LXR linux/drivers/block/virtio

   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
  11static int major, index;
  12
  13struct 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
  35struct 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
  44static 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
  82static 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
 162static 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
 185static 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
 191static 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 */
 208static 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
 232static const struct block_device_operations virtblk_fops = {
 233        .locked_ioctl = virtblk_ioctl,
 234        .owner  = THIS_MODULE,
 235        .getgeo = virtblk_getgeo,
 236};
 237
 238static int index_to_minor(int index)
 239{
 240        return index << PART_BITS;
 241}
 242
 243static int __devinit virtblk_probe(struct virtio_device *vdev)
 244{
 245        struct virtio_blk *vblk;
 246        int err;
 247        u64 cap;
 248        u32 v;
 249        u32 blk_size, sg_elems;
 250
 251        if (index_to_minor(index) >= 1 << MINORBITS)
 252                return -ENOSPC;
 253
 254        /* We need to know how many segments before we allocate. */
 255        err = virtio_config_val(vdev, VIRTIO_BLK_F_SEG_MAX,
 256                                offsetof(struct virtio_blk_config, seg_max),
 257                                &sg_elems);
 258        if (err)
 259                sg_elems = 1;
 260
 261        /* We need an extra sg elements at head and tail. */
 262        sg_elems += 2;
 263        vdev->priv = vblk = kmalloc(sizeof(*vblk) +
 264                                    sizeof(vblk->sg[0]) * sg_elems, GFP_KERNEL);
 265        if (!vblk) {
 266                err = -ENOMEM;
 267                goto out;
 268        }
 269
 270        INIT_LIST_HEAD(&vblk->reqs);
 271        spin_lock_init(&vblk->lock);
 272        vblk->vdev = vdev;
 273        vblk->sg_elems = sg_elems;
 274        sg_init_table(vblk->sg, vblk->sg_elems);
 275
 276        /* We expect one virtqueue, for output. */
 277        vblk->vq = virtio_find_single_vq(vdev, blk_done, "requests");
 278        if (IS_ERR(vblk->vq)) {
 279                err = PTR_ERR(vblk->vq);
 280                goto out_free_vblk;
 281        }
 282
 283        vblk->pool = mempool_create_kmalloc_pool(1,sizeof(struct virtblk_req));
 284        if (!vblk->pool) {
 285                err = -ENOMEM;
 286                goto out_free_vq;
 287        }
 288
 289        /* FIXME: How many partitions?  How long is a piece of string? */
 290        vblk->disk = alloc_disk(1 << PART_BITS);
 291        if (!vblk->disk) {
 292                err = -ENOMEM;
 293                goto out_mempool;
 294        }
 295
 296        vblk->disk->queue = blk_init_queue(do_virtblk_request, &vblk->lock);
 297        if (!vblk->disk->queue) {
 298                err = -ENOMEM;
 299                goto out_put_disk;
 300        }
 301
 302        vblk->disk->queue->queuedata = vblk;
 303
 304        if (index < 26) {
 305                sprintf(vblk->disk->disk_name, "vd%c", 'a' + index % 26);
 306        } else if (index < (26 + 1) * 26) {
 307                sprintf(vblk->disk->disk_name, "vd%c%c",
 308                        'a' + index / 26 - 1, 'a' + index % 26);
 309        } else {
 310                const unsigned int m1 = (index / 26 - 1) / 26 - 1;
 311                const unsigned int m2 = (index / 26 - 1) % 26;
 312                const unsigned int m3 =  index % 26;
 313                sprintf(vblk->disk->disk_name, "vd%c%c%c",
 314                        'a' + m1, 'a' + m2, 'a' + m3);
 315        }
 316
 317        vblk->disk->major = major;
 318        vblk->disk->first_minor = index_to_minor(index);
 319        vblk->disk->private_data = vblk;
 320        vblk->disk->fops = &virtblk_fops;
 321        vblk->disk->driverfs_dev = &vdev->dev;
 322        index++;
 323
 324        /* If barriers are supported, tell block layer that queue is ordered */
 325        if (virtio_has_feature(vdev, VIRTIO_BLK_F_FLUSH))
 326                blk_queue_ordered(vblk->disk->queue, QUEUE_ORDERED_DRAIN_FLUSH,
 327                                  virtblk_prepare_flush);
 328        else if (virtio_has_feature(vdev, VIRTIO_BLK_F_BARRIER))
 329                blk_queue_ordered(vblk->disk->queue, QUEUE_ORDERED_TAG, NULL);
 330
 331        /* If disk is read-only in the host, the guest should obey */
 332        if (virtio_has_feature(vdev, VIRTIO_BLK_F_RO))
 333                set_disk_ro(vblk->disk, 1);
 334
 335        /* Host must always specify the capacity. */
 336        vdev->config->get(vdev, offsetof(struct virtio_blk_config, capacity),
 337                          &cap, sizeof(cap));
 338
 339        /* If capacity is too big, truncate with warning. */
 340        if ((sector_t)cap != cap) {
 341                dev_warn(&vdev->dev, "Capacity %llu too large: truncating\n",
 342                         (unsigned long long)cap);
 343                cap = (sector_t)-1;
 344        }
 345        set_capacity(vblk->disk, cap);
 346
 347        /* We can handle whatever the host told us to handle. */
 348        blk_queue_max_phys_segments(vblk->disk->queue, vblk->sg_elems-2);
 349        blk_queue_max_hw_segments(vblk->disk->queue, vblk->sg_elems-2);
 350
 351        /* No need to bounce any requests */
 352        blk_queue_bounce_limit(vblk->disk->queue, BLK_BOUNCE_ANY);
 353
 354        /* No real sector limit. */
 355        blk_queue_max_sectors(vblk->disk->queue, -1U);
 356
 357        /* Host can optionally specify maximum segment size and number of
 358         * segments. */
 359        err = virtio_config_val(vdev, VIRTIO_BLK_F_SIZE_MAX,
 360                                offsetof(struct virtio_blk_config, size_max),
 361                                &v);
 362        if (!err)
 363                blk_queue_max_segment_size(vblk->disk->queue, v);
 364        else
 365                blk_queue_max_segment_size(vblk->disk->queue, -1U);
 366
 367        /* Host can optionally specify the block size of the device */
 368        err = virtio_config_val(vdev, VIRTIO_BLK_F_BLK_SIZE,
 369                                offsetof(struct virtio_blk_config, blk_size),
 370                                &blk_size);
 371        if (!err)
 372                blk_queue_logical_block_size(vblk->disk->queue, blk_size);
 373
 374        add_disk(vblk->disk);
 375        return 0;
 376
 377out_put_disk:
 378        put_disk(vblk->disk);
 379out_mempool:
 380        mempool_destroy(vblk->pool);
 381out_free_vq:
 382        vdev->config->del_vqs(vdev);
 383out_free_vblk:
 384        kfree(vblk);
 385out:
 386        return err;
 387}
 388
 389static void __devexit virtblk_remove(struct virtio_device *vdev)
 390{
 391        struct virtio_blk *vblk = vdev->priv;
 392
 393        /* Nothing should be pending. */
 394        BUG_ON(!list_empty(&vblk->reqs));
 395
 396        /* Stop all the virtqueues. */
 397        vdev->config->reset(vdev);
 398
 399        del_gendisk(vblk->disk);
 400        blk_cleanup_queue(vblk->disk->queue);
 401        put_disk(vblk->disk);
 402        mempool_destroy(vblk->pool);
 403        vdev->config->del_vqs(vdev);
 404        kfree(vblk);
 405}
 406
 407static struct virtio_device_id id_table[] = {
 408        { VIRTIO_ID_BLOCK, VIRTIO_DEV_ANY_ID },
 409        { 0 },
 410};
 411
 412static unsigned int features[] = {
 413        VIRTIO_BLK_F_BARRIER, VIRTIO_BLK_F_SEG_MAX, VIRTIO_BLK_F_SIZE_MAX,
 414        VIRTIO_BLK_F_GEOMETRY, VIRTIO_BLK_F_RO, VIRTIO_BLK_F_BLK_SIZE,
 415        VIRTIO_BLK_F_SCSI, VIRTIO_BLK_F_FLUSH
 416};
 417
 418/*
 419 * virtio_blk causes spurious section mismatch warning by
 420 * simultaneously referring to a __devinit and a __devexit function.
 421 * Use __refdata to avoid this warning.
 422 */
 423static struct virtio_driver __refdata virtio_blk = {
 424        .feature_table = features,
 425        .feature_table_size = ARRAY_SIZE(features),
 426        .driver.name =  KBUILD_MODNAME,
 427        .driver.owner = THIS_MODULE,
 428        .id_table =     id_table,
 429        .probe =        virtblk_probe,
 430        .remove =       __devexit_p(virtblk_remove),
 431};
 432
 433static int __init init(void)
 434{
 435        major = register_blkdev(0, "virtblk");
 436        if (major < 0)
 437                return major;
 438        return register_virtio_driver(&virtio_blk);
 439}
 440
 441static void __exit fini(void)
 442{
 443        unregister_blkdev(major, "virtblk");
 444        unregister_virtio_driver(&virtio_blk);
 445}
 446module_init(init);
 447module_exit(fini);
 448
 449MODULE_DEVICE_TABLE(virtio, id_table);
 450MODULE_DESCRIPTION("Virtio block driver");
 451MODULE_LICENSE("GPL");
 452