Re: [PATCH 2/3] virtio_blk: avoid repeating vblk->vqs[qid]

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在 2021/5/20 下午10:13, Stefan Hajnoczi 写道:
struct virtio_blk_vq is accessed in many places. Introduce "vbq" local
variables to avoid repeating vblk->vqs[qid] throughout the code. The
patches that follow will add more accesses, making the payoff even
greater.

virtio_commit_rqs() calls the local variable "vq", which is easily
confused with struct virtqueue. Rename to "vbq" for clarity.

Signed-off-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>


Acked-by: Jason Wang <jasowang@xxxxxxxxxx>


---
  drivers/block/virtio_blk.c | 34 +++++++++++++++++-----------------
  1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index b9fa3ef5b57c..fc0fb1dcd399 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -174,16 +174,16 @@ static inline void virtblk_request_done(struct request *req)
  static void virtblk_done(struct virtqueue *vq)
  {
  	struct virtio_blk *vblk = vq->vdev->priv;
+	struct virtio_blk_vq *vbq = &vblk->vqs[vq->index];
  	bool req_done = false;
-	int qid = vq->index;
  	struct virtblk_req *vbr;
  	unsigned long flags;
  	unsigned int len;
- spin_lock_irqsave(&vblk->vqs[qid].lock, flags);
+	spin_lock_irqsave(&vbq->lock, flags);
  	do {
  		virtqueue_disable_cb(vq);
-		while ((vbr = virtqueue_get_buf(vblk->vqs[qid].vq, &len)) != NULL) {
+		while ((vbr = virtqueue_get_buf(vq, &len)) != NULL) {
  			struct request *req = blk_mq_rq_from_pdu(vbr);
if (likely(!blk_should_fake_timeout(req->q)))
@@ -197,32 +197,32 @@ static void virtblk_done(struct virtqueue *vq)
  	/* In case queue is stopped waiting for more buffers. */
  	if (req_done)
  		blk_mq_start_stopped_hw_queues(vblk->disk->queue, true);
-	spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags);
+	spin_unlock_irqrestore(&vbq->lock, flags);
  }
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 *vbq = &vblk->vqs[hctx->queue_num];
  	bool kick;
- spin_lock_irq(&vq->lock);
-	kick = virtqueue_kick_prepare(vq->vq);
-	spin_unlock_irq(&vq->lock);
+	spin_lock_irq(&vbq->lock);
+	kick = virtqueue_kick_prepare(vbq->vq);
+	spin_unlock_irq(&vbq->lock);
if (kick)
-		virtqueue_notify(vq->vq);
+		virtqueue_notify(vbq->vq);
  }
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 *vbq = &vblk->vqs[hctx->queue_num];
  	struct request *req = bd->rq;
  	struct virtblk_req *vbr = blk_mq_rq_to_pdu(req);
  	unsigned long flags;
  	unsigned int num;
-	int qid = hctx->queue_num;
  	int err;
  	bool notify = false;
  	bool unmap = false;
@@ -274,16 +274,16 @@ static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx *hctx,
  			vbr->out_hdr.type |= cpu_to_virtio32(vblk->vdev, VIRTIO_BLK_T_IN);
  	}
- spin_lock_irqsave(&vblk->vqs[qid].lock, flags);
-	err = virtblk_add_req(vblk->vqs[qid].vq, vbr, vbr->sg, num);
+	spin_lock_irqsave(&vbq->lock, flags);
+	err = virtblk_add_req(vbq->vq, vbr, vbr->sg, num);
  	if (err) {
-		virtqueue_kick(vblk->vqs[qid].vq);
+		virtqueue_kick(vbq->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(&vbq->lock, flags);
  		switch (err) {
  		case -ENOSPC:
  			return BLK_STS_DEV_RESOURCE;
@@ -294,12 +294,12 @@ static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx *hctx,
  		}
  	}
- if (bd->last && virtqueue_kick_prepare(vblk->vqs[qid].vq))
+	if (bd->last && virtqueue_kick_prepare(vbq->vq))
  		notify = true;
-	spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags);
+	spin_unlock_irqrestore(&vbq->lock, flags);
if (notify)
-		virtqueue_notify(vblk->vqs[qid].vq);
+		virtqueue_notify(vbq->vq);
  	return BLK_STS_OK;
  }




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