linux-kernel - Re: [RFC PATCH] mm/vmalloc: fix vmalloc which may return null if called with __GFP

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Date: Thu, 9 May 2024 09:48:56 +0200
From: Michal Hocko <mhocko@...e.com>
To: hailong.liu@...o.com
Cc: akpm@...ux-foundation.org, urezki@...il.com, hch@...radead.org,
	lstoakes@...il.com, 21cnbao@...il.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, xiang@...nel.org, chao@...nel.org,
	Oven <liyangouwen1@...o.com>
Subject: Re: [RFC PATCH] mm/vmalloc: fix vmalloc which may return null if
 called with __GFP_NOFAIL

On Wed 08-05-24 20:58:08, hailong.liu@...o.com wrote:
> From: "Hailong.Liu" <hailong.liu@...o.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 belows:
> 
> process-a
> kvcalloc(n, m, GFP_KERNEL | __GFP_NOFAIL)
>     __vmalloc_node_range()
> 	__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.
> 
> Reported-by: Oven <liyangouwen1@...o.com>
> Signed-off-by: Hailong.Liu <hailong.liu@...o.com>
> ---
>  mm/vmalloc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 6641be0ca80b..2f359d08bf8d 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -3560,7 +3560,7 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
> 
>  	/* High-order pages or fallback path if "bulk" fails. */
>  	while (nr_allocated < nr_pages) {
> -		if (fatal_signal_pending(current))
> +		if (!(gfp & __GFP_NOFAIL) && fatal_signal_pending(current))

Use nofail instead of gfp & __GFP_NOFAIL.

Other than that looks good to me. After that is fixed, please feel free
to add Acked-by: Michal Hocko <mhocko@...e.com>

I believe this should also have Fixes: 9376130c390a ("mm/vmalloc: add support for __GFP_NOFAIL")
-- 
Michal Hocko
SUSE Labs