drivers/block/nbd.c

   1 /*
   2  * Network block device - make block devices work over TCP
   3  *
   4  * Note that you can not swap over this thing, yet. Seems to work but
   5  * deadlocks sometimes - you can not swap over TCP in general.
   6  *
   7  * Copyright 1997-2000 Pavel Machek <pavel@ucw.cz>
   8  * Parts copyright 2001 Steven Whitehouse <steve@chygwyn.com>
   9  *
  10  * This file is released under GPLv2 or later.
  11  *
  12  * (part of code stolen from loop.c)
  13  */
  14
  15 #include <linux/major.h>
  16
  17 #include <linux/blkdev.h>
  18 #include <linux/module.h>
  19 #include <linux/init.h>
  20 #include <linux/sched.h>
  21 #include <linux/fs.h>
  22 #include <linux/bio.h>
  23 #include <linux/stat.h>
  24 #include <linux/errno.h>
  25 #include <linux/file.h>
  26 #include <linux/ioctl.h>
  27 #include <linux/compiler.h>
  28 #include <linux/err.h>
  29 #include <linux/kernel.h>
  30 #include <net/sock.h>
  31
  32 #include <asm/uaccess.h>
  33 #include <asm/system.h>
  34 #include <asm/types.h>
  35
  36 #include <linux/nbd.h>
  37
  38 #define LO_MAGIC 0x68797548
  39
  40 #ifdef NDEBUG
  41 #define dprintk(flags, fmt...)
  42 #else /* NDEBUG */
  43 #define dprintk(flags, fmt...) do { \
  44         if (debugflags & (flags)) printk(KERN_DEBUG fmt); \
  45 } while (0)
  46 #define DBG_IOCTL       0x0004
  47 #define DBG_INIT        0x0010
  48 #define DBG_EXIT        0x0020
  49 #define DBG_BLKDEV      0x0100
  50 #define DBG_RX          0x0200
  51 #define DBG_TX          0x0400
  52 static unsigned int debugflags;
  53 static unsigned int nbds_max = 16;
  54 #endif /* NDEBUG */
  55
  56 static struct nbd_device nbd_dev[MAX_NBD];
  57
  58 /*
  59  * Use just one lock (or at most 1 per NIC). Two arguments for this:
  60  * 1. Each NIC is essentially a synchronization point for all servers
  61  *    accessed through that NIC so there's no need to have more locks
  62  *    than NICs anyway.
  63  * 2. More locks lead to more "Dirty cache line bouncing" which will slow
  64  *    down each lock to the point where they're actually slower than just
  65  *    a single lock.
  66  * Thanks go to Jens Axboe and Al Viro for their LKML emails explaining this!
  67  */
  68 static DEFINE_SPINLOCK(nbd_lock);
  69
  70 #ifndef NDEBUG
  71 static const char *ioctl_cmd_to_ascii(int cmd)
  72 {
  73         switch (cmd) {
  74         case NBD_SET_SOCK: return "set-sock";
  75         case NBD_SET_BLKSIZE: return "set-blksize";
  76         case NBD_SET_SIZE: return "set-size";
  77         case NBD_DO_IT: return "do-it";
  78         case NBD_CLEAR_SOCK: return "clear-sock";
  79         case NBD_CLEAR_QUE: return "clear-que";
  80         case NBD_PRINT_DEBUG: return "print-debug";
  81         case NBD_SET_SIZE_BLOCKS: return "set-size-blocks";
  82         case NBD_DISCONNECT: return "disconnect";
  83         case BLKROSET: return "set-read-only";
  84         case BLKFLSBUF: return "flush-buffer-cache";
  85         }
  86         return "unknown";
  87 }
  88
  89 static const char *nbdcmd_to_ascii(int cmd)
  90 {
  91         switch (cmd) {
  92         case  NBD_CMD_READ: return "read";
  93         case NBD_CMD_WRITE: return "write";
  94         case  NBD_CMD_DISC: return "disconnect";
  95         }
  96         return "invalid";
  97 }
  98 #endif /* NDEBUG */
  99
 100 static void nbd_end_request(struct request *req)
 101 {
 102         int uptodate = (req->errors == 0) ? 1 : 0;
 103         request_queue_t *q = req->q;
 104         unsigned long flags;
 105
 106         dprintk(DBG_BLKDEV, "%s: request %p: %s\n", req->rq_disk->disk_name,
 107                         req, uptodate? "done": "failed");
 108
 109         spin_lock_irqsave(q->queue_lock, flags);
 110         if (!end_that_request_first(req, uptodate, req->nr_sectors)) {
 111                 end_that_request_last(req, uptodate);
 112         }
 113         spin_unlock_irqrestore(q->queue_lock, flags);
 114 }
 115
 116 /*
 117  *  Send or receive packet.
 118  */
 119 static int sock_xmit(struct socket *sock, int send, void *buf, int size,
 120                 int msg_flags)
 121 {
 122         int result;
 123         struct msghdr msg;
 124         struct kvec iov;
 125         unsigned long flags;
 126         sigset_t oldset;
 127
 128         /* Allow interception of SIGKILL only
 129          * Don't allow other signals to interrupt the transmission */
 130         spin_lock_irqsave(&current->sighand->siglock, flags);
 131         oldset = current->blocked;
 132         sigfillset(&current->blocked);
 133         sigdelsetmask(&current->blocked, sigmask(SIGKILL));
 134         recalc_sigpending();
 135         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 136
 137         do {
 138                 sock->sk->sk_allocation = GFP_NOIO;
 139                 iov.iov_base = buf;
 140                 iov.iov_len = size;
 141                 msg.msg_name = NULL;
 142                 msg.msg_namelen = 0;
 143                 msg.msg_control = NULL;
 144                 msg.msg_controllen = 0;
 145                 msg.msg_flags = msg_flags | MSG_NOSIGNAL;
 146
 147                 if (send)
 148                         result = kernel_sendmsg(sock, &msg, &iov, 1, size);
 149                 else
 150                         result = kernel_recvmsg(sock, &msg, &iov, 1, size, 0);
 151
 152                 if (signal_pending(current)) {
 153                         siginfo_t info;
 154                         spin_lock_irqsave(&current->sighand->siglock, flags);
 155                         printk(KERN_WARNING "nbd (pid %d: %s) got signal %d\n",
 156                                 current->pid, current->comm,
 157                                 dequeue_signal(current, &current->blocked, &info));
 158                         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 159                         result = -EINTR;
 160                         break;
 161                 }
 162
 163                 if (result <= 0) {
 164                         if (result == 0)
 165                                 result = -EPIPE; /* short read */
 166                         break;
 167                 }
 168                 size -= result;
 169                 buf += result;
 170         } while (size > 0);
 171
 172         spin_lock_irqsave(&current->sighand->siglock, flags);
 173         current->blocked = oldset;
 174         recalc_sigpending();
 175         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 176
 177         return result;
 178 }
 179
 180 static inline int sock_send_bvec(struct socket *sock, struct bio_vec *bvec,
 181                 int flags)
 182 {
 183         int result;
 184         void *kaddr = kmap(bvec->bv_page);
 185         result = sock_xmit(sock, 1, kaddr + bvec->bv_offset, bvec->bv_len,
 186                         flags);
 187         kunmap(bvec->bv_page);
 188         return result;
 189 }
 190
 191 static int nbd_send_req(struct nbd_device *lo, struct request *req)
 192 {
 193         int result, i, flags;
 194         struct nbd_request request;
 195         unsigned long size = req->nr_sectors << 9;
 196         struct socket *sock = lo->sock;
 197
 198         request.magic = htonl(NBD_REQUEST_MAGIC);
 199         request.type = htonl(nbd_cmd(req));
 200         request.from = cpu_to_be64((u64) req->sector << 9);
 201         request.len = htonl(size);
 202         memcpy(request.handle, &req, sizeof(req));
 203
 204         dprintk(DBG_TX, "%s: request %p: sending control (%s@%llu,%luB)\n",
 205                         lo->disk->disk_name, req,
 206                         nbdcmd_to_ascii(nbd_cmd(req)),
 207                         (unsigned long long)req->sector << 9,
 208                         req->nr_sectors << 9);
 209         result = sock_xmit(sock, 1, &request, sizeof(request),
 210                         (nbd_cmd(req) == NBD_CMD_WRITE)? MSG_MORE: 0);
 211         if (result <= 0) {
 212                 printk(KERN_ERR "%s: Send control failed (result %d)\n",
 213                                 lo->disk->disk_name, result);
 214                 goto error_out;
 215         }
 216
 217         if (nbd_cmd(req) == NBD_CMD_WRITE) {
 218                 struct bio *bio;
 219                 /*
 220                  * we are really probing at internals to determine
 221                  * whether to set MSG_MORE or not...
 222                  */
 223                 rq_for_each_bio(bio, req) {
 224                         struct bio_vec *bvec;
 225                         bio_for_each_segment(bvec, bio, i) {
 226                                 flags = 0;
 227                                 if ((i < (bio->bi_vcnt - 1)) || bio->bi_next)
 228                                         flags = MSG_MORE;
 229                                 dprintk(DBG_TX, "%s: request %p: sending %d bytes data\n",
 230                                                 lo->disk->disk_name, req,
 231                                                 bvec->bv_len);
 232                                 result = sock_send_bvec(sock, bvec, flags);
 233                                 if (result <= 0) {
 234                                         printk(KERN_ERR "%s: Send data failed (result %d)\n",
 235                                                         lo->disk->disk_name,
 236                                                         result);
 237                                         goto error_out;
 238                                 }
 239                         }
 240                 }
 241         }
 242         return 0;
 243
 244 error_out:
 245         return 1;
 246 }
 247
 248 static struct request *nbd_find_request(struct nbd_device *lo, char *handle)
 249 {
 250         struct request *req;
 251         struct list_head *tmp;
 252         struct request *xreq;
 253         int err;
 254
 255         memcpy(&xreq, handle, sizeof(xreq));
 256
 257         err = wait_event_interruptible(lo->active_wq, lo->active_req != xreq);
 258         if (unlikely(err))
 259                 goto out;
 260
 261         spin_lock(&lo->queue_lock);
 262         list_for_each(tmp, &lo->queue_head) {
 263                 req = list_entry(tmp, struct request, queuelist);
 264                 if (req != xreq)
 265                         continue;
 266                 list_del_init(&req->queuelist);
 267                 spin_unlock(&lo->queue_lock);
 268                 return req;
 269         }
 270         spin_unlock(&lo->queue_lock);
 271
 272         err = -ENOENT;
 273
 274 out:
 275         return ERR_PTR(err);
 276 }
 277
 278 static inline int sock_recv_bvec(struct socket *sock, struct bio_vec *bvec)
 279 {
 280         int result;
 281         void *kaddr = kmap(bvec->bv_page);
 282         result = sock_xmit(sock, 0, kaddr + bvec->bv_offset, bvec->bv_len,
 283                         MSG_WAITALL);
 284         kunmap(bvec->bv_page);
 285         return result;
 286 }
 287
 288 /* NULL returned = something went wrong, inform userspace */
 289 static struct request *nbd_read_stat(struct nbd_device *lo)
 290 {
 291         int result;
 292         struct nbd_reply reply;
 293         struct request *req;
 294         struct socket *sock = lo->sock;
 295
 296         reply.magic = 0;
 297         result = sock_xmit(sock, 0, &reply, sizeof(reply), MSG_WAITALL);
 298         if (result <= 0) {
 299                 printk(KERN_ERR "%s: Receive control failed (result %d)\n",
 300                                 lo->disk->disk_name, result);
 301                 goto harderror;
 302         }
 303         req = nbd_find_request(lo, reply.handle);
 304         if (unlikely(IS_ERR(req))) {
 305                 result = PTR_ERR(req);
 306                 if (result != -ENOENT)
 307                         goto harderror;
 308
 309                 printk(KERN_ERR "%s: Unexpected reply (%p)\n",
 310                                 lo->disk->disk_name, reply.handle);
 311                 result = -EBADR;
 312                 goto harderror;
 313         }
 314
 315         if (ntohl(reply.magic) != NBD_REPLY_MAGIC) {
 316                 printk(KERN_ERR "%s: Wrong magic (0x%lx)\n",
 317                                 lo->disk->disk_name,
 318                                 (unsigned long)ntohl(reply.magic));
 319                 result = -EPROTO;
 320                 goto harderror;
 321         }
 322         if (ntohl(reply.error)) {
 323                 printk(KERN_ERR "%s: Other side returned error (%d)\n",
 324                                 lo->disk->disk_name, ntohl(reply.error));
 325                 req->errors++;
 326                 return req;
 327         }
 328
 329         dprintk(DBG_RX, "%s: request %p: got reply\n",
 330                         lo->disk->disk_name, req);
 331         if (nbd_cmd(req) == NBD_CMD_READ) {
 332                 int i;
 333                 struct bio *bio;
 334                 rq_for_each_bio(bio, req) {
 335                         struct bio_vec *bvec;
 336                         bio_for_each_segment(bvec, bio, i) {
 337                                 result = sock_recv_bvec(sock, bvec);
 338                                 if (result <= 0) {
 339                                         printk(KERN_ERR "%s: Receive data failed (result %d)\n",
 340                                                         lo->disk->disk_name,
 341                                                         result);
 342                                         goto harderror;
 343                                 }
 344                                 dprintk(DBG_RX, "%s: request %p: got %d bytes data\n",
 345                                         lo->disk->disk_name, req, bvec->bv_len);
 346                         }
 347                 }
 348         }
 349         return req;
 350 harderror:
 351         lo->harderror = result;
 352         return NULL;
 353 }
 354
 355 static void nbd_do_it(struct nbd_device *lo)
 356 {
 357         struct request *req;
 358
 359         BUG_ON(lo->magic != LO_MAGIC);
 360
 361         while ((req = nbd_read_stat(lo)) != NULL)
 362                 nbd_end_request(req);
 363         return;
 364 }
 365
 366 static void nbd_clear_que(struct nbd_device *lo)
 367 {
 368         struct request *req;
 369
 370         BUG_ON(lo->magic != LO_MAGIC);
 371
 372         /*
 373          * Because we have set lo->sock to NULL under the tx_lock, all
 374          * modifications to the list must have completed by now.  For
 375          * the same reason, the active_req must be NULL.
 376          *
 377          * As a consequence, we don't need to take the spin lock while
 378          * purging the list here.
 379          */
 380         BUG_ON(lo->sock);
 381         BUG_ON(lo->active_req);
 382
 383         while (!list_empty(&lo->queue_head)) {
 384                 req = list_entry(lo->queue_head.next, struct request,
 385                                  queuelist);
 386                 list_del_init(&req->queuelist);
 387                 req->errors++;
 388                 nbd_end_request(req);
 389         }
 390 }
 391
 392 /*
 393  * We always wait for result of write, for now. It would be nice to make it optional
 394  * in future
 395  * if ((req->cmd == WRITE) && (lo->flags & NBD_WRITE_NOCHK))
 396  *   { printk( "Warning: Ignoring result!\n"); nbd_end_request( req ); }
 397  */
 398
 399 static void do_nbd_request(request_queue_t * q)
 400 {
 401         struct request *req;
 402
 403         while ((req = elv_next_request(q)) != NULL) {
 404                 struct nbd_device *lo;
 405
 406                 blkdev_dequeue_request(req);
 407                 dprintk(DBG_BLKDEV, "%s: request %p: dequeued (flags=%lx)\n",
 408                                 req->rq_disk->disk_name, req, req->flags);
 409
 410                 if (!(req->flags & REQ_CMD))
 411                         goto error_out;
 412
 413                 lo = req->rq_disk->private_data;
 414
 415                 BUG_ON(lo->magic != LO_MAGIC);
 416
 417                 nbd_cmd(req) = NBD_CMD_READ;
 418                 if (rq_data_dir(req) == WRITE) {
 419                         nbd_cmd(req) = NBD_CMD_WRITE;
 420                         if (lo->flags & NBD_READ_ONLY) {
 421                                 printk(KERN_ERR "%s: Write on read-only\n",
 422                                                 lo->disk->disk_name);
 423                                 goto error_out;
 424                         }
 425                 }
 426
 427                 req->errors = 0;
 428                 spin_unlock_irq(q->queue_lock);
 429
 430                 mutex_lock(&lo->tx_lock);
 431                 if (unlikely(!lo->sock)) {
 432                         mutex_unlock(&lo->tx_lock);
 433                         printk(KERN_ERR "%s: Attempted send on closed socket\n",
 434                                lo->disk->disk_name);
 435                         req->errors++;
 436                         nbd_end_request(req);
 437                         spin_lock_irq(q->queue_lock);
 438                         continue;
 439                 }
 440
 441                 lo->active_req = req;
 442
 443                 if (nbd_send_req(lo, req) != 0) {
 444                         printk(KERN_ERR "%s: Request send failed\n",
 445                                         lo->disk->disk_name);
 446                         req->errors++;
 447                         nbd_end_request(req);
 448                 } else {
 449                         spin_lock(&lo->queue_lock);
 450                         list_add(&req->queuelist, &lo->queue_head);
 451                         spin_unlock(&lo->queue_lock);
 452                 }
 453
 454                 lo->active_req = NULL;
 455                 mutex_unlock(&lo->tx_lock);
 456                 wake_up_all(&lo->active_wq);
 457
 458                 spin_lock_irq(q->queue_lock);
 459                 continue;
 460
 461 error_out:
 462                 req->errors++;
 463                 spin_unlock(q->queue_lock);
 464                 nbd_end_request(req);
 465                 spin_lock(q->queue_lock);
 466         }
 467         return;
 468 }
 469
 470 static int nbd_ioctl(struct inode *inode, struct file *file,
 471                      unsigned int cmd, unsigned long arg)
 472 {
 473         struct nbd_device *lo = inode->i_bdev->bd_disk->private_data;
 474         int error;
 475         struct request sreq ;
 476
 477         if (!capable(CAP_SYS_ADMIN))
 478                 return -EPERM;
 479
 480         BUG_ON(lo->magic != LO_MAGIC);
 481
 482         /* Anyone capable of this syscall can do *real bad* things */
 483         dprintk(DBG_IOCTL, "%s: nbd_ioctl cmd=%s(0x%x) arg=%lu\n",
 484                         lo->disk->disk_name, ioctl_cmd_to_ascii(cmd), cmd, arg);
 485
 486         switch (cmd) {
 487         case NBD_DISCONNECT:
 488                 printk(KERN_INFO "%s: NBD_DISCONNECT\n", lo->disk->disk_name);
 489                 sreq.flags = REQ_SPECIAL;
 490                 nbd_cmd(&sreq) = NBD_CMD_DISC;
 491                 /*
 492                  * Set these to sane values in case server implementation
 493                  * fails to check the request type first and also to keep
 494                  * debugging output cleaner.
 495                  */
 496                 sreq.sector = 0;
 497                 sreq.nr_sectors = 0;
 498                 if (!lo->sock)
 499                         return -EINVAL;
 500                 nbd_send_req(lo, &sreq);
 501                 return 0;
 502
 503         case NBD_CLEAR_SOCK:
 504                 error = 0;
 505                 mutex_lock(&lo->tx_lock);
 506                 lo->sock = NULL;
 507                 mutex_unlock(&lo->tx_lock);
 508                 file = lo->file;
 509                 lo->file = NULL;
 510                 nbd_clear_que(lo);
 511                 BUG_ON(!list_empty(&lo->queue_head));
 512                 if (file)
 513                         fput(file);
 514                 return error;
 515         case NBD_SET_SOCK:
 516                 if (lo->file)
 517                         return -EBUSY;
 518                 error = -EINVAL;
 519                 file = fget(arg);
 520                 if (file) {
 521                         inode = file->f_dentry->d_inode;
 522                         if (S_ISSOCK(inode->i_mode)) {
 523                                 lo->file = file;
 524                                 lo->sock = SOCKET_I(inode);
 525                                 error = 0;
 526                         } else {
 527                                 fput(file);
 528                         }
 529                 }
 530                 return error;
 531         case NBD_SET_BLKSIZE:
 532                 lo->blksize = arg;
 533                 lo->bytesize &= ~(lo->blksize-1);
 534                 inode->i_bdev->bd_inode->i_size = lo->bytesize;
 535                 set_blocksize(inode->i_bdev, lo->blksize);
 536                 set_capacity(lo->disk, lo->bytesize >> 9);
 537                 return 0;
 538         case NBD_SET_SIZE:
 539                 lo->bytesize = arg & ~(lo->blksize-1);
 540                 inode->i_bdev->bd_inode->i_size = lo->bytesize;
 541                 set_blocksize(inode->i_bdev, lo->blksize);
 542                 set_capacity(lo->disk, lo->bytesize >> 9);
 543                 return 0;
 544         case NBD_SET_SIZE_BLOCKS:
 545                 lo->bytesize = ((u64) arg) * lo->blksize;
 546                 inode->i_bdev->bd_inode->i_size = lo->bytesize;
 547                 set_blocksize(inode->i_bdev, lo->blksize);
 548                 set_capacity(lo->disk, lo->bytesize >> 9);
 549                 return 0;
 550         case NBD_DO_IT:
 551                 if (!lo->file)
 552                         return -EINVAL;
 553                 nbd_do_it(lo);
 554                 /* on return tidy up in case we have a signal */
 555                 /* Forcibly shutdown the socket causing all listeners
 556                  * to error
 557                  *
 558                  * FIXME: This code is duplicated from sys_shutdown, but
 559                  * there should be a more generic interface rather than
 560                  * calling socket ops directly here */
 561                 mutex_lock(&lo->tx_lock);
 562                 if (lo->sock) {
 563                         printk(KERN_WARNING "%s: shutting down socket\n",
 564                                 lo->disk->disk_name);
 565                         lo->sock->ops->shutdown(lo->sock,
 566                                 SEND_SHUTDOWN|RCV_SHUTDOWN);
 567                         lo->sock = NULL;
 568                 }
 569                 mutex_unlock(&lo->tx_lock);
 570                 file = lo->file;
 571                 lo->file = NULL;
 572                 nbd_clear_que(lo);
 573                 printk(KERN_WARNING "%s: queue cleared\n", lo->disk->disk_name);
 574                 if (file)
 575                         fput(file);
 576                 return lo->harderror;
 577         case NBD_CLEAR_QUE:
 578                 /*
 579                  * This is for compatibility only.  The queue is always cleared
 580                  * by NBD_DO_IT or NBD_CLEAR_SOCK.
 581                  */
 582                 BUG_ON(!lo->sock && !list_empty(&lo->queue_head));
 583                 return 0;
 584         case NBD_PRINT_DEBUG:
 585                 printk(KERN_INFO "%s: next = %p, prev = %p, head = %p\n",
 586                         inode->i_bdev->bd_disk->disk_name,
 587                         lo->queue_head.next, lo->queue_head.prev,
 588                         &lo->queue_head);
 589                 return 0;
 590         }
 591         return -EINVAL;
 592 }
 593
 594 static struct block_device_operations nbd_fops =
 595 {
 596         .owner =        THIS_MODULE,
 597         .ioctl =        nbd_ioctl,
 598 };
 599
 600 /*
 601  * And here should be modules and kernel interface
 602  *  (Just smiley confuses emacs :-)
 603  */
 604
 605 static int __init nbd_init(void)
 606 {
 607         int err = -ENOMEM;
 608         int i;
 609
 610         BUILD_BUG_ON(sizeof(struct nbd_request) != 28);
 611
 612         if (nbds_max > MAX_NBD) {
 613                 printk(KERN_CRIT "nbd: cannot allocate more than %u nbds; %u requested.\n", MAX_NBD,
 614                                 nbds_max);
 615                 return -EINVAL;
 616         }
 617
 618         for (i = 0; i < nbds_max; i++) {
 619                 struct gendisk *disk = alloc_disk(1);
 620                 if (!disk)
 621                         goto out;
 622                 nbd_dev[i].disk = disk;
 623                 /*
 624                  * The new linux 2.5 block layer implementation requires
 625                  * every gendisk to have its very own request_queue struct.
 626                  * These structs are big so we dynamically allocate them.
 627                  */
 628                 disk->queue = blk_init_queue(do_nbd_request, &nbd_lock);
 629                 if (!disk->queue) {
 630                         put_disk(disk);
 631                         goto out;
 632                 }
 633         }
 634
 635         if (register_blkdev(NBD_MAJOR, "nbd")) {
 636                 err = -EIO;
 637                 goto out;
 638         }
 639
 640         printk(KERN_INFO "nbd: registered device at major %d\n", NBD_MAJOR);
 641         dprintk(DBG_INIT, "nbd: debugflags=0x%x\n", debugflags);
 642
 643         for (i = 0; i < nbds_max; i++) {
 644                 struct gendisk *disk = nbd_dev[i].disk;
 645                 nbd_dev[i].file = NULL;
 646                 nbd_dev[i].magic = LO_MAGIC;
 647                 nbd_dev[i].flags = 0;
 648                 spin_lock_init(&nbd_dev[i].queue_lock);
 649                 INIT_LIST_HEAD(&nbd_dev[i].queue_head);
 650                 mutex_init(&nbd_dev[i].tx_lock);
 651                 init_waitqueue_head(&nbd_dev[i].active_wq);
 652                 nbd_dev[i].blksize = 1024;
 653                 nbd_dev[i].bytesize = 0x7ffffc00ULL << 10; /* 2TB */
 654                 disk->major = NBD_MAJOR;
 655                 disk->first_minor = i;
 656                 disk->fops = &nbd_fops;
 657                 disk->private_data = &nbd_dev[i];
 658                 disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO;
 659                 sprintf(disk->disk_name, "nbd%d", i);
 660                 set_capacity(disk, 0x7ffffc00ULL << 1); /* 2 TB */
 661                 add_disk(disk);
 662         }
 663
 664         return 0;
 665 out:
 666         while (i--) {
 667                 blk_cleanup_queue(nbd_dev[i].disk->queue);
 668                 put_disk(nbd_dev[i].disk);
 669         }
 670         return err;
 671 }
 672
 673 static void __exit nbd_cleanup(void)
 674 {
 675         int i;
 676         for (i = 0; i < nbds_max; i++) {
 677                 struct gendisk *disk = nbd_dev[i].disk;
 678                 nbd_dev[i].magic = 0;
 679                 if (disk) {
 680                         del_gendisk(disk);
 681                         blk_cleanup_queue(disk->queue);
 682                         put_disk(disk);
 683                 }
 684         }
 685         unregister_blkdev(NBD_MAJOR, "nbd");
 686         printk(KERN_INFO "nbd: unregistered device at major %d\n", NBD_MAJOR);
 687 }
 688
 689 module_init(nbd_init);
 690 module_exit(nbd_cleanup);
 691
 692 MODULE_DESCRIPTION("Network Block Device");
 693 MODULE_LICENSE("GPL");
 694
 695 module_param(nbds_max, int, 0444);
 696 MODULE_PARM_DESC(nbds_max, "How many network block devices to initialize.");
 697 #ifndef NDEBUG
 698 module_param(debugflags, int, 0644);
 699 MODULE_PARM_DESC(debugflags, "flags for controlling debug output");
 700 #endif