From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Brian Geffon <bgeffon@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
"Michael S . Tsirkin" <mst@redhat.com>,
Arnd Bergmann <arnd@arndb.de>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
linux-api@vger.kernel.org, Andy Lutomirski <luto@amacapital.net>,
Andrea Arcangeli <aarcange@redhat.com>,
Sonny Rao <sonnyrao@google.com>, Minchan Kim <minchan@kernel.org>,
Joel Fernandes <joel@joelfernandes.org>,
Yu Zhao <yuzhao@google.com>, Jesse Barnes <jsbarnes@google.com>
Subject: Re: [PATCH v2] mm: Add MREMAP_DONTUNMAP to mremap().
Date: Mon, 10 Feb 2020 13:35:56 +0300 [thread overview]
Message-ID: <20200210103556.wz72op4g554qn5jm@box> (raw)
In-Reply-To: <CADyq12x98QspiWSqNui1OH8+FEUzVyJwxia+ho00S2+Q+PmTjw@mail.gmail.com>
On Fri, Feb 07, 2020 at 12:42:15PM -0800, Brian Geffon wrote:
> Hi Kirill,
> I started a new thread https://lkml.org/lkml/2020/2/7/640 for my v4
> patch. But I wanted to quickly address your comments. Regarding the
> concern around the rmap, no changes actually need to be made. If we
> were to unlink_anon_vma(vma) and then set vma->anon_vma = NULL, that
> would be fine but then as soon as there was a fault the same anon_vma
> would be attached since it's a private anonymous mapping. So there is
> really nothing to do regarding the rmap.
Okay.
My worry was that we create a new VMA with the same anon_vma *and*
vm_pgoff, but I just realized we can do the same with the current
mremap(2) plus following mmap(2) in the old place. So it's not regression.
I guess we are fine here.
> I considered the two flag approach but since I could not come up with
> a concrete use case of MREMAP_MUSTMOVE I decided to just leave the
> single MREMAP_DONTUNMAP flag, the two flag approach would be only for
> clarifying the operations so I'm not sure it's worth it. (Still trying
> to come up with a better name). But I've attached a man page diff to
> the latest patch.
At least it doesn't have 'FIXED' semantics forced on user. It's fine with
me.
--
Kirill A. Shutemov
WARNING: multiple messages have this Message-ID (diff)
From: "Kirill A. Shutemov" <kirill-oKw7cIdHH8eLwutG50LtGA@public.gmane.org>
To: Brian Geffon <bgeffon-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Cc: Andrew Morton
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
"Michael S . Tsirkin"
<mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>,
LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
linux-mm <linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org>,
linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>,
Andrea Arcangeli
<aarcange-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Sonny Rao <sonnyrao-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
Minchan Kim <minchan-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Joel Fernandes
<joel-QYYGw3jwrUn5owFQY34kdNi2O/JbrIOy@public.gmane.org>,
Yu Zhao <yuzhao-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
Jesse Barnes <jsbarnes-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Subject: Re: [PATCH v2] mm: Add MREMAP_DONTUNMAP to mremap().
Date: Mon, 10 Feb 2020 13:35:56 +0300 [thread overview]
Message-ID: <20200210103556.wz72op4g554qn5jm@box> (raw)
In-Reply-To: <CADyq12x98QspiWSqNui1OH8+FEUzVyJwxia+ho00S2+Q+PmTjw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
On Fri, Feb 07, 2020 at 12:42:15PM -0800, Brian Geffon wrote:
> Hi Kirill,
> I started a new thread https://lkml.org/lkml/2020/2/7/640 for my v4
> patch. But I wanted to quickly address your comments. Regarding the
> concern around the rmap, no changes actually need to be made. If we
> were to unlink_anon_vma(vma) and then set vma->anon_vma = NULL, that
> would be fine but then as soon as there was a fault the same anon_vma
> would be attached since it's a private anonymous mapping. So there is
> really nothing to do regarding the rmap.
Okay.
My worry was that we create a new VMA with the same anon_vma *and*
vm_pgoff, but I just realized we can do the same with the current
mremap(2) plus following mmap(2) in the old place. So it's not regression.
I guess we are fine here.
> I considered the two flag approach but since I could not come up with
> a concrete use case of MREMAP_MUSTMOVE I decided to just leave the
> single MREMAP_DONTUNMAP flag, the two flag approach would be only for
> clarifying the operations so I'm not sure it's worth it. (Still trying
> to come up with a better name). But I've attached a man page diff to
> the latest patch.
At least it doesn't have 'FIXED' semantics forced on user. It's fine with
me.
--
Kirill A. Shutemov
next prev parent reply other threads:[~2020-02-10 10:35 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-23 1:46 [PATCH] mm: Add MREMAP_DONTUNMAP to mremap() Brian Geffon
2020-01-23 1:46 ` Brian Geffon
2020-01-23 1:46 ` Brian Geffon
2020-01-23 3:02 ` Andy Lutomirski
2020-01-23 3:02 ` Andy Lutomirski
2020-01-23 18:47 ` Lokesh Gidra
2020-01-23 19:02 ` Brian Geffon
2020-01-23 19:03 ` Brian Geffon
2020-01-23 19:03 ` Brian Geffon
2020-01-24 19:06 ` [PATCH v2] " Brian Geffon
2020-01-24 19:06 ` Brian Geffon
2020-01-24 19:06 ` Brian Geffon
2020-01-26 5:16 ` Nathan Chancellor
2020-01-26 5:16 ` Nathan Chancellor
2020-01-27 2:21 ` Brian Geffon
2020-01-27 2:21 ` Brian Geffon
2020-01-27 2:21 ` Brian Geffon
2020-01-26 22:06 ` Kirill A. Shutemov
2020-01-26 22:06 ` Kirill A. Shutemov
2020-01-28 1:35 ` Brian Geffon
2020-01-28 1:35 ` Brian Geffon
2020-01-29 10:46 ` Kirill A. Shutemov
2020-01-29 10:46 ` Kirill A. Shutemov
2020-02-01 21:03 ` Brian Geffon
2020-02-01 21:03 ` Brian Geffon
2020-02-01 21:03 ` Brian Geffon
2020-02-02 4:17 ` Brian Geffon
2020-02-02 4:17 ` Brian Geffon
2020-02-03 13:09 ` Kirill A. Shutemov
2020-02-07 20:42 ` Brian Geffon
2020-02-07 20:42 ` Brian Geffon
2020-02-10 10:35 ` Kirill A. Shutemov [this message]
2020-02-10 10:35 ` Kirill A. Shutemov
2020-01-27 10:13 ` Florian Weimer
2020-01-27 10:13 ` Florian Weimer
2020-01-27 10:13 ` Florian Weimer
2020-01-27 22:33 ` Brian Geffon
2020-01-27 22:33 ` Brian Geffon
2020-01-27 22:33 ` Brian Geffon
2020-01-30 12:19 ` Florian Weimer
2020-01-30 12:19 ` Florian Weimer
2020-01-30 12:19 ` Florian Weimer
2020-01-27 4:46 ` [PATCH] " Dan Carpenter
2020-01-27 4:46 ` Dan Carpenter
2020-01-27 4:46 ` Dan Carpenter
2020-01-27 4:46 ` Dan Carpenter
2020-01-27 5:30 ` [PATCH v3] " Brian Geffon
2020-01-27 5:30 ` Brian Geffon
2020-01-27 5:30 ` Brian Geffon
2020-01-28 15:26 ` Will Deacon
2020-01-28 15:26 ` Will Deacon
2020-01-30 10:12 ` Will Deacon
2020-01-30 10:12 ` Will Deacon
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