From: "Jörn Engel" <joern@logfs.org>
To: Josef Sipek <jsipek@fsl.cs.sunysb.edu>
Cc: Dave Kleikamp <shaggy@linux.vnet.ibm.com>,
Jan Blunck <jblunck@suse.de>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
Bharata B Rao <bharata@linux.vnet.ibm.com>,
hch@infradead.org
Subject: Re: [RFC 12/26] ext2 white-out support
Date: Thu, 2 Aug 2007 19:50:09 +0200 [thread overview]
Message-ID: <20070802175008.GA12627@lazybastard.org> (raw)
In-Reply-To: <20070801193330.GA20928@filer.fsl.cs.sunysb.edu>
On Wed, 1 August 2007 15:33:30 -0400, Josef Sipek wrote:
>
> This brings up an very interesting (but painful) question...which makes more
> sense? Allowing the modifications in only the top-most branch, or any branch
> (given the user allows it at mount-time)?
>
> This is really question to the community at large, not just you, Dave :)
Only write to top-most layer.
There are two reasons for this. First it allows users to create a union
mount, test something (e.g. update the distribution) and remove every
trace from the test by umounting the top-most layer. Such a thing can
be quite valuable.
The second reason is simplicity. I personally couldn't even start to
describe the semantics. If the user does a rename, which layer will the
change end up in? What if source or target exist in multiple layers?
How to rename a directory in a lower layer containing a new file in an
upper layer?
Finding new and interesting corner cases for such a beast can be quite
entertaining. And until someone has properly documented the semantics
for _all_ the corner cases, my enthusiasm is below freezing point. Does
such a documentation exist?
Jörn
--
A surrounded army must be given a way out.
-- Sun Tzu
next prev parent reply other threads:[~2007-08-02 17:54 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-07-30 16:13 [RFC 00/26] VFS based Union Mount (V2) Jan Blunck
2007-07-30 16:13 ` [RFC 01/26] [PATCH 14/18] shmem: convert to using splice instead of sendfile() Jan Blunck
2007-07-30 16:13 ` [RFC 02/26] VFS: Export dput_path() and path_to_nameidata() Jan Blunck
2007-07-30 16:13 ` [RFC 03/26] VFS: Make lookup_hash() return a struct path Jan Blunck
2007-07-30 16:13 ` [RFC 04/26] VFS: Make lookup_create() " Jan Blunck
2007-07-30 16:13 ` [RFC 05/26] VFS: cache_lookup() cleanup Jan Blunck
2007-07-30 16:13 ` [RFC 06/26] VFS: Make real_lookup() return a struct path Jan Blunck
2007-07-30 16:13 ` [RFC 07/26] VFS: Introduce dput() variante that maintains a kill-list Jan Blunck
2007-07-30 16:13 ` [RFC 08/26] VFS: Export lives_below_in_same_fs() Jan Blunck
2007-07-30 16:13 ` [RFC 09/26] linux/stat.h: Add the filetype white-out Jan Blunck
2007-07-30 16:13 ` [RFC 10/26] VFS white-out handling Jan Blunck
2007-07-30 16:13 ` [RFC 11/26] tmpfs white-out support Jan Blunck
2007-08-01 15:13 ` Hugh Dickins
2007-08-02 2:48 ` Matt Mackall
2007-07-30 16:13 ` [RFC 12/26] ext2 " Jan Blunck
2007-07-31 3:45 ` Theodore Tso
2007-07-31 7:44 ` Jan Blunck
2007-07-31 8:32 ` Andreas Dilger
2007-07-31 9:08 ` Jan Blunck
2007-07-31 10:53 ` Theodore Tso
2007-08-02 19:31 ` Pavel Machek
2007-07-31 16:36 ` Josef Sipek
2007-07-31 17:00 ` Jan Blunck
2007-07-31 17:11 ` Josef Sipek
2007-08-01 15:23 ` Dave Kleikamp
2007-08-01 18:44 ` Josef Sipek
2007-08-01 19:10 ` Dave Kleikamp
2007-08-01 19:33 ` Josef Sipek
2007-08-01 19:52 ` Dave Kleikamp
2007-08-01 22:06 ` Erez Zadok
2007-08-02 12:05 ` Jan Blunck
2007-08-02 11:55 ` Jan Blunck
2007-08-02 17:50 ` Jörn Engel [this message]
2007-08-02 18:15 ` Jeremy Maitin-Shepard
2007-08-02 5:24 ` Ph. Marek
2007-08-02 12:12 ` Jan Blunck
2007-08-02 10:26 ` Jan Blunck
2007-08-01 10:00 ` Hans-Peter Jansen
2007-08-01 11:43 ` Josef Sipek
2007-08-01 18:01 ` Jan Engelhardt
2007-07-31 17:03 ` Mark Williamson
2007-07-31 17:16 ` Josef Sipek
2007-08-01 17:58 ` Jan Engelhardt
2007-08-01 18:03 ` Josef Sipek
2007-07-30 16:13 ` [RFC 13/26] ext3 whiteout support Jan Blunck
2007-07-30 16:13 ` [RFC 14/26] union-mount: Documentation Jan Blunck
2007-07-30 16:13 ` [RFC 15/26] union-mount: Add union-mount mount flag Jan Blunck
2007-07-30 16:13 ` [RFC 16/26] union-mount: Introduce union_mount structure Jan Blunck
2007-08-06 5:57 ` Bharata B Rao
2007-07-30 16:13 ` [RFC 17/26] union-mount: Drive the union cache via dcache Jan Blunck
2007-07-30 16:13 ` [RFC 18/26] union-mount: Changes to the namespace handling Jan Blunck
2007-08-08 10:10 ` Bharata B Rao
2007-07-30 16:13 ` [RFC 19/26] union-mount: Make lookup work for union-mounted file systems Jan Blunck
2007-08-09 5:42 ` Bharata B Rao
2007-07-30 16:13 ` [RFC 20/26] union-mount: Simple union-mount readdir implementation Jan Blunck
2007-08-06 11:08 ` Bharata B Rao
2007-07-30 16:13 ` [RFC 21/26] union-mount: in-kernel file copy between union mounted filesystems Jan Blunck
2007-07-30 16:13 ` [RFC 22/26] union-mount: white-out changes for copy-on-open Jan Blunck
2007-07-30 16:13 ` [RFC 23/26] union-mount: copyup on rename Jan Blunck
2007-07-30 16:13 ` [RFC 24/26] union-mount: dont report EROFS for union mounts Jan Blunck
2007-07-30 16:13 ` [RFC 25/26] union-mount: Debug Infrastructure Jan Blunck
2007-07-30 16:13 ` [RFC 26/26] union-mount: Debug code Jan Blunck
2007-07-30 18:23 ` [RFC 00/26] VFS based Union Mount (V2) Al Boldi
2007-08-02 6:49 ` Bharata B Rao
2007-08-02 10:17 ` Jan Blunck
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