Re: [Qemu-devel] [PATCH v2 0/7] virtio-scsi: Asynchronous cancellation

[Paolo Bonzini <pbonzini@redhat.com>]

Il 24/09/2014 10:27, Fam Zheng ha scritto:
> v2: Address Paolo's comments:
>     - Drop scsi_req_abort.
>     - Split patch 1.
>     - Use NotifierList.
>     - Track the number of cancelled requests in virtio-scsi.
> 
> This series changes VIRTIO_SCSI_T_TMF_ABORT_TASK and
> VIRTIO_SCSI_T_TMF_ABORT_TASK_SET emulation to asynchronous by making use of
> bdrv_aio_cancel_async.
> 
> Before, when guest cancels a SCSI command, we use a nested poll loop to wait
> until the request is cancelled or completed before returning. This blocks the
> whole vm and makes the guest unresponsive if the backend block device takes
> time to complete it, possibly because of slow IO, throttling, network issue,
> etc..
> 
> Now we return to the guest to allow vcpus to run before completing the TMF, and
> only after all the requests have been canceled, we notify the guest about the
> completing of the TMF command.
> 
> 
> 
> Fam Zheng (7):
>   scsi: Drop scsi_req_abort
>   scsi-generic: Handle canceled request in scsi_command_complete
>   scsi-bus: Unify request unref in scsi_req_cancel
>   scsi: Drop SCSIReqOps.cancel_io
>   scsi: Introduce scsi_req_canceled
>   scsi: Introduce scsi_req_cancel_async
>   virtio-scsi: Handle TMF request cancellation asynchronously
> 
>  hw/scsi/scsi-bus.c     | 48 +++++++++++++++++++----------
>  hw/scsi/scsi-disk.c    | 59 ++++++++++-------------------------
>  hw/scsi/scsi-generic.c | 37 ++++++----------------
>  hw/scsi/spapr_vscsi.c  | 11 +++++--
>  hw/scsi/virtio-scsi.c  | 84 +++++++++++++++++++++++++++++++++++++++++++++-----
>  include/hw/scsi/scsi.h |  5 ++-
>  6 files changed, 146 insertions(+), 98 deletions(-)
> 

I didn't review 5-7 yet, and they are more complicated so I'll start by
applying the nice cleanup part (1-4).

Thanks!

Paolo