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Subject: Re: USB: on suspend to ram/disk all usb devices are replugged
From: Nigel Cunningham <nigel@nigel.suspend2.net>
Reply-To: nigel@nigel.suspend2.net
To: Pavel Machek <pavel@ucw.cz>
Cc: Chuck Ebbert <cebbert@redhat.com>, Alan Stern <stern@rowland.harvard.edu>,
       David Zeuthen <davidz@redhat.com>, Maxim <maximlevitsky@gmail.com>,
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Date: Sat, 07 Apr 2007 08:23:50 +1000
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Hi.

On Mon, 2007-04-02 at 21:36 +0200, Pavel Machek wrote:
> Hi!
> 
> > > But you're still likely to run into trouble if you unplug a storage
> > > device, move it to another system and write on it, then plug it back into
> > > the original system.  The PLVM would somehow have to recognize that the
> > > data had been changed.  I don't know a foolproof way of doing that.
> > > 
> > 
> > Mark the filesystem as in-use with a one-time UUID in the superblock at
> > mount time. If one moved the drive to another system it would require
> > an fsck to clear the UUID before the other system could use it; then
> > the original machine would refuse to use the drive when the UUID didn't
> > match on resume.
> 
> You still need fs-specific code, I'm afraid... plus userland tool
> to reset signatures back.

You don't need userland to reset the signatures. More kernel code, sure.
But it doesn't _need_ to be userland.

Regards,

Nigel