linux-kernel - Re: [PATCH] mm: memcontrol: clarify swapaccount=0 deprecation warning

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Message-ID: <CAJD7tkbQmTQJU4-L_CD=aG-k5uLSWL=W=M7NKM2OgawS8xCiVg@mail.gmail.com>
Date: Tue, 13 Feb 2024 00:24:38 -0800
From: Yosry Ahmed <yosryahmed@...gle.com>
To: Johannes Weiner <hannes@...xchg.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Michal Hocko <mhocko@...nel.org>, 
	Shakeel Butt <shakeelb@...gle.com>, Roman Gushchin <roman.gushchin@...ux.dev>, linux-mm@...ck.org, 
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Jonas Schäfer <jonas@...licki.name>, 
	Narcis Garcia <debianlists@...iu.net>
Subject: Re: [PATCH] mm: memcontrol: clarify swapaccount=0 deprecation warning

On Tue, Feb 13, 2024 at 12:16 AM Johannes Weiner <hannes@...xchg.org> wrote:
>
> The swapaccount deprecation warning is throwing false positives. Since
> we deprecated the knob and defaulted to enabling, the only reports
> we've been getting are from folks that set swapaccount=1. While this
> is a nice affirmation that always-enabling was the right choice, we
> certainly don't want to warn when users request the supported mode.
>
> Only warn when disabling is requested, and clarify the warning.
>
> Fixes: b25806dcd3d5 ("mm: memcontrol: deprecate swapaccounting=0 mode")
> Cc: stable@...r.kernel.org
> Reported-by: "Jonas Schäfer" <jonas@...licki.name>
> Reported-by: Narcis Garcia <debianlists@...iu.net>
> Suggested-by: Yosry Ahmed <yosryahmed@...gle.com>
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

Reviewed-by: Yosry Ahmed <yosryahmed@...gle.com>

> ---
>  mm/memcontrol.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 1ed40f9d3a27..107ec5d36819 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -7971,9 +7971,13 @@ bool mem_cgroup_swap_full(struct folio *folio)
>
>  static int __init setup_swap_account(char *s)
>  {
> -       pr_warn_once("The swapaccount= commandline option is deprecated "
> -                    "Please report your usecase to linux-mm@...ck.org if you "
> -                    "depend on this functionality.\n");
> +       bool res;
> +
> +       if (!kstrtobool(s, &res) && !res)
> +               pr_warn_once("The swapaccount=0 commdandline option is deprecated "
> +                            "in favor of configuring swap control via cgroupfs. "
> +                            "Please report your usecase to linux-mm@...ck.org if you "
> +                            "depend on this functionality.\n");

This line is surely getting long, but I see other similar instances so
I guess that's okay.

>         return 1;
>  }
>  __setup("swapaccount=", setup_swap_account);
> --
> 2.43.0
>