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xfs: flatten the dquot lock ordering

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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 <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
This commit is contained in:
Christoph Hellwig 2011-12-06 21:58:18 +00:00 committed by Ben Myers
parent be7ffc38a8
commit 92678554ab
4 changed files with 109 additions and 156 deletions
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123
fs/xfs/xfs_dquot.c
View file

@ -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;
}
/*
* 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.
*/
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));
list_del_init(&dqp->q_hashlist);
qh->qh_version++;
list_del_init(&dqp->q_mplist);
mp->m_quotainfo->qi_dqreclaims++;
mp->m_quotainfo->qi_dquots--;
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_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--;
mutex_unlock(&xfs_Gqm->qm_dqfrlist_lock);
xfs_qm_dqdestroy(dqp);
return 0;
}
/*

2
fs/xfs/xfs_dquot.h
View file

@ -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 *);

134
fs/xfs/xfs_qm.c
View file

@ -398,7 +398,8 @@ again:
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 @@ again:
/* 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;
struct xfs_dquot *dqp;
int restarts = 0;
restarts = 0;
dqpout = NULL;
/* 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 @@ again:
list_del_init(&dqp->q_freelist);
xfs_Gqm->qm_dqfrlist_cnt--;
restarts++;
startagain = 1;
goto dqunlock;
}
@ -1737,57 +1716,42 @@ again:
}
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;
}
/*

4
fs/xfs/xfs_quota.h
View file

@ -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,