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Re: Filesystem Consistency Issues

To: Andi Kleen <ak@xxxxxxx>
Subject: Re: Filesystem Consistency Issues
From: Stephen Lord <lord@xxxxxxx>
Date: Mon, 05 Dec 2005 07:23:10 -0600
Cc: David Brown <xfs@xxxxxxxxxx>, linux-xfs@xxxxxxxxxxx
In-reply-to: <p734q5nsre6.fsf@xxxxxxxxxxxxx>
References: <20051204142506.GE2605@xxxxxxxxxxx> <20051205014137.GA7685@xxxxxxxxxxxxxx> <p734q5nsre6.fsf@xxxxxxxxxxxxx>
Sender: linux-xfs-bounce@xxxxxxxxxxx
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XFS runs recovery on a readonly filesystem. It has been doing that
for years. There are log messages which come out when recovery runs,
you should see them in dmesg or the syslog after boot up.


Andi Kleen wrote:
David Brown <xfs@xxxxxxxxxx> writes:

On Sun, Dec 04, 2005 at 10:25:06PM +0800, Federico Sevilla III wrote:

When I investigated one of the machines, mounting the filesystem in
read/write mode after having booted from a rescue CD automatically fixed
part of it, freeing about 60% of the filesystem. Running xfs_repair
further freed up space by moving disconnected inodes to lost+found.
Most likely, the problem is that the root filesystem is being mounted
readonly by the kernel.  This is default, and I believe Debian leaves that
as the default.  The problem is that the readonly root mount prevents the
recovery when the filesystem is mounted.  Apparently, remounting as
read/write doesn't cause this recovery to happen.

That sounds like a bug. Shouldn't log replay happening on ro->rw mount?
BTW I think ext3/reiser solve the problem by replaying the logs even
when the mount is ro. That would be another alternative.

Perhaps this should be added to the XFS FAQ, rather than just saying that
"Yes", XFS can be used for the root FS.

It's a nasty trap that I bet most people and distributions get wrong.


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