linux-kernel - Re: [PATCH v3] mm: fix unexpected changes to {failslab|fail_page

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Date:   Fri, 18 Nov 2022 08:47:45 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Qi Zheng <zhengqi.arch@...edance.com>
Cc:     akpm@...ux-foundation.org, akinobu.mita@...il.com,
        dvyukov@...gle.com, willy@...radead.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v3] mm: fix unexpected changes to
 {failslab|fail_page_alloc}.attr

On Fri, Nov 18, 2022 at 06:00:11PM +0800, Qi Zheng wrote:
> When we specify __GFP_NOWARN, we only expect that no warnings
> will be issued for current caller. But in the __should_failslab()
> and __should_fail_alloc_page(), the local GFP flags alter the
> global {failslab|fail_page_alloc}.attr, which is persistent and
> shared by all tasks. This is not what we expected, let's fix it.
> 
> Cc: stable@...r.kernel.org
> Fixes: 3f913fc5f974 ("mm: fix missing handler for __GFP_NOWARN")
> Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
> Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
> Reviewed-by: Akinobu Mita <akinobu.mita@...il.com>
> ---
>  v1: https://lore.kernel.org/lkml/20221107033109.59709-1-zhengqi.arch@bytedance.com/
>  v2: https://lore.kernel.org/lkml/20221108035232.87180-1-zhengqi.arch@bytedance.com/

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

Jason