From: Michal Hocko <mhocko@kernel.org>
To: John Hubbard <jhubbard@nvidia.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>,
linux-api@vger.kernel.org, Khalid Aziz <khalid.aziz@oracle.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Andrew Morton <akpm@linux-foundation.org>,
Russell King - ARM Linux <linux@armlinux.org.uk>,
Andrea Arcangeli <aarcange@redhat.com>,
linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
linux-arch@vger.kernel.org, Florian Weimer <fweimer@redhat.com>
Subject: Re: [PATCH v2] mmap.2: document new MAP_FIXED_SAFE flag
Date: Thu, 30 Nov 2017 19:39:14 +0100 [thread overview]
Message-ID: <20171130183914.xknl33pxij62hdhp@dhcp22.suse.cz> (raw)
In-Reply-To: <1a96e274-a986-12b7-6e47-fc6355cbf637@nvidia.com>
On Thu 30-11-17 10:31:12, John Hubbard wrote:
> On 11/30/2017 12:24 AM, Michal Hocko wrote:
> > Updated version based on feedback from John.
> > ---
> > From ade1eba229b558431581448e7d7838f0e1fe2c49 Mon Sep 17 00:00:00 2001
> > From: Michal Hocko <mhocko@suse.com>
> > Date: Wed, 29 Nov 2017 15:32:08 +0100
> > Subject: [PATCH] mmap.2: document new MAP_FIXED_SAFE flag
> >
> > 4.16+ kernels offer a new MAP_FIXED_SAFE flag which allows the caller to
> > atomicaly probe for a given address range.
> >
> > [wording heavily updated by John Hubbard <jhubbard@nvidia.com>]
> > Signed-off-by: Michal Hocko <mhocko@suse.com>
> > ---
> > man2/mmap.2 | 22 ++++++++++++++++++++++
> > 1 file changed, 22 insertions(+)
> >
> > diff --git a/man2/mmap.2 b/man2/mmap.2
> > index 385f3bfd5393..923bbb290875 100644
> > --- a/man2/mmap.2
> > +++ b/man2/mmap.2
> > @@ -225,6 +225,22 @@ will fail.
> > Because requiring a fixed address for a mapping is less portable,
> > the use of this option is discouraged.
> > .TP
> > +.BR MAP_FIXED_SAFE " (since Linux 4.16)"
> > +Similar to MAP_FIXED with respect to the
> > +.I
> > +addr
> > +enforcement, but different in that MAP_FIXED_SAFE never clobbers a pre-existing
> > +mapped range. If the requested range would collide with an existing
> > +mapping, then this call fails with
> > +.B EEXIST.
> > +This flag can therefore be used as a way to atomically (with respect to other
> > +threads) attempt to map an address range: one thread will succeed; all others
> > +will report failure. Please note that older kernels which do not recognize this
> > +flag will typically (upon detecting a collision with a pre-existing mapping)
> > +fall back a "non-MAP_FIXED" type of behavior: they will return an address that
>
> ...and now I've created my own typo: please make that "fall back to a" (the
> "to" was missing).
>
> Sorry about the churn. It turns out that the compiler doesn't catch these. :)
Fixed. I will resubmit after there is more feedback review.
Thanks
--
Michal Hocko
SUSE Labs
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next prev parent reply other threads:[~2017-11-30 18:39 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-29 14:42 [PATCH 0/2] mm: introduce MAP_FIXED_SAFE Michal Hocko
2017-11-29 14:42 ` [PATCH 1/2] " Michal Hocko
2017-12-06 5:15 ` Michael Ellerman
2017-12-06 9:27 ` Michal Hocko
2017-12-06 10:02 ` Michal Hocko
2017-12-07 12:07 ` Pavel Machek
2017-11-29 14:42 ` [PATCH 2/2] fs, elf: drop MAP_FIXED usage from elf_map Michal Hocko
2017-11-29 17:45 ` Khalid Aziz
2018-05-29 22:21 ` Mike Kravetz
2018-05-30 8:02 ` Michal Hocko
2018-05-30 15:00 ` Mike Kravetz
2018-05-30 16:25 ` Michal Hocko
2018-05-31 0:51 ` Mike Kravetz
2018-05-31 9:24 ` Michal Hocko
2018-05-31 21:46 ` Mike Kravetz
2017-11-29 14:45 ` [PATCH] mmap.2: document new MAP_FIXED_SAFE flag Michal Hocko
2017-11-30 3:16 ` John Hubbard
2017-11-30 8:23 ` Michal Hocko
2017-11-30 8:24 ` [PATCH v2] " Michal Hocko
2017-11-30 18:31 ` John Hubbard
2017-11-30 18:39 ` Michal Hocko [this message]
2017-11-29 15:13 ` [PATCH 0/2] mm: introduce MAP_FIXED_SAFE Rasmus Villemoes
2017-11-29 15:50 ` Michal Hocko
2017-11-29 22:15 ` Kees Cook
2017-11-29 22:12 ` Kees Cook
2017-11-29 22:25 ` Kees Cook
2017-11-30 6:58 ` Michal Hocko
2017-12-01 15:26 ` Cyril Hrubis
2017-12-06 4:51 ` Michael Ellerman
2017-12-06 4:54 ` Matthew Wilcox
2017-12-06 7:03 ` Matthew Wilcox
2017-12-06 7:33 ` John Hubbard
2017-12-06 7:35 ` Florian Weimer
2017-12-06 8:06 ` John Hubbard
2017-12-06 8:54 ` Florian Weimer
2017-12-07 5:46 ` Michael Ellerman
2017-12-07 19:14 ` Kees Cook
2017-12-07 19:57 ` Matthew Wilcox
2017-12-08 8:33 ` Michal Hocko
2017-12-08 20:13 ` Kees Cook
2017-12-08 20:57 ` Matthew Wilcox
2017-12-08 11:08 ` Michael Ellerman
2017-12-08 14:27 ` Pavel Machek
2017-12-08 20:31 ` Cyril Hrubis
2017-12-08 20:47 ` Florian Weimer
2017-12-08 14:33 ` David Laight
2017-12-06 4:50 ` Michael Ellerman
2017-12-06 7:33 ` Rasmus Villemoes
2017-12-06 9:08 ` Michal Hocko
2017-12-07 0:19 ` Kees Cook
2017-12-07 1:08 ` John Hubbard
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