From: Andreas Dilger <adilger@sun.com>
To: Jamie Lokier <jamie@shareable.org>
Cc: Theodore Tso <tytso@mit.edu>,
Christoph Hellwig <hch@infradead.org>, jim owens <jowens@hp.com>,
linux-fsdevel@vger.kernel.org, Mark Fasheh <mfasheh@suse.com>,
Michael Kerrisk <mtk.manpages@googlemail.com>,
linux-abi@vger.kernel.org
Subject: Re: [PATCH 1/4] vfs: vfs-level fiemap interface
Date: Thu, 09 Oct 2008 14:40:17 -0600 [thread overview]
Message-ID: <20081009204017.GP2009@webber.adilger.int> (raw)
In-Reply-To: <20081007234351.GA20134@shareable.org>
On Oct 08, 2008 00:43 +0100, Jamie Lokier wrote:
> How can you safely use !(flags & FLAG_EXTENT_ENCODED) anyway in
> userspace code which is filesystem-independent? What tells you that
> the data isn't moved after calling FIEMAP and before unmounting, by
> unrelated activity on the filesystem?
>
> So should filesystems also set FLAG_EXTENT_ENCODED if there is any
> chance the data will move without any explicit operation on that file,
> even though the data itself is stored unencoded in data blocks?
The safest way of using !EXTENT_ENCODED is having a static snapshot
of the filesystem so nothing can change. It is probably acceptably
safe to do FIEMAP before and after a read and verify the file hasn't
changed, but this is not completely foolproof. For some applications
(e.g. dump) they don't even have this level of checking and are
still valuable, so this is really an application/user decision IMHO.
The presence of EXTENT_ENCODED just means "this is never going to work".
Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.
next prev parent reply other threads:[~2008-10-09 20:40 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-10-03 21:59 [PATCH 0/4] Updated fiemap patches Theodore Ts'o
2008-10-03 21:59 ` [PATCH 1/4] vfs: vfs-level fiemap interface Theodore Ts'o
2008-10-03 21:59 ` [PATCH 2/4] ocfs2: fiemap support Theodore Ts'o
2008-10-03 21:59 ` [PATCH 3/4] generic block based fiemap implementation Theodore Ts'o
2008-10-03 21:59 ` [PATCH 4/4] Hook ext4 to the vfs fiemap interface Theodore Ts'o
2008-10-06 11:35 ` [PATCH 3/4] generic block based fiemap implementation steve
2008-10-06 21:14 ` Theodore Tso
2008-10-07 8:14 ` steve
2008-10-04 2:12 ` [PATCH 1/4] vfs: vfs-level fiemap interface Theodore Tso
2008-10-06 18:15 ` jim owens
2008-10-06 21:07 ` Theodore Tso
2008-10-07 10:12 ` Christoph Hellwig
2008-10-07 10:56 ` Andreas Dilger
2008-10-07 12:52 ` Theodore Tso
2008-10-07 13:00 ` Jamie Lokier
2008-10-07 13:02 ` Christoph Hellwig
2008-10-07 13:24 ` Jamie Lokier
2008-10-07 13:28 ` Christoph Hellwig
2008-10-07 15:45 ` Theodore Tso
2008-10-07 16:01 ` jim owens
[not found] ` <48EB87DE.4090607-VXdhtT5mjnY@public.gmane.org>
2008-10-07 18:52 ` Theodore Tso
[not found] ` <20081007185219.GD15929-3s7WtUTddSA@public.gmane.org>
2008-10-07 20:31 ` Christoph Hellwig
2008-10-07 13:48 ` Theodore Tso
2008-10-07 23:43 ` Jamie Lokier
2008-10-09 20:40 ` Andreas Dilger [this message]
2008-10-06 13:07 ` steve
-- strict thread matches above, loose matches on Subject: below --
2008-10-09 1:48 PATCH [0/4] Updated**3 fiemap patches Theodore Ts'o
[not found] ` <1223516913-17612-1-git-send-email-tytso-3s7WtUTddSA@public.gmane.org>
2008-10-09 1:48 ` [PATCH 1/4] vfs: vfs-level fiemap interface Theodore Ts'o
2008-10-07 1:06 PATCH [0/4] Updated**2 fiemap patches Theodore Ts'o
2008-10-07 1:06 ` [PATCH 1/4] vfs: vfs-level fiemap interface Theodore Ts'o
[not found] ` <1223341581-13802-2-git-send-email-tytso-3s7WtUTddSA@public.gmane.org>
2008-10-07 1:09 ` Theodore Tso
2008-09-13 18:47 YET ANOTHER resend of the fiemap patches Theodore Ts'o
2008-09-13 18:49 ` [PATCH 1/4] vfs: vfs-level fiemap interface Theodore Ts'o
2008-09-13 21:17 ` Anton Altaparmakov
2008-09-13 21:29 ` Theodore Tso
2008-09-13 21:45 ` Matthew Wilcox
2008-09-13 22:41 ` Theodore Tso
2008-09-13 21:59 ` Anton Altaparmakov
2008-09-14 13:51 ` Christoph Hellwig
2008-09-14 13:48 ` Christoph Hellwig
2008-09-14 17:58 ` Theodore Tso
2008-09-15 14:49 ` Christoph Hellwig
2008-09-15 17:53 ` Mark Fasheh
2008-09-16 6:51 ` Andreas Dilger
2008-09-16 21:31 ` Theodore Tso
2008-09-20 16:47 ` Josef 'Jeff' Sipek
2008-09-29 1:07 ` Theodore Tso
2008-09-29 21:13 ` Mark Fasheh
2008-09-29 22:10 ` Theodore Tso
2008-09-14 13:47 ` Christoph Hellwig
2008-09-14 18:01 ` Theodore Tso
2008-09-14 18:08 ` Christoph Hellwig
2008-09-14 19:58 ` Theodore Tso
2008-09-15 14:47 ` Christoph Hellwig
2008-09-16 6:49 ` Andreas Dilger
2008-09-16 22:03 ` Theodore Tso
2008-09-17 14:18 ` Jörn Engel
2008-09-17 15:02 ` Jamie Lokier
2008-09-17 15:25 ` Theodore Tso
2008-09-19 14:05 ` Chris Mason
2008-09-19 17:38 ` Jamie Lokier
2008-09-20 7:43 ` Dave Chinner
2008-09-20 13:50 ` Chris Mason
[not found] ` <20080920135048.GA15698@think.oraclecorp.com>
2008-09-20 15:36 ` Jamie Lokier
2008-09-20 15:44 ` Christoph Hellwig
2008-06-25 22:18 Mark Fasheh
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