From: Benjamin Thery <benjamin.thery@bull.net>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>,
Greg Kroah-Hartman <gregkh@suse.de>,
Andrew Morton <akpm@linux-foundation.org>,
Tejun Heo <htejun@gmail.com>,
linux-kernel@vger.kernel.org, Al Viro <viro@ftp.linux.org.uk>,
Linux Containers <containers@lists.osdl.org>,
"Serge E. Hallyn" <serue@us.ibm.com>,
Daniel Lezcano <dlezcano@fr.ibm.com>
Subject: Re: [PATCH 01/11] sysfs: Support for preventing unmounts.
Date: Thu, 19 Jun 2008 10:54:49 +0200 [thread overview]
Message-ID: <485A1ED9.5040704@bull.net> (raw)
In-Reply-To: <m18wx2o638.fsf@frodo.ebiederm.org>
Eric W. Biederman wrote:
> Dave Hansen <dave@linux.vnet.ibm.com> writes:
>
>> On Wed, 2008-06-18 at 19:07 +0200, Benjamin Thery wrote:
>>> To support mounting multiple instances of sysfs occassionally I
>>> need to walk through all of the currently present sysfs super blocks.
>> I know you may have addressed this before, but I forgot and it didn't
>> make it into the changelogs.
>>
>> Why are you doing this again? It seems like an awfully blunt
>> instrument.
>
> So the fundamentals.
> - The data in sysfs fundamentally changes behind the back of the
> VFS and we need to keep the VFS in sync. Essentially this is the
> distributed filesystem problem.
>
> - In particular for sysfs_rename and sysfs_move_dir we need to support finding
> the dcache entries and calling d_move. So that the dcache does not
> get into an inconsistent state. Timeouts and invalidates like NFS
> uses are to be avoided if at all possible.
>
> - Coming through the vfs we are guaranteed that the filesystem will
> not be unmounted while we have a reference on a dentry, and with
> multiple mounts we do not get that guarantee. Therefore to get that
> guarantee for all of the superblocks we need the blunt instrument.
>
> - Since mount/unmount are rare blocking them is no big deal.
>
> I believe any distributed filesystem that is together enough to tell
> us about renames (so we can update the dcache) instead of doing the
> NFS timeout will need the ability to block mount/unmount while it is
> executing d_move.
>
> Currently sysfs does not need to block mounts only because we perform
> an internal mount and then never unmount sysfs.
Thanks Eric for detailing this.
I think you explained it in much better way than I could do.
You're the author of the patch after all ;-)
Benjamin
>
> Eric
>
>
--
B e n j a m i n T h e r y - BULL/DT/Open Software R&D
http://www.bull.com
next prev parent reply other threads:[~2008-06-19 8:59 UTC|newest]
Thread overview: 138+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-18 17:07 [PATCH 00/11] sysfs tagged directories V6 Benjamin Thery
2008-06-18 17:07 ` [PATCH 01/11] sysfs: Support for preventing unmounts Benjamin Thery
2008-06-18 17:44 ` Dave Hansen
2008-06-18 20:12 ` Eric W. Biederman
2008-06-19 8:54 ` Benjamin Thery [this message]
2008-06-19 16:32 ` Dave Hansen
2008-06-19 20:19 ` Benjamin Thery
2008-06-18 17:07 ` [PATCH 02/11] sysfs: sysfs_get_dentry add a sb parameter Benjamin Thery
2008-06-18 17:07 ` [PATCH 03/11] sysfs: Implement __sysfs_get_dentry Benjamin Thery
2008-06-18 17:08 ` [PATCH 04/11] sysfs: Rename Support multiple superblocks Benjamin Thery
2008-06-18 17:08 ` [PATCH 05/11] sysfs: sysfs_chmod_file handle " Benjamin Thery
2008-06-22 4:46 ` Tejun Heo
2008-06-23 21:42 ` Daniel Lezcano
2008-06-24 4:45 ` Tejun Heo
2008-06-24 10:39 ` Daniel Lezcano
2008-06-24 13:37 ` Daniel Lezcano
2008-06-25 12:31 ` Tejun Heo
2008-06-18 17:08 ` [PATCH 06/11] sysfs: Implement sysfs tagged directory support Benjamin Thery
2008-06-23 2:05 ` Tejun Heo
2008-06-26 20:21 ` Eric W. Biederman
2008-06-29 3:51 ` Tejun Heo
2008-06-30 18:56 ` Eric W. Biederman
2008-06-30 21:44 ` Serge E. Hallyn
2008-07-01 7:50 ` Eric W. Biederman
2008-07-01 6:47 ` Tejun Heo
2008-07-01 9:20 ` Eric W. Biederman
2008-07-01 10:30 ` Tejun Heo
2008-07-01 12:30 ` Eric W. Biederman
2008-07-02 3:24 ` Tejun Heo
2008-07-02 3:53 ` Eric W. Biederman
2008-07-02 4:37 ` Tejun Heo
2008-07-02 16:49 ` Eric W. Biederman
2008-07-03 0:15 ` Greg KH
2008-07-03 3:18 ` Tejun Heo
2008-07-03 5:11 ` Eric W. Biederman
2008-07-03 10:56 ` Daniel Lezcano
2008-07-03 12:27 ` Eric W. Biederman
2008-07-03 12:37 ` Benjamin Thery
2008-07-03 19:57 ` Eric W. Biederman
2008-07-03 12:55 ` Daniel Lezcano
2008-07-03 15:58 ` Tejun Heo
2008-07-03 18:29 ` Daniel Lezcano
2008-07-03 20:08 ` Eric W. Biederman
2008-07-04 0:48 ` [PATCH 00/15] sysfs support for namespaces Eric W. Biederman
2008-07-04 1:05 ` [PATCH 01/15] kobject: Cleanup kobject_rename and !CONFIG_SYSFS Eric W. Biederman
2008-07-04 1:07 ` [PATCH 02/15] sysfs: Support for preventing unmounts Eric W. Biederman
2008-07-04 1:08 ` [PATCH 03/15] sysfs: sysfs_get_dentry add a sb parameter Eric W. Biederman
2008-07-04 1:09 ` [PATCH 04/15] sysfs: Implement __sysfs_get_dentry Eric W. Biederman
2008-07-04 1:10 ` [PATCH 05/15] sysfs: Rename Support multiple superblocks Eric W. Biederman
2008-07-04 1:11 ` [PATCH 06/15] Introduce sysfs_sd_setattr and fix sysfs_chmod Eric W. Biederman
2008-07-04 1:13 ` [PATCH 07/15] sysfs: sysfs_chmod_file handle multiple superblocks Eric W. Biederman
2008-07-04 1:14 ` [PATCH 08/15] sysfs: Make sysfs_mount static once again Eric W. Biederman
2008-07-04 1:16 ` [PATCH 09/15] sysfs: Implement sysfs tagged directory support Eric W. Biederman
2008-07-04 1:17 ` [PATCH 10/15] sysfs: Merge sysfs_rename_dir and sysfs_move_dir Eric W. Biederman
2008-07-04 1:18 ` [PATCH 11/15] sysfs: Implement sysfs_delete_link and sysfs_rename_link Eric W. Biederman
2008-07-04 1:20 ` [PATCH 12/15] driver core: Implement tagged directory support for device classes Eric W. Biederman
2008-07-04 1:21 ` [PATCH 13/15] Revert "netns: Fix device renaming for sysfs" Eric W. Biederman
2008-07-04 1:22 ` [PATCH 14/15] netns: Enable tagging for net_class directories in sysfs Eric W. Biederman
2008-07-04 1:23 ` [PATCH 15/15] sysfs: user namespaces: fix bug with clone(CLONE_NEWUSER) with fairsched Eric W. Biederman
2008-07-04 7:50 ` [PATCH 12/15] driver core: Implement tagged directory support for device classes Tejun Heo
2008-07-04 13:31 ` Eric W. Biederman
2008-07-04 13:57 ` Tejun Heo
2008-07-04 16:12 ` Greg KH
2008-07-04 21:49 ` Eric W. Biederman
2008-07-14 1:54 ` Eric W. Biederman
2008-07-16 3:25 ` Tejun Heo
2008-07-16 5:41 ` Eric W. Biederman
2008-07-16 5:50 ` Tejun Heo
2008-07-16 6:32 ` Eric W. Biederman
2008-07-16 6:48 ` Tejun Heo
2008-07-16 7:02 ` Tejun Heo
2008-07-16 19:07 ` Eric W. Biederman
2008-07-16 21:09 ` Eric W. Biederman
2008-07-17 23:08 ` Greg KH
2008-07-18 12:41 ` Tejun Heo
2008-07-18 18:49 ` Greg KH
2008-07-18 20:19 ` Eric W. Biederman
2008-07-19 1:07 ` Tejun Heo
2008-08-03 6:59 ` Eric W. Biederman
2008-09-11 12:45 ` Jiri Slaby
2008-09-11 13:05 ` Benjamin Thery
2008-09-12 6:32 ` Jiri Slaby
2008-07-04 22:00 ` Eric W. Biederman
2008-08-20 2:17 ` [PATCH 09/15] sysfs: Implement sysfs tagged directory support Greg KH
2008-08-20 6:58 ` Eric W. Biederman
2008-08-21 6:31 ` [PATCH 0/8] sysfs namespace support Eric W. Biederman
2008-08-21 6:33 ` [PATCH 1/8] sysfs: Implement sysfs tagged directory support Eric W. Biederman
2008-08-21 6:34 ` [PATCH 2/8] sysfs: Merge sysfs_rename_dir and sysfs_move_dir Eric W. Biederman
2008-08-21 6:35 ` [PATCH 3/8] sysfs: Implement sysfs_delete_link and sysfs_rename_link Eric W. Biederman
2008-08-21 6:36 ` [PATCH 5/8] sysfs: Remove sysfs_create_link_nowarn Eric W. Biederman
2008-08-21 6:38 ` [PATCH 6/8] Revert "netns: Fix device renaming for sysfs" Eric W. Biederman
2008-08-21 6:39 ` [PATCH 7/8] netns: Enable tagging for net_class directories in sysfs Eric W. Biederman
2008-08-21 6:40 ` [PATCH 8/8] sysfs: user namespaces: fix bug with clone(CLONE_NEWUSER) with fairsched Eric W. Biederman
2008-08-21 6:47 ` [PATCH 7/8] netns: Enable tagging for net_class directories in sysfs David Miller
2008-08-21 6:47 ` [PATCH 6/8] Revert "netns: Fix device renaming for sysfs" David Miller
2008-08-21 6:37 ` [PATCH 4/8] driver core: Implement tagged directory support for device classes Eric W. Biederman
2008-08-27 15:18 ` [PATCH 1/8] sysfs: Implement sysfs tagged directory support Benjamin Thery
2008-09-02 13:54 ` Mark Ryden
2008-09-02 14:03 ` Benjamin Thery
2008-09-02 17:01 ` Greg KH
2008-09-04 5:33 ` David Shwatrz
2008-09-04 6:44 ` Benjamin Thery
2008-09-08 18:39 ` Mark Ryden
2008-10-07 16:39 ` Mark Ryden
2008-10-07 16:48 ` Greg KH
2008-10-07 20:31 ` Eric W. Biederman
2008-10-07 21:09 ` Greg KH
2008-10-07 22:27 ` Eric W. Biederman
2008-10-08 13:00 ` Christoph Hellwig
2008-10-14 3:20 ` Eric W. Biederman
2008-10-07 16:52 ` Daniel Lezcano
2008-08-21 6:37 ` [PATCH 0/8] sysfs namespace support David Miller
2008-07-04 6:44 ` [PATCH 08/15] sysfs: Make sysfs_mount static once again Tejun Heo
2008-07-04 6:44 ` [PATCH 07/15] sysfs: sysfs_chmod_file handle multiple superblocks Tejun Heo
2008-07-04 6:40 ` [PATCH 06/15] Introduce sysfs_sd_setattr and fix sysfs_chmod Tejun Heo
2008-07-04 6:33 ` [PATCH 01/15] kobject: Cleanup kobject_rename and !CONFIG_SYSFS Tejun Heo
2008-07-04 1:27 ` [PATCH 00/15] sysfs support for namespaces Eric W. Biederman
2008-07-06 4:42 ` Eric W. Biederman
2008-07-07 11:41 ` Cornelia Huck
2008-07-07 12:22 ` Eric W. Biederman
2008-06-18 17:08 ` [PATCH 07/11] sysfs: Implement sysfs_delete_link and sysfs_rename_link Benjamin Thery
2008-06-23 2:13 ` Tejun Heo
2008-06-26 20:24 ` Eric W. Biederman
2008-06-29 3:35 ` Tejun Heo
2008-06-30 3:02 ` Eric W. Biederman
2008-06-18 17:08 ` [PATCH 08/11] driver core: Implement tagged directory support for device classes Benjamin Thery
2008-06-18 17:08 ` [PATCH 09/11] sysfs: add sysfs_ns_exit routine Benjamin Thery
2008-06-18 20:19 ` Eric W. Biederman
2008-06-23 2:16 ` Tejun Heo
2008-06-18 17:09 ` [PATCH 10/11] netns: Enable tagging for net_class directories in sysfs Benjamin Thery
2008-06-23 2:18 ` Tejun Heo
2008-06-18 17:09 ` [PATCH 11/11] sysfs: user namespaces: fix bug with clone(CLONE_NEWUSER) with fairsched Benjamin Thery
2008-06-23 2:18 ` Tejun Heo
2008-06-25 18:44 ` Serge E. Hallyn
2008-06-25 21:11 ` Eric W. Biederman
2008-06-26 13:07 ` Serge E. Hallyn
-- strict thread matches above, loose matches on Subject: below --
2008-06-06 15:46 [PATCH 00/11] sysfs tagged directories V5 Benjamin Thery
2008-06-06 15:47 ` [PATCH 01/11] sysfs: Support for preventing unmounts Benjamin Thery
2008-05-06 17:30 [RESEND][PATCH 00/11] sysfs tagged directories Benjamin Thery
2008-05-06 17:30 ` [PATCH 01/11] sysfs: Support for preventing unmounts Benjamin Thery
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