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 struct request_queue *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 sigset_t blocked, oldset; 126 127 /* Allow interception of SIGKILL only 128 * Don't allow other signals to interrupt the transmission */ 129 siginitsetinv(&blocked, sigmask(SIGKILL)); 130 sigprocmask(SIG_SETMASK, &blocked, &oldset); 131 132 do { 133 sock->sk->sk_allocation = GFP_NOIO; 134 iov.iov_base = buf; 135 iov.iov_len = size; 136 msg.msg_name = NULL; 137 msg.msg_namelen = 0; 138 msg.msg_control = NULL; 139 msg.msg_controllen = 0; 140 msg.msg_flags = msg_flags | MSG_NOSIGNAL; 141 142 if (send) 143 result = kernel_sendmsg(sock, &msg, &iov, 1, size); 144 else 145 result = kernel_recvmsg(sock, &msg, &iov, 1, size, 0); 146 147 if (signal_pending(current)) { 148 siginfo_t info; 149 printk(KERN_WARNING "nbd (pid %d: %s) got signal %d\n", 150 current->pid, current->comm, 151 dequeue_signal_lock(current, ¤t->blocked, &info)); 152 result = -EINTR; 153 break; 154 } 155 156 if (result <= 0) { 157 if (result == 0) 158 result = -EPIPE; /* short read */ 159 break; 160 } 161 size -= result; 162 buf += result; 163 } while (size > 0); 164 165 sigprocmask(SIG_SETMASK, &oldset, NULL); 166 167 return result; 168 } 169 170 static inline int sock_send_bvec(struct socket *sock, struct bio_vec *bvec, 171 int flags) 172 { 173 int result; 174 void *kaddr = kmap(bvec->bv_page); 175 result = sock_xmit(sock, 1, kaddr + bvec->bv_offset, bvec->bv_len, 176 flags); 177 kunmap(bvec->bv_page); 178 return result; 179 } 180 181 static int nbd_send_req(struct nbd_device *lo, struct request *req) 182 { 183 int result, i, flags; 184 struct nbd_request request; 185 unsigned long size = req->nr_sectors << 9; 186 struct socket *sock = lo->sock; 187 188 request.magic = htonl(NBD_REQUEST_MAGIC); 189 request.type = htonl(nbd_cmd(req)); 190 request.from = cpu_to_be64((u64) req->sector << 9); 191 request.len = htonl(size); 192 memcpy(request.handle, &req, sizeof(req)); 193 194 dprintk(DBG_TX, "%s: request %p: sending control (%s@%llu,%luB)\n", 195 lo->disk->disk_name, req, 196 nbdcmd_to_ascii(nbd_cmd(req)), 197 (unsigned long long)req->sector << 9, 198 req->nr_sectors << 9); 199 result = sock_xmit(sock, 1, &request, sizeof(request), 200 (nbd_cmd(req) == NBD_CMD_WRITE)? MSG_MORE: 0); 201 if (result <= 0) { 202 printk(KERN_ERR "%s: Send control failed (result %d)\n", 203 lo->disk->disk_name, result); 204 goto error_out; 205 } 206 207 if (nbd_cmd(req) == NBD_CMD_WRITE) { 208 struct bio *bio; 209 /* 210 * we are really probing at internals to determine 211 * whether to set MSG_MORE or not... 212 */ 213 rq_for_each_bio(bio, req) { 214 struct bio_vec *bvec; 215 bio_for_each_segment(bvec, bio, i) { 216 flags = 0; 217 if ((i < (bio->bi_vcnt - 1)) || bio->bi_next) 218 flags = MSG_MORE; 219 dprintk(DBG_TX, "%s: request %p: sending %d bytes data\n", 220 lo->disk->disk_name, req, 221 bvec->bv_len); 222 result = sock_send_bvec(sock, bvec, flags); 223 if (result <= 0) { 224 printk(KERN_ERR "%s: Send data failed (result %d)\n", 225 lo->disk->disk_name, 226 result); 227 goto error_out; 228 } 229 } 230 } 231 } 232 return 0; 233 234 error_out: 235 return 1; 236 } 237 238 static struct request *nbd_find_request(struct nbd_device *lo, char *handle) 239 { 240 struct request *req; 241 struct list_head *tmp; 242 struct request *xreq; 243 int err; 244 245 memcpy(&xreq, handle, sizeof(xreq)); 246 247 err = wait_event_interruptible(lo->active_wq, lo->active_req != xreq); 248 if (unlikely(err)) 249 goto out; 250 251 spin_lock(&lo->queue_lock); 252 list_for_each(tmp, &lo->queue_head) { 253 req = list_entry(tmp, struct request, queuelist); 254 if (req != xreq) 255 continue; 256 list_del_init(&req->queuelist); 257 spin_unlock(&lo->queue_lock); 258 return req; 259 } 260 spin_unlock(&lo->queue_lock); 261 262 err = -ENOENT; 263 264 out: 265 return ERR_PTR(err); 266 } 267 268 static inline int sock_recv_bvec(struct socket *sock, struct bio_vec *bvec) 269 { 270 int result; 271 void *kaddr = kmap(bvec->bv_page); 272 result = sock_xmit(sock, 0, kaddr + bvec->bv_offset, bvec->bv_len, 273 MSG_WAITALL); 274 kunmap(bvec->bv_page); 275 return result; 276 } 277 278 /* NULL returned = something went wrong, inform userspace */ 279 static struct request *nbd_read_stat(struct nbd_device *lo) 280 { 281 int result; 282 struct nbd_reply reply; 283 struct request *req; 284 struct socket *sock = lo->sock; 285 286 reply.magic = 0; 287 result = sock_xmit(sock, 0, &reply, sizeof(reply), MSG_WAITALL); 288 if (result <= 0) { 289 printk(KERN_ERR "%s: Receive control failed (result %d)\n", 290 lo->disk->disk_name, result); 291 goto harderror; 292 } 293 294 if (ntohl(reply.magic) != NBD_REPLY_MAGIC) { 295 printk(KERN_ERR "%s: Wrong magic (0x%lx)\n", 296 lo->disk->disk_name, 297 (unsigned long)ntohl(reply.magic)); 298 result = -EPROTO; 299 goto harderror; 300 } 301 302 req = nbd_find_request(lo, reply.handle); 303 if (unlikely(IS_ERR(req))) { 304 result = PTR_ERR(req); 305 if (result != -ENOENT) 306 goto harderror; 307 308 printk(KERN_ERR "%s: Unexpected reply (%p)\n", 309 lo->disk->disk_name, reply.handle); 310 result = -EBADR; 311 goto harderror; 312 } 313 314 if (ntohl(reply.error)) { 315 printk(KERN_ERR "%s: Other side returned error (%d)\n", 316 lo->disk->disk_name, ntohl(reply.error)); 317 req->errors++; 318 return req; 319 } 320 321 dprintk(DBG_RX, "%s: request %p: got reply\n", 322 lo->disk->disk_name, req); 323 if (nbd_cmd(req) == NBD_CMD_READ) { 324 int i; 325 struct bio *bio; 326 rq_for_each_bio(bio, req) { 327 struct bio_vec *bvec; 328 bio_for_each_segment(bvec, bio, i) { 329 result = sock_recv_bvec(sock, bvec); 330 if (result <= 0) { 331 printk(KERN_ERR "%s: Receive data failed (result %d)\n", 332 lo->disk->disk_name, 333 result); 334 req->errors++; 335 return req; 336 } 337 dprintk(DBG_RX, "%s: request %p: got %d bytes data\n", 338 lo->disk->disk_name, req, bvec->bv_len); 339 } 340 } 341 } 342 return req; 343 harderror: 344 lo->harderror = result; 345 return NULL; 346 } 347 348 static ssize_t pid_show(struct gendisk *disk, char *page) 349 { 350 return sprintf(page, "%ld\n", 351 (long) ((struct nbd_device *)disk->private_data)->pid); 352 } 353 354 static struct disk_attribute pid_attr = { 355 .attr = { .name = "pid", .mode = S_IRUGO }, 356 .show = pid_show, 357 }; 358 359 static int nbd_do_it(struct nbd_device *lo) 360 { 361 struct request *req; 362 int ret; 363 364 BUG_ON(lo->magic != LO_MAGIC); 365 366 lo->pid = current->pid; 367 ret = sysfs_create_file(&lo->disk->kobj, &pid_attr.attr); 368 if (ret) { 369 printk(KERN_ERR "nbd: sysfs_create_file failed!"); 370 return ret; 371 } 372 373 while ((req = nbd_read_stat(lo)) != NULL) 374 nbd_end_request(req); 375 376 sysfs_remove_file(&lo->disk->kobj, &pid_attr.attr); 377 return 0; 378 } 379 380 static void nbd_clear_que(struct nbd_device *lo) 381 { 382 struct request *req; 383 384 BUG_ON(lo->magic != LO_MAGIC); 385 386 /* 387 * Because we have set lo->sock to NULL under the tx_lock, all 388 * modifications to the list must have completed by now. For 389 * the same reason, the active_req must be NULL. 390 * 391 * As a consequence, we don't need to take the spin lock while 392 * purging the list here. 393 */ 394 BUG_ON(lo->sock); 395 BUG_ON(lo->active_req); 396 397 while (!list_empty(&lo->queue_head)) { 398 req = list_entry(lo->queue_head.next, struct request, 399 queuelist); 400 list_del_init(&req->queuelist); 401 req->errors++; 402 nbd_end_request(req); 403 } 404 } 405 406 /* 407 * We always wait for result of write, for now. It would be nice to make it optional 408 * in future 409 * if ((rq_data_dir(req) == WRITE) && (lo->flags & NBD_WRITE_NOCHK)) 410 * { printk( "Warning: Ignoring result!\n"); nbd_end_request( req ); } 411 */ 412 413 static void do_nbd_request(struct request_queue * q) 414 { 415 struct request *req; 416 417 while ((req = elv_next_request(q)) != NULL) { 418 struct nbd_device *lo; 419 420 blkdev_dequeue_request(req); 421 dprintk(DBG_BLKDEV, "%s: request %p: dequeued (flags=%x)\n", 422 req->rq_disk->disk_name, req, req->cmd_type); 423 424 if (!blk_fs_request(req)) 425 goto error_out; 426 427 lo = req->rq_disk->private_data; 428 429 BUG_ON(lo->magic != LO_MAGIC); 430 431 nbd_cmd(req) = NBD_CMD_READ; 432 if (rq_data_dir(req) == WRITE) { 433 nbd_cmd(req) = NBD_CMD_WRITE; 434 if (lo->flags & NBD_READ_ONLY) { 435 printk(KERN_ERR "%s: Write on read-only\n", 436 lo->disk->disk_name); 437 goto error_out; 438 } 439 } 440 441 req->errors = 0; 442 spin_unlock_irq(q->queue_lock); 443 444 mutex_lock(&lo->tx_lock); 445 if (unlikely(!lo->sock)) { 446 mutex_unlock(&lo->tx_lock); 447 printk(KERN_ERR "%s: Attempted send on closed socket\n", 448 lo->disk->disk_name); 449 req->errors++; 450 nbd_end_request(req); 451 spin_lock_irq(q->queue_lock); 452 continue; 453 } 454 455 lo->active_req = req; 456 457 if (nbd_send_req(lo, req) != 0) { 458 printk(KERN_ERR "%s: Request send failed\n", 459 lo->disk->disk_name); 460 req->errors++; 461 nbd_end_request(req); 462 } else { 463 spin_lock(&lo->queue_lock); 464 list_add(&req->queuelist, &lo->queue_head); 465 spin_unlock(&lo->queue_lock); 466 } 467 468 lo->active_req = NULL; 469 mutex_unlock(&lo->tx_lock); 470 wake_up_all(&lo->active_wq); 471 472 spin_lock_irq(q->queue_lock); 473 continue; 474 475 error_out: 476 req->errors++; 477 spin_unlock(q->queue_lock); 478 nbd_end_request(req); 479 spin_lock(q->queue_lock); 480 } 481 return; 482 } 483 484 static int nbd_ioctl(struct inode *inode, struct file *file, 485 unsigned int cmd, unsigned long arg) 486 { 487 struct nbd_device *lo = inode->i_bdev->bd_disk->private_data; 488 int error; 489 struct request sreq ; 490 491 if (!capable(CAP_SYS_ADMIN)) 492 return -EPERM; 493 494 BUG_ON(lo->magic != LO_MAGIC); 495 496 /* Anyone capable of this syscall can do *real bad* things */ 497 dprintk(DBG_IOCTL, "%s: nbd_ioctl cmd=%s(0x%x) arg=%lu\n", 498 lo->disk->disk_name, ioctl_cmd_to_ascii(cmd), cmd, arg); 499 500 switch (cmd) { 501 case NBD_DISCONNECT: 502 printk(KERN_INFO "%s: NBD_DISCONNECT\n", lo->disk->disk_name); 503 sreq.cmd_type = REQ_TYPE_SPECIAL; 504 nbd_cmd(&sreq) = NBD_CMD_DISC; 505 /* 506 * Set these to sane values in case server implementation 507 * fails to check the request type first and also to keep 508 * debugging output cleaner. 509 */ 510 sreq.sector = 0; 511 sreq.nr_sectors = 0; 512 if (!lo->sock) 513 return -EINVAL; 514 nbd_send_req(lo, &sreq); 515 return 0; 516 517 case NBD_CLEAR_SOCK: 518 error = 0; 519 mutex_lock(&lo->tx_lock); 520 lo->sock = NULL; 521 mutex_unlock(&lo->tx_lock); 522 file = lo->file; 523 lo->file = NULL; 524 nbd_clear_que(lo); 525 BUG_ON(!list_empty(&lo->queue_head)); 526 if (file) 527 fput(file); 528 return error; 529 case NBD_SET_SOCK: 530 if (lo->file) 531 return -EBUSY; 532 error = -EINVAL; 533 file = fget(arg); 534 if (file) { 535 inode = file->f_path.dentry->d_inode; 536 if (S_ISSOCK(inode->i_mode)) { 537 lo->file = file; 538 lo->sock = SOCKET_I(inode); 539 error = 0; 540 } else { 541 fput(file); 542 } 543 } 544 return error; 545 case NBD_SET_BLKSIZE: 546 lo->blksize = arg; 547 lo->bytesize &= ~(lo->blksize-1); 548 inode->i_bdev->bd_inode->i_size = lo->bytesize; 549 set_blocksize(inode->i_bdev, lo->blksize); 550 set_capacity(lo->disk, lo->bytesize >> 9); 551 return 0; 552 case NBD_SET_SIZE: 553 lo->bytesize = arg & ~(lo->blksize-1); 554 inode->i_bdev->bd_inode->i_size = lo->bytesize; 555 set_blocksize(inode->i_bdev, lo->blksize); 556 set_capacity(lo->disk, lo->bytesize >> 9); 557 return 0; 558 case NBD_SET_SIZE_BLOCKS: 559 lo->bytesize = ((u64) arg) * lo->blksize; 560 inode->i_bdev->bd_inode->i_size = lo->bytesize; 561 set_blocksize(inode->i_bdev, lo->blksize); 562 set_capacity(lo->disk, lo->bytesize >> 9); 563 return 0; 564 case NBD_DO_IT: 565 if (!lo->file) 566 return -EINVAL; 567 error = nbd_do_it(lo); 568 if (error) 569 return error; 570 /* on return tidy up in case we have a signal */ 571 /* Forcibly shutdown the socket causing all listeners 572 * to error 573 * 574 * FIXME: This code is duplicated from sys_shutdown, but 575 * there should be a more generic interface rather than 576 * calling socket ops directly here */ 577 mutex_lock(&lo->tx_lock); 578 if (lo->sock) { 579 printk(KERN_WARNING "%s: shutting down socket\n", 580 lo->disk->disk_name); 581 lo->sock->ops->shutdown(lo->sock, 582 SEND_SHUTDOWN|RCV_SHUTDOWN); 583 lo->sock = NULL; 584 } 585 mutex_unlock(&lo->tx_lock); 586 file = lo->file; 587 lo->file = NULL; 588 nbd_clear_que(lo); 589 printk(KERN_WARNING "%s: queue cleared\n", lo->disk->disk_name); 590 if (file) 591 fput(file); 592 return lo->harderror; 593 case NBD_CLEAR_QUE: 594 /* 595 * This is for compatibility only. The queue is always cleared 596 * by NBD_DO_IT or NBD_CLEAR_SOCK. 597 */ 598 BUG_ON(!lo->sock && !list_empty(&lo->queue_head)); 599 return 0; 600 case NBD_PRINT_DEBUG: 601 printk(KERN_INFO "%s: next = %p, prev = %p, head = %p\n", 602 inode->i_bdev->bd_disk->disk_name, 603 lo->queue_head.next, lo->queue_head.prev, 604 &lo->queue_head); 605 return 0; 606 } 607 return -EINVAL; 608 } 609 610 static struct block_device_operations nbd_fops = 611 { 612 .owner = THIS_MODULE, 613 .ioctl = nbd_ioctl, 614 }; 615 616 /* 617 * And here should be modules and kernel interface 618 * (Just smiley confuses emacs :-) 619 */ 620 621 static int __init nbd_init(void) 622 { 623 int err = -ENOMEM; 624 int i; 625 626 BUILD_BUG_ON(sizeof(struct nbd_request) != 28); 627 628 if (nbds_max > MAX_NBD) { 629 printk(KERN_CRIT "nbd: cannot allocate more than %u nbds; %u requested.\n", MAX_NBD, 630 nbds_max); 631 return -EINVAL; 632 } 633 634 for (i = 0; i < nbds_max; i++) { 635 struct gendisk *disk = alloc_disk(1); 636 if (!disk) 637 goto out; 638 nbd_dev[i].disk = disk; 639 /* 640 * The new linux 2.5 block layer implementation requires 641 * every gendisk to have its very own request_queue struct. 642 * These structs are big so we dynamically allocate them. 643 */ 644 disk->queue = blk_init_queue(do_nbd_request, &nbd_lock); 645 if (!disk->queue) { 646 put_disk(disk); 647 goto out; 648 } 649 } 650 651 if (register_blkdev(NBD_MAJOR, "nbd")) { 652 err = -EIO; 653 goto out; 654 } 655 656 printk(KERN_INFO "nbd: registered device at major %d\n", NBD_MAJOR); 657 dprintk(DBG_INIT, "nbd: debugflags=0x%x\n", debugflags); 658 659 for (i = 0; i < nbds_max; i++) { 660 struct gendisk *disk = nbd_dev[i].disk; 661 nbd_dev[i].file = NULL; 662 nbd_dev[i].magic = LO_MAGIC; 663 nbd_dev[i].flags = 0; 664 spin_lock_init(&nbd_dev[i].queue_lock); 665 INIT_LIST_HEAD(&nbd_dev[i].queue_head); 666 mutex_init(&nbd_dev[i].tx_lock); 667 init_waitqueue_head(&nbd_dev[i].active_wq); 668 nbd_dev[i].blksize = 1024; 669 nbd_dev[i].bytesize = 0x7ffffc00ULL << 10; /* 2TB */ 670 disk->major = NBD_MAJOR; 671 disk->first_minor = i; 672 disk->fops = &nbd_fops; 673 disk->private_data = &nbd_dev[i]; 674 disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO; 675 sprintf(disk->disk_name, "nbd%d", i); 676 set_capacity(disk, 0x7ffffc00ULL << 1); /* 2 TB */ 677 add_disk(disk); 678 } 679 680 return 0; 681 out: 682 while (i--) { 683 blk_cleanup_queue(nbd_dev[i].disk->queue); 684 put_disk(nbd_dev[i].disk); 685 } 686 return err; 687 } 688 689 static void __exit nbd_cleanup(void) 690 { 691 int i; 692 for (i = 0; i < nbds_max; i++) { 693 struct gendisk *disk = nbd_dev[i].disk; 694 nbd_dev[i].magic = 0; 695 if (disk) { 696 del_gendisk(disk); 697 blk_cleanup_queue(disk->queue); 698 put_disk(disk); 699 } 700 } 701 unregister_blkdev(NBD_MAJOR, "nbd"); 702 printk(KERN_INFO "nbd: unregistered device at major %d\n", NBD_MAJOR); 703 } 704 705 module_init(nbd_init); 706 module_exit(nbd_cleanup); 707 708 MODULE_DESCRIPTION("Network Block Device"); 709 MODULE_LICENSE("GPL"); 710 711 module_param(nbds_max, int, 0444); 712 MODULE_PARM_DESC(nbds_max, "How many network block devices to initialize."); 713 #ifndef NDEBUG 714 module_param(debugflags, int, 0644); 715 MODULE_PARM_DESC(debugflags, "flags for controlling debug output"); 716 #endif 717