linux-kernel - Re: Bugs in MMC [was: [Bug 10030] Suspend doesn't work when SD card is inserted]

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Date:	Thu, 6 Mar 2008 21:53:44 +0100
From:	"Zdenek Kabelac" <zdenek.kabelac@...il.com>
To:	"Alan Stern" <stern@...land.harvard.edu>
Cc:	"Pavel Machek" <pavel@....cz>,
	"David Brownell" <david-b@...bell.net>,
	"Pierre Ossman" <drzeus-mmc@...eus.cx>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	"pm list" <linux-pm@...ts.linux-foundation.org>,
	"Kernel development list" <linux-kernel@...r.kernel.org>
Subject: Re: Bugs in MMC [was: [Bug 10030] Suspend doesn't work when SD card is inserted]

2008/3/6, Alan Stern <stern@...land.harvard.edu>:
> On Thu, 6 Mar 2008, Pavel Machek wrote:
>
>  > On Tue 2008-03-04 16:00:51, Alan Stern wrote:
>  > > On Tue, 4 Mar 2008, David Brownell wrote:
>  > >
>  > > > > What's wrong with a superfluous probe at resume time, besides the waste
>  > > > > of a few milliseconds?
>  > > >
>  > > > I'm more concerned with the undesirable removal of devices at suspend
>  > > > time ... ones with mounted filesystems etc.
>  > >
>  > > On that we can agree.  The removal is done if the host doesn't define a
>  > > resume method.  There doesn't seem to be any point to that, given that
>  > > the probing during resume will determine whether a card has in fact
>  > > been removed.
>  >
>  > Hmm, if the driver is sleeping too deeply, user might have removed the
>  > card and put in different one, without driver noticing. That would be
>  > _bad_.
>
>
> Ironically, the very same problem now exists with the USB mass-storage
>  driver.  I don't see any way for the driver itself to solve it,
>  especially during a hibernation (which can be a _very_ deep sleep).
>
>  One thing that could be done is for filesystems to verify, after a
>  system sleep, that their superblocks haven't changed.  There could
>  still be issues with non-mounted partitions, if they have live entries
>  in the block cache, but it would be an improvement.
>
>  Do you know the right people to mention this to?  Anybody in filesystem
>  development interested in suspend/hibernation issues?


IMHO the way would be to try to unmount fs if it's possible - if not -
user should be notified on suspend/hibernation that he must preserve
media in its place after resume and it should be checked and user
should be notified if different devices/fs were find...

Zdenek
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