linux-kernel - Re: [PATCH] Make XFS workqueues nonfreezable

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Date:	Thu, 1 Mar 2007 10:15:21 +0100
From:	Pavel Machek <pavel@....cz>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>, Oleg Nesterov <oleg@...sign.ru>,
	vatsa@...ibm.com, Gautham R Shenoy <ego@...ibm.com>,
	Johannes Berg <johannes@...solutions.net>,
	LKML <linux-kernel@...r.kernel.org>, David Chinner <dgc@....com>,
	Nigel Cunningham <ncunningham@...uxmail.org>
Subject: Re: [PATCH] Make XFS workqueues nonfreezable

Hi!

> > Since freezable workqueues are broken in 2.6.21-rc
> > (cf. http://marc.theaimsgroup.com/?l=linux-kernel&m=116855740612755,
> > http://marc.theaimsgroup.com/?l=linux-kernel&m=117261312523921&w=2)
> > it's better to change the only user of them, which is XFS, to use "normal"
> > nonfreezable workqueues.
> > 
> > Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> > ---
> >  fs/xfs/linux-2.6/xfs_buf.c |    4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > Index: linux-2.6.21-rc2/fs/xfs/linux-2.6/xfs_buf.c
> > ===================================================================
> > --- linux-2.6.21-rc2.orig/fs/xfs/linux-2.6/xfs_buf.c
> > +++ linux-2.6.21-rc2/fs/xfs/linux-2.6/xfs_buf.c
> > @@ -1829,11 +1829,11 @@ xfs_buf_init(void)
> >  	if (!xfs_buf_zone)
> >  		goto out_free_trace_buf;
> >  
> > -	xfslogd_workqueue = create_freezeable_workqueue("xfslogd");
> > +	xfslogd_workqueue = create_workqueue("xfslogd");
> >  	if (!xfslogd_workqueue)
> >  		goto out_free_buf_zone;
> >  
> > -	xfsdatad_workqueue = create_freezeable_workqueue("xfsdatad");
> > +	xfsdatad_workqueue = create_workqueue("xfsdatad");
> >  	if (!xfsdatad_workqueue)
> >  		goto out_destroy_xfslogd_workqueue;
> >  
> 
> Won't this break suspend+XFS?
> 
> If so, and given that nobody seems to be reporting this deadlock, perhaps
> we'd be better off leaving things as-is for the while?

Worst case is not breaking suspend+XFS, worst case is XFS writing to
disk after freeze(), leading to subtle fs corruption.

(But noone could reproduce corruption before, and I was told XFS will
not do those writes these days).
								Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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