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virtio_blk.c

//#define DEBUG
#include <linux/spinlock.h>
#include <linux/blkdev.h>
#include <linux/hdreg.h>
#include <linux/virtio.h>
#include <linux/virtio_blk.h>
#include <linux/scatterlist.h>

#define VIRTIO_MAX_SG   (3+MAX_PHYS_SEGMENTS)

static unsigned char virtblk_index = 'a';
struct virtio_blk
{
      spinlock_t lock;

      struct virtio_device *vdev;
      struct virtqueue *vq;

      /* The disk structure for the kernel. */
      struct gendisk *disk;

      /* Request tracking. */
      struct list_head reqs;

      mempool_t *pool;

      /* Scatterlist: can be too big for stack. */
      struct scatterlist sg[VIRTIO_MAX_SG];
};

struct virtblk_req
{
      struct list_head list;
      struct request *req;
      struct virtio_blk_outhdr out_hdr;
      struct virtio_blk_inhdr in_hdr;
};

static bool blk_done(struct virtqueue *vq)
{
      struct virtio_blk *vblk = vq->vdev->priv;
      struct virtblk_req *vbr;
      unsigned int len;
      unsigned long flags;

      spin_lock_irqsave(&vblk->lock, flags);
      while ((vbr = vblk->vq->vq_ops->get_buf(vblk->vq, &len)) != NULL) {
            int uptodate;
            switch (vbr->in_hdr.status) {
            case VIRTIO_BLK_S_OK:
                  uptodate = 1;
                  break;
            case VIRTIO_BLK_S_UNSUPP:
                  uptodate = -ENOTTY;
                  break;
            default:
                  uptodate = 0;
                  break;
            }

            end_dequeued_request(vbr->req, uptodate);
            list_del(&vbr->list);
            mempool_free(vbr, vblk->pool);
      }
      /* In case queue is stopped waiting for more buffers. */
      blk_start_queue(vblk->disk->queue);
      spin_unlock_irqrestore(&vblk->lock, flags);
      return true;
}

static bool do_req(struct request_queue *q, struct virtio_blk *vblk,
               struct request *req)
{
      unsigned long num, out, in;
      struct virtblk_req *vbr;

      vbr = mempool_alloc(vblk->pool, GFP_ATOMIC);
      if (!vbr)
            /* When another request finishes we'll try again. */
            return false;

      vbr->req = req;
      if (blk_fs_request(vbr->req)) {
            vbr->out_hdr.type = 0;
            vbr->out_hdr.sector = vbr->req->sector;
            vbr->out_hdr.ioprio = vbr->req->ioprio;
      } else if (blk_pc_request(vbr->req)) {
            vbr->out_hdr.type = VIRTIO_BLK_T_SCSI_CMD;
            vbr->out_hdr.sector = 0;
            vbr->out_hdr.ioprio = vbr->req->ioprio;
      } else {
            /* We don't put anything else in the queue. */
            BUG();
      }

      if (blk_barrier_rq(vbr->req))
            vbr->out_hdr.type |= VIRTIO_BLK_T_BARRIER;

      /* This init could be done at vblk creation time */
      sg_init_table(vblk->sg, VIRTIO_MAX_SG);
      sg_set_buf(&vblk->sg[0], &vbr->out_hdr, sizeof(vbr->out_hdr));
      num = blk_rq_map_sg(q, vbr->req, vblk->sg+1);
      sg_set_buf(&vblk->sg[num+1], &vbr->in_hdr, sizeof(vbr->in_hdr));

      if (rq_data_dir(vbr->req) == WRITE) {
            vbr->out_hdr.type |= VIRTIO_BLK_T_OUT;
            out = 1 + num;
            in = 1;
      } else {
            vbr->out_hdr.type |= VIRTIO_BLK_T_IN;
            out = 1;
            in = 1 + num;
      }

      if (vblk->vq->vq_ops->add_buf(vblk->vq, vblk->sg, out, in, vbr)) {
            mempool_free(vbr, vblk->pool);
            return false;
      }

      list_add_tail(&vbr->list, &vblk->reqs);
      return true;
}

static void do_virtblk_request(struct request_queue *q)
{
      struct virtio_blk *vblk = NULL;
      struct request *req;
      unsigned int issued = 0;

      while ((req = elv_next_request(q)) != NULL) {
            vblk = req->rq_disk->private_data;
            BUG_ON(req->nr_phys_segments > ARRAY_SIZE(vblk->sg));

            /* If this request fails, stop queue and wait for something to
               finish to restart it. */
            if (!do_req(q, vblk, req)) {
                  blk_stop_queue(q);
                  break;
            }
            blkdev_dequeue_request(req);
            issued++;
      }

      if (issued)
            vblk->vq->vq_ops->kick(vblk->vq);
}

static int virtblk_ioctl(struct inode *inode, struct file *filp,
                   unsigned cmd, unsigned long data)
{
      return scsi_cmd_ioctl(filp, inode->i_bdev->bd_disk->queue,
                        inode->i_bdev->bd_disk, cmd,
                        (void __user *)data);
}

static struct block_device_operations virtblk_fops = {
      .ioctl = virtblk_ioctl,
      .owner = THIS_MODULE,
};

static int virtblk_probe(struct virtio_device *vdev)
{
      struct virtio_blk *vblk;
      int err, major;
      void *token;
      unsigned int len;
      u64 cap;
      u32 v;

      vdev->priv = vblk = kmalloc(sizeof(*vblk), GFP_KERNEL);
      if (!vblk) {
            err = -ENOMEM;
            goto out;
      }

      INIT_LIST_HEAD(&vblk->reqs);
      spin_lock_init(&vblk->lock);
      vblk->vdev = vdev;

      /* We expect one virtqueue, for output. */
      vblk->vq = vdev->config->find_vq(vdev, blk_done);
      if (IS_ERR(vblk->vq)) {
            err = PTR_ERR(vblk->vq);
            goto out_free_vblk;
      }

      vblk->pool = mempool_create_kmalloc_pool(1,sizeof(struct virtblk_req));
      if (!vblk->pool) {
            err = -ENOMEM;
            goto out_free_vq;
      }

      major = register_blkdev(0, "virtblk");
      if (major < 0) {
            err = major;
            goto out_mempool;
      }

      /* FIXME: How many partitions?  How long is a piece of string? */
      vblk->disk = alloc_disk(1 << 4);
      if (!vblk->disk) {
            err = -ENOMEM;
            goto out_unregister_blkdev;
      }

      vblk->disk->queue = blk_init_queue(do_virtblk_request, &vblk->lock);
      if (!vblk->disk->queue) {
            err = -ENOMEM;
            goto out_put_disk;
      }

      sprintf(vblk->disk->disk_name, "vd%c", virtblk_index++);
      vblk->disk->major = major;
      vblk->disk->first_minor = 0;
      vblk->disk->private_data = vblk;
      vblk->disk->fops = &virtblk_fops;

      /* If barriers are supported, tell block layer that queue is ordered */
      token = vdev->config->find(vdev, VIRTIO_CONFIG_BLK_F, &len);
      if (virtio_use_bit(vdev, token, len, VIRTIO_BLK_F_BARRIER))
            blk_queue_ordered(vblk->disk->queue, QUEUE_ORDERED_TAG, NULL);

      err = virtio_config_val(vdev, VIRTIO_CONFIG_BLK_F_CAPACITY, &cap);
      if (err) {
            dev_err(&vdev->dev, "Bad/missing capacity in config\n");
            goto out_cleanup_queue;
      }

      /* If capacity is too big, truncate with warning. */
      if ((sector_t)cap != cap) {
            dev_warn(&vdev->dev, "Capacity %llu too large: truncating\n",
                   (unsigned long long)cap);
            cap = (sector_t)-1;
      }
      set_capacity(vblk->disk, cap);

      err = virtio_config_val(vdev, VIRTIO_CONFIG_BLK_F_SIZE_MAX, &v);
      if (!err)
            blk_queue_max_segment_size(vblk->disk->queue, v);
      else if (err != -ENOENT) {
            dev_err(&vdev->dev, "Bad SIZE_MAX in config\n");
            goto out_cleanup_queue;
      }

      err = virtio_config_val(vdev, VIRTIO_CONFIG_BLK_F_SEG_MAX, &v);
      if (!err)
            blk_queue_max_hw_segments(vblk->disk->queue, v);
      else if (err != -ENOENT) {
            dev_err(&vdev->dev, "Bad SEG_MAX in config\n");
            goto out_cleanup_queue;
      }

      add_disk(vblk->disk);
      return 0;

out_cleanup_queue:
      blk_cleanup_queue(vblk->disk->queue);
out_put_disk:
      put_disk(vblk->disk);
out_unregister_blkdev:
      unregister_blkdev(major, "virtblk");
out_mempool:
      mempool_destroy(vblk->pool);
out_free_vq:
      vdev->config->del_vq(vblk->vq);
out_free_vblk:
      kfree(vblk);
out:
      return err;
}

static void virtblk_remove(struct virtio_device *vdev)
{
      struct virtio_blk *vblk = vdev->priv;
      int major = vblk->disk->major;

      BUG_ON(!list_empty(&vblk->reqs));
      blk_cleanup_queue(vblk->disk->queue);
      put_disk(vblk->disk);
      unregister_blkdev(major, "virtblk");
      mempool_destroy(vblk->pool);
      /* There should be nothing in the queue now, so no need to shutdown */
      vdev->config->del_vq(vblk->vq);
      kfree(vblk);
}

static struct virtio_device_id id_table[] = {
      { VIRTIO_ID_BLOCK, VIRTIO_DEV_ANY_ID },
      { 0 },
};

static struct virtio_driver virtio_blk = {
      .driver.name =    KBUILD_MODNAME,
      .driver.owner =   THIS_MODULE,
      .id_table = id_table,
      .probe =    virtblk_probe,
      .remove =   __devexit_p(virtblk_remove),
};

static int __init init(void)
{
      return register_virtio_driver(&virtio_blk);
}

static void __exit fini(void)
{
      unregister_virtio_driver(&virtio_blk);
}
module_init(init);
module_exit(fini);

MODULE_DEVICE_TABLE(virtio, id_table);
MODULE_DESCRIPTION("Virtio block driver");
MODULE_LICENSE("GPL");

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