[PATCH v6 0/2] virtio-blk: support polling I/O and mq_ops->queue_rqs()

[Suwan Kim <suwan.kim027@gmail.com>]

This patch serise adds support for polling I/O and mq_ops->queue_rqs()
to virtio-blk driver.

Changes

v5 -> v6
    - patch1 : virtblk_poll
        - Remove memset in init_vq()
        - Fix space indent in init_vq()
        - Replace if condition with positive check in virtblk_map_queues()
                if (i == HCTX_TYPE_POLL)
                        blk_mq_map_queues(&set->map[i]);
                else
                        blk_mq_virtio_map_queues(&set->map[i], vblk->vdev, 0);
        - Add Reviewed-by tags
    
    - patch2 : virtio_queue_rqs
        - Add Reviewed-by tags

v4 -> v5
    - patch1 : virtblk_poll
        - Replace "req_done" with "found" in virtblk_poll()
        - Split for loop into two distinct for loop in init_vq()
          that sets callback function for each default/poll queues
        - Replace "if (i == HCTX_TYPE_DEFAULT)" with "i != HCTX_TYPE_POLL"
          in virtblk_map_queues()
        - Replace "virtblk_unmap_data(req, vbr);" with
          "virtblk_unmap_data(req, blk_mq_rq_to_pdu(req);"
          in virtblk_complete_batch()
    
    - patch2 : virtio_queue_rqs
        - Instead of using vbr.sg_num field, use vbr->sg_table.nents.
          So, remove sg_num field in struct virtblk_req
        - Drop the unnecessary argument of virtblk_add_req() because it
          doens't need "data_sg" and "have_data". It can be derived from "vbr"
          argument.
        - Add Reviewed-by tag from Stefan

v3 -> v4
    - patch1 : virtblk_poll
        - Add print the number of default/read/poll queues in init_vq()
        - Add blk_mq_start_stopped_hw_queues() to virtblk_poll()
              virtblk_poll()
                  ...
                  if (req_done)
                                   blk_mq_start_stopped_hw_queues(vblk->disk->queue, true);
                  ...

    - patch2 : virtio_queue_rqs
        - Modify virtio_queue_rqs() to hold lock only once when it adds
          requests to virtqueue just before virtqueue notify.
          It will guarantee that virtio_queue_rqs() will not use
          previous req again.

v2 -> v3
        - Fix warning by kernel test robot
          
            static int virtblk_poll()
                ...
                if (!blk_mq_add_to_batch(req, iob, virtblk_result(vbr),
                                                   -> vbr->status,

v1 -> v2
        - To receive the number of poll queues from user,
          use module parameter instead of QEMU uapi change.

        - Add the comment about virtblk_map_queues().

        - Add support for mq_ops->queue_rqs() to implement submit side
          batch.

Suwan Kim (2):
  virtio-blk: support polling I/O
  virtio-blk: support mq_ops->queue_rqs()

 drivers/block/virtio_blk.c | 220 +++++++++++++++++++++++++++++++++----
 1 file changed, 201 insertions(+), 19 deletions(-)

-- 
2.26.3