Re: [PATCH 5/5] mm, slub: fix incorrect memcg slab count for bulk free

[Vlastimil Babka <vbabka@suse.cz>]

On 9/16/21 14:39, Miaohe Lin wrote:
> kmem_cache_free_bulk() will call memcg_slab_free_hook() for all objects
> when doing bulk free. So we shouldn't call memcg_slab_free_hook() again
> for bulk free to avoid incorrect memcg slab count.
> 
> Fixes: d1b2cf6cb84a ("mm: memcg/slab: uncharge during kmem_cache_free_bulk()")
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>

Reviewed-by: Vlastimil Babka <vbabka@suse.cz>

I now noticed the series doesn't Cc: stable and it should, so I hope Andrew
can add those together with the review tags. Thanks.

> ---
>  mm/slub.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index f3df0f04a472..d8f77346376d 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -3420,7 +3420,9 @@ static __always_inline void do_slab_free(struct kmem_cache *s,
>  	struct kmem_cache_cpu *c;
>  	unsigned long tid;
>  
> -	memcg_slab_free_hook(s, &head, 1);
> +	/* memcg_slab_free_hook() is already called for bulk free. */
> +	if (!tail)
> +		memcg_slab_free_hook(s, &head, 1);
>  redo:
>  	/*
>  	 * Determine the currently cpus per cpu slab.
>