From 945b407486a0072ec7dd117a0bde2f72d52eb445 Mon Sep 17 00:00:00 2001 From: Mariusz Zaborski Date: Tue, 8 Nov 2022 21:40:22 +0100 Subject: [PATCH] quota: disable quota check for ZVOL The quota for ZVOLs is set to the size of the volume. When the quota reaches the maximum, there isn't an excellent way to check if the new writers are overwriting the data or if they are inserting a new one. Because of that, when we reach the maximum quota, we wait till txg is flushed. This is causing a significant fluctuation in bandwidth. In the case of ZVOL, the quota is enforced by the volsize, so we can omit it. This commit adds a sysctl thats allow to control if the quota mechanism should be enforced or not. Reviewed-by: Brian Behlendorf Signed-off-by: Mariusz Zaborski Sponsored-by: Zededa Inc. Sponsored-by: Klara Inc. Closes #13838 --- man/man4/zfs.4 | 6 +++++- module/zfs/dsl_dir.c | 22 ++++++++++++++++++---- 2 files changed, 23 insertions(+), 5 deletions(-) diff --git a/man/man4/zfs.4 b/man/man4/zfs.4 index 5b53b1310e..ad3d8810e9 100644 --- a/man/man4/zfs.4 +++ b/man/man4/zfs.4 @@ -15,7 +15,7 @@ .\" own identifying information: .\" Portions Copyright [yyyy] [name of copyright owner] .\" -.Dd June 1, 2021 +.Dd November 7, 2022 .Dt ZFS 4 .Os . @@ -2386,6 +2386,10 @@ Defines zvol block devices behaviour when .It Sy 3 .No equivalent to Sy none .El +. +.It Sy zvol_enforce_quotas Ns = Ns Sy 0 Ns | Ns 1 Pq uint +Enable strict ZVOL quota enforcement. +The strict quota enforcement may have a performance impact. .El . .Sh ZFS I/O SCHEDULER diff --git a/module/zfs/dsl_dir.c b/module/zfs/dsl_dir.c index 9af7601774..486f50108b 100644 --- a/module/zfs/dsl_dir.c +++ b/module/zfs/dsl_dir.c @@ -53,6 +53,15 @@ #include "zfs_namecheck.h" #include "zfs_prop.h" +/* + * This controls if we verify the ZVOL quota or not. + * Currently, quotas are not implemented for ZVOLs. + * The quota size is the size of the ZVOL. + * The size of the volume already implies the ZVOL size quota. + * The quota mechanism can introduce a significant performance drop. + */ +static int zvol_enforce_quotas = B_TRUE; + /* * Filesystem and Snapshot Limits * ------------------------------ @@ -1311,7 +1320,9 @@ top_of_function: * If this transaction will result in a net free of space, * we want to let it through. */ - if (ignorequota || netfree || dsl_dir_phys(dd)->dd_quota == 0) + if (ignorequota || netfree || dsl_dir_phys(dd)->dd_quota == 0 || + (dmu_objset_type(tx->tx_objset) == DMU_OST_ZVOL && + zvol_enforce_quotas == B_FALSE)) quota = UINT64_MAX; else quota = dsl_dir_phys(dd)->dd_quota; @@ -1399,10 +1410,9 @@ top_of_function: ignorequota = (dsl_dir_phys(dd)->dd_head_dataset_obj == 0); first = B_FALSE; goto top_of_function; - - } else { - return (0); } + + return (0); } /* @@ -2483,3 +2493,7 @@ dsl_dir_cancel_waiters(dsl_dir_t *dd) EXPORT_SYMBOL(dsl_dir_set_quota); EXPORT_SYMBOL(dsl_dir_set_reservation); #endif + +/* CSTYLED */ +ZFS_MODULE_PARAM(zfs, , zvol_enforce_quotas, INT, ZMOD_RW, + "Enable strict ZVOL quota enforcment");