This Xen blkfront patch (recently submitted to LKML with positive feedback)
is required by AWS. It is probably eventually destined for all supported
Ubuntu kernels but we'd like it to land in linux-aws immediately.
Patch looks proper to me and applies cleanly to linux-aws (xenial).
When a blkfront device is resized from dom0, emit a KOBJ_CHANGE uevent to
notify the guest about the change. This allows for custom udev rules, such
as automatically resizing a filesystem, when an event occurs.