From: Joel Becker <jlbec@evilplan.org>
To: Amir Goldstein <amir73il@gmail.com>
Cc: Tao Ma <tm@tao.ma>, linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Ext4 Developers List <linux-ext4@vger.kernel.org>,
Theodore Tso <tytso@mit.edu>,
Chris Mason <chris.mason@oracle.com>,
Josef Bacik <josef@redhat.com>
Subject: Re: [LSF/FS TOPIC] Ext4 snapshots status update
Date: Wed, 30 Mar 2011 03:33:23 -0700 [thread overview]
Message-ID: <20110330103321.GB1564@noexit> (raw)
In-Reply-To: <AANLkTinV-WSj2c+dtNyaS-r8xf_c0R5UB-_f73XLm0Z8@mail.gmail.com>
On Wed, Mar 30, 2011 at 08:05:38AM +0200, Amir Goldstein wrote:
> Just wanted to clarify there are 2 differences I notice between mmap
> write to a hole
> and mmap write to COWed file with ENOSPC:
>
> 1. A "good" application can avoid mmap write to a hole.
>
> 2. when initiating a hole, the mkwrite callback is in used (in ext4) to
> reserve disk space for delayed allocation when a page becomes writable.
> with COW a page may already be writable when the flush encounters COW
> with ENOSPC. that flush can even happen after the application has exited,
> so the data will be dropped on the floor silently (like in ext3).
ocfs2 doesn't have delayed allocation yet, so we try and fail
the allocation in write_begin() right under mkwrite().
Joel
--
The Graham Corollary:
The longer a socially-moderated news website exists, the
probability of an old Paul Graham link appearing at the top
approaches certainty.
http://www.jlbec.org/
jlbec@evilplan.org
next prev parent reply other threads:[~2011-03-30 10:33 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-03 22:33 [LSF/FS TOPIC] Ext4 snapshots status update Amir Goldstein
2011-02-04 0:20 ` Joel Becker
2011-02-04 5:52 ` Amir Goldstein
2011-03-23 20:19 ` Amir Goldstein
2011-03-30 0:34 ` Joel Becker
2011-03-30 4:16 ` Amir Goldstein
2011-03-30 5:52 ` Tao Ma
2011-03-30 6:05 ` Amir Goldstein
2011-03-30 10:33 ` Joel Becker [this message]
2011-03-30 10:46 ` Amir Goldstein
2011-03-30 11:50 ` Chris Mason
2011-03-30 12:08 ` Amir Goldstein
2011-04-01 0:10 ` [Lsf-pc] " Trond Myklebust
2011-04-01 3:58 ` Amir Goldstein
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