89bdafd88dbdb84bcddec3487fdbc3967a6284c6
[sfrench/cifs-2.6.git] / 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         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, &current->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,
235                                         struct request *xreq)
236 {
237         struct request *req, *tmp;
238         int err;
239
240         err = wait_event_interruptible(lo->active_wq, lo->active_req != xreq);
241         if (unlikely(err))
242                 goto out;
243
244         spin_lock(&lo->queue_lock);
245         list_for_each_entry_safe(req, tmp, &lo->queue_head, queuelist) {
246                 if (req != xreq)
247                         continue;
248                 list_del_init(&req->queuelist);
249                 spin_unlock(&lo->queue_lock);
250                 return req;
251         }
252         spin_unlock(&lo->queue_lock);
253
254         err = -ENOENT;
255
256 out:
257         return ERR_PTR(err);
258 }
259
260 static inline int sock_recv_bvec(struct socket *sock, struct bio_vec *bvec)
261 {
262         int result;
263         void *kaddr = kmap(bvec->bv_page);
264         result = sock_xmit(sock, 0, kaddr + bvec->bv_offset, bvec->bv_len,
265                         MSG_WAITALL);
266         kunmap(bvec->bv_page);
267         return result;
268 }
269
270 /* NULL returned = something went wrong, inform userspace */
271 static struct request *nbd_read_stat(struct nbd_device *lo)
272 {
273         int result;
274         struct nbd_reply reply;
275         struct request *req;
276         struct socket *sock = lo->sock;
277
278         reply.magic = 0;
279         result = sock_xmit(sock, 0, &reply, sizeof(reply), MSG_WAITALL);
280         if (result <= 0) {
281                 printk(KERN_ERR "%s: Receive control failed (result %d)\n",
282                                 lo->disk->disk_name, result);
283                 goto harderror;
284         }
285
286         if (ntohl(reply.magic) != NBD_REPLY_MAGIC) {
287                 printk(KERN_ERR "%s: Wrong magic (0x%lx)\n",
288                                 lo->disk->disk_name,
289                                 (unsigned long)ntohl(reply.magic));
290                 result = -EPROTO;
291                 goto harderror;
292         }
293
294         req = nbd_find_request(lo, *(struct request **)reply.handle);
295         if (unlikely(IS_ERR(req))) {
296                 result = PTR_ERR(req);
297                 if (result != -ENOENT)
298                         goto harderror;
299
300                 printk(KERN_ERR "%s: Unexpected reply (%p)\n",
301                                 lo->disk->disk_name, reply.handle);
302                 result = -EBADR;
303                 goto harderror;
304         }
305
306         if (ntohl(reply.error)) {
307                 printk(KERN_ERR "%s: Other side returned error (%d)\n",
308                                 lo->disk->disk_name, ntohl(reply.error));
309                 req->errors++;
310                 return req;
311         }
312
313         dprintk(DBG_RX, "%s: request %p: got reply\n",
314                         lo->disk->disk_name, req);
315         if (nbd_cmd(req) == NBD_CMD_READ) {
316                 struct req_iterator iter;
317                 struct bio_vec *bvec;
318
319                 rq_for_each_segment(bvec, req, iter) {
320                         result = sock_recv_bvec(sock, bvec);
321                         if (result <= 0) {
322                                 printk(KERN_ERR "%s: Receive data failed (result %d)\n",
323                                                 lo->disk->disk_name, result);
324                                 req->errors++;
325                                 return req;
326                         }
327                         dprintk(DBG_RX, "%s: request %p: got %d bytes data\n",
328                                 lo->disk->disk_name, req, bvec->bv_len);
329                 }
330         }
331         return req;
332 harderror:
333         lo->harderror = result;
334         return NULL;
335 }
336
337 static ssize_t pid_show(struct gendisk *disk, char *page)
338 {
339         return sprintf(page, "%ld\n",
340                 (long) ((struct nbd_device *)disk->private_data)->pid);
341 }
342
343 static struct disk_attribute pid_attr = {
344         .attr = { .name = "pid", .mode = S_IRUGO },
345         .show = pid_show,
346 };
347
348 static int nbd_do_it(struct nbd_device *lo)
349 {
350         struct request *req;
351         int ret;
352
353         BUG_ON(lo->magic != LO_MAGIC);
354
355         lo->pid = current->pid;
356         ret = sysfs_create_file(&lo->disk->kobj, &pid_attr.attr);
357         if (ret) {
358                 printk(KERN_ERR "nbd: sysfs_create_file failed!");
359                 return ret;
360         }
361
362         while ((req = nbd_read_stat(lo)) != NULL)
363                 nbd_end_request(req);
364
365         sysfs_remove_file(&lo->disk->kobj, &pid_attr.attr);
366         return 0;
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 ((rq_data_dir(req) == WRITE) && (lo->flags & NBD_WRITE_NOCHK))
399  *   { printk( "Warning: Ignoring result!\n"); nbd_end_request( req ); }
400  */
401
402 static void do_nbd_request(struct request_queue * 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_path.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                 error = nbd_do_it(lo);
557                 if (error)
558                         return error;
559                 /* on return tidy up in case we have a signal */
560                 /* Forcibly shutdown the socket causing all listeners
561                  * to error
562                  *
563                  * FIXME: This code is duplicated from sys_shutdown, but
564                  * there should be a more generic interface rather than
565                  * calling socket ops directly here */
566                 mutex_lock(&lo->tx_lock);
567                 if (lo->sock) {
568                         printk(KERN_WARNING "%s: shutting down socket\n",
569                                 lo->disk->disk_name);
570                         lo->sock->ops->shutdown(lo->sock,
571                                 SEND_SHUTDOWN|RCV_SHUTDOWN);
572                         lo->sock = NULL;
573                 }
574                 mutex_unlock(&lo->tx_lock);
575                 file = lo->file;
576                 lo->file = NULL;
577                 nbd_clear_que(lo);
578                 printk(KERN_WARNING "%s: queue cleared\n", lo->disk->disk_name);
579                 if (file)
580                         fput(file);
581                 lo->bytesize = 0;
582                 inode->i_bdev->bd_inode->i_size = 0;
583                 set_capacity(lo->disk, 0);
584                 return lo->harderror;
585         case NBD_CLEAR_QUE:
586                 /*
587                  * This is for compatibility only.  The queue is always cleared
588                  * by NBD_DO_IT or NBD_CLEAR_SOCK.
589                  */
590                 BUG_ON(!lo->sock && !list_empty(&lo->queue_head));
591                 return 0;
592         case NBD_PRINT_DEBUG:
593                 printk(KERN_INFO "%s: next = %p, prev = %p, head = %p\n",
594                         inode->i_bdev->bd_disk->disk_name,
595                         lo->queue_head.next, lo->queue_head.prev,
596                         &lo->queue_head);
597                 return 0;
598         }
599         return -EINVAL;
600 }
601
602 static struct block_device_operations nbd_fops =
603 {
604         .owner =        THIS_MODULE,
605         .ioctl =        nbd_ioctl,
606 };
607
608 /*
609  * And here should be modules and kernel interface 
610  *  (Just smiley confuses emacs :-)
611  */
612
613 static int __init nbd_init(void)
614 {
615         int err = -ENOMEM;
616         int i;
617
618         BUILD_BUG_ON(sizeof(struct nbd_request) != 28);
619
620         if (nbds_max > MAX_NBD) {
621                 printk(KERN_CRIT "nbd: cannot allocate more than %u nbds; %u requested.\n", MAX_NBD,
622                                 nbds_max);
623                 return -EINVAL;
624         }
625
626         for (i = 0; i < nbds_max; i++) {
627                 struct gendisk *disk = alloc_disk(1);
628                 if (!disk)
629                         goto out;
630                 nbd_dev[i].disk = disk;
631                 /*
632                  * The new linux 2.5 block layer implementation requires
633                  * every gendisk to have its very own request_queue struct.
634                  * These structs are big so we dynamically allocate them.
635                  */
636                 disk->queue = blk_init_queue(do_nbd_request, &nbd_lock);
637                 if (!disk->queue) {
638                         put_disk(disk);
639                         goto out;
640                 }
641         }
642
643         if (register_blkdev(NBD_MAJOR, "nbd")) {
644                 err = -EIO;
645                 goto out;
646         }
647
648         printk(KERN_INFO "nbd: registered device at major %d\n", NBD_MAJOR);
649         dprintk(DBG_INIT, "nbd: debugflags=0x%x\n", debugflags);
650
651         for (i = 0; i < nbds_max; i++) {
652                 struct gendisk *disk = nbd_dev[i].disk;
653                 nbd_dev[i].file = NULL;
654                 nbd_dev[i].magic = LO_MAGIC;
655                 nbd_dev[i].flags = 0;
656                 spin_lock_init(&nbd_dev[i].queue_lock);
657                 INIT_LIST_HEAD(&nbd_dev[i].queue_head);
658                 mutex_init(&nbd_dev[i].tx_lock);
659                 init_waitqueue_head(&nbd_dev[i].active_wq);
660                 nbd_dev[i].blksize = 1024;
661                 nbd_dev[i].bytesize = 0;
662                 disk->major = NBD_MAJOR;
663                 disk->first_minor = i;
664                 disk->fops = &nbd_fops;
665                 disk->private_data = &nbd_dev[i];
666                 disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO;
667                 sprintf(disk->disk_name, "nbd%d", i);
668                 set_capacity(disk, 0);
669                 add_disk(disk);
670         }
671
672         return 0;
673 out:
674         while (i--) {
675                 blk_cleanup_queue(nbd_dev[i].disk->queue);
676                 put_disk(nbd_dev[i].disk);
677         }
678         return err;
679 }
680
681 static void __exit nbd_cleanup(void)
682 {
683         int i;
684         for (i = 0; i < nbds_max; i++) {
685                 struct gendisk *disk = nbd_dev[i].disk;
686                 nbd_dev[i].magic = 0;
687                 if (disk) {
688                         del_gendisk(disk);
689                         blk_cleanup_queue(disk->queue);
690                         put_disk(disk);
691                 }
692         }
693         unregister_blkdev(NBD_MAJOR, "nbd");
694         printk(KERN_INFO "nbd: unregistered device at major %d\n", NBD_MAJOR);
695 }
696
697 module_init(nbd_init);
698 module_exit(nbd_cleanup);
699
700 MODULE_DESCRIPTION("Network Block Device");
701 MODULE_LICENSE("GPL");
702
703 module_param(nbds_max, int, 0444);
704 MODULE_PARM_DESC(nbds_max, "How many network block devices to initialize.");
705 #ifndef NDEBUG
706 module_param(debugflags, int, 0644);
707 MODULE_PARM_DESC(debugflags, "flags for controlling debug output");
708 #endif