From: Michal Hocko <mhocko@kernel.org>
To: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: "Potyra, Stefan" <Stefan.Potyra@elektrobit.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Jordan, Tobias" <Tobias.Jordan@elektrobit.com>,
akpm@linux-foundation.org, vbabka@suse.cz,
kirill.shutemov@linux.intel.com, linux-api@vger.kernel.org
Subject: Re: [PATCH] mm: mlockall error for flag MCL_ONFAULT
Date: Mon, 27 May 2019 09:04:15 +0200 [thread overview]
Message-ID: <20190527070415.GA1658@dhcp22.suse.cz> (raw)
In-Reply-To: <20190524214304.enntpu4tvzpyxzfe@ca-dmjordan1.us.oracle.com>
On Fri 24-05-19 17:43:04, Daniel Jordan wrote:
> [ Adding linux-api and some of the people who were involved in the
> MCL_ONFAULT/mlock2/etc discussions. Author of the Fixes patch appears to
> have moved on. ]
>
> On Wed, May 22, 2019 at 11:23:37AM +0000, Potyra, Stefan wrote:
> > If mlockall() is called with only MCL_ONFAULT as flag,
> > it removes any previously applied lockings and does
> > nothing else.
>
> The change looks reasonable. Hard to imagine any application relies on it, and
> they really shouldn't be if they are. Debian codesearch turned up only a few
> cases where stress-ng was doing this for unknown reasons[1] and this change
> isn't gonna break those. In this case I think changing the syscall's behavior
> is justified.
>
> > This behavior is counter-intuitive and doesn't match the
> > Linux man page.
>
> I'd quote it for the changelog:
>
> For mlockall():
>
> EINVAL Unknown flags were specified or MCL_ONFAULT was specified with‐
> out either MCL_FUTURE or MCL_CURRENT.
>
> With that you can add
>
> Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
>
> [1] https://sources.debian.org/src/stress-ng/0.09.50-1/stress-mlock.c/?hl=203#L203
Well spotted and the fix looks reasonable as well. Quoting the man page
seems useful as well.
Acked-by: Michal Hocko <mhocko@suse.com>
Thanks!
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-05-27 7:04 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-22 11:23 [PATCH] mm: mlockall error for flag MCL_ONFAULT Potyra, Stefan
2019-05-24 21:43 ` Daniel Jordan
2019-05-27 7:04 ` Michal Hocko [this message]
2019-05-27 7:53 ` [PATCH v2] " Potyra, Stefan
2019-05-27 13:19 ` Vlastimil Babka
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