linux-kernel - Re: [PATCH] mm: ensure alloc_flags in slow path are initialized

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Message-ID: <CAK8P3a29aAA-YCkk=2h3iW=KTW=kq=gSniWfCzZs4nmpa8Adfw@mail.gmail.com>
Date:   Mon, 23 Jan 2017 17:02:34 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Michal Hocko <mhocko@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>, linux-mm@...ck.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: ensure alloc_flags in slow path are initialized

On Mon, Jan 23, 2017 at 1:55 PM, Vlastimil Babka <vbabka@...e.cz> wrote:
> On 01/23/2017 01:16 PM, Arnd Bergmann wrote:

>> To be honest, I can't figure that out either, maybe it is or
>> maybe not,
>
>
> Seems the report is correct and not false positive, in scenario when we goto
> nopage before the assignment, and then goto retry because of __GFP_NOFAIL.

Ok, thanks for checking!

>> but moving the existing initialization up a little
>> higher looks safe and makes it obvious to both me and gcc that
>> the initialization comes before the first use.
>>
>> Fixes: 74eaa4a97e8e ("mm: consolidate GFP_NOFAIL checks in the allocator
>> slowpath")
>
>
> That's a non-stable -next commit ID for mmotm patch:
> mm-consolidate-gfp_nofail-checks-in-the-allocator-slowpath.patch
>
> The patch itself was OK, the problem only comes from integration with
> another mmotm patch (also independently OK):
> mm-page_alloc-fix-premature-oom-when-racing-with-cpuset-mems-update.patch
>
> By their ordering in mmotm, it would work to treat this as a fix for the
> GFP_NOFAIL patch, possibly merged into it.

Ok. I only tracked down which commit introduced the warning, which was
the one above.

    Arnd