Re: [PATCH 1/1] virtio_blk: implement init_hctx MQ operation

Max Gurtovoy
2024-08-01T15:17:45Z

On 01/08/2024 18:13, Michael S. Tsirkin wrote:
> On Thu, Aug 01, 2024 at 06:11:37PM +0300, Max Gurtovoy wrote:
>> In this operation set the driver data of the hctx to point to the virtio
>> block queue. By doing so, we can use this reference in the and reduce
> in the .... ?

sorry for the type.

should be :

"By doing so, we can use this reference and reduce the number of operations in the fast path."

>
>> the number of operations in the fast path.
>>
>> Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
>> ---
>> drivers/block/virtio_blk.c | 42 ++++++++++++++++++++------------------
>> 1 file changed, 22 insertions(+), 20 deletions(-)
>>
>> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
>> index 2351f411fa46..35a7a586f6f5 100644
>> --- a/drivers/block/virtio_blk.c
>> +++ b/drivers/block/virtio_blk.c
>> @@ -129,14 +129,6 @@ static inline blk_status_t virtblk_result(u8 status)
>> }
>> }
>>
>> -static inline struct virtio_blk_vq *get_virtio_blk_vq(struct blk_mq_hw_ctx *hctx)
>> -{
>> - struct virtio_blk *vblk = hctx->queue->queuedata;
>> - struct virtio_blk_vq *vq = &vblk->vqs[hctx->queue_num];
>> -
>> - return vq;
>> -}
>> -
>> static int virtblk_add_req(struct virtqueue *vq, struct virtblk_req *vbr)
>> {
>> struct scatterlist out_hdr, in_hdr, *sgs[3];
>> @@ -377,8 +369,7 @@ static void virtblk_done(struct virtqueue *vq)
>>
>> static void virtio_commit_rqs(struct blk_mq_hw_ctx *hctx)
>> {
>> - struct virtio_blk *vblk = hctx->queue->queuedata;
>> - struct virtio_blk_vq *vq = &vblk->vqs[hctx->queue_num];
>> + struct virtio_blk_vq *vq = hctx->driver_data;
>> bool kick;
>>
>> spin_lock_irq(&vq->lock);
>> @@ -428,10 +419,10 @@ static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx *hctx,
>> const struct blk_mq_queue_data *bd)
>> {
>> struct virtio_blk *vblk = hctx->queue->queuedata;
>> + struct virtio_blk_vq *vq = hctx->driver_data;
>> struct request *req = bd->rq;
>> struct virtblk_req *vbr = blk_mq_rq_to_pdu(req);
>> unsigned long flags;
>> - int qid = hctx->queue_num;
>> bool notify = false;
>> blk_status_t status;
>> int err;
>> @@ -440,26 +431,26 @@ static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx *hctx,
>> if (unlikely(status))
>> return status;
>>
>> - spin_lock_irqsave(&vblk->vqs[qid].lock, flags);
>> - err = virtblk_add_req(vblk->vqs[qid].vq, vbr);
>> + spin_lock_irqsave(&vq->lock, flags);
>> + err = virtblk_add_req(vq->vq, vbr);
>> if (err) {
>> - virtqueue_kick(vblk->vqs[qid].vq);
>> + virtqueue_kick(vq->vq);
>> /* Don't stop the queue if -ENOMEM: we may have failed to
>> * bounce the buffer due to global resource outage.
>> */
>> if (err == -ENOSPC)
>> blk_mq_stop_hw_queue(hctx);
>> - spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags);
>> + spin_unlock_irqrestore(&vq->lock, flags);
>> virtblk_unmap_data(req, vbr);
>> return virtblk_fail_to_queue(req, err);
>> }
>>
>> - if (bd->last && virtqueue_kick_prepare(vblk->vqs[qid].vq))
>> + if (bd->last && virtqueue_kick_prepare(vq->vq))
>> notify = true;
>> - spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags);
>> + spin_unlock_irqrestore(&vq->lock, flags);
>>
>> if (notify)
>> - virtqueue_notify(vblk->vqs[qid].vq);
>> + virtqueue_notify(vq->vq);
>> return BLK_STS_OK;
>> }
>>
>> @@ -504,7 +495,7 @@ static void virtio_queue_rqs(struct request **rqlist)
>> struct request *requeue_list = NULL;
>>
>> rq_list_for_each_safe(rqlist, req, next) {
>> - struct virtio_blk_vq *vq = get_virtio_blk_vq(req->mq_hctx);
>> + struct virtio_blk_vq *vq = req->mq_hctx->driver_data;
>> bool kick;
>>
>> if (!virtblk_prep_rq_batch(req)) {
>> @@ -1164,6 +1155,16 @@ static const struct attribute_group *virtblk_attr_groups[] = {
>> NULL,
>> };
>>
>> +static int virtblk_init_hctx(struct blk_mq_hw_ctx *hctx, void *data,
>> + unsigned int hctx_idx)
>> +{
>> + struct virtio_blk *vblk = data;
>> + struct virtio_blk_vq *vq = &vblk->vqs[hctx_idx];
>> +
>> + hctx->driver_data = vq;
>> + return 0;
>> +}
>> +
>> static void virtblk_map_queues(struct blk_mq_tag_set *set)
>> {
>> struct virtio_blk *vblk = set->driver_data;
>> @@ -1205,7 +1206,7 @@ static void virtblk_complete_batch(struct io_comp_batch *iob)
>> static int virtblk_poll(struct blk_mq_hw_ctx *hctx, struct io_comp_batch *iob)
>> {
>> struct virtio_blk *vblk = hctx->queue->queuedata;
>> - struct virtio_blk_vq *vq = get_virtio_blk_vq(hctx);
>> + struct virtio_blk_vq *vq = hctx->driver_data;
>> struct virtblk_req *vbr;
>> unsigned long flags;
>> unsigned int len;
>> @@ -1236,6 +1237,7 @@ static const struct blk_mq_ops virtio_mq_ops = {
>> .queue_rqs = virtio_queue_rqs,
>> .commit_rqs = virtio_commit_rqs,
>> .complete = virtblk_request_done,
>> + .init_hctx = virtblk_init_hctx,
>> .map_queues = virtblk_map_queues,
>> .poll = virtblk_poll,
>> };
>> --
>> 2.18.1