[PATCH] mm/vmscan: make do_shrink_slab more robust.

[Jiang Biao]

When running ltp stress test for 7*24 hours, the kernel occasionally
complains the following warning continuously,

mb_cache_shrink_scan+0x0/0x3f0 negative objects to delete
nr=-9222526086287711848
mb_cache_shrink_scan+0x0/0x3f0 negative objects to delete
nr=-9222420761333860545
mb_cache_shrink_scan+0x0/0x3f0 negative objects to delete
nr=-9222287677544280360
...

The tracing result shows the freeable(mb_cache_shrink_scan returns)
is -1, which causes the continuous accumulation and overflow of
total_scan.

This patch make do_shrink_slab more robust when
shrinker->count_objects return negative freeable.

Signed-off-by: Jiang Biao <jiang.biao2@xxxxxxxxxx>
---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index eb2f031..3ea28f0 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -323,7 +323,7 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
 	long scanned = 0, next_deferred;
 
 	freeable = shrinker->count_objects(shrinker, shrinkctl);
-	if (freeable == 0)
+	if (freeable <= 0)
 		return 0;
 
 	/*
-- 
2.7.4