linux-kernel - Re: [PATCH v3] mm: Fixed incorrect comment for _kmem_cache

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Message-ID: <031c79dd-1927-0d81-bfef-6dc64adcad12@suse.cz>
Date:   Tue, 18 Apr 2023 09:10:07 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     zhaoxinchao <ChrisXinchao@...look.com>
Cc:     akpm@...ux-foundation.org, bagasdotme@...il.com, cl@...ux.com,
        iamjoonsoo.kim@....com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, penberg@...nel.org, rientjes@...gle.com
Subject: Re: [PATCH v3] mm: Fixed incorrect comment for _kmem_cache_create
 function

On 4/18/23 04:05, zhaoxinchao wrote:
> From: zhaoxinchao <chrisxinchao@...look.com>
> 
> Actually __kmem_cache_create() returns a status :
> 0 is success
> nonezero are failed.
> 
> This function has three return positions. In addition to successfully
> return 0, the first failed position will return - E2BIG, and the second
> position will return nonzero value for setup_cpu_cache function failure.

Adjusted a bit.

> Signed-off-by: zhaoxinchao <chrisxinchao@...look.com>
> ---
>  mm/slab.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/slab.c b/mm/slab.c
> index edbe722fb..ebd326f07 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -1888,14 +1888,17 @@ static bool set_on_slab_cache(struct kmem_cache *cachep,
>  	return true;
>  }
>  
> -/**
> +/*
>   * __kmem_cache_create - Create a cache.
>   * @cachep: cache management descriptor
>   * @flags: SLAB flags
>   *
> - * Returns a ptr to the cache on success, NULL on failure.
> - * Cannot be called within an int, but can be interrupted.
> - * The @ctor is run when new pages are allocated by the cache.
> + * Returns zero on success, nonzero on failure.
> + * This function has three return positions.
> + * In addition to successfully return 0, the
> + * first failed position will return - E2BIG,
> + * and the second position will return nonzero
> + * value for setup_cpu_cache function failure.

In v2 I recommended dropping the detailed description. Removed it when
merging. The result is merged for 6.5 here:

https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab.git/log/?h=slab/for-6.5/trivial

Thanks!

>   *
>   * The flags are
>   *
> @@ -1908,8 +1911,6 @@ static bool set_on_slab_cache(struct kmem_cache *cachep,
>   * %SLAB_HWCACHE_ALIGN - Align the objects in this cache to a hardware
>   * cacheline.  This can be beneficial if you're counting cycles as closely
>   * as davem.
> - *
> - * Return: a pointer to the created cache or %NULL in case of error
>   */
>  int __kmem_cache_create(struct kmem_cache *cachep, slab_flags_t flags)
>  {