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