linux-kernel - Re: [PATCH] mm, compaction: fast_find_migrateblock() should return pfn in the target zone

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Message-Id: <20220512134945.fe74df5e322b98ae4046ce15@linux-foundation.org>
Date:   Thu, 12 May 2022 13:49:45 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Rei Yamamoto <yamamoto.rei@...fujitsu.com>
Cc:     linmiaohe@...wei.com, aquini@...hat.com, ddutile@...hat.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        mgorman@...hsingularity.net, vvghjk1234@...il.com
Subject: Re: [PATCH] mm, compaction: fast_find_migrateblock() should return
 pfn in the target zone

On Thu, 12 May 2022 13:27:33 +0900 Rei Yamamoto <yamamoto.rei@...fujitsu.com> wrote:

> >> Thank you for your review.
> >> The runtime effect is that compaction become unintended behavior.
> >> For example, pages not in the target zone are added to cc->migratepages list in isolate_migratepages_block().
> >> As a result, pages migrate between nodes unintentionally.
> >
> > Many thanks for clarifying. :) Is this worth a Fixes tag or even CC stable?
> >
> > Thanks!
> 
> Thank you for your reply.
> 
> If add a Fixes tag, I think the following commit:
>   Fixes: 70b4459 ("mm, compaction: use free lists to quickly locate a migration source")
> 
> Andrew, how do you think about this? 

Thanks, I added that and also a paragraph describing the effect of the bug:

https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-compaction-fast_find_migrateblock-should-return-pfn-in-the-target-zone.patch

I assume this problem isn't sufficiently serious to require a -stable
backport of the fix?