[libvirt] [PATCH 0/4] Multiple problems with saving to block devices

[Daniel P. Berrange]

This patch series makes it possible to save to a block device,
instead of a plain file. There were multiple problems 

 - WHen save failed, we might de-reference a NULL pointer
 - When save failed, we unlinked the device node !!
 - The approach of using >> to append, doesn't work with block devices
 - CGroups was blocking QEMU access to the block device when enabled

One remaining problem is not in libvirt, but rather QEMU. The QEMU
exec: based migration often fails to detect failure of the command
and will thus hang forever attempting a migration that'll never
succeed! Fortunately you can now work around this in libvirt using
the virsh domjobabort command