linux-kernel - Re: [dm-devel] [PATCH] deadlock with suspend and quotas

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Message-ID: <20111130130514.GU7595@agk-dp.fab.redhat.com>
Date:	Wed, 30 Nov 2011 13:05:14 +0000
From:	Alasdair G Kergon <agk@...hat.com>
To:	Mikulas Patocka <mpatocka@...hat.com>, Jan Kara <jack@...e.cz>,
	Alasdair G Kergon <agk@...hat.com>, esandeen@...hat.com,
	Surbhi Palande <csurbhi@...il.com>,
	linux-kernel@...r.kernel.org, dm-devel@...hat.com,
	linux-fsdevel@...r.kernel.org,
	Christopher Chaltain <christopher.chaltain@...onical.com>,
	Valerie Aurora <val@...consulting.com>
Subject: Re: [dm-devel] [PATCH] deadlock with suspend and quotas

On Wed, Nov 30, 2011 at 07:14:18AM -0500, Mikulas Patocka wrote:
> On Wed, 30 Nov 2011, Jan Kara wrote:
> > > So if you skip sync of frozen filesystems, you introduce a data
> > > corruption if someone takes a snapshot of ext2.
> >   Yes, because ext2 cannot really be frozen, it is (errorneously) marked
> > as such but it is not frozen...

This is just getting into semantics.  AFAIK (and it was before my involvement)
LVM used the term 'lockfs' for this operation when it was introduced to ext2.
It later got renamed in-kernel to 'frozen' to bring it into line with newer
filesystems.  But userspace and the interface still retain the original
'lockfs' name.

There is no further I/O sent to the filesystem during the 'lockfs' operation:
LVM uses dm to block that.

Alasdair

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