//#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 <scsi/scsi_cmnd.h>
#include <linux/idr.h>
#include <linux/blk-mq.h>
#include <linux/blk-mq-virtio.h>
#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;

        /* 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;

        /* 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 {
#ifdef CONFIG_VIRTIO_BLK_SCSI
        struct scsi_request sreq;       /* for SCSI passthrough, must be first */
        u8 sense[SCSI_SENSE_BUFFERSIZE];
        struct virtio_scsi_inhdr in_hdr;
#endif
        struct virtio_blk_outhdr out_hdr;
        u8 status;
        struct scatterlist sg[];
};

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;
        }
}

/*
 * 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.
 */
#ifdef CONFIG_VIRTIO_BLK_SCSI
static int virtblk_add_req_scsi(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;

        sg_init_one(&hdr, &vbr->out_hdr, sizeof(vbr->out_hdr));
        sgs[num_out++] = &hdr;
        sg_init_one(&cmd, vbr->sreq.cmd, vbr->sreq.cmd_len);
        sgs[num_out++] = &cmd;

        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(&sense, vbr->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 inline void virtblk_scsi_reques_done(struct request *req)
{
        struct virtblk_req *vbr = blk_mq_rq_to_pdu(req);
        struct virtio_blk *vblk = req->q->queuedata;
        struct scsi_request *sreq = &vbr->sreq;

        sreq->resid_len = virtio32_to_cpu(vblk->vdev, vbr->in_hdr.residual);
        sreq->sense_len = virtio32_to_cpu(vblk->vdev, vbr->in_hdr.sense_len);
        req->errors = virtio32_to_cpu(vblk->vdev, vbr->in_hdr.errors);
}

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);
}
#else
static inline int virtblk_add_req_scsi(struct virtqueue *vq,
                struct virtblk_req *vbr, struct scatterlist *data_sg,
                bool have_data)
{
        return -EIO;
}
static inline void virtblk_scsi_reques_done(struct request *req)
{
}
#define virtblk_ioctl   NULL
#endif /* CONFIG_VIRTIO_BLK_SCSI */

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 inline void virtblk_request_done(struct request *req)
{
        struct virtblk_req *vbr = blk_mq_rq_to_pdu(req);
        int error = virtblk_result(vbr);

        switch (req_op(req)) {
        case REQ_OP_SCSI_IN:
        case REQ_OP_SCSI_OUT:
                virtblk_scsi_reques_done(req);
                break;
        case REQ_OP_DRV_IN:
                req->errors = (error != 0);
                break;
        }

        blk_mq_end_request(req, error);
}

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);

                        blk_mq_complete_request(req, req->errors);
                        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 int 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;
        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_SCSI_IN:
        case REQ_OP_SCSI_OUT:
                type = VIRTIO_BLK_T_SCSI_CMD;
                break;
        case REQ_OP_DRV_IN:
                type = VIRTIO_BLK_T_GET_ID;
                break;
        default:
                WARN_ON_ONCE(1);
                return BLK_MQ_RQ_QUEUE_ERROR;
        }

        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);

        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);
        if (req_op(req) == REQ_OP_SCSI_IN || req_op(req) == REQ_OP_SCSI_OUT)
                err = virtblk_add_req_scsi(vblk->vqs[qid].vq, vbr, vbr->sg, num);
        else
                err = virtblk_add_req(vblk->vqs[qid].vq, vbr, vbr->sg, num);
        if (err) {
                virtqueue_kick(vblk->vqs[qid].vq);
                blk_mq_stop_hw_queue(hctx);
                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)
                        return BLK_MQ_RQ_QUEUE_BUSY;
                return BLK_MQ_RQ_QUEUE_ERROR;
        }

        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_MQ_RQ_QUEUE_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, GFP_KERNEL);
        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;

        err = blk_execute_rq(vblk->disk->queue, vblk->disk, req, false);
out:
        blk_put_request(req);
        return err;
}

/* 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;

        /* 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;
        }
        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;
}

static 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;

        /* 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;
        }

        string_get_size(capacity, queue_logical_block_size(q),
                        STRING_UNITS_2, cap_str_2, sizeof(cap_str_2));
        string_get_size(capacity, queue_logical_block_size(q),
                        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);
}

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;

        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 = vdev->config->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(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;

        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;

        virtio_cwrite8(vdev, offsetof(struct virtio_blk_config, wce), i);
        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_init_request(void *data, struct request *rq,
                unsigned int hctx_idx, unsigned int request_idx,
                unsigned int numa_node)
{
        struct virtio_blk *vblk = data;
        struct virtblk_req *vbr = blk_mq_rq_to_pdu(rq);

#ifdef CONFIG_VIRTIO_BLK_SCSI
        vbr->sreq.sense = vbr->sense;
#endif
        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, vblk->vdev, 0);
}

static struct blk_mq_ops virtio_mq_ops = {
        .queue_rq       = virtio_queue_rq,
        .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;

        u64 cap;
        u32 v, blk_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;
        }

        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);

        /* Host must always specify the capacity. */
        virtio_cread(vdev, struct virtio_blk_config, capacity, &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_cread_feature(vdev, VIRTIO_BLK_F_SIZE_MAX,
                                   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_cread_feature(vdev, VIRTIO_BLK_F_BLK_SIZE,
                                   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_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);

        virtio_device_ready(vdev);

        device_add_disk(&vdev->dev, 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_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);
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;

        /* 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);

        /* Stop all the virtqueues. */
        vdev->config->reset(vdev);

        refc = kref_read(&disk_to_dev(vblk->disk)->kobj.kref);
        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 */
        if (refc == 1)
                ida_simple_remove(&vd_index_ida, index);
}

#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_stop_hw_queues(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;

        ret = init_vq(vdev->priv);
        if (ret)
                return ret;

        virtio_device_ready(vdev);

        blk_mq_start_stopped_hw_queues(vblk->disk->queue, true);
        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,
#ifdef CONFIG_VIRTIO_BLK_SCSI
        VIRTIO_BLK_F_SCSI,
#endif
        VIRTIO_BLK_F_FLUSH, VIRTIO_BLK_F_TOPOLOGY, VIRTIO_BLK_F_CONFIG_WCE,
        VIRTIO_BLK_F_MQ,
}
;
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,
};

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");