On 11/27/18 7:10 PM, Ming Lei wrote:
> On Mon, Nov 26, 2018 at 09:35:53AM -0700, Jens Axboe wrote:
>> We need this for blk-mq to kick things into gear, if we told it that
>> we had more IO coming, but then failed to deliver on that promise.
>>
>> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
>> ---
>> drivers/block/virtio_blk.c | 15 +++++++++++++++
>> 1 file changed, 15 insertions(+)
>>
>> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
>> index 6e869d05f91e..b49c57e77780 100644
>> --- a/drivers/block/virtio_blk.c
>> +++ b/drivers/block/virtio_blk.c
>> @@ -214,6 +214,20 @@ static void virtblk_done(struct virtqueue *vq)
>> spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags);
>> }
>>
>> +static void virtio_commit_rqs(struct blk_mq_hw_ctx *hctx)
>> +{
>> + struct virtio_blk *vblk = hctx->queue->queuedata;
>> + int qid = hctx->queue_num;
>> + bool kick;
>> +
>> + spin_lock_irq(&vblk->vqs[qid].lock);
>> + kick = virtqueue_kick_prepare(vblk->vqs[qid].vq);
>> + spin_unlock_irq(&vblk->vqs[qid].lock);
>> +
>> + if (kick)
>> + virtqueue_notify(vblk->vqs[qid].vq);
>> +}
>> +
>> static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx *hctx,
>> const struct blk_mq_queue_data *bd)
>> {
>> @@ -638,6 +652,7 @@ static void virtblk_initialize_rq(struct request *req)
>>
>> static const struct blk_mq_ops virtio_mq_ops = {
>> .queue_rq = virtio_queue_rq,
>> + .commit_rqs = virtio_commit_rqs,
>> .complete = virtblk_request_done,
>> .init_request = virtblk_init_request,
>> #ifdef CONFIG_VIRTIO_BLK_SCSI
>> --
>> 2.17.1
>>
>
> If .commit_rqs() is implemented, virtqueue_notify() in virtio_queue_rq()
> should have been removed for saving the world switch per .queue_rq()
->commits_rqs() is only for the case where bd->last is set to false,
and we never make it to the end and flag bd->last == true. If bd->last
is true, the driver should kick things into gear.
--
Jens Axboe
