virtio-blk: support per-device queue depth

module parameter 'virtblk_queue_depth' was firstly introduced for
testing/benchmarking purposes described in commit fc4324b4597c
("virtio-blk: base queue-depth on virtqueue ringsize or module param").
And currently 'virtblk_queue_depth' is used as a saved value for the
first probed device.
Since we have different virtio-blk devices which have different
capabilities, it requires that we support per-device queue depth instead
of per-module. So defaultly use vq free elements if module parameter
'virtblk_queue_depth' is not set.

Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/1611307306-71067-1-git-send-email-joseph.qi@linux.alibaba.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 145606d..fd168a2 100644 (file)
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -705,6 +705,7 @@ static int virtblk_probe(struct virtio_device *vdev)
        u32 v, blk_size, max_size, sg_elems, opt_io_size;
        u16 min_io_size;
        u8 physical_block_exp, alignment_offset;
+       unsigned int queue_depth;
 
        if (!vdev->config->get) {
                dev_err(&vdev->dev, "%s failure: config access disabled\n",
@@ -756,16 +757,18 @@ static int virtblk_probe(struct virtio_device *vdev)
        }
 
        /* Default queue sizing is to fill the ring. */
-       if (!virtblk_queue_depth) {
-               virtblk_queue_depth = vblk->vqs[0].vq->num_free;
+       if (likely(!virtblk_queue_depth)) {
+               queue_depth = vblk->vqs[0].vq->num_free;
                /* ... but without indirect descs, we use 2 descs per req */
                if (!virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC))
-                       virtblk_queue_depth /= 2;
+                       queue_depth /= 2;
+       } else {
+               queue_depth = virtblk_queue_depth;
        }
 
        memset(&vblk->tag_set, 0, sizeof(vblk->tag_set));
        vblk->tag_set.ops = &virtio_mq_ops;
-       vblk->tag_set.queue_depth = virtblk_queue_depth;
+       vblk->tag_set.queue_depth = queue_depth;
        vblk->tag_set.numa_node = NUMA_NO_NODE;
        vblk->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
        vblk->tag_set.cmd_size =