[PATCH 3.15 026/109] quota: missing lock in dqcache_shrink_scan()

[Greg Kroah-Hartman]

3.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Niu Yawei <yawei.niu@xxxxxxxxx>

commit d68aab6b8f572406aa93b45ef6483934dd3b54a6 upstream.

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.

Fixes: 1ab6c4997e04a00c50c6d786c2f046adc0d1f5de
Signed-off-by: Niu Yawei <yawei.niu@xxxxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/quota/dquot.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -702,6 +702,7 @@ dqcache_shrink_scan(struct shrinker *shr
 	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 *shr
 		freed++;
 		head = free_dquots.prev;
 	}
+	spin_unlock(&dq_list_lock);
 	return freed;
 }
 


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