From 0fbca4d1c3932c27c4794bf5c2b5fc961cf5a54f Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Fri, 28 Jan 2011 11:20:46 +1100 Subject: [PATCH] xfs: fix dquot shaker deadlock Commit 368e136 ("xfs: remove duplicate code from dquot reclaim") fails to unlock the dquot freelist when the number of loop restarts is exceeded in xfs_qm_dqreclaim_one(). This causes hangs in memory reclaim. Rework the loop control logic into an unwind stack that all the different cases jump into. This means there is only one set of code that processes the loop exit criteria, and simplifies the unlocking of all the items from different points in the loop. It also fixes a double increment of the restart counter from the qi_dqlist_lock case. Reported-by: Malcolm Scott Signed-off-by: Dave Chinner Reviewed-by: Alex Elder --- fs/xfs/quota/xfs_qm.c | 46 ++++++++++++++++++++----------------------- 1 file changed, 21 insertions(+), 25 deletions(-) diff --git a/fs/xfs/quota/xfs_qm.c b/fs/xfs/quota/xfs_qm.c index f8e854b4fde8..206a2815ced6 100644 --- a/fs/xfs/quota/xfs_qm.c +++ b/fs/xfs/quota/xfs_qm.c @@ -1863,12 +1863,14 @@ xfs_qm_dqreclaim_one(void) xfs_dquot_t *dqpout; xfs_dquot_t *dqp; int restarts; + int startagain; restarts = 0; dqpout = NULL; /* lockorder: hashchainlock, freelistlock, mplistlock, dqlock, dqflock */ -startagain: +again: + startagain = 0; mutex_lock(&xfs_Gqm->qm_dqfrlist_lock); list_for_each_entry(dqp, &xfs_Gqm->qm_dqfrlist, q_freelist) { @@ -1885,13 +1887,10 @@ startagain: ASSERT(! (dqp->dq_flags & XFS_DQ_INACTIVE)); trace_xfs_dqreclaim_want(dqp); - - xfs_dqunlock(dqp); - mutex_unlock(&xfs_Gqm->qm_dqfrlist_lock); - if (++restarts >= XFS_QM_RECLAIM_MAX_RESTARTS) - return NULL; XQM_STATS_INC(xqmstats.xs_qm_dqwants); - goto startagain; + restarts++; + startagain = 1; + goto dqunlock; } /* @@ -1906,23 +1905,20 @@ startagain: ASSERT(list_empty(&dqp->q_mplist)); list_del_init(&dqp->q_freelist); xfs_Gqm->qm_dqfrlist_cnt--; - xfs_dqunlock(dqp); dqpout = dqp; XQM_STATS_INC(xqmstats.xs_qm_dqinact_reclaims); - break; + goto dqunlock; } ASSERT(dqp->q_hash); ASSERT(!list_empty(&dqp->q_mplist)); /* - * Try to grab the flush lock. If this dquot is in the process of - * getting flushed to disk, we don't want to reclaim it. + * Try to grab the flush lock. If this dquot is in the process + * of getting flushed to disk, we don't want to reclaim it. */ - if (!xfs_dqflock_nowait(dqp)) { - xfs_dqunlock(dqp); - continue; - } + if (!xfs_dqflock_nowait(dqp)) + goto dqunlock; /* * We have the flush lock so we know that this is not in the @@ -1944,8 +1940,7 @@ startagain: xfs_fs_cmn_err(CE_WARN, mp, "xfs_qm_dqreclaim: dquot %p flush failed", dqp); } - xfs_dqunlock(dqp); /* dqflush unlocks dqflock */ - continue; + goto dqunlock; } /* @@ -1967,13 +1962,8 @@ startagain: */ if (!mutex_trylock(&mp->m_quotainfo->qi_dqlist_lock)) { restarts++; - mutex_unlock(&dqp->q_hash->qh_lock); - xfs_dqfunlock(dqp); - xfs_dqunlock(dqp); - mutex_unlock(&xfs_Gqm->qm_dqfrlist_lock); - if (restarts++ >= XFS_QM_RECLAIM_MAX_RESTARTS) - return NULL; - goto startagain; + startagain = 1; + goto qhunlock; } ASSERT(dqp->q_nrefs == 0); @@ -1986,14 +1976,20 @@ startagain: 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); +dqunlock: xfs_dqunlock(dqp); if (dqpout) break; if (restarts >= XFS_QM_RECLAIM_MAX_RESTARTS) - return NULL; + break; + if (startagain) { + mutex_unlock(&xfs_Gqm->qm_dqfrlist_lock); + goto again; + } } mutex_unlock(&xfs_Gqm->qm_dqfrlist_lock); return dqpout; -- 2.30.2