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Re: Xfs_repair and journalling

To: xfs@xxxxxxxxxxx
Subject: Re: Xfs_repair and journalling
From: Martin Steigerwald <Martin@xxxxxxxxxxxx>
Date: Mon, 18 Mar 2013 21:58:30 +0100
Cc: Ben Myers <bpm@xxxxxxx>, Subranshu Patel <spatel.ml@xxxxxxxxx>, stan@xxxxxxxxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20130318182202.GD22182@xxxxxxx>
References: <CAEUQceh-Xcabr0KErxF6EAdafDDP1PY_AeHwgYB82QeUdyGp-g@xxxxxxxxxxxxxx> <CAEUQceie41dh7h6uZSMu4-JB_BDu82X5CrKxHb=9wVQVAPzKgQ@xxxxxxxxxxxxxx> <20130318182202.GD22182@xxxxxxx> (sfid-20130318_205600_822442_7E5CA7C2)
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Am Montag, 18. MÃrz 2013 schrieb Ben Myers:
> Hi Subranshu,
[â]
> > In case of EXT4, journal will not be replayed on performing mount. One
> > need to invoke fsck which performs journal playback and then other
> > corruption checks/recovery.
> 
> I can't speak for ext4.  I do think that your expectation that
> fsck/repair be able to replay a journal is pretty reasonable.  That's
> just not how it is implemented here.  In xfs, log recovery is in the
> kernel and xfs_repair knows just enough about the log to avoid
> clobbering your precious metadata when it needs to be recovered.  There
> was some discussion in the past about making xfs_repair able to recover
> the log but I wouldn't expect that any time soon.

Yes, fsck.ext4 is able to replay the journal, and also able to *just* replay 
the journal and do nothing else. I just checked its manpage.

Thanks for not speaking for Ext4 unless you really think you know it.

Being able to replay in userspace might help when the filesystem cannot be 
mounted correctly due to reasons laying outside the journal. Cause then one 
can attempt to replay the journal in userspace and run a repair on the 
filesystem then.

-- 
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA  B82F 991B EAAC A599 84C7

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