1 files changed, 1005 insertions, 0 deletions

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
new file mode 100644
index 00000000..64723953
--- /dev/null
+++ b/drivers/block/virtio_blk.c
@@ -0,0 +1,1005 @@
+//#define DEBUG
+#include <linux/spinlock.h>
+#include <linux/slab.h>
+#include <linux/blkdev.h>
+#include <linux/hdreg.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/virtio.h>
+#include <linux/virtio_blk.h>
+#include <linux/scatterlist.h>
+#include <linux/string_helpers.h>
+#include <scsi/scsi_cmnd.h>
+#include <linux/idr.h>
+
+#define PART_BITS 4
+
+static bool use_bio;
+module_param(use_bio, bool, S_IRUGO);
+
+static int major;
+static DEFINE_IDA(vd_index_ida);
+
+struct workqueue_struct *virtblk_wq;
+
+struct virtio_blk
+{
+	struct virtio_device *vdev;
+	struct virtqueue *vq;
+	wait_queue_head_t queue_wait;
+
+	/* The disk structure for the kernel. */
+	struct gendisk *disk;
+
+	mempool_t *pool;
+
+	/* Process context for config space updates */
+	struct work_struct config_work;
+
+	/* Lock for config space updates */
+	struct mutex config_lock;
+
+	/* enable config space updates */
+	bool config_enable;
+
+	/* What host tells us, plus 2 for header & tailer. */
+	unsigned int sg_elems;
+
+	/* Ida index - used to track minor number allocations. */
+	int index;
+
+	/* Scatterlist: can be too big for stack. */
+	struct scatterlist sg[/*sg_elems*/];
+};
+
+struct virtblk_req
+{
+	struct request *req;
+	struct bio *bio;
+	struct virtio_blk_outhdr out_hdr;
+	struct virtio_scsi_inhdr in_hdr;
+	struct work_struct work;
+	struct virtio_blk *vblk;
+	int flags;
+	u8 status;
+	struct scatterlist sg[];
+};
+
+enum {
+	VBLK_IS_FLUSH		= 1,
+	VBLK_REQ_FLUSH		= 2,
+	VBLK_REQ_DATA		= 4,
+	VBLK_REQ_FUA		= 8,
+};
+
+static inline int virtblk_result(struct virtblk_req *vbr)
+{
+	switch (vbr->status) {
+	case VIRTIO_BLK_S_OK:
+		return 0;
+	case VIRTIO_BLK_S_UNSUPP:
+		return -ENOTTY;
+	default:
+		return -EIO;
+	}
+}
+
+static inline struct virtblk_req *virtblk_alloc_req(struct virtio_blk *vblk,
+						    gfp_t gfp_mask)
+{
+	struct virtblk_req *vbr;
+
+	vbr = mempool_alloc(vblk->pool, gfp_mask);
+	if (!vbr)
+		return NULL;
+
+	vbr->vblk = vblk;
+	if (use_bio)
+		sg_init_table(vbr->sg, vblk->sg_elems);
+
+	return vbr;
+}
+
+static int __virtblk_add_req(struct virtqueue *vq,
+			     struct virtblk_req *vbr,
+			     struct scatterlist *data_sg,
+			     bool have_data)
+{
+	struct scatterlist hdr, status, cmd, sense, inhdr, *sgs[6];
+	unsigned int num_out = 0, num_in = 0;
+	int type = vbr->out_hdr.type & ~VIRTIO_BLK_T_OUT;
+
+	sg_init_one(&hdr, &vbr->out_hdr, sizeof(vbr->out_hdr));
+	sgs[num_out++] = &hdr;
+
+	/*
+	 * If this is a packet command we need a couple of additional headers.
+	 * Behind the normal outhdr we put a segment with the scsi command
+	 * block, and before the normal inhdr we put the sense data and the
+	 * inhdr with additional status information.
+	 */
+	if (type == VIRTIO_BLK_T_SCSI_CMD) {
+		sg_init_one(&cmd, vbr->req->cmd, vbr->req->cmd_len);
+		sgs[num_out++] = &cmd;
+	}
+
+	if (have_data) {
+		if (vbr->out_hdr.type & VIRTIO_BLK_T_OUT)
+			sgs[num_out++] = data_sg;
+		else
+			sgs[num_out + num_in++] = data_sg;
+	}
+
+	if (type == VIRTIO_BLK_T_SCSI_CMD) {
+		sg_init_one(&sense, vbr->req->sense, SCSI_SENSE_BUFFERSIZE);
+		sgs[num_out + num_in++] = &sense;
+		sg_init_one(&inhdr, &vbr->in_hdr, sizeof(vbr->in_hdr));
+		sgs[num_out + num_in++] = &inhdr;
+	}
+
+	sg_init_one(&status, &vbr->status, sizeof(vbr->status));
+	sgs[num_out + num_in++] = &status;
+
+	return virtqueue_add_sgs(vq, sgs, num_out, num_in, vbr, GFP_ATOMIC);
+}
+
+static void virtblk_add_req(struct virtblk_req *vbr, bool have_data)
+{
+	struct virtio_blk *vblk = vbr->vblk;
+	DEFINE_WAIT(wait);
+	int ret;
+
+	spin_lock_irq(vblk->disk->queue->queue_lock);
+	while (unlikely((ret = __virtblk_add_req(vblk->vq, vbr, vbr->sg,
+						 have_data)) < 0)) {
+		prepare_to_wait_exclusive(&vblk->queue_wait, &wait,
+					  TASK_UNINTERRUPTIBLE);
+
+		spin_unlock_irq(vblk->disk->queue->queue_lock);
+		io_schedule();
+		spin_lock_irq(vblk->disk->queue->queue_lock);
+
+		finish_wait(&vblk->queue_wait, &wait);
+	}
+
+	virtqueue_kick(vblk->vq);
+	spin_unlock_irq(vblk->disk->queue->queue_lock);
+}
+
+static void virtblk_bio_send_flush(struct virtblk_req *vbr)
+{
+	vbr->flags |= VBLK_IS_FLUSH;
+	vbr->out_hdr.type = VIRTIO_BLK_T_FLUSH;
+	vbr->out_hdr.sector = 0;
+	vbr->out_hdr.ioprio = 0;
+
+	virtblk_add_req(vbr, false);
+}
+
+static void virtblk_bio_send_data(struct virtblk_req *vbr)
+{
+	struct virtio_blk *vblk = vbr->vblk;
+	struct bio *bio = vbr->bio;
+	bool have_data;
+
+	vbr->flags &= ~VBLK_IS_FLUSH;
+	vbr->out_hdr.type = 0;
+	vbr->out_hdr.sector = bio->bi_sector;
+	vbr->out_hdr.ioprio = bio_prio(bio);
+
+	if (blk_bio_map_sg(vblk->disk->queue, bio, vbr->sg)) {
+		have_data = true;
+		if (bio->bi_rw & REQ_WRITE)
+			vbr->out_hdr.type |= VIRTIO_BLK_T_OUT;
+		else
+			vbr->out_hdr.type |= VIRTIO_BLK_T_IN;
+	} else
+		have_data = false;
+
+	virtblk_add_req(vbr, have_data);
+}
+
+static void virtblk_bio_send_data_work(struct work_struct *work)
+{
+	struct virtblk_req *vbr;
+
+	vbr = container_of(work, struct virtblk_req, work);
+
+	virtblk_bio_send_data(vbr);
+}
+
+static void virtblk_bio_send_flush_work(struct work_struct *work)
+{
+	struct virtblk_req *vbr;
+
+	vbr = container_of(work, struct virtblk_req, work);
+
+	virtblk_bio_send_flush(vbr);
+}
+
+static inline void virtblk_request_done(struct virtblk_req *vbr)
+{
+	struct virtio_blk *vblk = vbr->vblk;
+	struct request *req = vbr->req;
+	int error = virtblk_result(vbr);
+
+	if (req->cmd_type == REQ_TYPE_BLOCK_PC) {
+		req->resid_len = vbr->in_hdr.residual;
+		req->sense_len = vbr->in_hdr.sense_len;
+		req->errors = vbr->in_hdr.errors;
+	} else if (req->cmd_type == REQ_TYPE_SPECIAL) {
+		req->errors = (error != 0);
+	}
+
+	__blk_end_request_all(req, error);
+	mempool_free(vbr, vblk->pool);
+}
+
+static inline void virtblk_bio_flush_done(struct virtblk_req *vbr)
+{
+	struct virtio_blk *vblk = vbr->vblk;
+
+	if (vbr->flags & VBLK_REQ_DATA) {
+		/* Send out the actual write data */
+		INIT_WORK(&vbr->work, virtblk_bio_send_data_work);
+		queue_work(virtblk_wq, &vbr->work);
+	} else {
+		bio_endio(vbr->bio, virtblk_result(vbr));
+		mempool_free(vbr, vblk->pool);
+	}
+}
+
+static inline void virtblk_bio_data_done(struct virtblk_req *vbr)
+{
+	struct virtio_blk *vblk = vbr->vblk;
+
+	if (unlikely(vbr->flags & VBLK_REQ_FUA)) {
+		/* Send out a flush before end the bio */
+		vbr->flags &= ~VBLK_REQ_DATA;
+		INIT_WORK(&vbr->work, virtblk_bio_send_flush_work);
+		queue_work(virtblk_wq, &vbr->work);
+	} else {
+		bio_endio(vbr->bio, virtblk_result(vbr));
+		mempool_free(vbr, vblk->pool);
+	}
+}
+
+static inline void virtblk_bio_done(struct virtblk_req *vbr)
+{
+	if (unlikely(vbr->flags & VBLK_IS_FLUSH))
+		virtblk_bio_flush_done(vbr);
+	else
+		virtblk_bio_data_done(vbr);
+}
+
+static void virtblk_done(struct virtqueue *vq)
+{
+	struct virtio_blk *vblk = vq->vdev->priv;
+	bool bio_done = false, req_done = false;
+	struct virtblk_req *vbr;
+	unsigned long flags;
+	unsigned int len;
+
+	spin_lock_irqsave(vblk->disk->queue->queue_lock, flags);
+	do {
+		virtqueue_disable_cb(vq);
+		while ((vbr = virtqueue_get_buf(vblk->vq, &len)) != NULL) {
+			if (vbr->bio) {
+				virtblk_bio_done(vbr);
+				bio_done = true;
+			} else {
+				virtblk_request_done(vbr);
+				req_done = true;
+			}
+		}
+	} while (!virtqueue_enable_cb(vq));
+	/* In case queue is stopped waiting for more buffers. */
+	if (req_done)
+		blk_start_queue(vblk->disk->queue);
+	spin_unlock_irqrestore(vblk->disk->queue->queue_lock, flags);
+
+	if (bio_done)
+		wake_up(&vblk->queue_wait);
+}
+
+static bool do_req(struct request_queue *q, struct virtio_blk *vblk,
+		   struct request *req)
+{
+	unsigned int num;
+	struct virtblk_req *vbr;
+
+	vbr = virtblk_alloc_req(vblk, GFP_ATOMIC);
+	if (!vbr)
+		/* When another request finishes we'll try again. */
+		return false;
+
+	vbr->req = req;
+	vbr->bio = NULL;
+	if (req->cmd_flags & REQ_FLUSH) {
+		vbr->out_hdr.type = VIRTIO_BLK_T_FLUSH;
+		vbr->out_hdr.sector = 0;
+		vbr->out_hdr.ioprio = req_get_ioprio(vbr->req);
+	} else {
+		switch (req->cmd_type) {
+		case REQ_TYPE_FS:
+			vbr->out_hdr.type = 0;
+			vbr->out_hdr.sector = blk_rq_pos(vbr->req);
+			vbr->out_hdr.ioprio = req_get_ioprio(vbr->req);
+			break;
+		case REQ_TYPE_BLOCK_PC:
+			vbr->out_hdr.type = VIRTIO_BLK_T_SCSI_CMD;
+			vbr->out_hdr.sector = 0;
+			vbr->out_hdr.ioprio = req_get_ioprio(vbr->req);
+			break;
+		case REQ_TYPE_SPECIAL:
+			vbr->out_hdr.type = VIRTIO_BLK_T_GET_ID;
+			vbr->out_hdr.sector = 0;
+			vbr->out_hdr.ioprio = req_get_ioprio(vbr->req);
+			break;
+		default:
+			/* We don't put anything else in the queue. */
+			BUG();
+		}
+	}
+
+	num = blk_rq_map_sg(q, vbr->req, vblk->sg);
+	if (num) {
+		if (rq_data_dir(vbr->req) == WRITE)
+			vbr->out_hdr.type |= VIRTIO_BLK_T_OUT;
+		else
+			vbr->out_hdr.type |= VIRTIO_BLK_T_IN;
+	}
+
+	if (__virtblk_add_req(vblk->vq, vbr, vblk->sg, num) < 0) {
+		mempool_free(vbr, vblk->pool);
+		return false;
+	}
+
+	return true;
+}
+
+static void virtblk_request(struct request_queue *q)
+{
+	struct virtio_blk *vblk = q->queuedata;
+	struct request *req;
+	unsigned int issued = 0;
+
+	while ((req = blk_peek_request(q)) != NULL) {
+		BUG_ON(req->nr_phys_segments + 2 > vblk->sg_elems);
+
+		/* 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;
+		}
+		blk_start_request(req);
+		issued++;
+	}
+
+	if (issued)
+		virtqueue_kick(vblk->vq);
+}
+
+static void virtblk_make_request(struct request_queue *q, struct bio *bio)
+{
+	struct virtio_blk *vblk = q->queuedata;
+	struct virtblk_req *vbr;
+
+	BUG_ON(bio->bi_phys_segments + 2 > vblk->sg_elems);
+
+	vbr = virtblk_alloc_req(vblk, GFP_NOIO);
+	if (!vbr) {
+		bio_endio(bio, -ENOMEM);
+		return;
+	}
+
+	vbr->bio = bio;
+	vbr->flags = 0;
+	if (bio->bi_rw & REQ_FLUSH)
+		vbr->flags |= VBLK_REQ_FLUSH;
+	if (bio->bi_rw & REQ_FUA)
+		vbr->flags |= VBLK_REQ_FUA;
+	if (bio->bi_size)
+		vbr->flags |= VBLK_REQ_DATA;
+
+	if (unlikely(vbr->flags & VBLK_REQ_FLUSH))
+		virtblk_bio_send_flush(vbr);
+	else
+		virtblk_bio_send_data(vbr);
+}
+
+/* return id (s/n) string for *disk to *id_str
+ */
+static int virtblk_get_id(struct gendisk *disk, char *id_str)
+{
+	struct virtio_blk *vblk = disk->private_data;
+	struct request *req;
+	struct bio *bio;
+	int err;
+
+	bio = bio_map_kern(vblk->disk->queue, id_str, VIRTIO_BLK_ID_BYTES,
+			   GFP_KERNEL);
+	if (IS_ERR(bio))
+		return PTR_ERR(bio);
+
+	req = blk_make_request(vblk->disk->queue, bio, GFP_KERNEL);
+	if (IS_ERR(req)) {
+		bio_put(bio);
+		return PTR_ERR(req);
+	}
+
+	req->cmd_type = REQ_TYPE_SPECIAL;
+	err = blk_execute_rq(vblk->disk->queue, vblk->disk, req, false);
+	blk_put_request(req);
+
+	return err;
+}
+
+static int virtblk_ioctl(struct block_device *bdev, fmode_t mode,
+			     unsigned int cmd, unsigned long data)
+{
+	struct gendisk *disk = bdev->bd_disk;
+	struct virtio_blk *vblk = disk->private_data;
+
+	/*
+	 * Only allow the generic SCSI ioctls if the host can support it.
+	 */
+	if (!virtio_has_feature(vblk->vdev, VIRTIO_BLK_F_SCSI))
+		return -ENOTTY;
+
+	return scsi_cmd_blk_ioctl(bdev, mode, cmd,
+				  (void __user *)data);
+}
+
+/* We provide getgeo only to please some old bootloader/partitioning tools */
+static int virtblk_getgeo(struct block_device *bd, struct hd_geometry *geo)
+{
+	struct virtio_blk *vblk = bd->bd_disk->private_data;
+	struct virtio_blk_geometry vgeo;
+	int err;
+
+	/* see if the host passed in geometry config */
+	err = virtio_config_val(vblk->vdev, VIRTIO_BLK_F_GEOMETRY,
+				offsetof(struct virtio_blk_config, geometry),
+				&vgeo);
+
+	if (!err) {
+		geo->heads = vgeo.heads;
+		geo->sectors = vgeo.sectors;
+		geo->cylinders = vgeo.cylinders;
+	} else {
+		/* some standard values, similar to sd */
+		geo->heads = 1 << 6;
+		geo->sectors = 1 << 5;
+		geo->cylinders = get_capacity(bd->bd_disk) >> 11;
+	}
+	return 0;
+}
+
+static const struct block_device_operations virtblk_fops = {
+	.ioctl  = virtblk_ioctl,
+	.owner  = THIS_MODULE,
+	.getgeo = virtblk_getgeo,
+};
+
+static int index_to_minor(int index)
+{
+	return index << PART_BITS;
+}
+
+static int minor_to_index(int minor)
+{
+	return minor >> PART_BITS;
+}
+
+static ssize_t virtblk_serial_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct gendisk *disk = dev_to_disk(dev);
+	int err;
+
+	/* sysfs gives us a PAGE_SIZE buffer */
+	BUILD_BUG_ON(PAGE_SIZE < VIRTIO_BLK_ID_BYTES);
+
+	buf[VIRTIO_BLK_ID_BYTES] = '\0';
+	err = virtblk_get_id(disk, buf);
+	if (!err)
+		return strlen(buf);
+
+	if (err == -EIO) /* Unsupported? Make it empty. */
+		return 0;
+
+	return err;
+}
+DEVICE_ATTR(serial, S_IRUGO, virtblk_serial_show, NULL);
+
+static void virtblk_config_changed_work(struct work_struct *work)
+{
+	struct virtio_blk *vblk =
+		container_of(work, struct virtio_blk, config_work);
+	struct virtio_device *vdev = vblk->vdev;
+	struct request_queue *q = vblk->disk->queue;
+	char cap_str_2[10], cap_str_10[10];
+	char *envp[] = { "RESIZE=1", NULL };
+	u64 capacity, size;
+
+	mutex_lock(&vblk->config_lock);
+	if (!vblk->config_enable)
+		goto done;
+
+	/* Host must always specify the capacity. */
+	vdev->config->get(vdev, offsetof(struct virtio_blk_config, capacity),
+			  &capacity, sizeof(capacity));
+
+	/* If capacity is too big, truncate with warning. */
+	if ((sector_t)capacity != capacity) {
+		dev_warn(&vdev->dev, "Capacity %llu too large: truncating\n",
+			 (unsigned long long)capacity);
+		capacity = (sector_t)-1;
+	}
+
+	size = capacity * queue_logical_block_size(q);
+	string_get_size(size, STRING_UNITS_2, cap_str_2, sizeof(cap_str_2));
+	string_get_size(size, STRING_UNITS_10, cap_str_10, sizeof(cap_str_10));
+
+	dev_notice(&vdev->dev,
+		  "new size: %llu %d-byte logical blocks (%s/%s)\n",
+		  (unsigned long long)capacity,
+		  queue_logical_block_size(q),
+		  cap_str_10, cap_str_2);
+
+	set_capacity(vblk->disk, capacity);
+	revalidate_disk(vblk->disk);
+	kobject_uevent_env(&disk_to_dev(vblk->disk)->kobj, KOBJ_CHANGE, envp);
+done:
+	mutex_unlock(&vblk->config_lock);
+}
+
+static void virtblk_config_changed(struct virtio_device *vdev)
+{
+	struct virtio_blk *vblk = vdev->priv;
+
+	queue_work(virtblk_wq, &vblk->config_work);
+}
+
+static int init_vq(struct virtio_blk *vblk)
+{
+	int err = 0;
+
+	/* 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);
+
+	return err;
+}
+
+/*
+ * Legacy naming scheme used for virtio devices.  We are stuck with it for
+ * virtio blk but don't ever use it for any new driver.
+ */
+static int virtblk_name_format(char *prefix, int index, char *buf, int buflen)
+{
+	const int base = 'z' - 'a' + 1;
+	char *begin = buf + strlen(prefix);
+	char *end = buf + buflen;
+	char *p;
+	int unit;
+
+	p = end - 1;
+	*p = '\0';
+	unit = base;
+	do {
+		if (p == begin)
+			return -EINVAL;
+		*--p = 'a' + (index % unit);
+		index = (index / unit) - 1;
+	} while (index >= 0);
+
+	memmove(begin, p, end - p);
+	memcpy(buf, prefix, strlen(prefix));
+
+	return 0;
+}
+
+static int virtblk_get_cache_mode(struct virtio_device *vdev)
+{
+	u8 writeback;
+	int err;
+
+	err = virtio_config_val(vdev, VIRTIO_BLK_F_CONFIG_WCE,
+				offsetof(struct virtio_blk_config, wce),
+				&writeback);
+	if (err)
+		writeback = virtio_has_feature(vdev, VIRTIO_BLK_F_WCE);
+
+	return writeback;
+}
+
+static void virtblk_update_cache_mode(struct virtio_device *vdev)
+{
+	u8 writeback = virtblk_get_cache_mode(vdev);
+	struct virtio_blk *vblk = vdev->priv;
+
+	if (writeback)
+		blk_queue_flush(vblk->disk->queue, REQ_FLUSH);
+	else
+		blk_queue_flush(vblk->disk->queue, 0);
+
+	revalidate_disk(vblk->disk);
+}
+
+static const char *const virtblk_cache_types[] = {
+	"write through", "write back"
+};
+
+static ssize_t
+virtblk_cache_type_store(struct device *dev, struct device_attribute *attr,
+			 const char *buf, size_t count)
+{
+	struct gendisk *disk = dev_to_disk(dev);
+	struct virtio_blk *vblk = disk->private_data;
+	struct virtio_device *vdev = vblk->vdev;
+	int i;
+	u8 writeback;
+
+	BUG_ON(!virtio_has_feature(vblk->vdev, VIRTIO_BLK_F_CONFIG_WCE));
+	for (i = ARRAY_SIZE(virtblk_cache_types); --i >= 0; )
+		if (sysfs_streq(buf, virtblk_cache_types[i]))
+			break;
+
+	if (i < 0)
+		return -EINVAL;
+
+	writeback = i;
+	vdev->config->set(vdev,
+			  offsetof(struct virtio_blk_config, wce),
+			  &writeback, sizeof(writeback));
+
+	virtblk_update_cache_mode(vdev);
+	return count;
+}
+
+static ssize_t
+virtblk_cache_type_show(struct device *dev, struct device_attribute *attr,
+			 char *buf)
+{
+	struct gendisk *disk = dev_to_disk(dev);
+	struct virtio_blk *vblk = disk->private_data;
+	u8 writeback = virtblk_get_cache_mode(vblk->vdev);
+
+	BUG_ON(writeback >= ARRAY_SIZE(virtblk_cache_types));
+	return snprintf(buf, 40, "%s\n", virtblk_cache_types[writeback]);
+}
+
+static const struct device_attribute dev_attr_cache_type_ro =
+	__ATTR(cache_type, S_IRUGO,
+	       virtblk_cache_type_show, NULL);
+static const struct device_attribute dev_attr_cache_type_rw =
+	__ATTR(cache_type, S_IRUGO|S_IWUSR,
+	       virtblk_cache_type_show, virtblk_cache_type_store);
+
+static int virtblk_probe(struct virtio_device *vdev)
+{
+	struct virtio_blk *vblk;
+	struct request_queue *q;
+	int err, index;
+	int pool_size;
+
+	u64 cap;
+	u32 v, blk_size, sg_elems, opt_io_size;
+	u16 min_io_size;
+	u8 physical_block_exp, alignment_offset;
+
+	err = ida_simple_get(&vd_index_ida, 0, minor_to_index(1 << MINORBITS),
+			     GFP_KERNEL);
+	if (err < 0)
+		goto out;
+	index = err;
+
+	/* We need to know how many segments before we allocate. */
+	err = virtio_config_val(vdev, VIRTIO_BLK_F_SEG_MAX,
+				offsetof(struct virtio_blk_config, seg_max),
+				&sg_elems);
+
+	/* We need at least one SG element, whatever they say. */
+	if (err || !sg_elems)
+		sg_elems = 1;
+
+	/* We need an extra sg elements at head and tail. */
+	sg_elems += 2;
+	vdev->priv = vblk = kmalloc(sizeof(*vblk) +
+				    sizeof(vblk->sg[0]) * sg_elems, GFP_KERNEL);
+	if (!vblk) {
+		err = -ENOMEM;
+		goto out_free_index;
+	}
+
+	init_waitqueue_head(&vblk->queue_wait);
+	vblk->vdev = vdev;
+	vblk->sg_elems = sg_elems;
+	sg_init_table(vblk->sg, vblk->sg_elems);
+	mutex_init(&vblk->config_lock);
+
+	INIT_WORK(&vblk->config_work, virtblk_config_changed_work);
+	vblk->config_enable = true;
+
+	err = init_vq(vblk);
+	if (err)
+		goto out_free_vblk;
+
+	pool_size = sizeof(struct virtblk_req);
+	if (use_bio)
+		pool_size += sizeof(struct scatterlist) * sg_elems;
+	vblk->pool = mempool_create_kmalloc_pool(1, pool_size);
+	if (!vblk->pool) {
+		err = -ENOMEM;
+		goto out_free_vq;
+	}
+
+	/* FIXME: How many partitions?  How long is a piece of string? */
+	vblk->disk = alloc_disk(1 << PART_BITS);
+	if (!vblk->disk) {
+		err = -ENOMEM;
+		goto out_mempool;
+	}
+
+	q = vblk->disk->queue = blk_init_queue(virtblk_request, NULL);
+	if (!q) {
+		err = -ENOMEM;
+		goto out_put_disk;
+	}
+
+	if (use_bio)
+		blk_queue_make_request(q, virtblk_make_request);
+	q->queuedata = vblk;
+
+	virtblk_name_format("vd", index, vblk->disk->disk_name, DISK_NAME_LEN);
+
+	vblk->disk->major = major;
+	vblk->disk->first_minor = index_to_minor(index);
+	vblk->disk->private_data = vblk;
+	vblk->disk->fops = &virtblk_fops;
+	vblk->disk->driverfs_dev = &vdev->dev;
+	vblk->index = index;
+
+	/* configure queue flush support */
+	virtblk_update_cache_mode(vdev);
+
+	/* If disk is read-only in the host, the guest should obey */
+	if (virtio_has_feature(vdev, VIRTIO_BLK_F_RO))
+		set_disk_ro(vblk->disk, 1);
+
+	/* Host must always specify the capacity. */
+	vdev->config->get(vdev, offsetof(struct virtio_blk_config, capacity),
+			  &cap, sizeof(cap));
+
+	/* 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);
+
+	/* We can handle whatever the host told us to handle. */
+	blk_queue_max_segments(q, vblk->sg_elems-2);
+
+	/* No need to bounce any requests */
+	blk_queue_bounce_limit(q, BLK_BOUNCE_ANY);
+
+	/* No real sector limit. */
+	blk_queue_max_hw_sectors(q, -1U);
+
+	/* Host can optionally specify maximum segment size and number of
+	 * segments. */
+	err = virtio_config_val(vdev, VIRTIO_BLK_F_SIZE_MAX,
+				offsetof(struct virtio_blk_config, size_max),
+				&v);
+	if (!err)
+		blk_queue_max_segment_size(q, v);
+	else
+		blk_queue_max_segment_size(q, -1U);
+
+	/* Host can optionally specify the block size of the device */
+	err = virtio_config_val(vdev, VIRTIO_BLK_F_BLK_SIZE,
+				offsetof(struct virtio_blk_config, blk_size),
+				&blk_size);
+	if (!err)
+		blk_queue_logical_block_size(q, blk_size);
+	else
+		blk_size = queue_logical_block_size(q);
+
+	/* Use topology information if available */
+	err = virtio_config_val(vdev, VIRTIO_BLK_F_TOPOLOGY,
+			offsetof(struct virtio_blk_config, physical_block_exp),
+			&physical_block_exp);
+	if (!err && physical_block_exp)
+		blk_queue_physical_block_size(q,
+				blk_size * (1 << physical_block_exp));
+
+	err = virtio_config_val(vdev, VIRTIO_BLK_F_TOPOLOGY,
+			offsetof(struct virtio_blk_config, alignment_offset),
+			&alignment_offset);
+	if (!err && alignment_offset)
+		blk_queue_alignment_offset(q, blk_size * alignment_offset);
+
+	err = virtio_config_val(vdev, VIRTIO_BLK_F_TOPOLOGY,
+			offsetof(struct virtio_blk_config, min_io_size),
+			&min_io_size);
+	if (!err && min_io_size)
+		blk_queue_io_min(q, blk_size * min_io_size);
+
+	err = virtio_config_val(vdev, VIRTIO_BLK_F_TOPOLOGY,
+			offsetof(struct virtio_blk_config, opt_io_size),
+			&opt_io_size);
+	if (!err && opt_io_size)
+		blk_queue_io_opt(q, blk_size * opt_io_size);
+
+	add_disk(vblk->disk);
+	err = device_create_file(disk_to_dev(vblk->disk), &dev_attr_serial);
+	if (err)
+		goto out_del_disk;
+
+	if (virtio_has_feature(vdev, VIRTIO_BLK_F_CONFIG_WCE))
+		err = device_create_file(disk_to_dev(vblk->disk),
+					 &dev_attr_cache_type_rw);
+	else
+		err = device_create_file(disk_to_dev(vblk->disk),
+					 &dev_attr_cache_type_ro);
+	if (err)
+		goto out_del_disk;
+	return 0;
+
+out_del_disk:
+	del_gendisk(vblk->disk);
+	blk_cleanup_queue(vblk->disk->queue);
+out_put_disk:
+	put_disk(vblk->disk);
+out_mempool:
+	mempool_destroy(vblk->pool);
+out_free_vq:
+	vdev->config->del_vqs(vdev);
+out_free_vblk:
+	kfree(vblk);
+out_free_index:
+	ida_simple_remove(&vd_index_ida, index);
+out:
+	return err;
+}
+
+static void virtblk_remove(struct virtio_device *vdev)
+{
+	struct virtio_blk *vblk = vdev->priv;
+	int index = vblk->index;
+	int refc;
+
+	/* Prevent config work handler from accessing the device. */
+	mutex_lock(&vblk->config_lock);
+	vblk->config_enable = false;
+	mutex_unlock(&vblk->config_lock);
+
+	del_gendisk(vblk->disk);
+	blk_cleanup_queue(vblk->disk->queue);
+
+	/* Stop all the virtqueues. */
+	vdev->config->reset(vdev);
+
+	flush_work(&vblk->config_work);
+
+	refc = atomic_read(&disk_to_dev(vblk->disk)->kobj.kref.refcount);
+	put_disk(vblk->disk);
+	mempool_destroy(vblk->pool);
+	vdev->config->del_vqs(vdev);
+	kfree(vblk);
+
+	/* Only free device id if we don't have any users */
+	if (refc == 1)
+		ida_simple_remove(&vd_index_ida, index);
+}
+
+#ifdef CONFIG_PM
+static int virtblk_freeze(struct virtio_device *vdev)
+{
+	struct virtio_blk *vblk = vdev->priv;
+
+	/* Ensure we don't receive any more interrupts */
+	vdev->config->reset(vdev);
+
+	/* Prevent config work handler from accessing the device. */
+	mutex_lock(&vblk->config_lock);
+	vblk->config_enable = false;
+	mutex_unlock(&vblk->config_lock);
+
+	flush_work(&vblk->config_work);
+
+	spin_lock_irq(vblk->disk->queue->queue_lock);
+	blk_stop_queue(vblk->disk->queue);
+	spin_unlock_irq(vblk->disk->queue->queue_lock);
+	blk_sync_queue(vblk->disk->queue);
+
+	vdev->config->del_vqs(vdev);
+	return 0;
+}
+
+static int virtblk_restore(struct virtio_device *vdev)
+{
+	struct virtio_blk *vblk = vdev->priv;
+	int ret;
+
+	vblk->config_enable = true;
+	ret = init_vq(vdev->priv);
+	if (!ret) {
+		spin_lock_irq(vblk->disk->queue->queue_lock);
+		blk_start_queue(vblk->disk->queue);
+		spin_unlock_irq(vblk->disk->queue->queue_lock);
+	}
+	return ret;
+}
+#endif
+
+static const struct virtio_device_id id_table[] = {
+	{ VIRTIO_ID_BLOCK, VIRTIO_DEV_ANY_ID },
+	{ 0 },
+};
+
+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
+};
+
+static struct virtio_driver virtio_blk = {
+	.feature_table		= features,
+	.feature_table_size	= ARRAY_SIZE(features),
+	.driver.name		= KBUILD_MODNAME,
+	.driver.owner		= THIS_MODULE,
+	.id_table		= id_table,
+	.probe			= virtblk_probe,
+	.remove			= virtblk_remove,
+	.config_changed		= virtblk_config_changed,
+#ifdef CONFIG_PM
+	.freeze			= virtblk_freeze,
+	.restore		= virtblk_restore,
+#endif
+};
+
+static int __init init(void)
+{
+	int error;
+
+	virtblk_wq = alloc_workqueue("virtio-blk", 0, 0);
+	if (!virtblk_wq)
+		return -ENOMEM;
+
+	major = register_blkdev(0, "virtblk");
+	if (major < 0) {
+		error = major;
+		goto out_destroy_workqueue;
+	}
+
+	error = register_virtio_driver(&virtio_blk);
+	if (error)
+		goto out_unregister_blkdev;
+	return 0;
+
+out_unregister_blkdev:
+	unregister_blkdev(major, "virtblk");
+out_destroy_workqueue:
+	destroy_workqueue(virtblk_wq);
+	return error;
+}
+
+static void __exit fini(void)
+{
+	unregister_blkdev(major, "virtblk");
+	unregister_virtio_driver(&virtio_blk);
+	destroy_workqueue(virtblk_wq);
+}
+module_init(init);
+module_exit(fini);
+
+MODULE_DEVICE_TABLE(virtio, id_table);
+MODULE_DESCRIPTION("Virtio block driver");
+MODULE_LICENSE("GPL");