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