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

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Date: Wed, 8 May 2024 22:13:37 +0800
From: Gao Xiang <hsiangkao@...ux.alibaba.com>
To: hailong.liu@...o.com, akpm@...ux-foundation.org,
 Michal Hocko <mhocko@...e.com>
Cc: 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 2024/5/8 21:41, Gao Xiang wrote:
> 
> +Cc Michal,
> 
> On 2024/5/8 20:58, 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>
> 
> Why taging this as RFC here?  It seems a corner-case fix of
> commit a421ef303008

BTW, I guess maybe commit e9c3cda4d86e ("mm, vmalloc: fix high order
__GFP_NOFAIL allocations") misses fatal_signal_pending() handling
anyway..

> 
> Thanks,
> Gao Xiang
>