On Mon 27-11-17 11:30:19, Jiang Biao wrote: > When running ltp stress test for 7*24 hours, the vmscan occasionally > complains the following warning continuously, > > mb_cache_scan+0x0/0x3f0 negative objects to delete > nr=-9232265467809300450 > ... > > The tracing result shows the freeable(mb_cache_count returns) > is -1, which causes the continuous accumulation and overflow of > total_scan. > > This patch make sure the mb_cache_count not return negative value, > which make the mbcache shrinker more robust. > > Signed-off-by: Jiang Biao <jiang.biao2@xxxxxxxxxx> Going through some old email... a) c_entry_count is unsigned so your patch is a nop as Coverity properly noticed. b) c_entry_count being outside 0..2*cache->c_max_entries is a plain bug. I went through the logic and cannot find out how that could happen though. But in either case your patch just does not make sense. Honza > --- > fs/mbcache.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/fs/mbcache.c b/fs/mbcache.c > index d818fd2..b8b8b9c 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; > } > > -- > 2.7.4 > -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
