quota: missing lock in dqcache_shrink_scan()

Commit 1ab6c4997e04 (fs: convert fs shrinkers to new scan/count API)
accidentally removed locking from quota shrinker. Fix it -
dqcache_shrink_scan() should use dq_list_lock to protect the
scan on free_dquots list.

CC: stable@vger.kernel.org
Fixes: 1ab6c4997e04a00c50c6d786c2f046adc0d1f5de
Signed-off-by: Niu Yawei <yawei.niu@intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 9cd5f63715c0..7f30bdc57d13 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -702,6 +702,7 @@ dqcache_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
         struct dquot *dquot;
         unsigned long freed = 0;
 
+        spin_lock(&dq_list_lock);
         head = free_dquots.prev;
         while (head != &free_dquots && sc->nr_to_scan) {
                 dquot = list_entry(head, struct dquot, dq_free);
@@ -713,6 +714,7 @@ dqcache_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
                 freed++;
                 head = free_dquots.prev;
         }
+        spin_unlock(&dq_list_lock);
         return freed;
 }