vmscan: fix shrinker callback bug in fs/super.c

The callback must not return -1 when nr_to_scan is zero. Fix the bug in
fs/super.c and add this requirement to the callback specification.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/super.c b/fs/super.c
index 3f56a269a4f4..32a81f3467e0 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -61,7 +61,7 @@ static int prune_super(struct shrinker *shrink, struct shrink_control *sc)
                 return -1;
 
         if (!grab_super_passive(sb))
-                return -1;
+                return !sc->nr_to_scan ? 0 : -1;
 
         if (sb->s_op && sb->s_op->nr_cached_objects)
                 fs_objects = sb->s_op->nr_cached_objects(sb);