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Subject: Re: [PATCH] kernel: sysctl: make drop_caches write-only
To:     Johannes Weiner <hannes@cmpxchg.org>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        kernel-team@fb.com
References: <20191031221602.9375-1-hannes@cmpxchg.org>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat GmbH
Message-ID: <39ae67e9-fc2b-5c85-63a2-a149cd99b0b3@redhat.com>
Date:   Mon, 4 Nov 2019 11:37:34 +0100
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On 31.10.19 23:16, Johannes Weiner wrote:
> Currently, the drop_caches proc file and sysctl read back the last
> value written, suggesting this is somehow a stateful setting instead
> of a one-time command. Make it write-only, like e.g. compact_memory.
>=20
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
> ---
>   kernel/sysctl.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>=20
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 31ece1120aa4..50373984a5e2 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -1474,7 +1474,7 @@ static struct ctl_table vm_table[] =3D {
>   =09=09.procname=09=3D "drop_caches",
>   =09=09.data=09=09=3D &sysctl_drop_caches,
>   =09=09.maxlen=09=09=3D sizeof(int),
> -=09=09.mode=09=09=3D 0644,
> +=09=09.mode=09=09=3D 0200,
>   =09=09.proc_handler=09=3D drop_caches_sysctl_handler,
>   =09=09.extra1=09=09=3D SYSCTL_ONE,
>   =09=09.extra2=09=09=3D &four,
>=20

Makes perfect sense to me (and we might notice while in next/master if=20
this breaks something, hopefully)

Acked-by: David Hildenbrand <david@redhat.com>

--=20

Thanks,

David / dhildenb