LXR linux/drivers/block/virtio

   1//#define DEBUG
   2#include <linux/spinlock.h>
   3#include <linux/blkdev.h>
   4#include <linux/hdreg.h>
   5#include <linux/virtio.h>
   6#include <linux/virtio_blk.h>
   7#include <linux/scatterlist.h>
   8
   9#define PART_BITS 4
  10
  11static int major, index;
  12
  13struct virtio_blk
  14{
  15        spinlock_t lock;
  16
  17        struct virtio_device *vdev;
  18        struct virtqueue *vq;
  19
  20        /* The disk structure for the kernel. */
  21        struct gendisk *disk;
  22
  23        /* Request tracking. */
  24        struct list_head reqs;
  25
  26        mempool_t *pool;
  27
  28        /* What host tells us, plus 2 for header & tailer. */
  29        unsigned int sg_elems;
  30
  31        /* Scatterlist: can be too big for stack. */
  32        struct scatterlist sg[/*sg_elems*/];
  33};
  34
  35struct virtblk_req
  36{
  37        struct list_head list;
  38        struct request *req;
  39        struct virtio_blk_outhdr out_hdr;
  40        u8 status;
  41};
  42
  43static void blk_done(struct virtqueue *vq)
  44{
  45        struct virtio_blk *vblk = vq->vdev->priv;
  46        struct virtblk_req *vbr;
  47        unsigned int len;
  48        unsigned long flags;
  49
  50        spin_lock_irqsave(&vblk->lock, flags);
  51        while ((vbr = vblk->vq->vq_ops->get_buf(vblk->vq, &len)) != NULL) {
  52                int error;
  53                switch (vbr->status) {
  54                case VIRTIO_BLK_S_OK:
  55                        error = 0;
  56                        break;
  57                case VIRTIO_BLK_S_UNSUPP:
  58                        error = -ENOTTY;
  59                        break;
  60                default:
  61                        error = -EIO;
  62                        break;
  63                }
  64
  65                __blk_end_request(vbr->req, error, blk_rq_bytes(vbr->req));
  66                list_del(&vbr->list);
  67                mempool_free(vbr, vblk->pool);
  68        }
  69        /* In case queue is stopped waiting for more buffers. */
  70        blk_start_queue(vblk->disk->queue);
  71        spin_unlock_irqrestore(&vblk->lock, flags);
  72}
  73
  74static bool do_req(struct request_queue *q, struct virtio_blk *vblk,
  75                   struct request *req)
  76{
  77        unsigned long num, out, in;
  78        struct virtblk_req *vbr;
  79
  80        vbr = mempool_alloc(vblk->pool, GFP_ATOMIC);
  81        if (!vbr)
  82                /* When another request finishes we'll try again. */
  83                return false;
  84
  85        vbr->req = req;
  86        if (blk_fs_request(vbr->req)) {
  87                vbr->out_hdr.type = 0;
  88                vbr->out_hdr.sector = vbr->req->sector;
  89                vbr->out_hdr.ioprio = req_get_ioprio(vbr->req);
  90        } else if (blk_pc_request(vbr->req)) {
  91                vbr->out_hdr.type = VIRTIO_BLK_T_SCSI_CMD;
  92                vbr->out_hdr.sector = 0;
  93                vbr->out_hdr.ioprio = req_get_ioprio(vbr->req);
  94        } else {
  95                /* We don't put anything else in the queue. */
  96                BUG();
  97        }
  98
  99        if (blk_barrier_rq(vbr->req))
 100                vbr->out_hdr.type |= VIRTIO_BLK_T_BARRIER;
 101
 102        sg_set_buf(&vblk->sg[0], &vbr->out_hdr, sizeof(vbr->out_hdr));
 103        num = blk_rq_map_sg(q, vbr->req, vblk->sg+1);
 104        sg_set_buf(&vblk->sg[num+1], &vbr->status, sizeof(vbr->status));
 105
 106        if (rq_data_dir(vbr->req) == WRITE) {
 107                vbr->out_hdr.type |= VIRTIO_BLK_T_OUT;
 108                out = 1 + num;
 109                in = 1;
 110        } else {
 111                vbr->out_hdr.type |= VIRTIO_BLK_T_IN;
 112                out = 1;
 113                in = 1 + num;
 114        }
 115
 116        if (vblk->vq->vq_ops->add_buf(vblk->vq, vblk->sg, out, in, vbr)) {
 117                mempool_free(vbr, vblk->pool);
 118                return false;
 119        }
 120
 121        list_add_tail(&vbr->list, &vblk->reqs);
 122        return true;
 123}
 124
 125static void do_virtblk_request(struct request_queue *q)
 126{
 127        struct virtio_blk *vblk = NULL;
 128        struct request *req;
 129        unsigned int issued = 0;
 130
 131        while ((req = elv_next_request(q)) != NULL) {
 132                vblk = req->rq_disk->private_data;
 133                BUG_ON(req->nr_phys_segments + 2 > vblk->sg_elems);
 134
 135                /* If this request fails, stop queue and wait for something to
 136                   finish to restart it. */
 137                if (!do_req(q, vblk, req)) {
 138                        blk_stop_queue(q);
 139                        break;
 140                }
 141                blkdev_dequeue_request(req);
 142                issued++;
 143        }
 144
 145        if (issued)
 146                vblk->vq->vq_ops->kick(vblk->vq);
 147}
 148
 149static int virtblk_ioctl(struct block_device *bdev, fmode_t mode,
 150                         unsigned cmd, unsigned long data)
 151{
 152        return scsi_cmd_ioctl(bdev->bd_disk->queue,
 153                              bdev->bd_disk, mode, cmd,
 154                              (void __user *)data);
 155}
 156
 157/* We provide getgeo only to please some old bootloader/partitioning tools */
 158static int virtblk_getgeo(struct block_device *bd, struct hd_geometry *geo)
 159{
 160        struct virtio_blk *vblk = bd->bd_disk->private_data;
 161        struct virtio_blk_geometry vgeo;
 162        int err;
 163
 164        /* see if the host passed in geometry config */
 165        err = virtio_config_val(vblk->vdev, VIRTIO_BLK_F_GEOMETRY,
 166                                offsetof(struct virtio_blk_config, geometry),
 167                                &vgeo);
 168
 169        if (!err) {
 170                geo->heads = vgeo.heads;
 171                geo->sectors = vgeo.sectors;
 172                geo->cylinders = vgeo.cylinders;
 173        } else {
 174                /* some standard values, similar to sd */
 175                geo->heads = 1 << 6;
 176                geo->sectors = 1 << 5;
 177                geo->cylinders = get_capacity(bd->bd_disk) >> 11;
 178        }
 179        return 0;
 180}
 181
 182static struct block_device_operations virtblk_fops = {
 183        .locked_ioctl = virtblk_ioctl,
 184        .owner  = THIS_MODULE,
 185        .getgeo = virtblk_getgeo,
 186};
 187
 188static int index_to_minor(int index)
 189{
 190        return index << PART_BITS;
 191}
 192
 193static int virtblk_probe(struct virtio_device *vdev)
 194{
 195        struct virtio_blk *vblk;
 196        int err;
 197        u64 cap;
 198        u32 v;
 199        u32 blk_size, sg_elems;
 200
 201        if (index_to_minor(index) >= 1 << MINORBITS)
 202                return -ENOSPC;
 203
 204        /* We need to know how many segments before we allocate. */
 205        err = virtio_config_val(vdev, VIRTIO_BLK_F_SEG_MAX,
 206                                offsetof(struct virtio_blk_config, seg_max),
 207                                &sg_elems);
 208        if (err)
 209                sg_elems = 1;
 210
 211        /* We need an extra sg elements at head and tail. */
 212        sg_elems += 2;
 213        vdev->priv = vblk = kmalloc(sizeof(*vblk) +
 214                                    sizeof(vblk->sg[0]) * sg_elems, GFP_KERNEL);
 215        if (!vblk) {
 216                err = -ENOMEM;
 217                goto out;
 218        }
 219
 220        INIT_LIST_HEAD(&vblk->reqs);
 221        spin_lock_init(&vblk->lock);
 222        vblk->vdev = vdev;
 223        vblk->sg_elems = sg_elems;
 224        sg_init_table(vblk->sg, vblk->sg_elems);
 225
 226        /* We expect one virtqueue, for output. */
 227        vblk->vq = vdev->config->find_vq(vdev, 0, blk_done);
 228        if (IS_ERR(vblk->vq)) {
 229                err = PTR_ERR(vblk->vq);
 230                goto out_free_vblk;
 231        }
 232
 233        vblk->pool = mempool_create_kmalloc_pool(1,sizeof(struct virtblk_req));
 234        if (!vblk->pool) {
 235                err = -ENOMEM;
 236                goto out_free_vq;
 237        }
 238
 239        /* FIXME: How many partitions?  How long is a piece of string? */
 240        vblk->disk = alloc_disk(1 << PART_BITS);
 241        if (!vblk->disk) {
 242                err = -ENOMEM;
 243                goto out_mempool;
 244        }
 245
 246        vblk->disk->queue = blk_init_queue(do_virtblk_request, &vblk->lock);
 247        if (!vblk->disk->queue) {
 248                err = -ENOMEM;
 249                goto out_put_disk;
 250        }
 251
 252        queue_flag_set_unlocked(QUEUE_FLAG_VIRT, vblk->disk->queue);
 253
 254        if (index < 26) {
 255                sprintf(vblk->disk->disk_name, "vd%c", 'a' + index % 26);
 256        } else if (index < (26 + 1) * 26) {
 257                sprintf(vblk->disk->disk_name, "vd%c%c",
 258                        'a' + index / 26 - 1, 'a' + index % 26);
 259        } else {
 260                const unsigned int m1 = (index / 26 - 1) / 26 - 1;
 261                const unsigned int m2 = (index / 26 - 1) % 26;
 262                const unsigned int m3 =  index % 26;
 263                sprintf(vblk->disk->disk_name, "vd%c%c%c",
 264                        'a' + m1, 'a' + m2, 'a' + m3);
 265        }
 266
 267        vblk->disk->major = major;
 268        vblk->disk->first_minor = index_to_minor(index);
 269        vblk->disk->private_data = vblk;
 270        vblk->disk->fops = &virtblk_fops;
 271        vblk->disk->driverfs_dev = &vdev->dev;
 272        index++;
 273
 274        /* If barriers are supported, tell block layer that queue is ordered */
 275        if (virtio_has_feature(vdev, VIRTIO_BLK_F_BARRIER))
 276                blk_queue_ordered(vblk->disk->queue, QUEUE_ORDERED_TAG, NULL);
 277
 278        /* If disk is read-only in the host, the guest should obey */
 279        if (virtio_has_feature(vdev, VIRTIO_BLK_F_RO))
 280                set_disk_ro(vblk->disk, 1);
 281
 282        /* Host must always specify the capacity. */
 283        vdev->config->get(vdev, offsetof(struct virtio_blk_config, capacity),
 284                          &cap, sizeof(cap));
 285
 286        /* If capacity is too big, truncate with warning. */
 287        if ((sector_t)cap != cap) {
 288                dev_warn(&vdev->dev, "Capacity %llu too large: truncating\n",
 289                         (unsigned long long)cap);
 290                cap = (sector_t)-1;
 291        }
 292        set_capacity(vblk->disk, cap);
 293
 294        /* We can handle whatever the host told us to handle. */
 295        blk_queue_max_phys_segments(vblk->disk->queue, vblk->sg_elems-2);
 296        blk_queue_max_hw_segments(vblk->disk->queue, vblk->sg_elems-2);
 297
 298        /* No real sector limit. */
 299        blk_queue_max_sectors(vblk->disk->queue, -1U);
 300
 301        /* Host can optionally specify maximum segment size and number of
 302         * segments. */
 303        err = virtio_config_val(vdev, VIRTIO_BLK_F_SIZE_MAX,
 304                                offsetof(struct virtio_blk_config, size_max),
 305                                &v);
 306        if (!err)
 307                blk_queue_max_segment_size(vblk->disk->queue, v);
 308        else
 309                blk_queue_max_segment_size(vblk->disk->queue, -1U);
 310
 311        /* Host can optionally specify the block size of the device */
 312        err = virtio_config_val(vdev, VIRTIO_BLK_F_BLK_SIZE,
 313                                offsetof(struct virtio_blk_config, blk_size),
 314                                &blk_size);
 315        if (!err)
 316                blk_queue_hardsect_size(vblk->disk->queue, blk_size);
 317
 318        add_disk(vblk->disk);
 319        return 0;
 320
 321out_put_disk:
 322        put_disk(vblk->disk);
 323out_mempool:
 324        mempool_destroy(vblk->pool);
 325out_free_vq:
 326        vdev->config->del_vq(vblk->vq);
 327out_free_vblk:
 328        kfree(vblk);
 329out:
 330        return err;
 331}
 332
 333static void virtblk_remove(struct virtio_device *vdev)
 334{
 335        struct virtio_blk *vblk = vdev->priv;
 336
 337        /* Nothing should be pending. */
 338        BUG_ON(!list_empty(&vblk->reqs));
 339
 340        /* Stop all the virtqueues. */
 341        vdev->config->reset(vdev);
 342
 343        del_gendisk(vblk->disk);
 344        blk_cleanup_queue(vblk->disk->queue);
 345        put_disk(vblk->disk);
 346        mempool_destroy(vblk->pool);
 347        vdev->config->del_vq(vblk->vq);
 348        kfree(vblk);
 349}
 350
 351static struct virtio_device_id id_table[] = {
 352        { VIRTIO_ID_BLOCK, VIRTIO_DEV_ANY_ID },
 353        { 0 },
 354};
 355
 356static unsigned int features[] = {
 357        VIRTIO_BLK_F_BARRIER, VIRTIO_BLK_F_SEG_MAX, VIRTIO_BLK_F_SIZE_MAX,
 358        VIRTIO_BLK_F_GEOMETRY, VIRTIO_BLK_F_RO, VIRTIO_BLK_F_BLK_SIZE,
 359};
 360
 361static struct virtio_driver virtio_blk = {
 362        .feature_table = features,
 363        .feature_table_size = ARRAY_SIZE(features),
 364        .driver.name =  KBUILD_MODNAME,
 365        .driver.owner = THIS_MODULE,
 366        .id_table =     id_table,
 367        .probe =        virtblk_probe,
 368        .remove =       __devexit_p(virtblk_remove),
 369};
 370
 371static int __init init(void)
 372{
 373        major = register_blkdev(0, "virtblk");
 374        if (major < 0)
 375                return major;
 376        return register_virtio_driver(&virtio_blk);
 377}
 378
 379static void __exit fini(void)
 380{
 381        unregister_blkdev(major, "virtblk");
 382        unregister_virtio_driver(&virtio_blk);
 383}
 384module_init(init);
 385module_exit(fini);
 386
 387MODULE_DEVICE_TABLE(virtio, id_table);
 388MODULE_DESCRIPTION("Virtio block driver");
 389MODULE_LICENSE("GPL");
 390