From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lb0-f182.google.com (mail-lb0-f182.google.com [209.85.217.182]) by kanga.kvack.org (Postfix) with ESMTP id D09186B019F for ; Thu, 20 Mar 2014 05:02:15 -0400 (EDT) Received: by mail-lb0-f182.google.com with SMTP id n15so365876lbi.13 for ; Thu, 20 Mar 2014 02:02:15 -0700 (PDT) Received: from relay.parallels.com (relay.parallels.com. [195.214.232.42]) by mx.google.com with ESMTPS id w4si987221lad.17.2014.03.20.02.02.13 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 20 Mar 2014 02:02:14 -0700 (PDT) Message-ID: <532AAE7B.2030501@parallels.com> Date: Thu, 20 Mar 2014 13:01:47 +0400 From: Pavel Emelyanov MIME-Version: 1.0 Subject: Re: [PATCH 3/6] shm: add memfd_create() syscall References: <1395256011-2423-1-git-send-email-dh.herrmann@gmail.com> <1395256011-2423-4-git-send-email-dh.herrmann@gmail.com> <20140320084748.GK1728@moon> In-Reply-To: <20140320084748.GK1728@moon> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Cyrill Gorcunov , David Herrmann Cc: linux-kernel@vger.kernel.org, Hugh Dickins , Alexander Viro , Matthew Wilcox , Karol Lewandowski , Kay Sievers , Daniel Mack , Lennart Poettering , =?ISO-8859-1?Q?Kristian_H=F8gsberg?= , john.stultz@linaro.org, Greg Kroah-Hartman , Tejun Heo , Johannes Weiner , dri-devel@lists.freedesktop.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Linus Torvalds , Ryan Lortie , "Michael Kerrisk (man-pages)" On 03/20/2014 12:47 PM, Cyrill Gorcunov wrote: > 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? Thanks, Cyrill. It is, but the map_files will work "in the opposite direction" :) In the memfd case one first gets an FD, then mmap()s it; in the /proc/pis/map_files case one should first mmap() a region, then open it via /proc/self/map_files. But I don't know whether this matters. Thanks, Pavel -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org