From be7ffc38a80a78e6b68d0f51fae8e8d57b55324c Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 6 Dec 2011 21:58:17 +0000 Subject: [PATCH] xfs: implement lazy removal for the dquot freelist Do not remove dquots from the freelist when we grab a reference to them in xfs_qm_dqlookup, but leave them on the freelist util scanning notices that they have a reference. This speeds up the lookup fastpath, and greatly simplifies the lock ordering constraints. Note that the same scheme is used by the VFS inode and dentry caches. Signed-off-by: Christoph Hellwig Reviewed-by: Dave Chinner Signed-off-by: Ben Myers --- fs/xfs/xfs_dquot.c | 67 +++++++++++++--------------------------------- fs/xfs/xfs_qm.c | 22 +++++++-------- fs/xfs/xfs_quota.h | 4 +-- fs/xfs/xfs_trace.h | 2 -- 4 files changed, 30 insertions(+), 65 deletions(-) diff --git a/fs/xfs/xfs_dquot.c b/fs/xfs/xfs_dquot.c index 3f94f2428a35..35d2b8aad0f9 100644 --- a/fs/xfs/xfs_dquot.c +++ b/fs/xfs/xfs_dquot.c @@ -722,58 +722,25 @@ xfs_qm_dqlookup( * dqlock to look at the id field of the dquot, since the * id can't be modified without the hashlock anyway. */ - if (be32_to_cpu(dqp->q_core.d_id) == id && dqp->q_mount == mp) { - trace_xfs_dqlookup_found(dqp); + if (be32_to_cpu(dqp->q_core.d_id) != id || dqp->q_mount != mp) + continue; - /* - * All in core dquots must be on the dqlist of mp - */ - ASSERT(!list_empty(&dqp->q_mplist)); - - xfs_dqlock(dqp); - if (dqp->q_nrefs == 0) { - ASSERT(!list_empty(&dqp->q_freelist)); - if (!mutex_trylock(&xfs_Gqm->qm_dqfrlist_lock)) { - trace_xfs_dqlookup_want(dqp); - - /* - * We may have raced with dqreclaim_one() - * (and lost). So, flag that we don't - * want the dquot to be reclaimed. - */ - dqp->dq_flags |= XFS_DQ_WANT; - xfs_dqunlock(dqp); - mutex_lock(&xfs_Gqm->qm_dqfrlist_lock); - xfs_dqlock(dqp); - dqp->dq_flags &= ~(XFS_DQ_WANT); - } - - if (dqp->q_nrefs == 0) { - /* take it off the freelist */ - trace_xfs_dqlookup_freelist(dqp); - list_del_init(&dqp->q_freelist); - xfs_Gqm->qm_dqfrlist_cnt--; - } - XFS_DQHOLD(dqp); - mutex_unlock(&xfs_Gqm->qm_dqfrlist_lock); - } else { - XFS_DQHOLD(dqp); - } + trace_xfs_dqlookup_found(dqp); - /* - * move the dquot to the front of the hashchain - */ - ASSERT(mutex_is_locked(&qh->qh_lock)); - list_move(&dqp->q_hashlist, &qh->qh_list); - trace_xfs_dqlookup_done(dqp); - *O_dqpp = dqp; - return 0; - } + xfs_dqlock(dqp); + XFS_DQHOLD(dqp); + + /* + * move the dquot to the front of the hashchain + */ + list_move(&dqp->q_hashlist, &qh->qh_list); + trace_xfs_dqlookup_done(dqp); + *O_dqpp = dqp; + return 0; } *O_dqpp = NULL; - ASSERT(mutex_is_locked(&qh->qh_lock)); - return (1); + return 1; } /* @@ -1033,8 +1000,10 @@ xfs_qm_dqput( if (--dqp->q_nrefs == 0) { trace_xfs_dqput_free(dqp); - list_add_tail(&dqp->q_freelist, &xfs_Gqm->qm_dqfrlist); - xfs_Gqm->qm_dqfrlist_cnt++; + 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 diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c index be1df6839237..6a0c4f0d9306 100644 --- a/fs/xfs/xfs_qm.c +++ b/fs/xfs/xfs_qm.c @@ -517,13 +517,12 @@ xfs_qm_dqpurge_int( * get them off mplist and hashlist, but leave them on freelist. */ list_for_each_entry_safe(dqp, n, &q->qi_dqlist, q_mplist) { - /* - * It's OK to look at the type without taking dqlock here. - * We're holding the mplist lock here, and that's needed for - * a dqreclaim. - */ - if ((dqp->dq_flags & dqtype) == 0) + xfs_dqlock(dqp); + if ((dqp->dq_flags & dqtype) == 0) { + xfs_dqunlock(dqp); continue; + } + xfs_dqunlock(dqp); if (!mutex_trylock(&dqp->q_hash->qh_lock)) { nrecl = q->qi_dqreclaims; @@ -1692,14 +1691,15 @@ xfs_qm_dqreclaim_one(void) xfs_dqlock(dqp); /* - * We are racing with dqlookup here. Naturally we don't - * want to reclaim a dquot that lookup wants. We release the - * freelist lock and start over, so that lookup will grab - * both the dquot and the freelistlock. + * This dquot has already been grabbed by dqlookup. + * Remove it from the freelist and try again. */ - if (dqp->dq_flags & XFS_DQ_WANT) { + if (dqp->q_nrefs) { trace_xfs_dqreclaim_want(dqp); XQM_STATS_INC(xqmstats.xs_qm_dqwants); + + list_del_init(&dqp->q_freelist); + xfs_Gqm->qm_dqfrlist_cnt--; restarts++; startagain = 1; goto dqunlock; diff --git a/fs/xfs/xfs_quota.h b/fs/xfs/xfs_quota.h index cbafdee8b98a..487653ddbef0 100644 --- a/fs/xfs/xfs_quota.h +++ b/fs/xfs/xfs_quota.h @@ -87,7 +87,6 @@ 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_WANT 0x0010 /* for lookup/reclaim race */ #define XFS_DQ_ALLTYPES (XFS_DQ_USER|XFS_DQ_PROJ|XFS_DQ_GROUP) @@ -95,8 +94,7 @@ typedef struct xfs_dqblk { { XFS_DQ_USER, "USER" }, \ { XFS_DQ_PROJ, "PROJ" }, \ { XFS_DQ_GROUP, "GROUP" }, \ - { XFS_DQ_DIRTY, "DIRTY" }, \ - { XFS_DQ_WANT, "WANT" } + { XFS_DQ_DIRTY, "DIRTY" } /* * In the worst case, when both user and group quotas are on, diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h index 494035798873..a9d5b1e06efe 100644 --- a/fs/xfs/xfs_trace.h +++ b/fs/xfs/xfs_trace.h @@ -743,8 +743,6 @@ DEFINE_DQUOT_EVENT(xfs_dqtobp_read); DEFINE_DQUOT_EVENT(xfs_dqread); DEFINE_DQUOT_EVENT(xfs_dqread_fail); DEFINE_DQUOT_EVENT(xfs_dqlookup_found); -DEFINE_DQUOT_EVENT(xfs_dqlookup_want); -DEFINE_DQUOT_EVENT(xfs_dqlookup_freelist); DEFINE_DQUOT_EVENT(xfs_dqlookup_done); DEFINE_DQUOT_EVENT(xfs_dqget_hit); DEFINE_DQUOT_EVENT(xfs_dqget_miss); -- GitLab