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