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From:   Shakeel Butt <shakeelb@google.com>
Date:   Tue, 28 Jul 2020 08:07:09 -0700
Message-ID: <CALvZod6nFiUvcCViwwiHY9x5xw=JCYM_NUOQCkLMeLD8-JNCaw@mail.gmail.com>
Subject: Re: [PATCH] mm: memcontrol: restore proper dirty throttling when
 memory.high changes
To:     Johannes Weiner <hannes@cmpxchg.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Michal Hocko <mhocko@suse.com>, Roman Gushchin <guro@fb.com>,
        Linux MM <linux-mm@kvack.org>,
        Cgroups <cgroups@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Kernel Team <kernel-team@fb.com>
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On Tue, Jul 28, 2020 at 6:53 AM Johannes Weiner <hannes@cmpxchg.org> wrote:
>
> Commit 8c8c383c04f6 ("mm: memcontrol: try harder to set a new
> memory.high") inadvertently removed a callback to recalculate the
> writeback cache size in light of a newly configured memory.high limit.
>
> Without letting the writeback cache know about a potentially heavily
> reduced limit, it may permit too many dirty pages, which can cause
> unnecessary reclaim latencies or even avoidable OOM situations.
>
> This was spotted while reading the code, it hasn't knowingly caused
> any problems in practice so far.
>
> Fixes: 8c8c383c04f6 ("mm: memcontrol: try harder to set a new memory.high")
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

Reviewed-by: Shakeel Butt <shakeelb@google.com>