drivers/block/virtio_blk.c

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