git.oblomov.eu Git - linux-2.6/blob - 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 #endif /* NDEBUG */
  54
  55 static unsigned int nbds_max = 16;
  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
 304         if (ntohl(reply.magic) != NBD_REPLY_MAGIC) {
 305                 printk(KERN_ERR "%s: Wrong magic (0x%lx)\n",
 306                                 lo->disk->disk_name,
 307                                 (unsigned long)ntohl(reply.magic));
 308                 result = -EPROTO;
 309                 goto harderror;
 310         }
 311
 312         req = nbd_find_request(lo, reply.handle);
 313         if (unlikely(IS_ERR(req))) {
 314                 result = PTR_ERR(req);
 315                 if (result != -ENOENT)
 316                         goto harderror;
 317
 318                 printk(KERN_ERR "%s: Unexpected reply (%p)\n",
 319                                 lo->disk->disk_name, reply.handle);
 320                 result = -EBADR;
 321                 goto harderror;
 322         }
 323
 324         if (ntohl(reply.error)) {
 325                 printk(KERN_ERR "%s: Other side returned error (%d)\n",
 326                                 lo->disk->disk_name, ntohl(reply.error));
 327                 req->errors++;
 328                 return req;
 329         }
 330
 331         dprintk(DBG_RX, "%s: request %p: got reply\n",
 332                         lo->disk->disk_name, req);
 333         if (nbd_cmd(req) == NBD_CMD_READ) {
 334                 int i;
 335                 struct bio *bio;
 336                 rq_for_each_bio(bio, req) {
 337                         struct bio_vec *bvec;
 338                         bio_for_each_segment(bvec, bio, i) {
 339                                 result = sock_recv_bvec(sock, bvec);
 340                                 if (result <= 0) {
 341                                         printk(KERN_ERR "%s: Receive data failed (result %d)\n",
 342                                                         lo->disk->disk_name,
 343                                                         result);
 344                                         req->errors++;
 345                                         return req;
 346                                 }
 347                                 dprintk(DBG_RX, "%s: request %p: got %d bytes data\n",
 348                                         lo->disk->disk_name, req, bvec->bv_len);
 349                         }
 350                 }
 351         }
 352         return req;
 353 harderror:
 354         lo->harderror = result;
 355         return NULL;
 356 }
 357
 358 static void nbd_do_it(struct nbd_device *lo)
 359 {
 360         struct request *req;
 361
 362         BUG_ON(lo->magic != LO_MAGIC);
 363
 364         while ((req = nbd_read_stat(lo)) != NULL)
 365                 nbd_end_request(req);
 366         return;
 367 }
 368
 369 static void nbd_clear_que(struct nbd_device *lo)
 370 {
 371         struct request *req;
 372
 373         BUG_ON(lo->magic != LO_MAGIC);
 374
 375         /*
 376          * Because we have set lo->sock to NULL under the tx_lock, all
 377          * modifications to the list must have completed by now.  For
 378          * the same reason, the active_req must be NULL.
 379          *
 380          * As a consequence, we don't need to take the spin lock while
 381          * purging the list here.
 382          */
 383         BUG_ON(lo->sock);
 384         BUG_ON(lo->active_req);
 385
 386         while (!list_empty(&lo->queue_head)) {
 387                 req = list_entry(lo->queue_head.next, struct request,
 388                                  queuelist);
 389                 list_del_init(&req->queuelist);
 390                 req->errors++;
 391                 nbd_end_request(req);
 392         }
 393 }
 394
 395 /*
 396  * We always wait for result of write, for now. It would be nice to make it optional
 397  * in future
 398  * if ((req->cmd == WRITE) && (lo->flags & NBD_WRITE_NOCHK))
 399  *   { printk( "Warning: Ignoring result!\n"); nbd_end_request( req ); }
 400  */
 401
 402 static void do_nbd_request(request_queue_t * q)
 403 {
 404         struct request *req;
 405
 406         while ((req = elv_next_request(q)) != NULL) {
 407                 struct nbd_device *lo;
 408
 409                 blkdev_dequeue_request(req);
 410                 dprintk(DBG_BLKDEV, "%s: request %p: dequeued (flags=%x)\n",
 411                                 req->rq_disk->disk_name, req, req->cmd_type);
 412
 413                 if (!blk_fs_request(req))
 414                         goto error_out;
 415
 416                 lo = req->rq_disk->private_data;
 417
 418                 BUG_ON(lo->magic != LO_MAGIC);
 419
 420                 nbd_cmd(req) = NBD_CMD_READ;
 421                 if (rq_data_dir(req) == WRITE) {
 422                         nbd_cmd(req) = NBD_CMD_WRITE;
 423                         if (lo->flags & NBD_READ_ONLY) {
 424                                 printk(KERN_ERR "%s: Write on read-only\n",
 425                                                 lo->disk->disk_name);
 426                                 goto error_out;
 427                         }
 428                 }
 429
 430                 req->errors = 0;
 431                 spin_unlock_irq(q->queue_lock);
 432
 433                 mutex_lock(&lo->tx_lock);
 434                 if (unlikely(!lo->sock)) {
 435                         mutex_unlock(&lo->tx_lock);
 436                         printk(KERN_ERR "%s: Attempted send on closed socket\n",
 437                                lo->disk->disk_name);
 438                         req->errors++;
 439                         nbd_end_request(req);
 440                         spin_lock_irq(q->queue_lock);
 441                         continue;
 442                 }
 443
 444                 lo->active_req = req;
 445
 446                 if (nbd_send_req(lo, req) != 0) {
 447                         printk(KERN_ERR "%s: Request send failed\n",
 448                                         lo->disk->disk_name);
 449                         req->errors++;
 450                         nbd_end_request(req);
 451                 } else {
 452                         spin_lock(&lo->queue_lock);
 453                         list_add(&req->queuelist, &lo->queue_head);
 454                         spin_unlock(&lo->queue_lock);
 455                 }
 456
 457                 lo->active_req = NULL;
 458                 mutex_unlock(&lo->tx_lock);
 459                 wake_up_all(&lo->active_wq);
 460
 461                 spin_lock_irq(q->queue_lock);
 462                 continue;
 463
 464 error_out:
 465                 req->errors++;
 466                 spin_unlock(q->queue_lock);
 467                 nbd_end_request(req);
 468                 spin_lock(q->queue_lock);
 469         }
 470         return;
 471 }
 472
 473 static int nbd_ioctl(struct inode *inode, struct file *file,
 474                      unsigned int cmd, unsigned long arg)
 475 {
 476         struct nbd_device *lo = inode->i_bdev->bd_disk->private_data;
 477         int error;
 478         struct request sreq ;
 479
 480         if (!capable(CAP_SYS_ADMIN))
 481                 return -EPERM;
 482
 483         BUG_ON(lo->magic != LO_MAGIC);
 484
 485         /* Anyone capable of this syscall can do *real bad* things */
 486         dprintk(DBG_IOCTL, "%s: nbd_ioctl cmd=%s(0x%x) arg=%lu\n",
 487                         lo->disk->disk_name, ioctl_cmd_to_ascii(cmd), cmd, arg);
 488
 489         switch (cmd) {
 490         case NBD_DISCONNECT:
 491                 printk(KERN_INFO "%s: NBD_DISCONNECT\n", lo->disk->disk_name);
 492                 sreq.cmd_type = REQ_TYPE_SPECIAL;
 493                 nbd_cmd(&sreq) = NBD_CMD_DISC;
 494                 /*
 495                  * Set these to sane values in case server implementation
 496                  * fails to check the request type first and also to keep
 497                  * debugging output cleaner.
 498                  */
 499                 sreq.sector = 0;
 500                 sreq.nr_sectors = 0;
 501                 if (!lo->sock)
 502                         return -EINVAL;
 503                 nbd_send_req(lo, &sreq);
 504                 return 0;
 505
 506         case NBD_CLEAR_SOCK:
 507                 error = 0;
 508                 mutex_lock(&lo->tx_lock);
 509                 lo->sock = NULL;
 510                 mutex_unlock(&lo->tx_lock);
 511                 file = lo->file;
 512                 lo->file = NULL;
 513                 nbd_clear_que(lo);
 514                 BUG_ON(!list_empty(&lo->queue_head));
 515                 if (file)
 516                         fput(file);
 517                 return error;
 518         case NBD_SET_SOCK:
 519                 if (lo->file)
 520                         return -EBUSY;
 521                 error = -EINVAL;
 522                 file = fget(arg);
 523                 if (file) {
 524                         inode = file->f_dentry->d_inode;
 525                         if (S_ISSOCK(inode->i_mode)) {
 526                                 lo->file = file;
 527                                 lo->sock = SOCKET_I(inode);
 528                                 error = 0;
 529                         } else {
 530                                 fput(file);
 531                         }
 532                 }
 533                 return error;
 534         case NBD_SET_BLKSIZE:
 535                 lo->blksize = arg;
 536                 lo->bytesize &= ~(lo->blksize-1);
 537                 inode->i_bdev->bd_inode->i_size = lo->bytesize;
 538                 set_blocksize(inode->i_bdev, lo->blksize);
 539                 set_capacity(lo->disk, lo->bytesize >> 9);
 540                 return 0;
 541         case NBD_SET_SIZE:
 542                 lo->bytesize = arg & ~(lo->blksize-1);
 543                 inode->i_bdev->bd_inode->i_size = lo->bytesize;
 544                 set_blocksize(inode->i_bdev, lo->blksize);
 545                 set_capacity(lo->disk, lo->bytesize >> 9);
 546                 return 0;
 547         case NBD_SET_SIZE_BLOCKS:
 548                 lo->bytesize = ((u64) arg) * lo->blksize;
 549                 inode->i_bdev->bd_inode->i_size = lo->bytesize;
 550                 set_blocksize(inode->i_bdev, lo->blksize);
 551                 set_capacity(lo->disk, lo->bytesize >> 9);
 552                 return 0;
 553         case NBD_DO_IT:
 554                 if (!lo->file)
 555                         return -EINVAL;
 556                 nbd_do_it(lo);
 557                 /* on return tidy up in case we have a signal */
 558                 /* Forcibly shutdown the socket causing all listeners
 559                  * to error
 560                  *
 561                  * FIXME: This code is duplicated from sys_shutdown, but
 562                  * there should be a more generic interface rather than
 563                  * calling socket ops directly here */
 564                 mutex_lock(&lo->tx_lock);
 565                 if (lo->sock) {
 566                         printk(KERN_WARNING "%s: shutting down socket\n",
 567                                 lo->disk->disk_name);
 568                         lo->sock->ops->shutdown(lo->sock,
 569                                 SEND_SHUTDOWN|RCV_SHUTDOWN);
 570                         lo->sock = NULL;
 571                 }
 572                 mutex_unlock(&lo->tx_lock);
 573                 file = lo->file;
 574                 lo->file = NULL;
 575                 nbd_clear_que(lo);
 576                 printk(KERN_WARNING "%s: queue cleared\n", lo->disk->disk_name);
 577                 if (file)
 578                         fput(file);
 579                 return lo->harderror;
 580         case NBD_CLEAR_QUE:
 581                 /*
 582                  * This is for compatibility only.  The queue is always cleared
 583                  * by NBD_DO_IT or NBD_CLEAR_SOCK.
 584                  */
 585                 BUG_ON(!lo->sock && !list_empty(&lo->queue_head));
 586                 return 0;
 587         case NBD_PRINT_DEBUG:
 588                 printk(KERN_INFO "%s: next = %p, prev = %p, head = %p\n",
 589                         inode->i_bdev->bd_disk->disk_name,
 590                         lo->queue_head.next, lo->queue_head.prev,
 591                         &lo->queue_head);
 592                 return 0;
 593         }
 594         return -EINVAL;
 595 }
 596
 597 static struct block_device_operations nbd_fops =
 598 {
 599         .owner =        THIS_MODULE,
 600         .ioctl =        nbd_ioctl,
 601 };
 602
 603 /*
 604  * And here should be modules and kernel interface
 605  *  (Just smiley confuses emacs :-)
 606  */
 607
 608 static int __init nbd_init(void)
 609 {
 610         int err = -ENOMEM;
 611         int i;
 612
 613         BUILD_BUG_ON(sizeof(struct nbd_request) != 28);
 614
 615         if (nbds_max > MAX_NBD) {
 616                 printk(KERN_CRIT "nbd: cannot allocate more than %u nbds; %u requested.\n", MAX_NBD,
 617                                 nbds_max);
 618                 return -EINVAL;
 619         }
 620
 621         for (i = 0; i < nbds_max; i++) {
 622                 struct gendisk *disk = alloc_disk(1);
 623                 if (!disk)
 624                         goto out;
 625                 nbd_dev[i].disk = disk;
 626                 /*
 627                  * The new linux 2.5 block layer implementation requires
 628                  * every gendisk to have its very own request_queue struct.
 629                  * These structs are big so we dynamically allocate them.
 630                  */
 631                 disk->queue = blk_init_queue(do_nbd_request, &nbd_lock);
 632                 if (!disk->queue) {
 633                         put_disk(disk);
 634                         goto out;
 635                 }
 636         }
 637
 638         if (register_blkdev(NBD_MAJOR, "nbd")) {
 639                 err = -EIO;
 640                 goto out;
 641         }
 642
 643         printk(KERN_INFO "nbd: registered device at major %d\n", NBD_MAJOR);
 644         dprintk(DBG_INIT, "nbd: debugflags=0x%x\n", debugflags);
 645
 646         for (i = 0; i < nbds_max; i++) {
 647                 struct gendisk *disk = nbd_dev[i].disk;
 648                 nbd_dev[i].file = NULL;
 649                 nbd_dev[i].magic = LO_MAGIC;
 650                 nbd_dev[i].flags = 0;
 651                 spin_lock_init(&nbd_dev[i].queue_lock);
 652                 INIT_LIST_HEAD(&nbd_dev[i].queue_head);
 653                 mutex_init(&nbd_dev[i].tx_lock);
 654                 init_waitqueue_head(&nbd_dev[i].active_wq);
 655                 nbd_dev[i].blksize = 1024;
 656                 nbd_dev[i].bytesize = 0x7ffffc00ULL << 10; /* 2TB */
 657                 disk->major = NBD_MAJOR;
 658                 disk->first_minor = i;
 659                 disk->fops = &nbd_fops;
 660                 disk->private_data = &nbd_dev[i];
 661                 disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO;
 662                 sprintf(disk->disk_name, "nbd%d", i);
 663                 set_capacity(disk, 0x7ffffc00ULL << 1); /* 2 TB */
 664                 add_disk(disk);
 665         }
 666
 667         return 0;
 668 out:
 669         while (i--) {
 670                 blk_cleanup_queue(nbd_dev[i].disk->queue);
 671                 put_disk(nbd_dev[i].disk);
 672         }
 673         return err;
 674 }
 675
 676 static void __exit nbd_cleanup(void)
 677 {
 678         int i;
 679         for (i = 0; i < nbds_max; i++) {
 680                 struct gendisk *disk = nbd_dev[i].disk;
 681                 nbd_dev[i].magic = 0;
 682                 if (disk) {
 683                         del_gendisk(disk);
 684                         blk_cleanup_queue(disk->queue);
 685                         put_disk(disk);
 686                 }
 687         }
 688         unregister_blkdev(NBD_MAJOR, "nbd");
 689         printk(KERN_INFO "nbd: unregistered device at major %d\n", NBD_MAJOR);
 690 }
 691
 692 module_init(nbd_init);
 693 module_exit(nbd_cleanup);
 694
 695 MODULE_DESCRIPTION("Network Block Device");
 696 MODULE_LICENSE("GPL");
 697
 698 module_param(nbds_max, int, 0444);
 699 MODULE_PARM_DESC(nbds_max, "How many network block devices to initialize.");
 700 #ifndef NDEBUG
 701 module_param(debugflags, int, 0644);
 702 MODULE_PARM_DESC(debugflags, "flags for controlling debug output");
 703 #endif