drivers/block/virtio_blk.c

   1 //#define DEBUG
   2 #include <linux/spinlock.h>
   3 #include <linux/slab.h>
   4 #include <linux/blkdev.h>
   5 #include <linux/hdreg.h>
   6 #include <linux/module.h>
   7 #include <linux/mutex.h>
   8 #include <linux/virtio.h>
   9 #include <linux/virtio_blk.h>
  10 #include <linux/scatterlist.h>
  11 #include <linux/string_helpers.h>
  12 #include <scsi/scsi_cmnd.h>
  13 #include <linux/idr.h>
  14
  15 #define PART_BITS 4
  16
  17 static int major;
  18 static DEFINE_IDA(vd_index_ida);
  19
  20 struct workqueue_struct *virtblk_wq;
  21
  22 struct virtio_blk
  23 {
  24         spinlock_t lock;
  25
  26         struct virtio_device *vdev;
  27         struct virtqueue *vq;
  28
  29         /* The disk structure for the kernel. */
  30         struct gendisk *disk;
  31
  32         /* Request tracking. */
  33         struct list_head reqs;
  34
  35         mempool_t *pool;
  36
  37         /* Process context for config space updates */
  38         struct work_struct config_work;
  39
  40         /* Lock for config space updates */
  41         struct mutex config_lock;
  42
  43         /* enable config space updates */
  44         bool config_enable;
  45
  46         /* What host tells us, plus 2 for header & tailer. */
  47         unsigned int sg_elems;
  48
  49         /* Ida index - used to track minor number allocations. */
  50         int index;
  51
  52         /* Scatterlist: can be too big for stack. */
  53         struct scatterlist sg[/*sg_elems*/];
  54 };
  55
  56 struct virtblk_req
  57 {
  58         struct list_head list;
  59         struct request *req;
  60         struct virtio_blk_outhdr out_hdr;
  61         struct virtio_scsi_inhdr in_hdr;
  62         u8 status;
  63 };
  64
  65 static void blk_done(struct virtqueue *vq)
  66 {
  67         struct virtio_blk *vblk = vq->vdev->priv;
  68         struct virtblk_req *vbr;
  69         unsigned int len;
  70         unsigned long flags;
  71
  72         spin_lock_irqsave(&vblk->lock, flags);
  73         while ((vbr = virtqueue_get_buf(vblk->vq, &len)) != NULL) {
  74                 int error;
  75
  76                 switch (vbr->status) {
  77                 case VIRTIO_BLK_S_OK:
  78                         error = 0;
  79                         break;
  80                 case VIRTIO_BLK_S_UNSUPP:
  81                         error = -ENOTTY;
  82                         break;
  83                 default:
  84                         error = -EIO;
  85                         break;
  86                 }
  87
  88                 switch (vbr->req->cmd_type) {
  89                 case REQ_TYPE_BLOCK_PC:
  90                         vbr->req->resid_len = vbr->in_hdr.residual;
  91                         vbr->req->sense_len = vbr->in_hdr.sense_len;
  92                         vbr->req->errors = vbr->in_hdr.errors;
  93                         break;
  94                 case REQ_TYPE_SPECIAL:
  95                         vbr->req->errors = (error != 0);
  96                         break;
  97                 default:
  98                         break;
  99                 }
 100
 101                 __blk_end_request_all(vbr->req, error);
 102                 list_del(&vbr->list);
 103                 mempool_free(vbr, vblk->pool);
 104         }
 105         /* In case queue is stopped waiting for more buffers. */
 106         blk_start_queue(vblk->disk->queue);
 107         spin_unlock_irqrestore(&vblk->lock, flags);
 108 }
 109
 110 static bool do_req(struct request_queue *q, struct virtio_blk *vblk,
 111                    struct request *req)
 112 {
 113         unsigned long num, out = 0, in = 0;
 114         struct virtblk_req *vbr;
 115
 116         vbr = mempool_alloc(vblk->pool, GFP_ATOMIC);
 117         if (!vbr)
 118                 /* When another request finishes we'll try again. */
 119                 return false;
 120
 121         vbr->req = req;
 122
 123         if (req->cmd_flags & REQ_FLUSH) {
 124                 vbr->out_hdr.type = VIRTIO_BLK_T_FLUSH;
 125                 vbr->out_hdr.sector = 0;
 126                 vbr->out_hdr.ioprio = req_get_ioprio(vbr->req);
 127         } else {
 128                 switch (req->cmd_type) {
 129                 case REQ_TYPE_FS:
 130                         vbr->out_hdr.type = 0;
 131                         vbr->out_hdr.sector = blk_rq_pos(vbr->req);
 132                         vbr->out_hdr.ioprio = req_get_ioprio(vbr->req);
 133                         break;
 134                 case REQ_TYPE_BLOCK_PC:
 135                         vbr->out_hdr.type = VIRTIO_BLK_T_SCSI_CMD;
 136                         vbr->out_hdr.sector = 0;
 137                         vbr->out_hdr.ioprio = req_get_ioprio(vbr->req);
 138                         break;
 139                 case REQ_TYPE_SPECIAL:
 140                         vbr->out_hdr.type = VIRTIO_BLK_T_GET_ID;
 141                         vbr->out_hdr.sector = 0;
 142                         vbr->out_hdr.ioprio = req_get_ioprio(vbr->req);
 143                         break;
 144                 default:
 145                         /* We don't put anything else in the queue. */
 146                         BUG();
 147                 }
 148         }
 149
 150         sg_set_buf(&vblk->sg[out++], &vbr->out_hdr, sizeof(vbr->out_hdr));
 151
 152         /*
 153          * If this is a packet command we need a couple of additional headers.
 154          * Behind the normal outhdr we put a segment with the scsi command
 155          * block, and before the normal inhdr we put the sense data and the
 156          * inhdr with additional status information before the normal inhdr.
 157          */
 158         if (vbr->req->cmd_type == REQ_TYPE_BLOCK_PC)
 159                 sg_set_buf(&vblk->sg[out++], vbr->req->cmd, vbr->req->cmd_len);
 160
 161         num = blk_rq_map_sg(q, vbr->req, vblk->sg + out);
 162
 163         if (vbr->req->cmd_type == REQ_TYPE_BLOCK_PC) {
 164                 sg_set_buf(&vblk->sg[num + out + in++], vbr->req->sense, SCSI_SENSE_BUFFERSIZE);
 165                 sg_set_buf(&vblk->sg[num + out + in++], &vbr->in_hdr,
 166                            sizeof(vbr->in_hdr));
 167         }
 168
 169         sg_set_buf(&vblk->sg[num + out + in++], &vbr->status,
 170                    sizeof(vbr->status));
 171
 172         if (num) {
 173                 if (rq_data_dir(vbr->req) == WRITE) {
 174                         vbr->out_hdr.type |= VIRTIO_BLK_T_OUT;
 175                         out += num;
 176                 } else {
 177                         vbr->out_hdr.type |= VIRTIO_BLK_T_IN;
 178                         in += num;
 179                 }
 180         }
 181
 182         if (virtqueue_add_buf(vblk->vq, vblk->sg, out, in, vbr, GFP_ATOMIC)<0) {
 183                 mempool_free(vbr, vblk->pool);
 184                 return false;
 185         }
 186
 187         list_add_tail(&vbr->list, &vblk->reqs);
 188         return true;
 189 }
 190
 191 static void do_virtblk_request(struct request_queue *q)
 192 {
 193         struct virtio_blk *vblk = q->queuedata;
 194         struct request *req;
 195         unsigned int issued = 0;
 196
 197         while ((req = blk_peek_request(q)) != NULL) {
 198                 BUG_ON(req->nr_phys_segments + 2 > vblk->sg_elems);
 199
 200                 /* If this request fails, stop queue and wait for something to
 201                    finish to restart it. */
 202                 if (!do_req(q, vblk, req)) {
 203                         blk_stop_queue(q);
 204                         break;
 205                 }
 206                 blk_start_request(req);
 207                 issued++;
 208         }
 209
 210         if (issued)
 211                 virtqueue_kick(vblk->vq);
 212 }
 213
 214 /* return id (s/n) string for *disk to *id_str
 215  */
 216 static int virtblk_get_id(struct gendisk *disk, char *id_str)
 217 {
 218         struct virtio_blk *vblk = disk->private_data;
 219         struct request *req;
 220         struct bio *bio;
 221         int err;
 222
 223         bio = bio_map_kern(vblk->disk->queue, id_str, VIRTIO_BLK_ID_BYTES,
 224                            GFP_KERNEL);
 225         if (IS_ERR(bio))
 226                 return PTR_ERR(bio);
 227
 228         req = blk_make_request(vblk->disk->queue, bio, GFP_KERNEL);
 229         if (IS_ERR(req)) {
 230                 bio_put(bio);
 231                 return PTR_ERR(req);
 232         }
 233
 234         req->cmd_type = REQ_TYPE_SPECIAL;
 235         err = blk_execute_rq(vblk->disk->queue, vblk->disk, req, false);
 236         blk_put_request(req);
 237
 238         return err;
 239 }
 240
 241 static int virtblk_ioctl(struct block_device *bdev, fmode_t mode,
 242                              unsigned int cmd, unsigned long data)
 243 {
 244         struct gendisk *disk = bdev->bd_disk;
 245         struct virtio_blk *vblk = disk->private_data;
 246
 247         /*
 248          * Only allow the generic SCSI ioctls if the host can support it.
 249          */
 250         if (!virtio_has_feature(vblk->vdev, VIRTIO_BLK_F_SCSI))
 251                 return -ENOTTY;
 252
 253         return scsi_cmd_blk_ioctl(bdev, mode, cmd,
 254                                   (void __user *)data);
 255 }
 256
 257 /* We provide getgeo only to please some old bootloader/partitioning tools */
 258 static int virtblk_getgeo(struct block_device *bd, struct hd_geometry *geo)
 259 {
 260         struct virtio_blk *vblk = bd->bd_disk->private_data;
 261         struct virtio_blk_geometry vgeo;
 262         int err;
 263
 264         /* see if the host passed in geometry config */
 265         err = virtio_config_val(vblk->vdev, VIRTIO_BLK_F_GEOMETRY,
 266                                 offsetof(struct virtio_blk_config, geometry),
 267                                 &vgeo);
 268
 269         if (!err) {
 270                 geo->heads = vgeo.heads;
 271                 geo->sectors = vgeo.sectors;
 272                 geo->cylinders = vgeo.cylinders;
 273         } else {
 274                 /* some standard values, similar to sd */
 275                 geo->heads = 1 << 6;
 276                 geo->sectors = 1 << 5;
 277                 geo->cylinders = get_capacity(bd->bd_disk) >> 11;
 278         }
 279         return 0;
 280 }
 281
 282 static const struct block_device_operations virtblk_fops = {
 283         .ioctl  = virtblk_ioctl,
 284         .owner  = THIS_MODULE,
 285         .getgeo = virtblk_getgeo,
 286 };
 287
 288 static int index_to_minor(int index)
 289 {
 290         return index << PART_BITS;
 291 }
 292
 293 static int minor_to_index(int minor)
 294 {
 295         return minor >> PART_BITS;
 296 }
 297
 298 static ssize_t virtblk_serial_show(struct device *dev,
 299                                 struct device_attribute *attr, char *buf)
 300 {
 301         struct gendisk *disk = dev_to_disk(dev);
 302         int err;
 303
 304         /* sysfs gives us a PAGE_SIZE buffer */
 305         BUILD_BUG_ON(PAGE_SIZE < VIRTIO_BLK_ID_BYTES);
 306
 307         buf[VIRTIO_BLK_ID_BYTES] = '\0';
 308         err = virtblk_get_id(disk, buf);
 309         if (!err)
 310                 return strlen(buf);
 311
 312         if (err == -EIO) /* Unsupported? Make it empty. */
 313                 return 0;
 314
 315         return err;
 316 }
 317 DEVICE_ATTR(serial, S_IRUGO, virtblk_serial_show, NULL);
 318
 319 static void virtblk_config_changed_work(struct work_struct *work)
 320 {
 321         struct virtio_blk *vblk =
 322                 container_of(work, struct virtio_blk, config_work);
 323         struct virtio_device *vdev = vblk->vdev;
 324         struct request_queue *q = vblk->disk->queue;
 325         char cap_str_2[10], cap_str_10[10];
 326         u64 capacity, size;
 327
 328         mutex_lock(&vblk->config_lock);
 329         if (!vblk->config_enable)
 330                 goto done;
 331
 332         /* Host must always specify the capacity. */
 333         vdev->config->get(vdev, offsetof(struct virtio_blk_config, capacity),
 334                           &capacity, sizeof(capacity));
 335
 336         /* If capacity is too big, truncate with warning. */
 337         if ((sector_t)capacity != capacity) {
 338                 dev_warn(&vdev->dev, "Capacity %llu too large: truncating\n",
 339                          (unsigned long long)capacity);
 340                 capacity = (sector_t)-1;
 341         }
 342
 343         size = capacity * queue_logical_block_size(q);
 344         string_get_size(size, STRING_UNITS_2, cap_str_2, sizeof(cap_str_2));
 345         string_get_size(size, STRING_UNITS_10, cap_str_10, sizeof(cap_str_10));
 346
 347         dev_notice(&vdev->dev,
 348                   "new size: %llu %d-byte logical blocks (%s/%s)\n",
 349                   (unsigned long long)capacity,
 350                   queue_logical_block_size(q),
 351                   cap_str_10, cap_str_2);
 352
 353         set_capacity(vblk->disk, capacity);
 354 done:
 355         mutex_unlock(&vblk->config_lock);
 356 }
 357
 358 static void virtblk_config_changed(struct virtio_device *vdev)
 359 {
 360         struct virtio_blk *vblk = vdev->priv;
 361
 362         queue_work(virtblk_wq, &vblk->config_work);
 363 }
 364
 365 static int init_vq(struct virtio_blk *vblk)
 366 {
 367         int err = 0;
 368
 369         /* We expect one virtqueue, for output. */
 370         vblk->vq = virtio_find_single_vq(vblk->vdev, blk_done, "requests");
 371         if (IS_ERR(vblk->vq))
 372                 err = PTR_ERR(vblk->vq);
 373
 374         return err;
 375 }
 376
 377 static int __devinit virtblk_probe(struct virtio_device *vdev)
 378 {
 379         struct virtio_blk *vblk;
 380         struct request_queue *q;
 381         int err, index;
 382         u64 cap;
 383         u32 v, blk_size, sg_elems, opt_io_size;
 384         u16 min_io_size;
 385         u8 physical_block_exp, alignment_offset;
 386
 387         err = ida_simple_get(&vd_index_ida, 0, minor_to_index(1 << MINORBITS),
 388                              GFP_KERNEL);
 389         if (err < 0)
 390                 goto out;
 391         index = err;
 392
 393         /* We need to know how many segments before we allocate. */
 394         err = virtio_config_val(vdev, VIRTIO_BLK_F_SEG_MAX,
 395                                 offsetof(struct virtio_blk_config, seg_max),
 396                                 &sg_elems);
 397
 398         /* We need at least one SG element, whatever they say. */
 399         if (err || !sg_elems)
 400                 sg_elems = 1;
 401
 402         /* We need an extra sg elements at head and tail. */
 403         sg_elems += 2;
 404         vdev->priv = vblk = kmalloc(sizeof(*vblk) +
 405                                     sizeof(vblk->sg[0]) * sg_elems, GFP_KERNEL);
 406         if (!vblk) {
 407                 err = -ENOMEM;
 408                 goto out_free_index;
 409         }
 410
 411         INIT_LIST_HEAD(&vblk->reqs);
 412         spin_lock_init(&vblk->lock);
 413         vblk->vdev = vdev;
 414         vblk->sg_elems = sg_elems;
 415         sg_init_table(vblk->sg, vblk->sg_elems);
 416         mutex_init(&vblk->config_lock);
 417         INIT_WORK(&vblk->config_work, virtblk_config_changed_work);
 418         vblk->config_enable = true;
 419
 420         err = init_vq(vblk);
 421         if (err)
 422                 goto out_free_vblk;
 423
 424         vblk->pool = mempool_create_kmalloc_pool(1,sizeof(struct virtblk_req));
 425         if (!vblk->pool) {
 426                 err = -ENOMEM;
 427                 goto out_free_vq;
 428         }
 429
 430         /* FIXME: How many partitions?  How long is a piece of string? */
 431         vblk->disk = alloc_disk(1 << PART_BITS);
 432         if (!vblk->disk) {
 433                 err = -ENOMEM;
 434                 goto out_mempool;
 435         }
 436
 437         q = vblk->disk->queue = blk_init_queue(do_virtblk_request, &vblk->lock);
 438         if (!q) {
 439                 err = -ENOMEM;
 440                 goto out_put_disk;
 441         }
 442
 443         q->queuedata = vblk;
 444
 445         if (index < 26) {
 446                 sprintf(vblk->disk->disk_name, "vd%c", 'a' + index % 26);
 447         } else if (index < (26 + 1) * 26) {
 448                 sprintf(vblk->disk->disk_name, "vd%c%c",
 449                         'a' + index / 26 - 1, 'a' + index % 26);
 450         } else {
 451                 const unsigned int m1 = (index / 26 - 1) / 26 - 1;
 452                 const unsigned int m2 = (index / 26 - 1) % 26;
 453                 const unsigned int m3 =  index % 26;
 454                 sprintf(vblk->disk->disk_name, "vd%c%c%c",
 455                         'a' + m1, 'a' + m2, 'a' + m3);
 456         }
 457
 458         vblk->disk->major = major;
 459         vblk->disk->first_minor = index_to_minor(index);
 460         vblk->disk->private_data = vblk;
 461         vblk->disk->fops = &virtblk_fops;
 462         vblk->disk->driverfs_dev = &vdev->dev;
 463         vblk->index = index;
 464
 465         /* configure queue flush support */
 466         if (virtio_has_feature(vdev, VIRTIO_BLK_F_FLUSH))
 467                 blk_queue_flush(q, REQ_FLUSH);
 468
 469         /* If disk is read-only in the host, the guest should obey */
 470         if (virtio_has_feature(vdev, VIRTIO_BLK_F_RO))
 471                 set_disk_ro(vblk->disk, 1);
 472
 473         /* Host must always specify the capacity. */
 474         vdev->config->get(vdev, offsetof(struct virtio_blk_config, capacity),
 475                           &cap, sizeof(cap));
 476
 477         /* If capacity is too big, truncate with warning. */
 478         if ((sector_t)cap != cap) {
 479                 dev_warn(&vdev->dev, "Capacity %llu too large: truncating\n",
 480                          (unsigned long long)cap);
 481                 cap = (sector_t)-1;
 482         }
 483         set_capacity(vblk->disk, cap);
 484
 485         /* We can handle whatever the host told us to handle. */
 486         blk_queue_max_segments(q, vblk->sg_elems-2);
 487
 488         /* No need to bounce any requests */
 489         blk_queue_bounce_limit(q, BLK_BOUNCE_ANY);
 490
 491         /* No real sector limit. */
 492         blk_queue_max_hw_sectors(q, -1U);
 493
 494         /* Host can optionally specify maximum segment size and number of
 495          * segments. */
 496         err = virtio_config_val(vdev, VIRTIO_BLK_F_SIZE_MAX,
 497                                 offsetof(struct virtio_blk_config, size_max),
 498                                 &v);
 499         if (!err)
 500                 blk_queue_max_segment_size(q, v);
 501         else
 502                 blk_queue_max_segment_size(q, -1U);
 503
 504         /* Host can optionally specify the block size of the device */
 505         err = virtio_config_val(vdev, VIRTIO_BLK_F_BLK_SIZE,
 506                                 offsetof(struct virtio_blk_config, blk_size),
 507                                 &blk_size);
 508         if (!err)
 509                 blk_queue_logical_block_size(q, blk_size);
 510         else
 511                 blk_size = queue_logical_block_size(q);
 512
 513         /* Use topology information if available */
 514         err = virtio_config_val(vdev, VIRTIO_BLK_F_TOPOLOGY,
 515                         offsetof(struct virtio_blk_config, physical_block_exp),
 516                         &physical_block_exp);
 517         if (!err && physical_block_exp)
 518                 blk_queue_physical_block_size(q,
 519                                 blk_size * (1 << physical_block_exp));
 520
 521         err = virtio_config_val(vdev, VIRTIO_BLK_F_TOPOLOGY,
 522                         offsetof(struct virtio_blk_config, alignment_offset),
 523                         &alignment_offset);
 524         if (!err && alignment_offset)
 525                 blk_queue_alignment_offset(q, blk_size * alignment_offset);
 526
 527         err = virtio_config_val(vdev, VIRTIO_BLK_F_TOPOLOGY,
 528                         offsetof(struct virtio_blk_config, min_io_size),
 529                         &min_io_size);
 530         if (!err && min_io_size)
 531                 blk_queue_io_min(q, blk_size * min_io_size);
 532
 533         err = virtio_config_val(vdev, VIRTIO_BLK_F_TOPOLOGY,
 534                         offsetof(struct virtio_blk_config, opt_io_size),
 535                         &opt_io_size);
 536         if (!err && opt_io_size)
 537                 blk_queue_io_opt(q, blk_size * opt_io_size);
 538
 539
 540         add_disk(vblk->disk);
 541         err = device_create_file(disk_to_dev(vblk->disk), &dev_attr_serial);
 542         if (err)
 543                 goto out_del_disk;
 544
 545         return 0;
 546
 547 out_del_disk:
 548         del_gendisk(vblk->disk);
 549         blk_cleanup_queue(vblk->disk->queue);
 550 out_put_disk:
 551         put_disk(vblk->disk);
 552 out_mempool:
 553         mempool_destroy(vblk->pool);
 554 out_free_vq:
 555         vdev->config->del_vqs(vdev);
 556 out_free_vblk:
 557         kfree(vblk);
 558 out_free_index:
 559         ida_simple_remove(&vd_index_ida, index);
 560 out:
 561         return err;
 562 }
 563
 564 static void __devexit virtblk_remove(struct virtio_device *vdev)
 565 {
 566         struct virtio_blk *vblk = vdev->priv;
 567         int index = vblk->index;
 568
 569         /* Prevent config work handler from accessing the device. */
 570         mutex_lock(&vblk->config_lock);
 571         vblk->config_enable = false;
 572         mutex_unlock(&vblk->config_lock);
 573
 574         /* Nothing should be pending. */
 575         BUG_ON(!list_empty(&vblk->reqs));
 576
 577         /* Stop all the virtqueues. */
 578         vdev->config->reset(vdev);
 579
 580         flush_work(&vblk->config_work);
 581
 582         del_gendisk(vblk->disk);
 583         blk_cleanup_queue(vblk->disk->queue);
 584         put_disk(vblk->disk);
 585         mempool_destroy(vblk->pool);
 586         vdev->config->del_vqs(vdev);
 587         kfree(vblk);
 588         ida_simple_remove(&vd_index_ida, index);
 589 }
 590
 591 #ifdef CONFIG_PM
 592 static int virtblk_freeze(struct virtio_device *vdev)
 593 {
 594         struct virtio_blk *vblk = vdev->priv;
 595
 596         /* Ensure we don't receive any more interrupts */
 597         vdev->config->reset(vdev);
 598
 599         /* Prevent config work handler from accessing the device. */
 600         mutex_lock(&vblk->config_lock);
 601         vblk->config_enable = false;
 602         mutex_unlock(&vblk->config_lock);
 603
 604         flush_work(&vblk->config_work);
 605
 606         spin_lock_irq(vblk->disk->queue->queue_lock);
 607         blk_stop_queue(vblk->disk->queue);
 608         spin_unlock_irq(vblk->disk->queue->queue_lock);
 609         blk_sync_queue(vblk->disk->queue);
 610
 611         vdev->config->del_vqs(vdev);
 612         return 0;
 613 }
 614
 615 static int virtblk_restore(struct virtio_device *vdev)
 616 {
 617         struct virtio_blk *vblk = vdev->priv;
 618         int ret;
 619
 620         vblk->config_enable = true;
 621         ret = init_vq(vdev->priv);
 622         if (!ret) {
 623                 spin_lock_irq(vblk->disk->queue->queue_lock);
 624                 blk_start_queue(vblk->disk->queue);
 625                 spin_unlock_irq(vblk->disk->queue->queue_lock);
 626         }
 627         return ret;
 628 }
 629 #endif
 630
 631 static const struct virtio_device_id id_table[] = {
 632         { VIRTIO_ID_BLOCK, VIRTIO_DEV_ANY_ID },
 633         { 0 },
 634 };
 635
 636 static unsigned int features[] = {
 637         VIRTIO_BLK_F_SEG_MAX, VIRTIO_BLK_F_SIZE_MAX, VIRTIO_BLK_F_GEOMETRY,
 638         VIRTIO_BLK_F_RO, VIRTIO_BLK_F_BLK_SIZE, VIRTIO_BLK_F_SCSI,
 639         VIRTIO_BLK_F_FLUSH, VIRTIO_BLK_F_TOPOLOGY
 640 };
 641
 642 /*
 643  * virtio_blk causes spurious section mismatch warning by
 644  * simultaneously referring to a __devinit and a __devexit function.
 645  * Use __refdata to avoid this warning.
 646  */
 647 static struct virtio_driver __refdata virtio_blk = {
 648         .feature_table          = features,
 649         .feature_table_size     = ARRAY_SIZE(features),
 650         .driver.name            = KBUILD_MODNAME,
 651         .driver.owner           = THIS_MODULE,
 652         .id_table               = id_table,
 653         .probe                  = virtblk_probe,
 654         .remove                 = __devexit_p(virtblk_remove),
 655         .config_changed         = virtblk_config_changed,
 656 #ifdef CONFIG_PM
 657         .freeze                 = virtblk_freeze,
 658         .restore                = virtblk_restore,
 659 #endif
 660 };
 661
 662 static int __init init(void)
 663 {
 664         int error;
 665
 666         virtblk_wq = alloc_workqueue("virtio-blk", 0, 0);
 667         if (!virtblk_wq)
 668                 return -ENOMEM;
 669
 670         major = register_blkdev(0, "virtblk");
 671         if (major < 0) {
 672                 error = major;
 673                 goto out_destroy_workqueue;
 674         }
 675
 676         error = register_virtio_driver(&virtio_blk);
 677         if (error)
 678                 goto out_unregister_blkdev;
 679         return 0;
 680
 681 out_unregister_blkdev:
 682         unregister_blkdev(major, "virtblk");
 683 out_destroy_workqueue:
 684         destroy_workqueue(virtblk_wq);
 685         return error;
 686 }
 687
 688 static void __exit fini(void)
 689 {
 690         unregister_blkdev(major, "virtblk");
 691         unregister_virtio_driver(&virtio_blk);
 692         destroy_workqueue(virtblk_wq);
 693 }
 694 module_init(init);
 695 module_exit(fini);
 696
 697 MODULE_DEVICE_TABLE(virtio, id_table);
 698 MODULE_DESCRIPTION("Virtio block driver");
 699 MODULE_LICENSE("GPL");