linux-kernel - Re: [PATCH for v5.9] mm/page_alloc: handle a missing case for memalloc_nocma

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Message-ID: <d587d057-75f1-288e-49d2-0c6ea387d414@suse.cz>
Date:   Fri, 25 Sep 2020 10:55:36 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Joonsoo Kim <js1304@...il.com>,
        Mel Gorman <mgorman@...hsingularity.net>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...nel.org>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        kernel-team@....com, Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH for v5.9] mm/page_alloc: handle a missing case for
 memalloc_nocma_{save/restore} APIs

On 9/25/20 6:59 AM, Joonsoo Kim wrote:
> 2020년 8월 28일 (금) 오전 8:54, Joonsoo Kim <js1304@...il.com>님이 작성:
> 
> Hello, Andrew and Vlastimil.
> 
> It's better to fix this possible bug introduced in v5.9-rc1 before
> v5.9 is released.
> Which approach do you prefer?
> If it is determined, I will immediately send a patch as you suggested.

Hmm both Mel and I preferred the bypass approach and nobody else weighted in, so
if you don't mind, you can use my suggestion. Hmm maybe alloc_flags & ALLOC_CMA
check should precede migratetype check in the if () to optimize for userspace
allocations?

Thanks,
Vlastimil

> Thanks.
>