From d5dabd633922ac5ee5bcc67748f7defb8b211469 Mon Sep 17 00:00:00 2001 From: Jiang Biao Date: Wed, 29 Nov 2017 16:11:01 -0800 Subject: [PATCH] fs/mbcache.c: make count_objects() more robust When running ltp stress test for 7*24 hours, vmscan occasionally emits the following warning continuously: mb_cache_scan+0x0/0x3f0 negative objects to delete nr=-9232265467809300450 ... Tracing shows the freeable(mb_cache_count returns) is -1, which causes the continuous accumulation and overflow of total_scan. This patch makes sure that mb_cache_count() cannot return a negative value, which makes the mbcache shrinker more robust. Link: http://lkml.kernel.org/r/1511753419-52328-1-git-send-email-jiang.biao2@zte.com.cn Signed-off-by: Jiang Biao Cc: Al Viro Cc: Minchan Kim Cc: Michal Hocko Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/mbcache.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/mbcache.c b/fs/mbcache.c index d818fd236787..b8b8b9ced9f8 100644 --- a/fs/mbcache.c +++ b/fs/mbcache.c @@ -269,6 +269,9 @@ static unsigned long mb_cache_count(struct shrinker *shrink, struct mb_cache *cache = container_of(shrink, struct mb_cache, c_shrink); + /* Unlikely, but not impossible */ + if (unlikely(cache->c_entry_count < 0)) + return 0; return cache->c_entry_count; } -- GitLab