From: Theodore Tso <tytso@MIT.EDU>
To: Christoph Hellwig <hch@infradead.org>
Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
akpm@linuxfoundation.org, Mark Fasheh <mfasheh@suse.com>,
mtk.manpages@gmail.com
Subject: Re: [PATCH 1/4] vfs: vfs-level fiemap interface
Date: Sun, 14 Sep 2008 14:01:32 -0400 [thread overview]
Message-ID: <20080914180132.GC13074@mit.edu> (raw)
In-Reply-To: <20080914134711.GA21746@infradead.org>
On Sun, Sep 14, 2008 at 09:47:11AM -0400, Christoph Hellwig wrote:
> On Sat, Sep 13, 2008 at 02:49:24PM -0400, Theodore Ts'o wrote:
> > +* FIEMAP_EXTENT_NO_BYPASS
> > +Direct access to the data in this extent is illegal or will have
> > +undefined results.
>
> This one is sitll misnamed and for sure utterly misdocumented. Direct
> access to the data is always illegal and has undefined results, and
> programs that do it anyway (e.g. grub) are in really deep trouble.
Programs like Grub *have* to. And in the case of a boot-loader, Lilo
and Grub have been able to do so safely for over 15 years. This is
basically a generic flag that indicates that they can't, but it
reflects the reality that for many filesystems, they *can*. The main
legal use is LILO and/or Grub, in fact. One could argue that programs
that try accessing data blocks directly while the filesystem is
mounted are doomed, but boot loaders do so while the filesystem are
unmounted.
The name isn't particularly important, but what it indicates is very
clearly useful.
- Ted
next prev parent reply other threads:[~2008-09-14 18:01 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
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 18:49 ` [PATCH 2/4] ocfs2: fiemap support Theodore Ts'o
2008-09-13 18:49 ` [PATCH 3/4] generic block based fiemap implementation Theodore Ts'o
2008-09-13 18:49 ` [PATCH 4/4] Hook ext4 to the vfs fiemap interface Theodore Ts'o
2008-09-13 21:17 ` [PATCH 1/4] vfs: vfs-level " 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 [this message]
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
-- 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
2008-10-03 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
2008-10-04 2:12 ` 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
2008-10-06 13:07 ` steve
2008-06-25 22:18 Mark Fasheh
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