1 files changed, 1058 insertions, 0 deletions

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
new file mode 100644
index 000000000..9b54eec9b
--- /dev/null
+++ b/drivers/block/virtio_blk.c
@@ -0,0 +1,1058 @@
+// SPDX-License-Identifier: GPL-2.0-only
+//#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/interrupt.h>
+#include <linux/virtio.h>
+#include <linux/virtio_blk.h>
+#include <linux/scatterlist.h>
+#include <linux/string_helpers.h>
+#include <linux/idr.h>
+#include <linux/blk-mq.h>
+#include <linux/blk-mq-virtio.h>
+#include <linux/numa.h>
+#include <uapi/linux/virtio_ring.h>
+
+#define PART_BITS 4
+#define VQ_NAME_LEN 16
+#define MAX_DISCARD_SEGMENTS 256u
+
+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 {
+	/*
+	 * This mutex must be held by anything that may run after
+	 * virtblk_remove() sets vblk->vdev to NULL.
+	 *
+	 * blk-mq, virtqueue processing, and sysfs attribute code paths are
+	 * shut down before vblk->vdev is set to NULL and therefore do not need
+	 * to hold this mutex.
+	 */
+	struct mutex vdev_mutex;
+	struct virtio_device *vdev;
+
+	/* The disk structure for the kernel. */
+	struct gendisk *disk;
+
+	/* Block layer tags. */
+	struct blk_mq_tag_set tag_set;
+
+	/* Process context for config space updates */
+	struct work_struct config_work;
+
+	/*
+	 * Tracks references from block_device_operations open/release and
+	 * virtio_driver probe/remove so this object can be freed once no
+	 * longer in use.
+	 */
+	refcount_t refs;
+
+	/* What host tells us, plus 2 for header & tailer. */
+	unsigned int sg_elems;
+
+	/* Ida index - used to track minor number allocations. */
+	int index;
+
+	/* num of vqs */
+	int num_vqs;
+	struct virtio_blk_vq *vqs;
+};
+
+struct virtblk_req {
+	struct virtio_blk_outhdr out_hdr;
+	u8 status;
+	struct scatterlist sg[];
+};
+
+static inline blk_status_t virtblk_result(struct virtblk_req *vbr)
+{
+	switch (vbr->status) {
+	case VIRTIO_BLK_S_OK:
+		return BLK_STS_OK;
+	case VIRTIO_BLK_S_UNSUPP:
+		return BLK_STS_NOTSUPP;
+	default:
+		return BLK_STS_IOERR;
+	}
+}
+
+static int virtblk_add_req(struct virtqueue *vq, struct virtblk_req *vbr,
+		struct scatterlist *data_sg, bool have_data)
+{
+	struct scatterlist hdr, status, *sgs[3];
+	unsigned int num_out = 0, num_in = 0;
+
+	sg_init_one(&hdr, &vbr->out_hdr, sizeof(vbr->out_hdr));
+	sgs[num_out++] = &hdr;
+
+	if (have_data) {
+		if (vbr->out_hdr.type & cpu_to_virtio32(vq->vdev, VIRTIO_BLK_T_OUT))
+			sgs[num_out++] = data_sg;
+		else
+			sgs[num_out + num_in++] = data_sg;
+	}
+
+	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 int virtblk_setup_discard_write_zeroes(struct request *req, bool unmap)
+{
+	unsigned short segments = blk_rq_nr_discard_segments(req);
+	unsigned short n = 0;
+	struct virtio_blk_discard_write_zeroes *range;
+	struct bio *bio;
+	u32 flags = 0;
+
+	if (unmap)
+		flags |= VIRTIO_BLK_WRITE_ZEROES_FLAG_UNMAP;
+
+	range = kmalloc_array(segments, sizeof(*range), GFP_ATOMIC);
+	if (!range)
+		return -ENOMEM;
+
+	/*
+	 * Single max discard segment means multi-range discard isn't
+	 * supported, and block layer only runs contiguity merge like
+	 * normal RW request. So we can't reply on bio for retrieving
+	 * each range info.
+	 */
+	if (queue_max_discard_segments(req->q) == 1) {
+		range[0].flags = cpu_to_le32(flags);
+		range[0].num_sectors = cpu_to_le32(blk_rq_sectors(req));
+		range[0].sector = cpu_to_le64(blk_rq_pos(req));
+		n = 1;
+	} else {
+		__rq_for_each_bio(bio, req) {
+			u64 sector = bio->bi_iter.bi_sector;
+			u32 num_sectors = bio->bi_iter.bi_size >> SECTOR_SHIFT;
+
+			range[n].flags = cpu_to_le32(flags);
+			range[n].num_sectors = cpu_to_le32(num_sectors);
+			range[n].sector = cpu_to_le64(sector);
+			n++;
+		}
+	}
+
+	WARN_ON_ONCE(n != segments);
+
+	req->special_vec.bv_page = virt_to_page(range);
+	req->special_vec.bv_offset = offset_in_page(range);
+	req->special_vec.bv_len = sizeof(*range) * segments;
+	req->rq_flags |= RQF_SPECIAL_PAYLOAD;
+
+	return 0;
+}
+
+static inline void virtblk_request_done(struct request *req)
+{
+	struct virtblk_req *vbr = blk_mq_rq_to_pdu(req);
+
+	if (req->rq_flags & RQF_SPECIAL_PAYLOAD) {
+		kfree(page_address(req->special_vec.bv_page) +
+		      req->special_vec.bv_offset);
+	}
+
+	blk_mq_end_request(req, virtblk_result(vbr));
+}
+
+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->vqs[qid].lock, flags);
+	do {
+		virtqueue_disable_cb(vq);
+		while ((vbr = virtqueue_get_buf(vblk->vqs[qid].vq, &len)) != NULL) {
+			struct request *req = blk_mq_rq_from_pdu(vbr);
+
+			if (likely(!blk_should_fake_timeout(req->q)))
+				blk_mq_complete_request(req);
+			req_done = true;
+		}
+		if (unlikely(virtqueue_is_broken(vq)))
+			break;
+	} while (!virtqueue_enable_cb(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);
+}
+
+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];
+	bool kick;
+
+	spin_lock_irq(&vq->lock);
+	kick = virtqueue_kick_prepare(vq->vq);
+	spin_unlock_irq(&vq->lock);
+
+	if (kick)
+		virtqueue_notify(vq->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 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;
+	u32 type;
+
+	BUG_ON(req->nr_phys_segments + 2 > vblk->sg_elems);
+
+	switch (req_op(req)) {
+	case REQ_OP_READ:
+	case REQ_OP_WRITE:
+		type = 0;
+		break;
+	case REQ_OP_FLUSH:
+		type = VIRTIO_BLK_T_FLUSH;
+		break;
+	case REQ_OP_DISCARD:
+		type = VIRTIO_BLK_T_DISCARD;
+		break;
+	case REQ_OP_WRITE_ZEROES:
+		type = VIRTIO_BLK_T_WRITE_ZEROES;
+		unmap = !(req->cmd_flags & REQ_NOUNMAP);
+		break;
+	case REQ_OP_DRV_IN:
+		type = VIRTIO_BLK_T_GET_ID;
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		return BLK_STS_IOERR;
+	}
+
+	vbr->out_hdr.type = cpu_to_virtio32(vblk->vdev, type);
+	vbr->out_hdr.sector = type ?
+		0 : cpu_to_virtio64(vblk->vdev, blk_rq_pos(req));
+	vbr->out_hdr.ioprio = cpu_to_virtio32(vblk->vdev, req_get_ioprio(req));
+
+	blk_mq_start_request(req);
+
+	if (type == VIRTIO_BLK_T_DISCARD || type == VIRTIO_BLK_T_WRITE_ZEROES) {
+		err = virtblk_setup_discard_write_zeroes(req, unmap);
+		if (err)
+			return BLK_STS_RESOURCE;
+	}
+
+	num = blk_rq_map_sg(hctx->queue, req, vbr->sg);
+	if (num) {
+		if (rq_data_dir(req) == WRITE)
+			vbr->out_hdr.type |= cpu_to_virtio32(vblk->vdev, VIRTIO_BLK_T_OUT);
+		else
+			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);
+	if (err) {
+		virtqueue_kick(vblk->vqs[qid].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);
+		switch (err) {
+		case -ENOSPC:
+			return BLK_STS_DEV_RESOURCE;
+		case -ENOMEM:
+			return BLK_STS_RESOURCE;
+		default:
+			return BLK_STS_IOERR;
+		}
+	}
+
+	if (bd->last && virtqueue_kick_prepare(vblk->vqs[qid].vq))
+		notify = true;
+	spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags);
+
+	if (notify)
+		virtqueue_notify(vblk->vqs[qid].vq);
+	return BLK_STS_OK;
+}
+
+/* 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_queue *q = vblk->disk->queue;
+	struct request *req;
+	int err;
+
+	req = blk_get_request(q, REQ_OP_DRV_IN, 0);
+	if (IS_ERR(req))
+		return PTR_ERR(req);
+
+	err = blk_rq_map_kern(q, req, id_str, VIRTIO_BLK_ID_BYTES, GFP_KERNEL);
+	if (err)
+		goto out;
+
+	blk_execute_rq(vblk->disk->queue, vblk->disk, req, false);
+	err = blk_status_to_errno(virtblk_result(blk_mq_rq_to_pdu(req)));
+out:
+	blk_put_request(req);
+	return err;
+}
+
+static void virtblk_get(struct virtio_blk *vblk)
+{
+	refcount_inc(&vblk->refs);
+}
+
+static void virtblk_put(struct virtio_blk *vblk)
+{
+	if (refcount_dec_and_test(&vblk->refs)) {
+		ida_simple_remove(&vd_index_ida, vblk->index);
+		mutex_destroy(&vblk->vdev_mutex);
+		kfree(vblk);
+	}
+}
+
+static int virtblk_open(struct block_device *bd, fmode_t mode)
+{
+	struct virtio_blk *vblk = bd->bd_disk->private_data;
+	int ret = 0;
+
+	mutex_lock(&vblk->vdev_mutex);
+
+	if (vblk->vdev)
+		virtblk_get(vblk);
+	else
+		ret = -ENXIO;
+
+	mutex_unlock(&vblk->vdev_mutex);
+	return ret;
+}
+
+static void virtblk_release(struct gendisk *disk, fmode_t mode)
+{
+	struct virtio_blk *vblk = disk->private_data;
+
+	virtblk_put(vblk);
+}
+
+/* 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;
+	int ret = 0;
+
+	mutex_lock(&vblk->vdev_mutex);
+
+	if (!vblk->vdev) {
+		ret = -ENXIO;
+		goto out;
+	}
+
+	/* see if the host passed in geometry config */
+	if (virtio_has_feature(vblk->vdev, VIRTIO_BLK_F_GEOMETRY)) {
+		virtio_cread(vblk->vdev, struct virtio_blk_config,
+			     geometry.cylinders, &geo->cylinders);
+		virtio_cread(vblk->vdev, struct virtio_blk_config,
+			     geometry.heads, &geo->heads);
+		virtio_cread(vblk->vdev, struct virtio_blk_config,
+			     geometry.sectors, &geo->sectors);
+	} else {
+		/* some standard values, similar to sd */
+		geo->heads = 1 << 6;
+		geo->sectors = 1 << 5;
+		geo->cylinders = get_capacity(bd->bd_disk) >> 11;
+	}
+out:
+	mutex_unlock(&vblk->vdev_mutex);
+	return ret;
+}
+
+static const struct block_device_operations virtblk_fops = {
+	.owner  = THIS_MODULE,
+	.open = virtblk_open,
+	.release = virtblk_release,
+	.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 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;
+}
+
+static DEVICE_ATTR_RO(serial);
+
+/* The queue's logical block size must be set before calling this */
+static void virtblk_update_capacity(struct virtio_blk *vblk, bool resize)
+{
+	struct virtio_device *vdev = vblk->vdev;
+	struct request_queue *q = vblk->disk->queue;
+	char cap_str_2[10], cap_str_10[10];
+	unsigned long long nblocks;
+	u64 capacity;
+
+	/* Host must always specify the capacity. */
+	virtio_cread(vdev, struct virtio_blk_config, capacity, &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;
+	}
+
+	nblocks = DIV_ROUND_UP_ULL(capacity, queue_logical_block_size(q) >> 9);
+
+	string_get_size(nblocks, queue_logical_block_size(q),
+			STRING_UNITS_2, cap_str_2, sizeof(cap_str_2));
+	string_get_size(nblocks, queue_logical_block_size(q),
+			STRING_UNITS_10, cap_str_10, sizeof(cap_str_10));
+
+	dev_notice(&vdev->dev,
+		   "[%s] %s%llu %d-byte logical blocks (%s/%s)\n",
+		   vblk->disk->disk_name,
+		   resize ? "new size: " : "",
+		   nblocks,
+		   queue_logical_block_size(q),
+		   cap_str_10,
+		   cap_str_2);
+
+	set_capacity_revalidate_and_notify(vblk->disk, capacity, true);
+}
+
+static void virtblk_config_changed_work(struct work_struct *work)
+{
+	struct virtio_blk *vblk =
+		container_of(work, struct virtio_blk, config_work);
+
+	virtblk_update_capacity(vblk, true);
+}
+
+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;
+	int i;
+	vq_callback_t **callbacks;
+	const char **names;
+	struct virtqueue **vqs;
+	unsigned short num_vqs;
+	struct virtio_device *vdev = vblk->vdev;
+	struct irq_affinity desc = { 0, };
+
+	err = virtio_cread_feature(vdev, VIRTIO_BLK_F_MQ,
+				   struct virtio_blk_config, num_queues,
+				   &num_vqs);
+	if (err)
+		num_vqs = 1;
+
+	num_vqs = min_t(unsigned int, nr_cpu_ids, num_vqs);
+
+	vblk->vqs = kmalloc_array(num_vqs, sizeof(*vblk->vqs), GFP_KERNEL);
+	if (!vblk->vqs)
+		return -ENOMEM;
+
+	names = kmalloc_array(num_vqs, sizeof(*names), GFP_KERNEL);
+	callbacks = kmalloc_array(num_vqs, sizeof(*callbacks), GFP_KERNEL);
+	vqs = kmalloc_array(num_vqs, sizeof(*vqs), GFP_KERNEL);
+	if (!names || !callbacks || !vqs) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	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 = virtio_find_vqs(vdev, num_vqs, vqs, callbacks, names, &desc);
+	if (err)
+		goto out;
+
+	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;
+
+out:
+	kfree(vqs);
+	kfree(callbacks);
+	kfree(names);
+	if (err)
+		kfree(vblk->vqs);
+	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_cread_feature(vdev, VIRTIO_BLK_F_CONFIG_WCE,
+				   struct virtio_blk_config, wce,
+				   &writeback);
+
+	/*
+	 * If WCE is not configurable and flush is not available,
+	 * assume no writeback cache is in use.
+	 */
+	if (err)
+		writeback = virtio_has_feature(vdev, VIRTIO_BLK_F_FLUSH);
+
+	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;
+
+	blk_queue_write_cache(vblk->disk->queue, writeback, false);
+	revalidate_disk_size(vblk->disk, true);
+}
+
+static const char *const virtblk_cache_types[] = {
+	"write through", "write back"
+};
+
+static ssize_t
+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;
+
+	BUG_ON(!virtio_has_feature(vblk->vdev, VIRTIO_BLK_F_CONFIG_WCE));
+	i = sysfs_match_string(virtblk_cache_types, buf);
+	if (i < 0)
+		return i;
+
+	virtio_cwrite8(vdev, offsetof(struct virtio_blk_config, wce), i);
+	virtblk_update_cache_mode(vdev);
+	return count;
+}
+
+static ssize_t
+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 DEVICE_ATTR_RW(cache_type);
+
+static struct attribute *virtblk_attrs[] = {
+	&dev_attr_serial.attr,
+	&dev_attr_cache_type.attr,
+	NULL,
+};
+
+static umode_t virtblk_attrs_are_visible(struct kobject *kobj,
+		struct attribute *a, int n)
+{
+	struct device *dev = kobj_to_dev(kobj);
+	struct gendisk *disk = dev_to_disk(dev);
+	struct virtio_blk *vblk = disk->private_data;
+	struct virtio_device *vdev = vblk->vdev;
+
+	if (a == &dev_attr_cache_type.attr &&
+	    !virtio_has_feature(vdev, VIRTIO_BLK_F_CONFIG_WCE))
+		return S_IRUGO;
+
+	return a->mode;
+}
+
+static const struct attribute_group virtblk_attr_group = {
+	.attrs = virtblk_attrs,
+	.is_visible = virtblk_attrs_are_visible,
+};
+
+static const struct attribute_group *virtblk_attr_groups[] = {
+	&virtblk_attr_group,
+	NULL,
+};
+
+static int virtblk_init_request(struct blk_mq_tag_set *set, struct request *rq,
+		unsigned int hctx_idx, unsigned int numa_node)
+{
+	struct virtio_blk *vblk = set->driver_data;
+	struct virtblk_req *vbr = blk_mq_rq_to_pdu(rq);
+
+	sg_init_table(vbr->sg, vblk->sg_elems);
+	return 0;
+}
+
+static int virtblk_map_queues(struct blk_mq_tag_set *set)
+{
+	struct virtio_blk *vblk = set->driver_data;
+
+	return blk_mq_virtio_map_queues(&set->map[HCTX_TYPE_DEFAULT],
+					vblk->vdev, 0);
+}
+
+static const struct blk_mq_ops virtio_mq_ops = {
+	.queue_rq	= virtio_queue_rq,
+	.commit_rqs	= virtio_commit_rqs,
+	.complete	= virtblk_request_done,
+	.init_request	= virtblk_init_request,
+	.map_queues	= virtblk_map_queues,
+};
+
+static unsigned int virtblk_queue_depth;
+module_param_named(queue_depth, virtblk_queue_depth, uint, 0444);
+
+static int virtblk_probe(struct virtio_device *vdev)
+{
+	struct virtio_blk *vblk;
+	struct request_queue *q;
+	int err, index;
+
+	u32 v, blk_size, max_size, sg_elems, opt_io_size;
+	u16 min_io_size;
+	u8 physical_block_exp, alignment_offset;
+
+	if (!vdev->config->get) {
+		dev_err(&vdev->dev, "%s failure: config access disabled\n",
+			__func__);
+		return -EINVAL;
+	}
+
+	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_cread_feature(vdev, VIRTIO_BLK_F_SEG_MAX,
+				   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), GFP_KERNEL);
+	if (!vblk) {
+		err = -ENOMEM;
+		goto out_free_index;
+	}
+
+	/* This reference is dropped in virtblk_remove(). */
+	refcount_set(&vblk->refs, 1);
+	mutex_init(&vblk->vdev_mutex);
+
+	vblk->vdev = vdev;
+	vblk->sg_elems = sg_elems;
+
+	INIT_WORK(&vblk->config_work, virtblk_config_changed_work);
+
+	err = init_vq(vblk);
+	if (err)
+		goto out_free_vblk;
+
+	/* 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_free_vq;
+	}
+
+	/* Default queue sizing is to fill the ring. */
+	if (!virtblk_queue_depth) {
+		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;
+	}
+
+	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.numa_node = NUMA_NO_NODE;
+	vblk->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
+	vblk->tag_set.cmd_size =
+		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)
+		goto out_put_disk;
+
+	q = blk_mq_init_queue(&vblk->tag_set);
+	if (IS_ERR(q)) {
+		err = -ENOMEM;
+		goto out_free_tags;
+	}
+	vblk->disk->queue = q;
+
+	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->flags |= GENHD_FL_EXT_DEVT;
+	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);
+
+	/* We can handle whatever the host told us to handle. */
+	blk_queue_max_segments(q, vblk->sg_elems-2);
+
+	/* No real sector limit. */
+	blk_queue_max_hw_sectors(q, -1U);
+
+	max_size = virtio_max_dma_size(vdev);
+
+	/* Host can optionally specify maximum segment size and number of
+	 * segments. */
+	err = virtio_cread_feature(vdev, VIRTIO_BLK_F_SIZE_MAX,
+				   struct virtio_blk_config, size_max, &v);
+	if (!err)
+		max_size = min(max_size, v);
+
+	blk_queue_max_segment_size(q, max_size);
+
+	/* Host can optionally specify the block size of the device */
+	err = virtio_cread_feature(vdev, VIRTIO_BLK_F_BLK_SIZE,
+				   struct virtio_blk_config, blk_size,
+				   &blk_size);
+	if (!err) {
+		err = blk_validate_block_size(blk_size);
+		if (err) {
+			dev_err(&vdev->dev,
+				"virtio_blk: invalid block size: 0x%x\n",
+				blk_size);
+			goto out_free_tags;
+		}
+
+		blk_queue_logical_block_size(q, blk_size);
+	} else
+		blk_size = queue_logical_block_size(q);
+
+	/* Use topology information if available */
+	err = virtio_cread_feature(vdev, VIRTIO_BLK_F_TOPOLOGY,
+				   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_cread_feature(vdev, VIRTIO_BLK_F_TOPOLOGY,
+				   struct virtio_blk_config, alignment_offset,
+				   &alignment_offset);
+	if (!err && alignment_offset)
+		blk_queue_alignment_offset(q, blk_size * alignment_offset);
+
+	err = virtio_cread_feature(vdev, VIRTIO_BLK_F_TOPOLOGY,
+				   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_cread_feature(vdev, VIRTIO_BLK_F_TOPOLOGY,
+				   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);
+
+	if (virtio_has_feature(vdev, VIRTIO_BLK_F_DISCARD)) {
+		virtio_cread(vdev, struct virtio_blk_config,
+			     discard_sector_alignment, &v);
+		if (v)
+			q->limits.discard_granularity = v << SECTOR_SHIFT;
+		else
+			q->limits.discard_granularity = blk_size;
+
+		virtio_cread(vdev, struct virtio_blk_config,
+			     max_discard_sectors, &v);
+		blk_queue_max_discard_sectors(q, v ? v : UINT_MAX);
+
+		virtio_cread(vdev, struct virtio_blk_config, max_discard_seg,
+			     &v);
+
+		/*
+		 * max_discard_seg == 0 is out of spec but we always
+		 * handled it.
+		 */
+		if (!v)
+			v = sg_elems - 2;
+		blk_queue_max_discard_segments(q,
+					       min(v, MAX_DISCARD_SEGMENTS));
+
+		blk_queue_flag_set(QUEUE_FLAG_DISCARD, q);
+	}
+
+	if (virtio_has_feature(vdev, VIRTIO_BLK_F_WRITE_ZEROES)) {
+		virtio_cread(vdev, struct virtio_blk_config,
+			     max_write_zeroes_sectors, &v);
+		blk_queue_max_write_zeroes_sectors(q, v ? v : UINT_MAX);
+	}
+
+	virtblk_update_capacity(vblk, false);
+	virtio_device_ready(vdev);
+
+	device_add_disk(&vdev->dev, vblk->disk, virtblk_attr_groups);
+	return 0;
+
+out_free_tags:
+	blk_mq_free_tag_set(&vblk->tag_set);
+out_put_disk:
+	put_disk(vblk->disk);
+out_free_vq:
+	vdev->config->del_vqs(vdev);
+	kfree(vblk->vqs);
+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;
+
+	/* Make sure no work handler is accessing the device. */
+	flush_work(&vblk->config_work);
+
+	del_gendisk(vblk->disk);
+	blk_cleanup_queue(vblk->disk->queue);
+
+	blk_mq_free_tag_set(&vblk->tag_set);
+
+	mutex_lock(&vblk->vdev_mutex);
+
+	/* Stop all the virtqueues. */
+	vdev->config->reset(vdev);
+
+	/* Virtqueues are stopped, nothing can use vblk->vdev anymore. */
+	vblk->vdev = NULL;
+
+	put_disk(vblk->disk);
+	vdev->config->del_vqs(vdev);
+	kfree(vblk->vqs);
+
+	mutex_unlock(&vblk->vdev_mutex);
+
+	virtblk_put(vblk);
+}
+
+#ifdef CONFIG_PM_SLEEP
+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);
+
+	/* Make sure no work handler is accessing the device. */
+	flush_work(&vblk->config_work);
+
+	blk_mq_quiesce_queue(vblk->disk->queue);
+
+	vdev->config->del_vqs(vdev);
+	kfree(vblk->vqs);
+
+	return 0;
+}
+
+static int virtblk_restore(struct virtio_device *vdev)
+{
+	struct virtio_blk *vblk = vdev->priv;
+	int ret;
+
+	ret = init_vq(vdev->priv);
+	if (ret)
+		return ret;
+
+	virtio_device_ready(vdev);
+
+	blk_mq_unquiesce_queue(vblk->disk->queue);
+	return 0;
+}
+#endif
+
+static const struct virtio_device_id id_table[] = {
+	{ VIRTIO_ID_BLOCK, VIRTIO_DEV_ANY_ID },
+	{ 0 },
+};
+
+static unsigned int features_legacy[] = {
+	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_FLUSH, VIRTIO_BLK_F_TOPOLOGY, VIRTIO_BLK_F_CONFIG_WCE,
+	VIRTIO_BLK_F_MQ, VIRTIO_BLK_F_DISCARD, VIRTIO_BLK_F_WRITE_ZEROES,
+}
+;
+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_FLUSH, VIRTIO_BLK_F_TOPOLOGY, VIRTIO_BLK_F_CONFIG_WCE,
+	VIRTIO_BLK_F_MQ, VIRTIO_BLK_F_DISCARD, VIRTIO_BLK_F_WRITE_ZEROES,
+};
+
+static struct virtio_driver virtio_blk = {
+	.feature_table			= features,
+	.feature_table_size		= ARRAY_SIZE(features),
+	.feature_table_legacy		= features_legacy,
+	.feature_table_size_legacy	= ARRAY_SIZE(features_legacy),
+	.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_SLEEP
+	.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_virtio_driver(&virtio_blk);
+	unregister_blkdev(major, "virtblk");
+	destroy_workqueue(virtblk_wq);
+}
+module_init(init);
+module_exit(fini);
+
+MODULE_DEVICE_TABLE(virtio, id_table);
+MODULE_DESCRIPTION("Virtio block driver");
+MODULE_LICENSE("GPL");