Merge remote-tracking branch 'remotes/bonzini/tags/for-upstream' into staging

This update brings dataplane to virtio-scsi (NOT
yet 100% thread-safe, though, which makes it really, really
experimental.  It also brings asynchronous cancellation to
the SCSI subsystem and implements it in virtio-scsi.  This
is a pretty important feature.  Almost all the work here
was done by Fam Zheng.

I also included the virtio refcount fixes from Gonglei,
because they had a small conflict with virtio-scsi dataplane.

This pull request is using the new subkey 4E6B09D7.

# gpg: Signature made Tue 30 Sep 2014 12:31:02 BST using RSA key ID 4E6B09D7
# gpg: Good signature from "Paolo Bonzini <pbonzini@redhat.com>"
# gpg:                 aka "Paolo Bonzini <bonzini@gnu.org>"

* remotes/bonzini/tags/for-upstream: (39 commits)
  block/iscsi: handle failure on malloc of the allocationmap
  util: introduce bitmap_try_new
  virtio-scsi: Handle TMF request cancellation asynchronously
  scsi: Introduce scsi_req_cancel_async
  scsi: Introduce scsi_req_cancel_complete
  scsi: Drop SCSIReqOps.cancel_io
  scsi: Unify request unref in scsi_req_cancel
  scsi-generic: Handle canceled request in scsi_command_complete
  scsi: Drop scsi_req_abort
  virtio-scsi: Process ".iothread" property
  virtio-scsi: Call bdrv_io_plug/bdrv_io_unplug in cmd request handling
  virtio-scsi: Batched prepare for cmd reqs
  virtio-scsi: Two stages processing of cmd request
  virtio-scsi: Add migration state notifier for dataplane code
  virtio-scsi: Hook up with dataplane
  virtio-scsi-dataplane: Code to run virtio-scsi on iothread
  virtio-scsi: Add VirtIOSCSIVring in VirtIOSCSIReq
  virtio-scsi: Add 'iothread' property to virtio-scsi
  virtio: add a wrapper for virtio-backend initialization
  virtio-9p: fix virtio-9p child refcount in transports
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>