linux-kernel - Re: [PATCH] mm: slab: comment __GFP_ZERO case for kmem_cache

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Date:   Sat, 8 Oct 2022 13:38:47 +0900
From:   Hyeonggon Yoo <42.hyeyoo@...il.com>
To:     Alexander Aring <aahringo@...hat.com>
Cc:     cl@...ux.com, penberg@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, akpm@...ux-foundation.org, vbabka@...e.cz,
        roman.gushchin@...ux.dev, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, cluster-devel@...hat.com
Subject: Re: [PATCH] mm: slab: comment __GFP_ZERO case for kmem_cache_alloc

On Fri, Oct 07, 2022 at 10:03:12PM -0400, Alexander Aring wrote:
> This patch will add a comment for the __GFP_ZERO flag case for
> kmem_cache_alloc(). As the current comment mentioned that the flags only
> matters if the cache has no available objects it's different for the
> __GFP_ZERO flag which will ensure that the returned object is always
> zeroed in any case.
> 
> I have the feeling I run into this question already two times if the
> user need to zero the object or not, but the user does not need to zero
> the object afterwards. However another use of __GFP_ZERO and only zero
> the object if the cache has no available objects would also make no
> sense.
> 
> Signed-off-by: Alexander Aring <aahringo@...hat.com>
> ---
>  mm/slab.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/slab.c b/mm/slab.c
> index 10e96137b44f..7a84c2aae85a 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -3482,7 +3482,8 @@ void *__kmem_cache_alloc_lru(struct kmem_cache *cachep, struct list_lru *lru,
>   * @flags: See kmalloc().
>   *
>   * Allocate an object from this cache.  The flags are only relevant
> - * if the cache has no available objects.
> + * if the cache has no available objects. Except flag __GFP_ZERO which
> + * will zero the returned object.
>   *
>   * Return: pointer to the new object or %NULL in case of error
>   */
> -- 
> 2.31.1
> 

Acked-by: Hyeonggon Yoo <42.hyeyoo@...il.com>

Thanks!

-- 
Thanks,
Hyeonggon