block: virtio-blk: support multi virt queues per virtio-blk device

Firstly this patch supports more than one virtual queues for virtio-blk
device.

Secondly this patch maps the virtual queue to blk-mq's hardware queue.

With this approach, both scalability and performance can be improved.

Signed-off-by: Ming Lei <ming.lei@canonical.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 84 insertions, 20 deletions

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index f63d358f3d93..0a581400de0f 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -15,17 +15,22 @@
 #include <linux/numa.h>
 
 #define PART_BITS 4
+#define VQ_NAME_LEN 16
 
 static int major;
 static DEFINE_IDA(vd_index_ida);
 
 static struct workqueue_struct *virtblk_wq;
 
+struct virtio_blk_vq {
+        struct virtqueue *vq;
+        spinlock_t lock;
+        char name[VQ_NAME_LEN];
+} ____cacheline_aligned_in_smp;
+
 struct virtio_blk
 {
         struct virtio_device *vdev;
-        struct virtqueue *vq;
-        spinlock_t vq_lock;
 
         /* The disk structure for the kernel. */
         struct gendisk *disk;
@@ -47,6 +52,10 @@ struct virtio_blk
 
         /* Ida index - used to track minor number allocations. */
         int index;
+
+        /* num of vqs */
+        int num_vqs;
+        struct virtio_blk_vq *vqs;
 };
 
 struct virtblk_req
@@ -133,14 +142,15 @@ static void virtblk_done(struct virtqueue *vq)
 {
         struct virtio_blk *vblk = vq->vdev->priv;
         bool req_done = false;
+        int qid = vq->index;
         struct virtblk_req *vbr;
         unsigned long flags;
         unsigned int len;
 
-        spin_lock_irqsave(&vblk->vq_lock, flags);
+        spin_lock_irqsave(&vblk->vqs[qid].lock, flags);
         do {
                 virtqueue_disable_cb(vq);
-                while ((vbr = virtqueue_get_buf(vblk->vq, &len)) != NULL) {
+                while ((vbr = virtqueue_get_buf(vblk->vqs[qid].vq, &len)) != NULL) {
                         blk_mq_complete_request(vbr->req);
                         req_done = true;
                 }
@@ -151,7 +161,7 @@ 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->vq_lock, flags);
+        spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags);
 }
 
 static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
@@ -160,6 +170,7 @@ static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
         struct virtblk_req *vbr = blk_mq_rq_to_pdu(req);
         unsigned long flags;
         unsigned int num;
+        int qid = hctx->queue_num;
         const bool last = (req->cmd_flags & REQ_END) != 0;
         int err;
         bool notify = false;
@@ -202,12 +213,12 @@ static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
                         vbr->out_hdr.type |= VIRTIO_BLK_T_IN;
         }
 
-        spin_lock_irqsave(&vblk->vq_lock, flags);
-        err = __virtblk_add_req(vblk->vq, vbr, vbr->sg, num);
+        spin_lock_irqsave(&vblk->vqs[qid].lock, flags);
+        err = __virtblk_add_req(vblk->vqs[qid].vq, vbr, vbr->sg, num);
         if (err) {
-                virtqueue_kick(vblk->vq);
+                virtqueue_kick(vblk->vqs[qid].vq);
                 blk_mq_stop_hw_queue(hctx);
-                spin_unlock_irqrestore(&vblk->vq_lock, flags);
+                spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags);
                 /* Out of mem doesn't actually happen, since we fall back
                  * to direct descriptors */
                 if (err == -ENOMEM || err == -ENOSPC)
@@ -215,12 +226,12 @@ static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
                 return BLK_MQ_RQ_QUEUE_ERROR;
         }
 
-        if (last && virtqueue_kick_prepare(vblk->vq))
+        if (last && virtqueue_kick_prepare(vblk->vqs[qid].vq))
                 notify = true;
-        spin_unlock_irqrestore(&vblk->vq_lock, flags);
+        spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags);
 
         if (notify)
-                virtqueue_notify(vblk->vq);
+                virtqueue_notify(vblk->vqs[qid].vq);
         return BLK_MQ_RQ_QUEUE_OK;
 }
 
@@ -377,12 +388,64 @@ static void virtblk_config_changed(struct virtio_device *vdev)
 static int init_vq(struct virtio_blk *vblk)
 {
         int err = 0;
+        int i;
+        vq_callback_t **callbacks;
+        const char **names;
+        struct virtqueue **vqs;
+        unsigned short num_vqs;
+        struct virtio_device *vdev = vblk->vdev;
+
+        err = virtio_cread_feature(vdev, VIRTIO_BLK_F_MQ,
+                                   struct virtio_blk_config, num_queues,
+                                   &num_vqs);
+        if (err)
+                num_vqs = 1;
+
+        vblk->vqs = kmalloc(sizeof(*vblk->vqs) * num_vqs, GFP_KERNEL);
+        if (!vblk->vqs) {
+                err = -ENOMEM;
+                goto out;
+        }
+
+        names = kmalloc(sizeof(*names) * num_vqs, GFP_KERNEL);
+        if (!names)
+                goto err_names;
+
+        callbacks = kmalloc(sizeof(*callbacks) * num_vqs, GFP_KERNEL);
+        if (!callbacks)
+                goto err_callbacks;
+
+        vqs = kmalloc(sizeof(*vqs) * num_vqs, GFP_KERNEL);
+        if (!vqs)
+                goto err_vqs;
 
-        /* We expect one virtqueue, for output. */
-        vblk->vq = virtio_find_single_vq(vblk->vdev, virtblk_done, "requests");
-        if (IS_ERR(vblk->vq))
-                err = PTR_ERR(vblk->vq);
+        for (i = 0; i < num_vqs; i++) {
+                callbacks[i] = virtblk_done;
+                snprintf(vblk->vqs[i].name, VQ_NAME_LEN, "req.%d", i);
+                names[i] = vblk->vqs[i].name;
+        }
+
+        /* Discover virtqueues and write information to configuration.  */
+        err = vdev->config->find_vqs(vdev, num_vqs, vqs, callbacks, names);
+        if (err)
+                goto err_find_vqs;
 
+        for (i = 0; i < num_vqs; i++) {
+                spin_lock_init(&vblk->vqs[i].lock);
+                vblk->vqs[i].vq = vqs[i];
+        }
+        vblk->num_vqs = num_vqs;
+
+ err_find_vqs:
+        kfree(vqs);
+ err_vqs:
+        kfree(callbacks);
+ err_callbacks:
+        kfree(names);
+ err_names:
+        if (err)
+                kfree(vblk->vqs);
+ out:
         return err;
 }
 
@@ -551,7 +614,6 @@ static int virtblk_probe(struct virtio_device *vdev)
         err = init_vq(vblk);
         if (err)
                 goto out_free_vblk;
-        spin_lock_init(&vblk->vq_lock);
 
         /* FIXME: How many partitions?  How long is a piece of string? */
         vblk->disk = alloc_disk(1 << PART_BITS);
@@ -562,7 +624,7 @@ static int virtblk_probe(struct virtio_device *vdev)
 
         /* Default queue sizing is to fill the ring. */
         if (!virtblk_queue_depth) {
-                virtblk_queue_depth = vblk->vq->num_free;
+                virtblk_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;
@@ -570,7 +632,6 @@ static int virtblk_probe(struct virtio_device *vdev)
 
         memset(&vblk->tag_set, 0, sizeof(vblk->tag_set));
         vblk->tag_set.ops = &virtio_mq_ops;
-        vblk->tag_set.nr_hw_queues = 1;
         vblk->tag_set.queue_depth = virtblk_queue_depth;
         vblk->tag_set.numa_node = NUMA_NO_NODE;
         vblk->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
@@ -578,6 +639,7 @@ static int virtblk_probe(struct virtio_device *vdev)
                 sizeof(struct virtblk_req) +
                 sizeof(struct scatterlist) * sg_elems;
         vblk->tag_set.driver_data = vblk;
+        vblk->tag_set.nr_hw_queues = vblk->num_vqs;
 
         err = blk_mq_alloc_tag_set(&vblk->tag_set);
         if (err)
@@ -727,6 +789,7 @@ static void virtblk_remove(struct virtio_device *vdev)
         refc = atomic_read(&disk_to_dev(vblk->disk)->kobj.kref.refcount);
         put_disk(vblk->disk);
         vdev->config->del_vqs(vdev);
+        kfree(vblk->vqs);
         kfree(vblk);
 
         /* Only free device id if we don't have any users */
@@ -777,7 +840,8 @@ static const struct virtio_device_id id_table[] = {
 static unsigned int features[] = {
         VIRTIO_BLK_F_SEG_MAX, VIRTIO_BLK_F_SIZE_MAX, VIRTIO_BLK_F_GEOMETRY,
         VIRTIO_BLK_F_RO, VIRTIO_BLK_F_BLK_SIZE, VIRTIO_BLK_F_SCSI,
-        VIRTIO_BLK_F_WCE, VIRTIO_BLK_F_TOPOLOGY, VIRTIO_BLK_F_CONFIG_WCE
+        VIRTIO_BLK_F_WCE, VIRTIO_BLK_F_TOPOLOGY, VIRTIO_BLK_F_CONFIG_WCE,
+        VIRTIO_BLK_F_MQ,
 };
 
 static struct virtio_driver virtio_blk = {