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