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  * (part of code stolen from loop.c)
  11  *
  12  * 97-3-25 compiled 0-th version, not yet tested it
  13  *   (it did not work, BTW) (later that day) HEY! it works!
  14  *   (bit later) hmm, not that much... 2:00am next day:
  15  *   yes, it works, but it gives something like 50kB/sec
  16  * 97-4-01 complete rewrite to make it possible for many requests at
  17  *   once to be processed
  18  * 97-4-11 Making protocol independent of endianity etc.
  19  * 97-9-13 Cosmetic changes
  20  * 98-5-13 Attempt to make 64-bit-clean on 64-bit machines
  21  * 99-1-11 Attempt to make 64-bit-clean on 32-bit machines <ankry@mif.pg.gda.pl>
  22  * 01-2-27 Fix to store proper blockcount for kernel (calculated using
  23  *   BLOCK_SIZE_BITS, not device blocksize) <aga@permonline.ru>
  24  * 01-3-11 Make nbd work with new Linux block layer code. It now supports
  25  *   plugging like all the other block devices. Also added in MSG_MORE to
  26  *   reduce number of partial TCP segments sent. <steve@chygwyn.com>
  27  * 01-12-6 Fix deadlock condition by making queue locks independent of
  28  *   the transmit lock. <steve@chygwyn.com>
  29  * 02-10-11 Allow hung xmit to be aborted via SIGKILL & various fixes.
  30  *   <Paul.Clements@SteelEye.com> <James.Bottomley@SteelEye.com>
  31  * 03-06-22 Make nbd work with new linux 2.5 block layer design. This fixes
  32  *   memory corruption from module removal and possible memory corruption
  33  *   from sending/receiving disk data. <ldl@aros.net>
  34  * 03-06-23 Cosmetic changes. <ldl@aros.net>
  35  * 03-06-23 Enhance diagnostics support. <ldl@aros.net>
  36  * 03-06-24 Remove unneeded blksize_bits field from nbd_device struct.
  37  *   <ldl@aros.net>
  38  * 03-06-24 Cleanup PARANOIA usage & code. <ldl@aros.net>
  39  * 04-02-19 Remove PARANOIA, plus various cleanups (Paul Clements)
  40  * possible FIXME: make set_sock / set_blksize / set_size / do_it one syscall
  41  * why not: would need access_ok and friends, would share yet another
  42  *          structure with userland
  43  */
  44
  45 #include <linux/major.h>
  46
  47 #include <linux/blkdev.h>
  48 #include <linux/module.h>
  49 #include <linux/init.h>
  50 #include <linux/sched.h>
  51 #include <linux/fs.h>
  52 #include <linux/bio.h>
  53 #include <linux/stat.h>
  54 #include <linux/errno.h>
  55 #include <linux/file.h>
  56 #include <linux/ioctl.h>
  57 #include <net/sock.h>
  58
  59 #include <linux/devfs_fs_kernel.h>
  60
  61 #include <asm/uaccess.h>
  62 #include <asm/types.h>
  63
  64 #include <linux/nbd.h>
  65
  66 #define LO_MAGIC 0x68797548
  67
  68 #ifdef NDEBUG
  69 #define dprintk(flags, fmt...)
  70 #else /* NDEBUG */
  71 #define dprintk(flags, fmt...) do { \
  72         if (debugflags & (flags)) printk(KERN_DEBUG fmt); \
  73 } while (0)
  74 #define DBG_IOCTL       0x0004
  75 #define DBG_INIT        0x0010
  76 #define DBG_EXIT        0x0020
  77 #define DBG_BLKDEV      0x0100
  78 #define DBG_RX          0x0200
  79 #define DBG_TX          0x0400
  80 static unsigned int debugflags;
  81 static unsigned int nbds_max = 16;
  82 #endif /* NDEBUG */
  83
  84 static struct nbd_device nbd_dev[MAX_NBD];
  85
  86 /*
  87  * Use just one lock (or at most 1 per NIC). Two arguments for this:
  88  * 1. Each NIC is essentially a synchronization point for all servers
  89  *    accessed through that NIC so there's no need to have more locks
  90  *    than NICs anyway.
  91  * 2. More locks lead to more "Dirty cache line bouncing" which will slow
  92  *    down each lock to the point where they're actually slower than just
  93  *    a single lock.
  94  * Thanks go to Jens Axboe and Al Viro for their LKML emails explaining this!
  95  */
  96 static DEFINE_SPINLOCK(nbd_lock);
  97
  98 #ifndef NDEBUG
  99 static const char *ioctl_cmd_to_ascii(int cmd)
 100 {
 101         switch (cmd) {
 102         case NBD_SET_SOCK: return "set-sock";
 103         case NBD_SET_BLKSIZE: return "set-blksize";
 104         case NBD_SET_SIZE: return "set-size";
 105         case NBD_DO_IT: return "do-it";
 106         case NBD_CLEAR_SOCK: return "clear-sock";
 107         case NBD_CLEAR_QUE: return "clear-que";
 108         case NBD_PRINT_DEBUG: return "print-debug";
 109         case NBD_SET_SIZE_BLOCKS: return "set-size-blocks";
 110         case NBD_DISCONNECT: return "disconnect";
 111         case BLKROSET: return "set-read-only";
 112         case BLKFLSBUF: return "flush-buffer-cache";
 113         }
 114         return "unknown";
 115 }
 116
 117 static const char *nbdcmd_to_ascii(int cmd)
 118 {
 119         switch (cmd) {
 120         case  NBD_CMD_READ: return "read";
 121         case NBD_CMD_WRITE: return "write";
 122         case  NBD_CMD_DISC: return "disconnect";
 123         }
 124         return "invalid";
 125 }
 126 #endif /* NDEBUG */
 127
 128 static void nbd_end_request(struct request *req)
 129 {
 130         int uptodate = (req->errors == 0) ? 1 : 0;
 131         request_queue_t *q = req->q;
 132         unsigned long flags;
 133
 134         dprintk(DBG_BLKDEV, "%s: request %p: %s\n", req->rq_disk->disk_name,
 135                         req, uptodate? "done": "failed");
 136
 137         spin_lock_irqsave(q->queue_lock, flags);
 138         if (!end_that_request_first(req, uptodate, req->nr_sectors)) {
 139                 end_that_request_last(req);
 140         }
 141         spin_unlock_irqrestore(q->queue_lock, flags);
 142 }
 143
 144 /*
 145  *  Send or receive packet.
 146  */
 147 static int sock_xmit(struct socket *sock, int send, void *buf, int size,
 148                 int msg_flags)
 149 {
 150         int result;
 151         struct msghdr msg;
 152         struct kvec iov;
 153         unsigned long flags;
 154         sigset_t oldset;
 155
 156         /* Allow interception of SIGKILL only
 157          * Don't allow other signals to interrupt the transmission */
 158         spin_lock_irqsave(&current->sighand->siglock, flags);
 159         oldset = current->blocked;
 160         sigfillset(&current->blocked);
 161         sigdelsetmask(&current->blocked, sigmask(SIGKILL));
 162         recalc_sigpending();
 163         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 164
 165         do {
 166                 sock->sk->sk_allocation = GFP_NOIO;
 167                 iov.iov_base = buf;
 168                 iov.iov_len = size;
 169                 msg.msg_name = NULL;
 170                 msg.msg_namelen = 0;
 171                 msg.msg_control = NULL;
 172                 msg.msg_controllen = 0;
 173                 msg.msg_namelen = 0;
 174                 msg.msg_flags = msg_flags | MSG_NOSIGNAL;
 175
 176                 if (send)
 177                         result = kernel_sendmsg(sock, &msg, &iov, 1, size);
 178                 else
 179                         result = kernel_recvmsg(sock, &msg, &iov, 1, size, 0);
 180
 181                 if (signal_pending(current)) {
 182                         siginfo_t info;
 183                         spin_lock_irqsave(&current->sighand->siglock, flags);
 184                         printk(KERN_WARNING "nbd (pid %d: %s) got signal %d\n",
 185                                 current->pid, current->comm,
 186                                 dequeue_signal(current, &current->blocked, &info));
 187                         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 188                         result = -EINTR;
 189                         break;
 190                 }
 191
 192                 if (result <= 0) {
 193                         if (result == 0)
 194                                 result = -EPIPE; /* short read */
 195                         break;
 196                 }
 197                 size -= result;
 198                 buf += result;
 199         } while (size > 0);
 200
 201         spin_lock_irqsave(&current->sighand->siglock, flags);
 202         current->blocked = oldset;
 203         recalc_sigpending();
 204         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 205
 206         return result;
 207 }
 208
 209 static inline int sock_send_bvec(struct socket *sock, struct bio_vec *bvec,
 210                 int flags)
 211 {
 212         int result;
 213         void *kaddr = kmap(bvec->bv_page);
 214         result = sock_xmit(sock, 1, kaddr + bvec->bv_offset, bvec->bv_len,
 215                         flags);
 216         kunmap(bvec->bv_page);
 217         return result;
 218 }
 219
 220 static int nbd_send_req(struct nbd_device *lo, struct request *req)
 221 {
 222         int result, i, flags;
 223         struct nbd_request request;
 224         unsigned long size = req->nr_sectors << 9;
 225         struct socket *sock = lo->sock;
 226
 227         request.magic = htonl(NBD_REQUEST_MAGIC);
 228         request.type = htonl(nbd_cmd(req));
 229         request.from = cpu_to_be64((u64) req->sector << 9);
 230         request.len = htonl(size);
 231         memcpy(request.handle, &req, sizeof(req));
 232
 233         down(&lo->tx_lock);
 234
 235         if (!sock || !lo->sock) {
 236                 printk(KERN_ERR "%s: Attempted send on closed socket\n",
 237                                 lo->disk->disk_name);
 238                 goto error_out;
 239         }
 240
 241         dprintk(DBG_TX, "%s: request %p: sending control (%s@%llu,%luB)\n",
 242                         lo->disk->disk_name, req,
 243                         nbdcmd_to_ascii(nbd_cmd(req)),
 244                         (unsigned long long)req->sector << 9,
 245                         req->nr_sectors << 9);
 246         result = sock_xmit(sock, 1, &request, sizeof(request),
 247                         (nbd_cmd(req) == NBD_CMD_WRITE)? MSG_MORE: 0);
 248         if (result <= 0) {
 249                 printk(KERN_ERR "%s: Send control failed (result %d)\n",
 250                                 lo->disk->disk_name, result);
 251                 goto error_out;
 252         }
 253
 254         if (nbd_cmd(req) == NBD_CMD_WRITE) {
 255                 struct bio *bio;
 256                 /*
 257                  * we are really probing at internals to determine
 258                  * whether to set MSG_MORE or not...
 259                  */
 260                 rq_for_each_bio(bio, req) {
 261                         struct bio_vec *bvec;
 262                         bio_for_each_segment(bvec, bio, i) {
 263                                 flags = 0;
 264                                 if ((i < (bio->bi_vcnt - 1)) || bio->bi_next)
 265                                         flags = MSG_MORE;
 266                                 dprintk(DBG_TX, "%s: request %p: sending %d bytes data\n",
 267                                                 lo->disk->disk_name, req,
 268                                                 bvec->bv_len);
 269                                 result = sock_send_bvec(sock, bvec, flags);
 270                                 if (result <= 0) {
 271                                         printk(KERN_ERR "%s: Send data failed (result %d)\n",
 272                                                         lo->disk->disk_name,
 273                                                         result);
 274                                         goto error_out;
 275                                 }
 276                         }
 277                 }
 278         }
 279         up(&lo->tx_lock);
 280         return 0;
 281
 282 error_out:
 283         up(&lo->tx_lock);
 284         return 1;
 285 }
 286
 287 static struct request *nbd_find_request(struct nbd_device *lo, char *handle)
 288 {
 289         struct request *req;
 290         struct list_head *tmp;
 291         struct request *xreq;
 292
 293         memcpy(&xreq, handle, sizeof(xreq));
 294
 295         spin_lock(&lo->queue_lock);
 296         list_for_each(tmp, &lo->queue_head) {
 297                 req = list_entry(tmp, struct request, queuelist);
 298                 if (req != xreq)
 299                         continue;
 300                 list_del_init(&req->queuelist);
 301                 spin_unlock(&lo->queue_lock);
 302                 return req;
 303         }
 304         spin_unlock(&lo->queue_lock);
 305         return NULL;
 306 }
 307
 308 static inline int sock_recv_bvec(struct socket *sock, struct bio_vec *bvec)
 309 {
 310         int result;
 311         void *kaddr = kmap(bvec->bv_page);
 312         result = sock_xmit(sock, 0, kaddr + bvec->bv_offset, bvec->bv_len,
 313                         MSG_WAITALL);
 314         kunmap(bvec->bv_page);
 315         return result;
 316 }
 317
 318 /* NULL returned = something went wrong, inform userspace */
 319 static struct request *nbd_read_stat(struct nbd_device *lo)
 320 {
 321         int result;
 322         struct nbd_reply reply;
 323         struct request *req;
 324         struct socket *sock = lo->sock;
 325
 326         reply.magic = 0;
 327         result = sock_xmit(sock, 0, &reply, sizeof(reply), MSG_WAITALL);
 328         if (result <= 0) {
 329                 printk(KERN_ERR "%s: Receive control failed (result %d)\n",
 330                                 lo->disk->disk_name, result);
 331                 goto harderror;
 332         }
 333         req = nbd_find_request(lo, reply.handle);
 334         if (req == NULL) {
 335                 printk(KERN_ERR "%s: Unexpected reply (%p)\n",
 336                                 lo->disk->disk_name, reply.handle);
 337                 result = -EBADR;
 338                 goto harderror;
 339         }
 340
 341         if (ntohl(reply.magic) != NBD_REPLY_MAGIC) {
 342                 printk(KERN_ERR "%s: Wrong magic (0x%lx)\n",
 343                                 lo->disk->disk_name,
 344                                 (unsigned long)ntohl(reply.magic));
 345                 result = -EPROTO;
 346                 goto harderror;
 347         }
 348         if (ntohl(reply.error)) {
 349                 printk(KERN_ERR "%s: Other side returned error (%d)\n",
 350                                 lo->disk->disk_name, ntohl(reply.error));
 351                 req->errors++;
 352                 return req;
 353         }
 354
 355         dprintk(DBG_RX, "%s: request %p: got reply\n",
 356                         lo->disk->disk_name, req);
 357         if (nbd_cmd(req) == NBD_CMD_READ) {
 358                 int i;
 359                 struct bio *bio;
 360                 rq_for_each_bio(bio, req) {
 361                         struct bio_vec *bvec;
 362                         bio_for_each_segment(bvec, bio, i) {
 363                                 result = sock_recv_bvec(sock, bvec);
 364                                 if (result <= 0) {
 365                                         printk(KERN_ERR "%s: Receive data failed (result %d)\n",
 366                                                         lo->disk->disk_name,
 367                                                         result);
 368                                         goto harderror;
 369                                 }
 370                                 dprintk(DBG_RX, "%s: request %p: got %d bytes data\n",
 371                                         lo->disk->disk_name, req, bvec->bv_len);
 372                         }
 373                 }
 374         }
 375         return req;
 376 harderror:
 377         lo->harderror = result;
 378         return NULL;
 379 }
 380
 381 static void nbd_do_it(struct nbd_device *lo)
 382 {
 383         struct request *req;
 384
 385         BUG_ON(lo->magic != LO_MAGIC);
 386
 387         while ((req = nbd_read_stat(lo)) != NULL)
 388                 nbd_end_request(req);
 389         return;
 390 }
 391
 392 static void nbd_clear_que(struct nbd_device *lo)
 393 {
 394         struct request *req;
 395
 396         BUG_ON(lo->magic != LO_MAGIC);
 397
 398         do {
 399                 req = NULL;
 400                 spin_lock(&lo->queue_lock);
 401                 if (!list_empty(&lo->queue_head)) {
 402                         req = list_entry(lo->queue_head.next, struct request, queuelist);
 403                         list_del_init(&req->queuelist);
 404                 }
 405                 spin_unlock(&lo->queue_lock);
 406                 if (req) {
 407                         req->errors++;
 408                         nbd_end_request(req);
 409                 }
 410         } while (req);
 411 }
 412
 413 /*
 414  * We always wait for result of write, for now. It would be nice to make it optional
 415  * in future
 416  * if ((req->cmd == WRITE) && (lo->flags & NBD_WRITE_NOCHK))
 417  *   { printk( "Warning: Ignoring result!\n"); nbd_end_request( req ); }
 418  */
 419
 420 static void do_nbd_request(request_queue_t * q)
 421 {
 422         struct request *req;
 423
 424         while ((req = elv_next_request(q)) != NULL) {
 425                 struct nbd_device *lo;
 426
 427                 blkdev_dequeue_request(req);
 428                 dprintk(DBG_BLKDEV, "%s: request %p: dequeued (flags=%lx)\n",
 429                                 req->rq_disk->disk_name, req, req->flags);
 430
 431                 if (!(req->flags & REQ_CMD))
 432                         goto error_out;
 433
 434                 lo = req->rq_disk->private_data;
 435
 436                 BUG_ON(lo->magic != LO_MAGIC);
 437
 438                 if (!lo->file) {
 439                         printk(KERN_ERR "%s: Request when not-ready\n",
 440                                         lo->disk->disk_name);
 441                         goto error_out;
 442                 }
 443                 nbd_cmd(req) = NBD_CMD_READ;
 444                 if (rq_data_dir(req) == WRITE) {
 445                         nbd_cmd(req) = NBD_CMD_WRITE;
 446                         if (lo->flags & NBD_READ_ONLY) {
 447                                 printk(KERN_ERR "%s: Write on read-only\n",
 448                                                 lo->disk->disk_name);
 449                                 goto error_out;
 450                         }
 451                 }
 452
 453                 req->errors = 0;
 454                 spin_unlock_irq(q->queue_lock);
 455
 456                 spin_lock(&lo->queue_lock);
 457
 458                 if (!lo->file) {
 459                         spin_unlock(&lo->queue_lock);
 460                         printk(KERN_ERR "%s: failed between accept and semaphore, file lost\n",
 461                                         lo->disk->disk_name);
 462                         req->errors++;
 463                         nbd_end_request(req);
 464                         spin_lock_irq(q->queue_lock);
 465                         continue;
 466                 }
 467
 468                 list_add(&req->queuelist, &lo->queue_head);
 469                 spin_unlock(&lo->queue_lock);
 470
 471                 if (nbd_send_req(lo, req) != 0) {
 472                         printk(KERN_ERR "%s: Request send failed\n",
 473                                         lo->disk->disk_name);
 474                         if (nbd_find_request(lo, (char *)&req) != NULL) {
 475                                 /* we still own req */
 476                                 req->errors++;
 477                                 nbd_end_request(req);
 478                         } else /* we're racing with nbd_clear_que */
 479                                 printk(KERN_DEBUG "nbd: can't find req\n");
 480                 }
 481
 482                 spin_lock_irq(q->queue_lock);
 483                 continue;
 484
 485 error_out:
 486                 req->errors++;
 487                 spin_unlock(q->queue_lock);
 488                 nbd_end_request(req);
 489                 spin_lock(q->queue_lock);
 490         }
 491         return;
 492 }
 493
 494 static int nbd_ioctl(struct inode *inode, struct file *file,
 495                      unsigned int cmd, unsigned long arg)
 496 {
 497         struct nbd_device *lo = inode->i_bdev->bd_disk->private_data;
 498         int error;
 499         struct request sreq ;
 500
 501         if (!capable(CAP_SYS_ADMIN))
 502                 return -EPERM;
 503
 504         BUG_ON(lo->magic != LO_MAGIC);
 505
 506         /* Anyone capable of this syscall can do *real bad* things */
 507         dprintk(DBG_IOCTL, "%s: nbd_ioctl cmd=%s(0x%x) arg=%lu\n",
 508                         lo->disk->disk_name, ioctl_cmd_to_ascii(cmd), cmd, arg);
 509
 510         switch (cmd) {
 511         case NBD_DISCONNECT:
 512                 printk(KERN_INFO "%s: NBD_DISCONNECT\n", lo->disk->disk_name);
 513                 sreq.flags = REQ_SPECIAL;
 514                 nbd_cmd(&sreq) = NBD_CMD_DISC;
 515                 /*
 516                  * Set these to sane values in case server implementation
 517                  * fails to check the request type first and also to keep
 518                  * debugging output cleaner.
 519                  */
 520                 sreq.sector = 0;
 521                 sreq.nr_sectors = 0;
 522                 if (!lo->sock)
 523                         return -EINVAL;
 524                 nbd_send_req(lo, &sreq);
 525                 return 0;
 526
 527         case NBD_CLEAR_SOCK:
 528                 error = 0;
 529                 down(&lo->tx_lock);
 530                 lo->sock = NULL;
 531                 up(&lo->tx_lock);
 532                 spin_lock(&lo->queue_lock);
 533                 file = lo->file;
 534                 lo->file = NULL;
 535                 spin_unlock(&lo->queue_lock);
 536                 nbd_clear_que(lo);
 537                 spin_lock(&lo->queue_lock);
 538                 if (!list_empty(&lo->queue_head)) {
 539                         printk(KERN_ERR "nbd: disconnect: some requests are in progress -> please try again.\n");
 540                         error = -EBUSY;
 541                 }
 542                 spin_unlock(&lo->queue_lock);
 543                 if (file)
 544                         fput(file);
 545                 return error;
 546         case NBD_SET_SOCK:
 547                 if (lo->file)
 548                         return -EBUSY;
 549                 error = -EINVAL;
 550                 file = fget(arg);
 551                 if (file) {
 552                         inode = file->f_dentry->d_inode;
 553                         if (S_ISSOCK(inode->i_mode)) {
 554                                 lo->file = file;
 555                                 lo->sock = SOCKET_I(inode);
 556                                 error = 0;
 557                         } else {
 558                                 fput(file);
 559                         }
 560                 }
 561                 return error;
 562         case NBD_SET_BLKSIZE:
 563                 lo->blksize = arg;
 564                 lo->bytesize &= ~(lo->blksize-1);
 565                 inode->i_bdev->bd_inode->i_size = lo->bytesize;
 566                 set_blocksize(inode->i_bdev, lo->blksize);
 567                 set_capacity(lo->disk, lo->bytesize >> 9);
 568                 return 0;
 569         case NBD_SET_SIZE:
 570                 lo->bytesize = arg & ~(lo->blksize-1);
 571                 inode->i_bdev->bd_inode->i_size = lo->bytesize;
 572                 set_blocksize(inode->i_bdev, lo->blksize);
 573                 set_capacity(lo->disk, lo->bytesize >> 9);
 574                 return 0;
 575         case NBD_SET_SIZE_BLOCKS:
 576                 lo->bytesize = ((u64) arg) * lo->blksize;
 577                 inode->i_bdev->bd_inode->i_size = lo->bytesize;
 578                 set_blocksize(inode->i_bdev, lo->blksize);
 579                 set_capacity(lo->disk, lo->bytesize >> 9);
 580                 return 0;
 581         case NBD_DO_IT:
 582                 if (!lo->file)
 583                         return -EINVAL;
 584                 nbd_do_it(lo);
 585                 /* on return tidy up in case we have a signal */
 586                 /* Forcibly shutdown the socket causing all listeners
 587                  * to error
 588                  *
 589                  * FIXME: This code is duplicated from sys_shutdown, but
 590                  * there should be a more generic interface rather than
 591                  * calling socket ops directly here */
 592                 down(&lo->tx_lock);
 593                 if (lo->sock) {
 594                         printk(KERN_WARNING "%s: shutting down socket\n",
 595                                 lo->disk->disk_name);
 596                         lo->sock->ops->shutdown(lo->sock,
 597                                 SEND_SHUTDOWN|RCV_SHUTDOWN);
 598                         lo->sock = NULL;
 599                 }
 600                 up(&lo->tx_lock);
 601                 spin_lock(&lo->queue_lock);
 602                 file = lo->file;
 603                 lo->file = NULL;
 604                 spin_unlock(&lo->queue_lock);
 605                 nbd_clear_que(lo);
 606                 printk(KERN_WARNING "%s: queue cleared\n", lo->disk->disk_name);
 607                 if (file)
 608                         fput(file);
 609                 return lo->harderror;
 610         case NBD_CLEAR_QUE:
 611                 down(&lo->tx_lock);
 612                 if (lo->sock) {
 613                         up(&lo->tx_lock);
 614                         return 0; /* probably should be error, but that would
 615                                    * break "nbd-client -d", so just return 0 */
 616                 }
 617                 up(&lo->tx_lock);
 618                 nbd_clear_que(lo);
 619                 return 0;
 620         case NBD_PRINT_DEBUG:
 621                 printk(KERN_INFO "%s: next = %p, prev = %p, head = %p\n",
 622                         inode->i_bdev->bd_disk->disk_name,
 623                         lo->queue_head.next, lo->queue_head.prev,
 624                         &lo->queue_head);
 625                 return 0;
 626         }
 627         return -EINVAL;
 628 }
 629
 630 static struct block_device_operations nbd_fops =
 631 {
 632         .owner =        THIS_MODULE,
 633         .ioctl =        nbd_ioctl,
 634 };
 635
 636 /*
 637  * And here should be modules and kernel interface
 638  *  (Just smiley confuses emacs :-)
 639  */
 640
 641 static int __init nbd_init(void)
 642 {
 643         int err = -ENOMEM;
 644         int i;
 645
 646         if (sizeof(struct nbd_request) != 28) {
 647                 printk(KERN_CRIT "nbd: sizeof nbd_request needs to be 28 in order to work!\n" );
 648                 return -EIO;
 649         }
 650
 651         if (nbds_max > MAX_NBD) {
 652                 printk(KERN_CRIT "nbd: cannot allocate more than %u nbds; %u requested.\n", MAX_NBD,
 653                                 nbds_max);
 654                 return -EINVAL;
 655         }
 656
 657         for (i = 0; i < nbds_max; i++) {
 658                 struct gendisk *disk = alloc_disk(1);
 659                 if (!disk)
 660                         goto out;
 661                 nbd_dev[i].disk = disk;
 662                 /*
 663                  * The new linux 2.5 block layer implementation requires
 664                  * every gendisk to have its very own request_queue struct.
 665                  * These structs are big so we dynamically allocate them.
 666                  */
 667                 disk->queue = blk_init_queue(do_nbd_request, &nbd_lock);
 668                 if (!disk->queue) {
 669                         put_disk(disk);
 670                         goto out;
 671                 }
 672         }
 673
 674         if (register_blkdev(NBD_MAJOR, "nbd")) {
 675                 err = -EIO;
 676                 goto out;
 677         }
 678
 679         printk(KERN_INFO "nbd: registered device at major %d\n", NBD_MAJOR);
 680         dprintk(DBG_INIT, "nbd: debugflags=0x%x\n", debugflags);
 681
 682         devfs_mk_dir("nbd");
 683         for (i = 0; i < nbds_max; i++) {
 684                 struct gendisk *disk = nbd_dev[i].disk;
 685                 nbd_dev[i].file = NULL;
 686                 nbd_dev[i].magic = LO_MAGIC;
 687                 nbd_dev[i].flags = 0;
 688                 spin_lock_init(&nbd_dev[i].queue_lock);
 689                 INIT_LIST_HEAD(&nbd_dev[i].queue_head);
 690                 init_MUTEX(&nbd_dev[i].tx_lock);
 691                 nbd_dev[i].blksize = 1024;
 692                 nbd_dev[i].bytesize = 0x7ffffc00ULL << 10; /* 2TB */
 693                 disk->major = NBD_MAJOR;
 694                 disk->first_minor = i;
 695                 disk->fops = &nbd_fops;
 696                 disk->private_data = &nbd_dev[i];
 697                 disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO;
 698                 sprintf(disk->disk_name, "nbd%d", i);
 699                 sprintf(disk->devfs_name, "nbd/%d", i);
 700                 set_capacity(disk, 0x7ffffc00ULL << 1); /* 2 TB */
 701                 add_disk(disk);
 702         }
 703
 704         return 0;
 705 out:
 706         while (i--) {
 707                 blk_cleanup_queue(nbd_dev[i].disk->queue);
 708                 put_disk(nbd_dev[i].disk);
 709         }
 710         return err;
 711 }
 712
 713 static void __exit nbd_cleanup(void)
 714 {
 715         int i;
 716         for (i = 0; i < nbds_max; i++) {
 717                 struct gendisk *disk = nbd_dev[i].disk;
 718                 nbd_dev[i].magic = 0;
 719                 if (disk) {
 720                         del_gendisk(disk);
 721                         blk_cleanup_queue(disk->queue);
 722                         put_disk(disk);
 723                 }
 724         }
 725         devfs_remove("nbd");
 726         unregister_blkdev(NBD_MAJOR, "nbd");
 727         printk(KERN_INFO "nbd: unregistered device at major %d\n", NBD_MAJOR);
 728 }
 729
 730 module_init(nbd_init);
 731 module_exit(nbd_cleanup);
 732
 733 MODULE_DESCRIPTION("Network Block Device");
 734 MODULE_LICENSE("GPL");
 735
 736 module_param(nbds_max, int, 0444);
 737 MODULE_PARM_DESC(nbds_max, "How many network block devices to initialize.");
 738 #ifndef NDEBUG
 739 module_param(debugflags, int, 0644);
 740 MODULE_PARM_DESC(debugflags, "flags for controlling debug output");
 741 #endif