linux-kernel - Re: [PATCH 3/3] mm/slub: Fix release all resources used by a slab cache

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Date:   Mon, 15 Jun 2020 15:23:00 +0900
From:   Joonsoo Kim <js1304@...il.com>
To:     Muchun Song <songmuchun@...edance.com>
Cc:     Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] mm/slub: Fix release all resources used by a slab cache

2020년 6월 14일 (일) 오후 9:39, Muchun Song <songmuchun@...edance.com>님이 작성:
>
> The function of __kmem_cache_shutdown() is that release all resources
> used by the slab cache, while currently it stop release resources when
> the preceding node is not empty.
>
> Signed-off-by: Muchun Song <songmuchun@...edance.com>
> ---
>  mm/slub.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index b73505df3de2..4e477ef0f2b9 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -3839,6 +3839,7 @@ bool __kmem_cache_empty(struct kmem_cache *s)
>   */
>  int __kmem_cache_shutdown(struct kmem_cache *s)
>  {
> +       int ret = 0;
>         int node;
>         struct kmem_cache_node *n;
>
> @@ -3846,11 +3847,11 @@ int __kmem_cache_shutdown(struct kmem_cache *s)
>         /* Attempt to free all objects */
>         for_each_kmem_cache_node(s, node, n) {
>                 free_partial(s, n);
> -               if (node_nr_slabs(n))
> -                       return 1;
> +               if (!ret && node_nr_slabs(n))
> +                       ret = 1;
>         }

I don't think that this is an improvement.

If the shutdown condition isn't met, we don't need to process further.
Just 'return 1' looks okay to me.

And, with this change, sysfs_slab_remove() is called even if the
shutdown is failed.
It's better not to have side effects when failing.

Thanks.