From: David Herrmann <dh.herrmann@gmail.com>
To: Michael Kerrisk-manpages <mtk.manpages@gmail.com>
Cc: lkml <linux-kernel@vger.kernel.org>, Ryan Lortie <desrt@desrt.ca>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
Linux API <linux-api@vger.kernel.org>,
Greg Kroah-Hartman <greg@kroah.com>,
John Stultz <john.stultz@linaro.org>,
Lennart Poettering <lennart@poettering.net>,
Daniel Mack <zonque@gmail.com>, Kay Sievers <kay@vrfy.org>,
Hugh Dickins <hughd@google.com>,
Tony Battersby <tonyb@cybernetics.com>,
Andy Lutomirski <luto@amacapital.net>
Subject: Re: [PATCH v3 3/7] shm: add memfd_create() syscall
Date: Fri, 13 Jun 2014 14:41:24 +0200 [thread overview]
Message-ID: <CANq1E4R2K+eq9AxtFewp4YUL2cujg+dg+sN19Anvf-zWuvgyWw@mail.gmail.com> (raw)
In-Reply-To: <CAKgNAkgnnWjrbE+2KAETsmiyrnrMQu0h7-MrYLvkiwj--_nxcQ@mail.gmail.com>
Hi
On Fri, Jun 13, 2014 at 2:27 PM, Michael Kerrisk (man-pages)
<mtk.manpages@gmail.com> wrote:
> Hi David,
>
> On Fri, Jun 13, 2014 at 12:36 PM, David Herrmann <dh.herrmann@gmail.com> wrote:
>> memfd_create() is similar to mmap(MAP_ANON), but returns a file-descriptor
>> that you can pass to mmap(). It can support 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() returns the raw shmem file, so calls like ftruncate() can
>> be used to modify the underlying inode. Also calls like fstat()
>> will return proper information and mark the file as regular file. If you
>> want sealing, you can specify MFD_ALLOW_SEALING. Otherwise, sealing is not
>> supported (like on all other regular files).
>>
>> Compared to O_TMPFILE, it does not require a tmpfs mount-point and is not
>> subject to quotas and alike. It is still properly accounted to memcg
>> limits, though.
>
> Where do I find / is there detailed documentation (ideally, a man
> page) for this new system call?
I did write a man-page proposal for memfd_create() and a patch for
fcntl() for v1, however, the API changed several times so I didn't
keep them up to date (the man-page patches are on LKML). However, I
wrote a short introduction to memfd+sealing v3, that I recommend
reading first:
http://dvdhrm.wordpress.com/2014/06/10/memfd_create2/
This explains the idea behind the new API and describes almost all
aspects of it. It's up-to-date to v3 and I will use it to write the
final man-pages once Hugh and Andrew ACKed the patches. Let me know if
anything is unclear.
Thanks for looking at it!
David
next prev parent reply other threads:[~2014-06-13 12:41 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-13 10:36 [PATCH v3 0/7] File Sealing & memfd_create() David Herrmann
2014-06-13 10:36 ` [PATCH v3 1/7] mm: allow drivers to prevent new writable mappings David Herrmann
2014-07-09 8:55 ` Hugh Dickins
2014-07-19 16:12 ` David Herrmann
2014-06-13 10:36 ` [PATCH v3 2/7] shm: add sealing API David Herrmann
2014-07-16 10:06 ` Hugh Dickins
2014-07-19 16:17 ` David Herrmann
2014-06-13 10:36 ` [PATCH v3 3/7] shm: add memfd_create() syscall David Herrmann
2014-06-13 12:27 ` Michael Kerrisk (man-pages)
2014-06-13 12:41 ` David Herrmann [this message]
2014-06-13 14:20 ` Michael Kerrisk (man-pages)
2014-06-13 16:20 ` John Stultz
2014-06-16 4:12 ` Michael Kerrisk (man-pages)
2014-07-08 18:39 ` David Herrmann
2014-06-15 10:50 ` Jann Horn
2014-07-16 10:07 ` Hugh Dickins
2014-07-19 16:29 ` David Herrmann
2014-06-13 10:36 ` [PATCH v3 4/7] selftests: add memfd_create() + sealing tests David Herrmann
2014-07-16 10:07 ` Hugh Dickins
2014-07-19 16:31 ` David Herrmann
2014-06-13 10:36 ` [PATCH v3 5/7] selftests: add memfd/sealing page-pinning tests David Herrmann
2014-07-16 10:08 ` Hugh Dickins
2014-07-19 16:32 ` David Herrmann
2014-06-13 10:36 ` [RFC v3 6/7] shm: wait for pins to be released when sealing David Herrmann
2014-07-16 10:09 ` Hugh Dickins
2014-07-19 16:36 ` David Herrmann
2014-06-13 10:36 ` [RFC v3 7/7] shm: isolate pinned pages when sealing files David Herrmann
2014-06-13 15:06 ` Andy Lutomirski
2014-06-13 15:27 ` David Herrmann
2014-06-13 17:23 ` Andy Lutomirski
2014-07-09 8:57 ` Hugh Dickins
2014-07-19 16:40 ` David Herrmann
2014-06-13 15:10 ` [PATCH v3 0/7] File Sealing & memfd_create() Andy Lutomirski
2014-06-13 15:15 ` David Herrmann
2014-06-13 15:17 ` Andy Lutomirski
2014-06-13 15:33 ` David Herrmann
2014-06-17 9:54 ` Florian Weimer
2014-06-17 10:01 ` David Herrmann
2014-06-17 10:04 ` Florian Weimer
2014-06-17 10:10 ` David Herrmann
2014-06-17 12:13 ` Florian Weimer
2014-06-17 13:26 ` David Herrmann
[not found] ` <CALCETrVpZ0vFM4usHK+tQhk234Y2jWzB1522kGcGvdQQFAqsZQ@mail.gmail.com>
2014-06-17 16:36 ` David Herrmann
2014-06-17 16:41 ` Andy Lutomirski
2014-06-17 16:51 ` David Herrmann
2014-06-17 17:01 ` Andy Lutomirski
2014-06-17 20:31 ` Hugh Dickins
2014-06-17 21:25 ` Andy Lutomirski
2014-07-08 16:54 ` David Herrmann
2014-07-09 8:53 ` Hugh Dickins
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