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Commit be7ffc38 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Ben Myers
Browse files

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: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
Signed-off-by: default avatarBen Myers <bpm@sgi.com>
parent 80a376bf

fs/xfs/xfs_dquot.c

+18 −49
Original line number Diff line number Diff line
@@ -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);



			/*

			 * All in core dquots must be on the dqlist of mp

			 */

			ASSERT(!list_empty(&dqp->q_mplist));

		if (be32_to_cpu(dqp->q_core.d_id) != id || dqp->q_mount != mp)

			continue;



			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);

		trace_xfs_dqlookup_found(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);

			}



		/*

		 * 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;

	}

	}



	*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);



			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

fs/xfs/xfs_qm.c

+11 −11
Original line number Diff line number Diff line
@@ -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;

fs/xfs/xfs_quota.h

+1 −3
Original line number Diff line number Diff line
@@ -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,

fs/xfs/xfs_trace.h

+0 −2
Original line number Diff line number Diff line
@@ -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);