From 6ff33d99fc5c96797103b48b7b0902c296f09c05 Mon Sep 17 00:00:00 2001
From: Dmitry Monakhov <dmtrmonakhov@yandex-team.ru>
Date: Thu, 31 Oct 2019 10:39:19 +0000
Subject: [PATCH] quota: fix livelock in dquot_writeback_dquots
Git-commit: 6ff33d99fc5c96797103b48b7b0902c296f09c05
Patch-mainline: v5.5-rc1
References: bsc#1163857
Write only quotas which are dirty at entry.
Xfstest: https://github.com/dmonakhov/xfstests/commit/b10ad23566a5bf75832a6f500e1236084083cddc
Link: https://lore.kernel.org/r/20191031103920.3919-1-dmonakhov@openvz.org
Cc: stable@vger.kernel.org
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Dmitry Monakhov <dmtrmonakhov@yandex-team.ru>
Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Jan Kara <jack@suse.cz>
---
fs/quota/dquot.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -611,7 +611,7 @@ EXPORT_SYMBOL(dquot_scan_active);
/* Write all dquot structures to quota files */
int dquot_writeback_dquots(struct super_block *sb, int type)
{
- struct list_head *dirty;
+ struct list_head dirty;
struct dquot *dquot;
struct quota_info *dqopt = sb_dqopt(sb);
int cnt;
@@ -625,9 +625,10 @@ int dquot_writeback_dquots(struct super_
if (!sb_has_quota_active(sb, cnt))
continue;
spin_lock(&dq_list_lock);
- dirty = &dqopt->info[cnt].dqi_dirty_list;
- while (!list_empty(dirty)) {
- dquot = list_first_entry(dirty, struct dquot,
+ /* Move list away to avoid livelock. */
+ list_replace_init(&dqopt->info[cnt].dqi_dirty_list, &dirty);
+ while (!list_empty(&dirty)) {
+ dquot = list_first_entry(&dirty, struct dquot,
dq_dirty);
/* Dirty and inactive can be only bad dquot... */
if (!test_bit(DQ_ACTIVE_B, &dquot->dq_flags)) {