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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: Wed, 29 Jan 2020 13:46:55 +0300	[thread overview]
Message-ID: <20200129104655.egvpavc2tzozlbqe@box> (raw)
In-Reply-To: <CADyq12xCK_3MhGi88Am5P6DVZvrW8vqtyJMHO0zjNhvhYegm1w@mail.gmail.com>

On Mon, Jan 27, 2020 at 05:35:40PM -0800, Brian Geffon wrote:
> Hi Kirill,
> Thanks for taking the time to look at this. I'll update the wording to
> make it clear that MREMAP_FIXED is required with MREMAP_DONTUNMAP.

I still think that chaining flags is strange. The new flag requires all
existing.

And based on the use case you probably don't really need 'fixed'
semantics all the time. The user should be fine with moving the mapping
*somewhere*, not neccessary to the given address.

BTW, name of the flag is confusing. My initial reaction was that it is
variant of MREMAP_FIXED that does't anything at the target address.
Like MAP_FIXED vs. MAP_FIXED_NOREPLACE.

Any better options for the flag name? (I have none)

> Regarding rmap, you're completely right I'm going to roll a new patch
> which will call unlink_anon_vmas() to make sure the rmap is correct,
> I'll also explicitly check that the vma is anonymous and not shared
> returning EINVAL if not, how does that sound?

Fine, I guess. But let me see the end result.

-- 
 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: Wed, 29 Jan 2020 13:46:55 +0300	[thread overview]
Message-ID: <20200129104655.egvpavc2tzozlbqe@box> (raw)
In-Reply-To: <CADyq12xCK_3MhGi88Am5P6DVZvrW8vqtyJMHO0zjNhvhYegm1w-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>

On Mon, Jan 27, 2020 at 05:35:40PM -0800, Brian Geffon wrote:
> Hi Kirill,
> Thanks for taking the time to look at this. I'll update the wording to
> make it clear that MREMAP_FIXED is required with MREMAP_DONTUNMAP.

I still think that chaining flags is strange. The new flag requires all
existing.

And based on the use case you probably don't really need 'fixed'
semantics all the time. The user should be fine with moving the mapping
*somewhere*, not neccessary to the given address.

BTW, name of the flag is confusing. My initial reaction was that it is
variant of MREMAP_FIXED that does't anything at the target address.
Like MAP_FIXED vs. MAP_FIXED_NOREPLACE.

Any better options for the flag name? (I have none)

> Regarding rmap, you're completely right I'm going to roll a new patch
> which will call unlink_anon_vmas() to make sure the rmap is correct,
> I'll also explicitly check that the vma is anonymous and not shared
> returning EINVAL if not, how does that sound?

Fine, I guess. But let me see the end result.

-- 
 Kirill A. Shutemov

  reply	other threads:[~2020-01-29 10:46 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 [this message]
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
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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