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