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                 if (blk_pc_request(vbr->req)) {
  69                         vbr->req->resid_len = vbr->in_hdr.residual;
  70                         vbr->req->sense_len = vbr->in_hdr.sense_len;
  71                         vbr->req->errors = vbr->in_hdr.errors;
  72                 }
  73                 if (blk_special_request(vbr->req))
  74                         vbr->req->errors = (error != 0);
  75
  76                 __blk_end_request_all(vbr->req, error);
  77                 list_del(&vbr->list);
  78                 mempool_free(vbr, vblk->pool);
  79         }
  80         /* In case queue is stopped waiting for more buffers. */
  81         blk_start_queue(vblk->disk->queue);
  82         spin_unlock_irqrestore(&vblk->lock, flags);
  83 }
  84
  85 static bool do_req(struct request_queue *q, struct virtio_blk *vblk,
  86                    struct request *req)
  87 {
  88         unsigned long num, out = 0, in = 0;
  89         struct virtblk_req *vbr;
  90
  91         vbr = mempool_alloc(vblk->pool, GFP_ATOMIC);
  92         if (!vbr)
  93                 /* When another request finishes we'll try again. */
  94                 return false;
  95
  96         vbr->req = req;
  97         switch (req->cmd_type) {
  98         case REQ_TYPE_FS:
  99                 vbr->out_hdr.type = 0;
 100                 vbr->out_hdr.sector = blk_rq_pos(vbr->req);
 101                 vbr->out_hdr.ioprio = req_get_ioprio(vbr->req);
 102                 break;
 103         case REQ_TYPE_BLOCK_PC:
 104                 vbr->out_hdr.type = VIRTIO_BLK_T_SCSI_CMD;
 105                 vbr->out_hdr.sector = 0;
 106                 vbr->out_hdr.ioprio = req_get_ioprio(vbr->req);
 107                 break;
 108         case REQ_TYPE_SPECIAL:
 109                 vbr->out_hdr.type = VIRTIO_BLK_T_GET_ID;
 110                 vbr->out_hdr.sector = 0;
 111                 vbr->out_hdr.ioprio = req_get_ioprio(vbr->req);
 112                 break;
 113         case REQ_TYPE_LINUX_BLOCK:
 114                 if (req->cmd[0] == REQ_LB_OP_FLUSH) {
 115                         vbr->out_hdr.type = VIRTIO_BLK_T_FLUSH;
 116                         vbr->out_hdr.sector = 0;
 117                         vbr->out_hdr.ioprio = req_get_ioprio(vbr->req);
 118                         break;
 119                 }
 120                 /*FALLTHRU*/
 121         default:
 122                 /* We don't put anything else in the queue. */
 123                 BUG();
 124         }
 125
 126         if (blk_barrier_rq(vbr->req))
 127                 vbr->out_hdr.type |= VIRTIO_BLK_T_BARRIER;
 128
 129         sg_set_buf(&vblk->sg[out++], &vbr->out_hdr, sizeof(vbr->out_hdr));
 130
 131         /*
 132          * If this is a packet command we need a couple of additional headers.
 133          * Behind the normal outhdr we put a segment with the scsi command
 134          * block, and before the normal inhdr we put the sense data and the
 135          * inhdr with additional status information before the normal inhdr.
 136          */
 137         if (blk_pc_request(vbr->req))
 138                 sg_set_buf(&vblk->sg[out++], vbr->req->cmd, vbr->req->cmd_len);
 139
 140         num = blk_rq_map_sg(q, vbr->req, vblk->sg + out);
 141
 142         if (blk_pc_request(vbr->req)) {
 143                 sg_set_buf(&vblk->sg[num + out + in++], vbr->req->sense, 96);
 144                 sg_set_buf(&vblk->sg[num + out + in++], &vbr->in_hdr,
 145                            sizeof(vbr->in_hdr));
 146         }
 147
 148         sg_set_buf(&vblk->sg[num + out + in++], &vbr->status,
 149                    sizeof(vbr->status));
 150
 151         if (num) {
 152                 if (rq_data_dir(vbr->req) == WRITE) {
 153                         vbr->out_hdr.type |= VIRTIO_BLK_T_OUT;
 154                         out += num;
 155                 } else {
 156                         vbr->out_hdr.type |= VIRTIO_BLK_T_IN;
 157                         in += num;
 158                 }
 159         }
 160
 161         if (virtqueue_add_buf(vblk->vq, vblk->sg, out, in, vbr) < 0) {
 162                 mempool_free(vbr, vblk->pool);
 163                 return false;
 164         }
 165
 166         list_add_tail(&vbr->list, &vblk->reqs);
 167         return true;
 168 }
 169
 170 static void do_virtblk_request(struct request_queue *q)
 171 {
 172         struct virtio_blk *vblk = q->queuedata;
 173         struct request *req;
 174         unsigned int issued = 0;
 175
 176         while ((req = blk_peek_request(q)) != NULL) {
 177                 BUG_ON(req->nr_phys_segments + 2 > vblk->sg_elems);
 178
 179                 /* If this request fails, stop queue and wait for something to
 180                    finish to restart it. */
 181                 if (!do_req(q, vblk, req)) {
 182                         blk_stop_queue(q);
 183                         break;
 184                 }
 185                 blk_start_request(req);
 186                 issued++;
 187         }
 188
 189         if (issued)
 190                 virtqueue_kick(vblk->vq);
 191 }
 192
 193 static void virtblk_prepare_flush(struct request_queue *q, struct request *req)
 194 {
 195         req->cmd_type = REQ_TYPE_LINUX_BLOCK;
 196         req->cmd[0] = REQ_LB_OP_FLUSH;
 197 }
 198
 199 /* return id (s/n) string for *disk to *id_str
 200  */
 201 static int virtblk_get_id(struct gendisk *disk, char *id_str)
 202 {
 203         struct virtio_blk *vblk = disk->private_data;
 204         struct request *req;
 205         struct bio *bio;
 206
 207         bio = bio_map_kern(vblk->disk->queue, id_str, VIRTIO_BLK_ID_BYTES,
 208                            GFP_KERNEL);
 209         if (IS_ERR(bio))
 210                 return PTR_ERR(bio);
 211
 212         req = blk_make_request(vblk->disk->queue, bio, GFP_KERNEL);
 213         if (IS_ERR(req)) {
 214                 bio_put(bio);
 215                 return PTR_ERR(req);
 216         }
 217
 218         req->cmd_type = REQ_TYPE_SPECIAL;
 219         return blk_execute_rq(vblk->disk->queue, vblk->disk, req, false);
 220 }
 221
 222 static int virtblk_ioctl(struct block_device *bdev, fmode_t mode,
 223                          unsigned cmd, unsigned long data)
 224 {
 225         struct gendisk *disk = bdev->bd_disk;
 226         struct virtio_blk *vblk = disk->private_data;
 227
 228         if (cmd == 0x56424944) { /* 'VBID' */
 229                 void __user *usr_data = (void __user *)data;
 230                 char id_str[VIRTIO_BLK_ID_BYTES];
 231                 int err;
 232
 233                 err = virtblk_get_id(disk, id_str);
 234                 if (!err && copy_to_user(usr_data, id_str, VIRTIO_BLK_ID_BYTES))
 235                         err = -EFAULT;
 236                 return err;
 237         }
 238         /*
 239          * Only allow the generic SCSI ioctls if the host can support it.
 240          */
 241         if (!virtio_has_feature(vblk->vdev, VIRTIO_BLK_F_SCSI))
 242                 return -ENOTTY;
 243
 244         return scsi_cmd_ioctl(disk->queue, disk, mode, cmd,
 245                               (void __user *)data);
 246 }
 247
 248 /* We provide getgeo only to please some old bootloader/partitioning tools */
 249 static int virtblk_getgeo(struct block_device *bd, struct hd_geometry *geo)
 250 {
 251         struct virtio_blk *vblk = bd->bd_disk->private_data;
 252         struct virtio_blk_geometry vgeo;
 253         int err;
 254
 255         /* see if the host passed in geometry config */
 256         err = virtio_config_val(vblk->vdev, VIRTIO_BLK_F_GEOMETRY,
 257                                 offsetof(struct virtio_blk_config, geometry),
 258                                 &vgeo);
 259
 260         if (!err) {
 261                 geo->heads = vgeo.heads;
 262                 geo->sectors = vgeo.sectors;
 263                 geo->cylinders = vgeo.cylinders;
 264         } else {
 265                 /* some standard values, similar to sd */
 266                 geo->heads = 1 << 6;
 267                 geo->sectors = 1 << 5;
 268                 geo->cylinders = get_capacity(bd->bd_disk) >> 11;
 269         }
 270         return 0;
 271 }
 272
 273 static const struct block_device_operations virtblk_fops = {
 274         .locked_ioctl = virtblk_ioctl,
 275         .owner  = THIS_MODULE,
 276         .getgeo = virtblk_getgeo,
 277 };
 278
 279 static int index_to_minor(int index)
 280 {
 281         return index << PART_BITS;
 282 }
 283
 284 static int __devinit virtblk_probe(struct virtio_device *vdev)
 285 {
 286         struct virtio_blk *vblk;
 287         struct request_queue *q;
 288         int err;
 289         u64 cap;
 290         u32 v, blk_size, sg_elems, opt_io_size;
 291         u16 min_io_size;
 292         u8 physical_block_exp, alignment_offset;
 293
 294         if (index_to_minor(index) >= 1 << MINORBITS)
 295                 return -ENOSPC;
 296
 297         /* We need to know how many segments before we allocate. */
 298         err = virtio_config_val(vdev, VIRTIO_BLK_F_SEG_MAX,
 299                                 offsetof(struct virtio_blk_config, seg_max),
 300                                 &sg_elems);
 301
 302         /* We need at least one SG element, whatever they say. */
 303         if (err || !sg_elems)
 304                 sg_elems = 1;
 305
 306         /* We need an extra sg elements at head and tail. */
 307         sg_elems += 2;
 308         vdev->priv = vblk = kmalloc(sizeof(*vblk) +
 309                                     sizeof(vblk->sg[0]) * sg_elems, GFP_KERNEL);
 310         if (!vblk) {
 311                 err = -ENOMEM;
 312                 goto out;
 313         }
 314
 315         INIT_LIST_HEAD(&vblk->reqs);
 316         spin_lock_init(&vblk->lock);
 317         vblk->vdev = vdev;
 318         vblk->sg_elems = sg_elems;
 319         sg_init_table(vblk->sg, vblk->sg_elems);
 320
 321         /* We expect one virtqueue, for output. */
 322         vblk->vq = virtio_find_single_vq(vdev, blk_done, "requests");
 323         if (IS_ERR(vblk->vq)) {
 324                 err = PTR_ERR(vblk->vq);
 325                 goto out_free_vblk;
 326         }
 327
 328         vblk->pool = mempool_create_kmalloc_pool(1,sizeof(struct virtblk_req));
 329         if (!vblk->pool) {
 330                 err = -ENOMEM;
 331                 goto out_free_vq;
 332         }
 333
 334         /* FIXME: How many partitions?  How long is a piece of string? */
 335         vblk->disk = alloc_disk(1 << PART_BITS);
 336         if (!vblk->disk) {
 337                 err = -ENOMEM;
 338                 goto out_mempool;
 339         }
 340
 341         q = vblk->disk->queue = blk_init_queue(do_virtblk_request, &vblk->lock);
 342         if (!q) {
 343                 err = -ENOMEM;
 344                 goto out_put_disk;
 345         }
 346
 347         q->queuedata = vblk;
 348
 349         if (index < 26) {
 350                 sprintf(vblk->disk->disk_name, "vd%c", 'a' + index % 26);
 351         } else if (index < (26 + 1) * 26) {
 352                 sprintf(vblk->disk->disk_name, "vd%c%c",
 353                         'a' + index / 26 - 1, 'a' + index % 26);
 354         } else {
 355                 const unsigned int m1 = (index / 26 - 1) / 26 - 1;
 356                 const unsigned int m2 = (index / 26 - 1) % 26;
 357                 const unsigned int m3 =  index % 26;
 358                 sprintf(vblk->disk->disk_name, "vd%c%c%c",
 359                         'a' + m1, 'a' + m2, 'a' + m3);
 360         }
 361
 362         vblk->disk->major = major;
 363         vblk->disk->first_minor = index_to_minor(index);
 364         vblk->disk->private_data = vblk;
 365         vblk->disk->fops = &virtblk_fops;
 366         vblk->disk->driverfs_dev = &vdev->dev;
 367         index++;
 368
 369         /* If barriers are supported, tell block layer that queue is ordered */
 370         if (virtio_has_feature(vdev, VIRTIO_BLK_F_FLUSH))
 371                 blk_queue_ordered(q, QUEUE_ORDERED_DRAIN_FLUSH,
 372                                   virtblk_prepare_flush);
 373         else if (virtio_has_feature(vdev, VIRTIO_BLK_F_BARRIER))
 374                 blk_queue_ordered(q, QUEUE_ORDERED_TAG, NULL);
 375
 376         /* If disk is read-only in the host, the guest should obey */
 377         if (virtio_has_feature(vdev, VIRTIO_BLK_F_RO))
 378                 set_disk_ro(vblk->disk, 1);
 379
 380         /* Host must always specify the capacity. */
 381         vdev->config->get(vdev, offsetof(struct virtio_blk_config, capacity),
 382                           &cap, sizeof(cap));
 383
 384         /* If capacity is too big, truncate with warning. */
 385         if ((sector_t)cap != cap) {
 386                 dev_warn(&vdev->dev, "Capacity %llu too large: truncating\n",
 387                          (unsigned long long)cap);
 388                 cap = (sector_t)-1;
 389         }
 390         set_capacity(vblk->disk, cap);
 391
 392         /* We can handle whatever the host told us to handle. */
 393         blk_queue_max_segments(q, vblk->sg_elems-2);
 394
 395         /* No need to bounce any requests */
 396         blk_queue_bounce_limit(q, BLK_BOUNCE_ANY);
 397
 398         /* No real sector limit. */
 399         blk_queue_max_hw_sectors(q, -1U);
 400
 401         /* Host can optionally specify maximum segment size and number of
 402          * segments. */
 403         err = virtio_config_val(vdev, VIRTIO_BLK_F_SIZE_MAX,
 404                                 offsetof(struct virtio_blk_config, size_max),
 405                                 &v);
 406         if (!err)
 407                 blk_queue_max_segment_size(q, v);
 408         else
 409                 blk_queue_max_segment_size(q, -1U);
 410
 411         /* Host can optionally specify the block size of the device */
 412         err = virtio_config_val(vdev, VIRTIO_BLK_F_BLK_SIZE,
 413                                 offsetof(struct virtio_blk_config, blk_size),
 414                                 &blk_size);
 415         if (!err)
 416                 blk_queue_logical_block_size(q, blk_size);
 417         else
 418                 blk_size = queue_logical_block_size(q);
 419
 420         /* Use topology information if available */
 421         err = virtio_config_val(vdev, VIRTIO_BLK_F_TOPOLOGY,
 422                         offsetof(struct virtio_blk_config, physical_block_exp),
 423                         &physical_block_exp);
 424         if (!err && physical_block_exp)
 425                 blk_queue_physical_block_size(q,
 426                                 blk_size * (1 << physical_block_exp));
 427
 428         err = virtio_config_val(vdev, VIRTIO_BLK_F_TOPOLOGY,
 429                         offsetof(struct virtio_blk_config, alignment_offset),
 430                         &alignment_offset);
 431         if (!err && alignment_offset)
 432                 blk_queue_alignment_offset(q, blk_size * alignment_offset);
 433
 434         err = virtio_config_val(vdev, VIRTIO_BLK_F_TOPOLOGY,
 435                         offsetof(struct virtio_blk_config, min_io_size),
 436                         &min_io_size);
 437         if (!err && min_io_size)
 438                 blk_queue_io_min(q, blk_size * min_io_size);
 439
 440         err = virtio_config_val(vdev, VIRTIO_BLK_F_TOPOLOGY,
 441                         offsetof(struct virtio_blk_config, opt_io_size),
 442                         &opt_io_size);
 443         if (!err && opt_io_size)
 444                 blk_queue_io_opt(q, blk_size * opt_io_size);
 445
 446
 447         add_disk(vblk->disk);
 448         return 0;
 449
 450 out_put_disk:
 451         put_disk(vblk->disk);
 452 out_mempool:
 453         mempool_destroy(vblk->pool);
 454 out_free_vq:
 455         vdev->config->del_vqs(vdev);
 456 out_free_vblk:
 457         kfree(vblk);
 458 out:
 459         return err;
 460 }
 461
 462 static void __devexit virtblk_remove(struct virtio_device *vdev)
 463 {
 464         struct virtio_blk *vblk = vdev->priv;
 465
 466         /* Nothing should be pending. */
 467         BUG_ON(!list_empty(&vblk->reqs));
 468
 469         /* Stop all the virtqueues. */
 470         vdev->config->reset(vdev);
 471
 472         del_gendisk(vblk->disk);
 473         blk_cleanup_queue(vblk->disk->queue);
 474         put_disk(vblk->disk);
 475         mempool_destroy(vblk->pool);
 476         vdev->config->del_vqs(vdev);
 477         kfree(vblk);
 478 }
 479
 480 static const struct virtio_device_id id_table[] = {
 481         { VIRTIO_ID_BLOCK, VIRTIO_DEV_ANY_ID },
 482         { 0 },
 483 };
 484
 485 static unsigned int features[] = {
 486         VIRTIO_BLK_F_BARRIER, VIRTIO_BLK_F_SEG_MAX, VIRTIO_BLK_F_SIZE_MAX,
 487         VIRTIO_BLK_F_GEOMETRY, VIRTIO_BLK_F_RO, VIRTIO_BLK_F_BLK_SIZE,
 488         VIRTIO_BLK_F_SCSI, VIRTIO_BLK_F_FLUSH, VIRTIO_BLK_F_TOPOLOGY
 489 };
 490
 491 /*
 492  * virtio_blk causes spurious section mismatch warning by
 493  * simultaneously referring to a __devinit and a __devexit function.
 494  * Use __refdata to avoid this warning.
 495  */
 496 static struct virtio_driver __refdata virtio_blk = {
 497         .feature_table = features,
 498         .feature_table_size = ARRAY_SIZE(features),
 499         .driver.name =  KBUILD_MODNAME,
 500         .driver.owner = THIS_MODULE,
 501         .id_table =     id_table,
 502         .probe =        virtblk_probe,
 503         .remove =       __devexit_p(virtblk_remove),
 504 };
 505
 506 static int __init init(void)
 507 {
 508         major = register_blkdev(0, "virtblk");
 509         if (major < 0)
 510                 return major;
 511         return register_virtio_driver(&virtio_blk);
 512 }
 513
 514 static void __exit fini(void)
 515 {
 516         unregister_blkdev(major, "virtblk");
 517         unregister_virtio_driver(&virtio_blk);
 518 }
 519 module_init(init);
 520 module_exit(fini);
 521
 522 MODULE_DEVICE_TABLE(virtio, id_table);
 523 MODULE_DESCRIPTION("Virtio block driver");
 524 MODULE_LICENSE("GPL");