linux-kernel - Re: [PATCH -mm 0/2] Use freezeable workqueues to avoid suspend-related XFS corruptions

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Message-Id: <1164061586.15714.1.camel@nigel.suspend2.net>
Date:	Tue, 21 Nov 2006 09:26:26 +1100
From:	Nigel Cunningham <nigel@...pend2.net>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	David Chinner <dgc@....com>, Andrew Morton <akpm@...l.org>,
	LKML <linux-kernel@...r.kernel.org>, Pavel Machek <pavel@....cz>
Subject: Re: [PATCH -mm 0/2] Use freezeable workqueues to avoid
	suspend-related XFS corruptions

Hi.

On Mon, 2006-11-20 at 23:18 +0100, Rafael J. Wysocki wrote:
> I think I/O can only be submitted from the process context.  Thus if we freeze
> all (and I mean _all_) threads that are used by filesystems, including worker
> threads, we should effectively prevent fs-related I/O from being submitted
> after tasks have been frozen.

I know that will work. It's what I used to do before the switch to bdev
freezing. I guess I need to look again at why I made the switch. Perhaps
it was just because you guys gave freezing kthreads a bad wrap as too
invasive or something. Bdev freezing is certainly fewer lines of code.

> This can be done with the help of create_freezeable_workqueue() introduced in
> this patch and I'd like to implement it (and there are only a few filesystems
> that use work queues).
> 
> The freezing of bdevs might be a good solution if:
> (1) we were sure it wouldn't interact with dm in a wrong way,
> (2) _all_ of the filesystems implemented it.
> For now, neither (1) nor (2) are satisfied and we need to know we're safe
> _now_.

Yeah.

Regards,

Nigel

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