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Re: XFS journal documentation?

To: æèç Yang Su Li <yangsuli@xxxxxxxxx>
Subject: Re: XFS journal documentation?
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Wed, 4 Dec 2013 08:18:56 +1100
Cc: xfs@xxxxxxxxxxx
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User-agent: Mutt/1.5.21 (2010-09-15)
On Tue, Dec 03, 2013 at 02:55:23PM -0600, æèç Yang Su Li wrote:
> Hi,
> I am trying to understand XFS a little bit better, especially its journal
> process. Unfortunately, I am having trouble find documentation in this
> regard.
> The general XFS documentation (
> http://xfs.org/docs/xfsdocs-xml-dev/XFS_Filesystem_Structure//tmp/en-US/html/index.html)
> has been quite helpful, but it doesn't describe the journal part of XFS. I
> also found some kernel documentation ablout XFS's delayed logging (
> https://www.kernel.org/doc/Documentation/filesystems/xfs-delayed-logging-design.txt),
> which talks about the journal process a bit. But it seems to assume a lot
> of prior knowledge of how the original XFS logging works to completely
> understand what the author is talking about; and the term it uses (like
> checkpoint) seem to have complete different meaning from, say, ext4.

Yes, I assumed that the reader has some familiarity with XFS
journalling - it's documentation for XFS developers, not users...

> So I am wondering, is there some kind of (any kind of ) documentation on
> XFS journaling? Ideally it will cover the major data structure and major
> code flow, but even a very high level, incomplete overview would be better
> than what I have now, which is essentially nothing. And if so, where can I
> find it?

The code is your only really option. go look at
fs/xfs/xfs_log_format.h where all the structures that are formatted
into the log are defined, and xfs_log_recovery.c for how it is all


Dave Chinner

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