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Re: how to replay log of a fs that has no log: is this supposed to work?

To: Linda Walsh <xfs@xxxxxxxxx>
Subject: Re: how to replay log of a fs that has no log: is this supposed to work? SW Defect?
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Fri, 5 Oct 2012 09:37:54 +1000
Cc: xfs-oss <xfs@xxxxxxxxxxx>
In-reply-to: <506DB419.2030902@xxxxxxxxx>
References: <506DAF66.2030507@xxxxxxxxx> <506DB419.2030902@xxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Thu, Oct 04, 2012 at 09:06:49AM -0700, Linda Walsh wrote:
> Linda Walsh wrote:
> (blah blah blah)...
> or more specifically:
> xfs_freeze -f /home/.snapdir/\@GMT-2012.10.04-03.06.17
> Ishtar:/# xfs_ncheck /dev/Home+Space/Home-2012.10.04-03.06.17
>    ERROR: The filesystem has valuable metadata changes in a log which needs to
>    be replayed.  Mount the filesystem to replay the log, and unmount it before
>    re-running xfs_ncheck.  If you are unable to mount the filesystem, then use
>    the xfs_repair -L option to destroy the log and attempt a repair.
>    Note that destroying the log may cause corruption -- please attempt a mount
>    of the filesystem before doing this.
>    must run blockget -n first
> ok -- lets mount/umount it:
> Ishtar:/# mount -o ro,nouuid
> /dev/Home+Space/Home-2012.10.04-03.06.17
> /home/.snapdir/@GMT-2012.10.04-03.06.17

So, a read only snapshot? If so what makes you think that recovery
can run and modify the filesystem/log?

THe whole point of freeze creating a consistent disk image is so you
can mount it without needing recovery to run. i.e:

# mount -o ro,nouuid,norecovery ....

> ---
> Um... looking at the above it would appear that I froze a fs.
> ncheck claimed the freeze didn't result in the logfile being written being put
> into a consistent state, but said to remount the fs to allow it to play then
> umount...
> So... did that.
> Log file is still in a corrupt state.

The log is not corrupt, just dirty.

> Am I wrong in assuming that doing xfs_repair -L to destroy the log on this
> dev, might be a bad thing to do and might screw up it's "Origin" file
> system (i.e. the current 'live' /home partition)?

It will try to write to the snapshot. If it is a read-only


Dave Chinner

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