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