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

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Message-ID: <20111129133239.GA9926@quack.suse.cz>
Date:	Tue, 29 Nov 2011 14:32:39 +0100
From:	Jan Kara <jack@...e.cz>
To:	Alasdair G Kergon <agk@...hat.com>
Cc:	Jan Kara <jack@...e.cz>, Mikulas Patocka <mpatocka@...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 Tue 29-11-11 13:18:11, Alasdair G Kergon wrote:
> On Tue, Nov 29, 2011 at 02:09:13PM +0100, Jan Kara wrote:
> >   Hmm, then why do these operations suspend the filesystem if they
> > apparently don't need it? Sorry for my ignorance, I never seriously worked
> > with LVM code...
> 
> They don't suspend it if they don't need to.
> 
> dm-ioctl.h:
> /*
>  * Set this to avoid attempting to freeze any filesystem when suspending.
>  */
> #define DM_SKIP_LOCKFS_FLAG     (1 << 10) /* In */
  Thanks. I was now checking in detail and indeed FIFREEZE fails if
->freeze_fs is not set. And only xfs, ext3, ext4, reiserfs, jfs, nilfs2,
and gfs2 provide this function. So I was correct in assuming that when
filesystem supports FIFREEZE it must make sure no modifications happen to
the filesystem. So I believe that my original plan for sync to skip frozen
filesystem is correct.

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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