linux-kernel - Re: [PATCH 1/2] mm/MADV_COLLAPSE: set EAGAIN on unexpected page refcount

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Message-ID: <1f344fc1-834d-f1df-8a2c-79918be5b22@google.com>
Date:   Thu, 9 Feb 2023 13:50:30 -0800 (PST)
From:   Hugh Dickins <hughd@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
cc:     Hugh Dickins <hughd@...gle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Yang Shi <shy828301@...il.com>,
        Zach O'Keefe <zokeefe@...gle.com>
Subject: Re: [PATCH 1/2] mm/MADV_COLLAPSE: set EAGAIN on unexpected page
 refcount

On Thu, 9 Feb 2023, Andrew Morton wrote:
> 
> Thanks, I'll merge [1/2] into mm-hotfixes.

Great, thanks.

> 
> I'm not seeing anything in the [1/2] changelog which indicates that a
> backport is needed.  IOW,

Correct: it's just changing the errno for some racy cases from "you're
wrong, don't bother me again" to "it might be worth having another go":
not fixing an instability, as 2/2 was.

> 
> # cat .signature
> When fixing a bug, please describe the end-user visible effects of that bug.

If whatever's being run by the end-user is coded to try again on -EAGAIN,
then the end-user will less often see occasional unexplained failures.

Hugh