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References: <20240419101643.11534-1-hailong.liu@oppo.com>
In-Reply-To: <20240419101643.11534-1-hailong.liu@oppo.com>
From: Barry Song <21cnbao@gmail.com>
Date: Mon, 22 Apr 2024 11:46:26 +0800
Message-ID: <CAGsJ_4zUhnAAUb77ktJxDvAQpZhGrs00+8iQU3dhwpy=C_CjDA@mail.gmail.com>
Subject: Re: [RFC PATCH v2] mm/vmalloc: fix return value of vb_alloc if size
 is 0.
To: hailong.liu@oppo.com
Cc: akpm@linux-foundation.org, urezki@gmail.com, hch@infradead.org, 
	lstoakes@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org
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On Fri, Apr 19, 2024 at 6:17=E2=80=AFPM <hailong.liu@oppo.com> wrote:
>
> From: "Hailong.Liu" <hailong.liu@oppo.com>
>
> vm_map_ram check return value of vb_alloc by IS_ERR. if
> vm_map_ram(page, 0, 0) , vb_alloc(0, GFP_KERNEL) would return NULL
> which cause kernel panic by vmap_pages_range_noflush=E3=80=82fix this by
> return ERR_PTR(-EINVAL) if size is 0.
>
> Signed-off-by: Hailong.Liu <hailong.liu@oppo.com>
> ---
> Changes since v1 [1]:
> - Return ERR_PTR(-EINVAL) or not check IS_ERR_OR_NULL
>
> BTW,  Barry suggests me that if count is 0, return directly, in my
> opinion, change return value is more resonable.
>
> [1] https://lore.kernel.org/all/84d7cd03-1cf8-401a-8edf-2524db0bd6d5@oppo=
com/
>
>  mm/vmalloc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index a3fedb3ee0db..c430a999805b 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2173,7 +2173,7 @@ static void *vb_alloc(unsigned long size, gfp_t gfp=
_mask)
>                  * get_order(0) returns funny result. Just warn and termi=
nate
>                  * early.
>                  */
> -               return NULL;
> +               return ERR_PTR(-EINVAL);

might be ZERO_SIZE_PTR.

>         }
>         order =3D get_order(size);
>
> --
> 2.34.1