Re: [linux-pm] Is it supposed to be ok to call del_gendisk while userspace is frozen?

[Maxim Levitsky <maximlevitsky@gmail.com>]

On Thu, 2010-03-04 at 14:53 +0100, Pavel Machek wrote: 
> Hi!
> 
> > > journalling assumptions broken: commit block is there, but previous
> > > blocks are not intact. Data loss.
> > > 
> > > ...and that was the first I could think about. Lets not do
> > >  this. Barriers were invented for a reason.
> > 
> > Very well.  Then we still need a solution to the original problem:  
> > Devices sometimes need to be unregistered during resume, but
> > del_gendisk() blocks on the writeback thread, which is frozen until
> > after the resume finishes.  How do you suggest this be fixed?
> 
> Avoid unregistering device during resume. Instead, return errors until
> resume is done and you can call del_gendisk? 

This won't help ether. The same driver needs to unregister perfectly
working device on suspend, because the user might replace the card
during suspend and fool the os.
There is a setting, CONFIG_MMC_UNSAFE_RESUME and I use it, but it isn't
default.

Anyway to revive that old thread, how about introducing new
del_gendisk_no_sync?

A less safe version of del_gendisk, but which won't sync the filesystem.
Since driver knows that card is gone, there is no point of syncing it.

(the sync is done by invalidate_partition, so some flag should be
propagated to it).



Best regards,
Maxim Levitsky