From mboxrd@z Thu Jan  1 00:00:00 1970
From: Cyrill Gorcunov <gorcunov@gmail.com>
Subject: Re: [PATCH 3/6] shm: add memfd_create() syscall
Date: Thu, 20 Mar 2014 12:47:48 +0400
Message-ID: <20140320084748.GK1728@moon>
References: <1395256011-2423-1-git-send-email-dh.herrmann@gmail.com>
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Cc: linux-kernel@vger.kernel.org, Hugh Dickins <hughd@google.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Matthew Wilcox <matthew@wil.cx>,
	Karol Lewandowski <k.lewandowsk@samsung.com>,
	Kay Sievers <kay@vrfy.org>, Daniel Mack <zonque@gmail.com>,
	Lennart Poettering <lennart@poettering.net>,
	Kristian =?iso-8859-1?Q?H=F8gsberg?= <krh@bitplanet.net>,
	john.stultz@linaro.org, Greg Kroah-Hartman <greg@kroah.com>,
	Tejun Heo <tj@kernel.org>, Johannes Weiner <hannes@cmpxchg.org>,
	dri-devel@lists.freedesktop.org, linux-fsdevel@vger.kernel.org,
	linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Ryan Lortie <desrt@desrt.ca>,
	"Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
To: David Herrmann <dh.herrmann@gmail.com>,
	Pavel Emelyanov <xemul@parallels.com>
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On Wed, Mar 19, 2014 at 08:06:48PM +0100, David Herrmann wrote:
> memfd_create() is similar to mmap(MAP_ANON), but returns a file-descriptor
> that you can pass to mmap(). It explicitly allows sealing and
> avoids any connection to user-visible mount-points. Thus, it's not
> subject to quotas on mounted file-systems, but can be used like
> malloc()'ed memory, but with a file-descriptor to it.
> 
> memfd_create() does not create a front-FD, but instead returns the raw
> shmem file, so calls like ftruncate() can be used. Also calls like fstat()
> will return proper information and mark the file as regular file. Sealing
> is explicitly supported on memfds.
> 
> Compared to O_TMPFILE, it does not require a tmpfs mount-point and is not
> subject to quotas and alike.

If I'm not mistaken in something obvious, this looks similar to /proc/pid/map_files
feature, Pavel?

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