From: Jiang Biao <jiang.biao2@xxxxxxxxxx> Subject: 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@xxxxxxxxxx Signed-off-by: Jiang Biao <jiang.biao2@xxxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Minchan Kim <minchan@xxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: <zhong.weidong@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/mbcache.c | 3 +++ 1 file changed, 3 insertions(+) diff -puN fs/mbcache.c~fs-mbcache-make-count_objects-more-robust fs/mbcache.c --- a/fs/mbcache.c~fs-mbcache-make-count_objects-more-robust +++ a/fs/mbcache.c @@ -269,6 +269,9 @@ static unsigned long mb_cache_count(stru 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; } _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
