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