linux-kernel - Re: Power Management with rootfs on SDMMC.

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Message-ID: <20090103231013.3591d027@lxorguk.ukuu.org.uk>
Date:	Sat, 3 Jan 2009 23:10:13 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Pavel Machek <pavel@...e.cz>, Andreas Mohr <andi@...as.de>,
	Sriram V <vshrirama@...il.com>,
	Pierre Ossman <drzeus-list@...eus.cx>,
	linux-kernel@...r.kernel.org
Subject: Re: Power Management with rootfs on SDMMC.

> Well, it goes both ways. You can make a nasty mess right now by suspending 
> and simply not having a working computer when it comes back - all your 
> work being lost.

Yes but these are both symptoms of the same problem.

> they actually get things right is pretty low, though. So I suspect we'd be 
> much better off having sane defaults in the kernel instead.

I don't believe "auto-destroy my music collection" is a sane default...

> So it boils down to the fact that if you have something like / or /home 
> mounted, we really _cannot_ do any better than "assume the user doesn't 
> screw us up".
> 
> A per-filesystem callback to re-verify at resume might be a good idea, but 
> a lot of filesystems cannot reasonably do a lot of verification.

A per file system sync and quiesce is I think also part of the
requirement. Having the file system media consistent but still mounted
before suspending is a good thing anyway (especially with stuff like USB
keys that people do then go and remove post suspend) and you can put the
device into a consistent state and revalidate it *regardless* of the
whether it is / or a music player. What you do if revalidating / fails is
another question ;)

Alan
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