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References: <20240510100131.1865-1-hailong.liu@oppo.com>
In-Reply-To: <20240510100131.1865-1-hailong.liu@oppo.com>
From: Barry Song <21cnbao@gmail.com>
Date: Fri, 10 May 2024 22:54:47 +1200
Message-ID: <CAGsJ_4y0adNv2ukxNeGct3yPDgscWXFKSvSjZiA3S=CeUWEftw@mail.gmail.com>
Subject: Re: [PATCH v2] mm/vmalloc: fix vmalloc which may return null if
 called with __GFP_NOFAIL
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, 
	xiang@kernel.org, chao@kernel.org, mhocko@suse.com, stable@vger.kernel.org, 
	Oven <liyangouwen1@oppo.com>
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On Fri, May 10, 2024 at 10:01=E2=80=AFPM <hailong.liu@oppo.com> wrote:
>
> From: "Hailong.Liu" <hailong.liu@oppo.com>
>
> commit a421ef303008 ("mm: allow !GFP_KERNEL allocations for kvmalloc")
> includes support for __GFP_NOFAIL, but it presents a conflict with
> commit dd544141b9eb ("vmalloc: back off when the current task is
> OOM-killed"). A possible scenario is as follows:
>
> process-a
> __vmalloc_node_range(GFP_KERNEL | __GFP_NOFAIL)
>     __vmalloc_area_node()
>         vm_area_alloc_pages()
>                 --> oom-killer send SIGKILL to process-a
>         if (fatal_signal_pending(current)) break;
> --> return NULL;
>
> To fix this, do not check fatal_signal_pending() in vm_area_alloc_pages()
> if __GFP_NOFAIL set.
>
> Fixes: 9376130c390a ("mm/vmalloc: add support for __GFP_NOFAIL")
> Cc: <stable@vger.kernel.org>
> Acked-by: Michal Hocko <mhocko@suse.com>
> Suggested-by: Barry Song <21cnbao@gmail.com>
> Reported-by: Oven <liyangouwen1@oppo.com>
> Signed-off-by: Hailong.Liu <hailong.liu@oppo.com>

Reviewed-by: Barry Song <baohua@kernel.org>

> ---
>  mm/vmalloc.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 125427cbdb87..109272b8ee2e 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -3492,7 +3492,7 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
>  {
>         unsigned int nr_allocated =3D 0;
>         gfp_t alloc_gfp =3D gfp;
> -       bool nofail =3D false;
> +       bool nofail =3D gfp & __GFP_NOFAIL;
>         struct page *page;
>         int i;
>
> @@ -3549,12 +3549,11 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
>                  * and compaction etc.
>                  */
>                 alloc_gfp &=3D ~__GFP_NOFAIL;
> -               nofail =3D true;
>         }
>
>         /* High-order pages or fallback path if "bulk" fails. */
>         while (nr_allocated < nr_pages) {
> -               if (fatal_signal_pending(current))
> +               if (!nofail && fatal_signal_pending(current))
>                         break;
>
>                 if (nid =3D=3D NUMA_NO_NODE)
> ---