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