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From: ebiederm@xmission.com (Eric W. Biederman)
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: <linux-kernel@vger.kernel.org>, <linux-pci@vger.kernel.org>,
	<linux-mm@kvack.org>, <linux-fsdevel@vger.kernel.org>,
	Hugh Dickins <hugh@veritas.com>, Tejun Heo <tj@kernel.org>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Alan Cox <alan@lxorguk.ukuu.org.uk>,
	Greg Kroah-Hartman <gregkh@suse.de>,
	Nick Piggin <npiggin@suse.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Christoph Hellwig <hch@infradead.org>
Subject: [PATCH 0/23] File descriptor hot-unplug support v2
Date: Mon, 01 Jun 2009 14:45:17 -0700
Message-ID: <m1oct739xu.fsf@fess.ebiederm.org> (raw)
In-Reply-To: <m1skkf761y.fsf@fess.ebiederm.org> (Eric W. Biederman's message of "Sat\, 11 Apr 2009 05\:01\:29 -0700")


I found myself looking at the uio, seeing that it does not support pci
hot-unplug, and thinking "Great yet another implementation of
hotunplug logic that needs to be added".

I decided to see what it would take to add a generic implementation of
the code we have for supporting hot unplugging devices in sysfs, proc,
sysctl, tty_io, and now almost in the tun driver.

Not long after I touched the tun driver and made it safe to delete the
network device while still holding it's file descriptor open I someone
else touch the code adding a different feature and my careful work
went up in flames.  Which brought home another point at the best of it
this is ultimately complex tricky code that subsystems should not need
to worry about.

What makes this even more interesting is that in the presence of pci
hot-unplug it looks like most subsystems and most devices will have to
deal with the issue one way or another.

This infrastructure could also be used to implement both force
unmounts and sys_revoke.  When I could not think of a better name for
I have drawn on that and used revoke.

The following changes draw on and generalize the work in tty_io sysfs,
proc, and sysctl and move it into the vfs level.  Where the basic
primitives are running faster, and the solution is more general.


... Changes since version 1.

All of that lead to the first version of this patchset.  The feedback
I got from that was generally positive but there was a concern about
performance  when two there are two simultaneous accessors to the tty
at the same time.

After looking into the performance concerns of what happens when
multiple programs access the same struct file and finding that I could
not rule out a performance regression I have gone back and redesigned
my mutual exclusion primitive creating something simpler and faster.

I have also changed my synchronization primitives extending them to
protect most of what is read-only in struct file today and abandoning
rcu-ness of struct file.

Giving up rcu-ness leads to true exclusion and makes the code much
easier to think about.

In this patchset is the basic code patchs 1-4 and a conversion of
the vfs except for the nfsd entry points.  Enough for a reasonable
result. 

These patches are based on Al's vfs/for-next tree.

The vfs changes in this patchset.

 Documentation/filesystems/vfs.txt |    5 +
 drivers/char/pty.c                |    2 +-
 drivers/char/tty_io.c             |   22 ++--
 fs/Kconfig                        |    4 +
 fs/aio.c                          |   51 +++++--
 fs/compat.c                       |   16 ++-
 fs/compat_ioctl.c                 |   14 ++-
 fs/eventpoll.c                    |   41 +++++-
 fs/fcntl.c                        |   28 +++--
 fs/file_table.c                   |  281 +++++++++++++++++++++++++++++--------
 fs/inode.c                        |    1 +
 fs/ioctl.c                        |    8 +-
 fs/locks.c                        |    8 +-
 fs/namei.c                        |   11 ++-
 fs/open.c                         |   81 +++++++++--
 fs/proc/base.c                    |   29 ++--
 fs/read_write.c                   |  122 ++++++++++++----
 fs/readdir.c                      |   20 ++-
 fs/select.c                       |   53 ++++++-
 fs/splice.c                       |  111 ++++++++++-----
 fs/super.c                        |    1 -
 fs/sync.c                         |    9 +-
 include/linux/fs.h                |   49 ++++++-
 include/linux/mm.h                |    2 +
 include/linux/poll.h              |    3 +
 include/linux/sched.h             |    7 +
 include/linux/tty.h               |    2 +-
 mm/fadvise.c                      |    7 +
 mm/filemap.c                      |   25 ++--
 mm/memory.c                       |   98 +++++++++++++
 mm/mmap.c                         |   78 +++++++----
 mm/nommu.c                        |   21 +++-
 security/selinux/hooks.c          |    8 +-
 33 files changed, 950 insertions(+), 268 deletions(-)

The necessary changes to proc to take advantage of this functionality.

 fs/proc/Kconfig         |    1 +
 fs/proc/generic.c       |   56 +++-----
 fs/proc/inode.c         |  354 ++++-------------------------------------------
 fs/proc/internal.h      |    1 +
 include/linux/proc_fs.h |    4 -
 5 files changed, 44 insertions(+), 372 deletions(-)

  parent reply index

Thread overview: 99+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-04-11 12:01 [RFC][PATCH 0/9] File descriptor hot-unplug support Eric W. Biederman
2009-04-11 12:03 ` [RFC][PATCH 1/9] mm: Introduce remap_file_mappings Eric W. Biederman
2009-04-11 12:05 ` [RFC][PATCH 2/9] mm: Implement generic support for revoking a mapping Eric W. Biederman
2009-04-11 12:06 ` [RFC][PATCH 3/9] sysfs: Use remap_file_mappings Eric W. Biederman
2009-04-11 12:07 ` [RFC][PATCH 4/9] vfs: Generalize the file_list Eric W. Biederman
2009-04-11 12:08 ` [RFC][PATCH 5/9] vfs: Introduce basic infrastructure for revoking a file Eric W. Biederman
2009-04-14 22:12   ` Jonathan Corbet
2009-04-15  2:55     ` Eric W. Biederman
2009-04-11 12:10 ` [RFC][PATCH 6/9] vfs: Utilize fops_read_lock where appropriate Eric W. Biederman
2009-04-11 12:11 ` [RFC][PATCH 7/9] vfs: Optimize fops_read_lock Eric W. Biederman
2009-04-11 12:13 ` [RFC][PATCH 8/9] vfs: Implement generic revoked file operations Eric W. Biederman
2009-04-12 18:56   ` Jamie Lokier
2009-04-12 20:04     ` Eric W. Biederman
2009-04-12 20:31       ` Jamie Lokier
2009-04-12 21:53         ` Eric W. Biederman
2009-04-12 20:54       ` Eric W. Biederman
2009-04-12 21:02         ` Jamie Lokier
2009-04-12 23:06           ` Eric W. Biederman
2009-04-11 12:14 ` [RFC][PATCH 9/9] proc: Use the generic vfs revoke facility that now exists Eric W. Biederman
2009-04-11 15:58 ` [RFC][PATCH 0/9] File descriptor hot-unplug support Al Viro
2009-04-11 16:49   ` Eric W. Biederman
2009-04-11 16:56     ` Al Viro
2009-04-11 23:57       ` Eric W. Biederman
2009-04-12 20:21       ` Eric W. Biederman
2009-04-14  3:16 ` Tejun Heo
2009-04-14  7:39   ` Eric W. Biederman
2009-04-14  7:45     ` Tejun Heo
2009-04-14  8:27       ` Eric W. Biederman
2009-04-14  8:49         ` Tejun Heo
2009-04-14 15:07         ` Jamie Lokier
2009-04-14 19:09           ` Eric W. Biederman
2009-06-01 21:45 ` Eric W. Biederman [this message]
2009-06-01 21:50   ` [PATCH 01/23] mm: Introduce revoke_file_mappings Eric W. Biederman
2009-06-01 22:25     ` Andrew Morton
2009-06-02  0:12       ` Eric W. Biederman
2009-06-01 21:50   ` [PATCH 02/23] vfs: Implement unpoll_file Eric W. Biederman
2009-06-06  8:08     ` Al Viro
2009-06-01 21:50   ` [PATCH 03/23] vfs: Generalize the file_list Eric W. Biederman
2009-06-02  7:06     ` Nick Piggin
2009-06-05 19:33       ` Eric W. Biederman
2009-06-09 10:38         ` Nick Piggin
2009-06-09 18:38           ` Eric W. Biederman
2009-06-10  6:05             ` Nick Piggin
2009-06-01 21:50   ` [PATCH 04/23] vfs: Introduce infrastructure for revoking a file Eric W. Biederman
2009-06-02  5:16     ` Pekka Enberg
2009-06-02  6:51       ` Eric W. Biederman
2009-06-02  7:08         ` Pekka Enberg
2009-06-02  7:14     ` Nick Piggin
2009-06-02 17:06       ` Linus Torvalds
2009-06-02 20:52         ` Eric W. Biederman
2009-06-03  6:37           ` Nick Piggin
2009-06-02 22:56       ` Eric W. Biederman
2009-06-03  6:38         ` Nick Piggin
2009-06-05  9:03     ` Miklos Szeredi
2009-06-05 19:06       ` Eric W. Biederman
2009-06-01 21:50   ` [PATCH 05/23] vfs: Teach lseek to use file_hotplug_lock Eric W. Biederman
2009-06-01 21:50   ` [PATCH 06/23] vfs: Teach read/write to use file_hotplug_read_lock Eric W. Biederman
2009-06-01 21:50   ` [PATCH 07/23] vfs: Teach sendfile,splice,tee,and vmsplice to use file_hotplug_lock Eric W. Biederman
2009-06-03 23:39     ` Badari Pulavarty
2009-06-05 19:37       ` Eric W. Biederman
2009-06-01 21:50   ` [PATCH 08/23] vfs: Teach readdir " Eric W. Biederman
2009-06-01 21:50   ` [PATCH 09/23] vfs: Teach poll and select " Eric W. Biederman
2009-06-01 21:50   ` [PATCH 10/23] vfs: Teach do_path_lookup " Eric W. Biederman
2009-06-01 21:50   ` [PATCH 11/23] mm: Teach mmap " Eric W. Biederman
2009-06-01 21:50   ` [PATCH 12/23] vfs: Teach fcntl " Eric W. Biederman
2009-06-01 21:50   ` [PATCH 13/23] vfs: Teach ioctl " Eric W. Biederman
2009-06-01 21:50   ` [PATCH 14/23] vfs: Teach flock " Eric W. Biederman
2009-06-01 21:50   ` [PATCH 15/23] vfs: Teach fallocate, and filp_close " Eric W. Biederman
2009-06-01 21:50   ` [PATCH 16/23] vfs: Teach fstatfs, fstatfs64, ftruncate, fchdir, fchmod, fchown " Eric W. Biederman
2009-06-01 21:50   ` [PATCH 17/23] proc: Teach /proc/<pid>/fd " Eric W. Biederman
2009-06-01 21:50   ` [PATCH 18/23] vfs: Teach epoll " Eric W. Biederman
2009-06-02 16:51     ` Davide Libenzi
2009-06-02 21:23       ` Eric W. Biederman
2009-06-02 21:52         ` Davide Libenzi
2009-06-02 22:51           ` Eric W. Biederman
2009-06-03 14:57             ` Davide Libenzi
2009-06-03 20:53               ` Eric W. Biederman
2009-06-04  0:50                 ` Davide Libenzi
2009-06-04  1:42                   ` Eric W. Biederman
2009-06-01 21:50   ` [PATCH 19/23] eventpoll: Fix comment Eric W. Biederman
2009-06-01 21:50   ` [PATCH 20/23] vfs: Teach aio to use file_hotplug_lock Eric W. Biederman
2009-06-01 21:50   ` [PATCH 21/23] vfs: Teach fsync " Eric W. Biederman
2009-06-01 21:50   ` [PATCH 22/23] vfs: Teach fadvice to file_hotplug_lock Eric W. Biederman
2009-06-01 21:50   ` [PATCH 23/23] vfs: Teach readahead to use the file_hotplug_lock Eric W. Biederman
2009-06-03 23:25     ` Badari Pulavarty
2009-06-06  8:03   ` [PATCH 0/23] File descriptor hot-unplug support v2 Al Viro
2009-06-08  9:41     ` Miklos Szeredi
2009-06-08 10:24       ` Jamie Lokier
2009-06-08 16:29       ` Al Viro
2009-06-08 16:44         ` Miklos Szeredi
2009-06-08 17:50           ` Al Viro
2009-06-08 18:01             ` Linus Torvalds
2009-06-08 18:50               ` Al Viro
2009-06-08 19:18                 ` Linus Torvalds
2009-06-09  6:42                   ` Eric W. Biederman
2009-06-09 10:52                     ` Nick Piggin
2009-06-09  5:50             ` Miklos Szeredi
2009-06-09  6:31               ` Eric W. Biederman
2009-06-09  6:22     ` Eric W. Biederman

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