linux-kernel - Re: freeze vs freezer

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Message-ID: <477D5C4F.8050800@nigel.suspend2.net>
Date:	Fri, 04 Jan 2008 09:06:07 +1100
From:	Nigel Cunningham <nigel@...el.suspend2.net>
To:	Oliver Neukum <oliver@...kum.org>
CC:	"Rafael J. Wysocki" <rjw@...k.pl>, Pavel Machek <pavel@....cz>,
	Kyle Moffett <mrmacman_g4@....com>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	David Chinner <dgc@....com>,
	Jeremy Fitzhardinge <jeremy@...p.org>, xfs-masters@....sgi.com,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: freeze vs freezer

Hi.

Oliver Neukum wrote:
> Am Donnerstag, 3. Januar 2008 10:52:53 schrieb Nigel Cunningham:
>> Hi.
>>
>> Oliver Neukum wrote:
>>> Am Donnerstag 03 Januar 2008 schrieb Nigel Cunningham:
>>>> On top of this, I made a (too simple at the moment) freeze_filesystems
>>>> function which iterates through &super_blocks in reverse order, freezing
>>>> fuse filesystems or ordinary ones. I say 'too simple' because it doesn't
>>>> currently allow for the possibility of someone mounting (say) ext3 on
>>>> fuse, but that would just be an extension of what's already done.
>>> How do you deal with fuse server tasks using other fuse filesystems?
>> Since they're frozen in reverse order, the dependant one would be frozen
>> first.
> 
> Say I do:
> 
> a) mount fuse on /tmp/first
> b) mount fuse on /tmp/second
> 
> Then the server task for (a) does "ls /tmp/second". So it will be frozen,
> right? How do you then freeze (a)? And keep in mind that the server task
> may have forked.

I guess I should first ask, is this a real life problem or a
hypothetical twisted web? I don't see why you would want to make two
filesystems interdependent - it sounds like the way to create livelock
and deadlocks in normal use, before we even begin to think about
hibernating.

Regards,

Nigel
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