linux-kernel - Re: MMC/SD Root filesystem suspend/resume problems

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Message-ID: <20070725190115.GB10208@ucw.cz>
Date:	Wed, 25 Jul 2007 19:01:15 +0000
From:	Pavel Machek <pavel@....cz>
To:	Richard Purdie <rpurdie@...ys.net>
Cc:	Pierre Ossman <drzeus-mmc@...eus.cx>,
	kernel list <linux-kernel@...r.kernel.org>
Subject: Re: MMC/SD Root filesystem suspend/resume problems

Hi!

> > > Lots of Linux handhelds use MMC/SD devices as the root file system.
> > > This has worked quite reliably for many kernel versions. In 2.6.22,
> > > it seems that if you suspend such a system then resume it, the device
> > > locks up. Trying to execute anything on the filesystem results in a
> > > "Permission Denied" message. I did see a message from the MMC
> > > subsystem saying it had redetected the card. There are also messages
> > > on the console like "MMC: killing requests for dead queue" each time
> > > you suspend/resume.
> > 
> > The card is removed when you suspend and readded when you resume.
> > That's the only safe thing we can do until we get suspend support in
> > the filesystems.
> > 
> > If you really want to shoot yourself in the foot, there is a Kconfig
> > option that keeps the card around across the suspend.
> 
> I enabled the MMC_UNSAFE_RESUME option and the problems I was seeing was
> "fixed". I think having this option is a bad idea (in its current form)
> as it doesn't actually stop filesystem corruption.
> 
> With the option disabled, if a filesystem is mounted when you suspend my
> tests show the filesystem is corrupted. At least if the option is
> enabled, the filesystem is only corrupted if you remove the card whilst
> suspended which is more preferable.

Are we talking _corruption_ here, or are we talking 'the kind of
corruption recoverable by fsck that happens on powerfail'?

							Pavel

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