From 797f55ef12d752d2a7fb04fae5d24e019adf2a1d Mon Sep 17 00:00:00 2001 From: Sam Atkinson Date: Fri, 20 Oct 2023 17:22:04 -0400 Subject: [PATCH] Do not persist user/group/project quota zap objects when unneeded In the zfs_id_over*quota functions, there is a short-circuit to skip the zap_lookup when the quota zap does not exist. If quotas are never used in a zpool, then the quota zap will never exist. But if user/group/project quotas are ever used, the zap objects will be created and will persist even if the quotas are deleted. The quota zap_lookup in the write path can become a bottleneck for write-heavy small I/O workloads. Before this commit, it was not possible to remove this lookup without creating a new zpool. Reviewed-by: Brian Behlendorf Signed-off-by: Sam Atkinson Closes #14721 --- module/zfs/zfs_quota.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/module/zfs/zfs_quota.c b/module/zfs/zfs_quota.c index 9b351eefc..56f9d22ed 100644 --- a/module/zfs/zfs_quota.c +++ b/module/zfs/zfs_quota.c @@ -347,18 +347,32 @@ zfs_set_userquota(zfsvfs_t *zfsvfs, zfs_userquota_prop_t type, if (*objp == 0) { *objp = zap_create(zfsvfs->z_os, DMU_OT_USERGROUP_QUOTA, DMU_OT_NONE, 0, tx); - VERIFY(0 == zap_add(zfsvfs->z_os, MASTER_NODE_OBJ, + VERIFY0(zap_add(zfsvfs->z_os, MASTER_NODE_OBJ, zfs_userquota_prop_prefixes[type], 8, 1, objp, tx)); } - mutex_exit(&zfsvfs->z_lock); if (quota == 0) { err = zap_remove(zfsvfs->z_os, *objp, buf, tx); if (err == ENOENT) err = 0; + /* + * If the quota contains no more entries after the entry + * was removed, destroy the quota zap and remove the + * reference from zfsvfs. This will save us unnecessary + * zap_lookups for the quota during writes. + */ + uint64_t zap_nentries; + VERIFY0(zap_count(zfsvfs->z_os, *objp, &zap_nentries)); + if (zap_nentries == 0) { + VERIFY0(zap_remove(zfsvfs->z_os, MASTER_NODE_OBJ, + zfs_userquota_prop_prefixes[type], tx)); + VERIFY0(zap_destroy(zfsvfs->z_os, *objp, tx)); + *objp = 0; + } } else { err = zap_update(zfsvfs->z_os, *objp, buf, 8, 1, "a, tx); } + mutex_exit(&zfsvfs->z_lock); ASSERT(err == 0); if (fuid_dirtied) zfs_fuid_sync(zfsvfs, tx);