[PATCH 5/8] virtio_blk: implement mq_ops->commit_rqs() hook

[axboe@kernel.dk (Jens Axboe)]

On 11/27/18 7:10 PM, Ming Lei wrote:
> On Mon, Nov 26, 2018@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 at kernel.dk>
>> ---
>>  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