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

On Mon, Nov 27, 2017 at 09:37:30AM +0800, Jiang Biao wrote:
> 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.

Good catch.

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

Shrinker.h says count_objects should return 0 if there are no
freeable objects, not -1.

So if something returns -1, changing it with returning 0 would
be more proper fix.

Thanks.


>
> Signed-off-by: Jiang Biao <jiang.biao2@zte.com.cn>
> ---
> 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
>
> --
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