[PATCH 00 of 10] blkfront pvops updates, v2

[Daniel Stodden <daniel.stodden@citrix.com>]

Updates since the last time:

 * Make sure everything applies against xen/frontend. That fortunately
   made no difference.

 * Two more loopholes:

    - The path freeing info in xenbus_remove took a more carefully
      sync with an unfortunate bdops->release. This is because the
      locking can't just nest. Fixed by resyncing the info pointer
      through disk->private_data.

    - Similar effect during bdev open. This also needs to anticipate
      the not-so-unlikely case where not only the gendisk but the
      entire info struct was deleted just before entry. Again, syncing
      on disk->private_data once holding bd_mutex does the trick.

    I chose to just merge those in.

 * To be honest, that dev_warn the last patch added was broken -- doh.

 * Found the switch [again] for HG to strip those headers -- cheers.

Feedback certainly welcome. I am aware this thing looks manic, but at
it stands, we recently happend to come across exactly that family of
races in XCP again, so I really want these paths fixed.

Thanks,
Daniel