q_hash->qh_version++; + mutex_unlock(&dqp->q_hash->qh_lock); - ASSERT(dqp->q_nrefs == 0); + mutex_lock(&mp->m_quotainfo->qi_dqlist_lock); list_del_init(&dqp->q_mplist); mp->m_quotainfo->qi_dquots--; mp->m_quotainfo->qi_dqreclaims++; - list_del_init(&dqp->q_hashlist); - dqp->q_hash->qh_version++; + mutex_unlock(&mp->m_quotainfo->qi_dqlist_lock); + + ASSERT(dqp->q_nrefs == 0); list_del_init(&dqp->q_freelist); xfs_Gqm->qm_dqfrlist_cnt--; - dqpout = dqp; - mutex_unlock(&mp->m_quotainfo->qi_dqlist_lock); -qhunlock: - mutex_unlock(&dqp->q_hash->qh_lock); -dqfunlock: - xfs_dqfunlock(dqp); + + mutex_unlock(&xfs_Gqm->qm_dqfrlist_lock); + return dqp; dqunlock: xfs_dqunlock(dqp); - if (dqpout) - break; if (restarts >= XFS_QM_RECLAIM_MAX_RESTARTS) break; - if (startagain) { - mutex_unlock(&xfs_Gqm->qm_dqfrlist_lock); - goto again; - } + goto restart; } + mutex_unlock(&xfs_Gqm->qm_dqfrlist_lock); - return dqpout; + return NULL; } /* diff --git a/fs/xfs/xfs_quota.h b/fs/xfs/xfs_quota.h index 487653ddbef0..b86c62f5eeba 100644 --- a/fs/xfs/xfs_quota.h +++ b/fs/xfs/xfs_quota.h @@ -87,6 +87,7 @@ typedef struct xfs_dqblk { #define XFS_DQ_PROJ 0x0002 /* project quota */ #define XFS_DQ_GROUP 0x0004 /* a group quota */ #define XFS_DQ_DIRTY 0x0008 /* dquot is dirty */ +#define XFS_DQ_FREEING 0x0010 /* dquot is beeing torn down */ #define XFS_DQ_ALLTYPES (XFS_DQ_USER|XFS_DQ_PROJ|XFS_DQ_GROUP) @@ -94,7 +95,8 @@ typedef struct xfs_dqblk { { XFS_DQ_USER, "USER" }, \ { XFS_DQ_PROJ, "PROJ" }, \ { XFS_DQ_GROUP, "GROUP" }, \ - { XFS_DQ_DIRTY, "DIRTY" } + { XFS_DQ_DIRTY, "DIRTY" }, \ + { XFS_DQ_FREEING, "FREEING" } /* * In the worst case, when both user and group quotas are on, -- GitLab