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