b4c0888aedc3113c8eb442726a4237c9f7d9dd92
[linux-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 #include <linux/net.h>
32
33 #include <asm/uaccess.h>
34 #include <asm/system.h>
35 #include <asm/types.h>
36
37 #include <linux/nbd.h>
38
39 #define LO_MAGIC 0x68797548
40
41 #ifdef NDEBUG
42 #define dprintk(flags, fmt...)
43 #else /* NDEBUG */
44 #define dprintk(flags, fmt...) do { \
45         if (debugflags & (flags)) printk(KERN_DEBUG fmt); \
46 } while (0)
47 #define DBG_IOCTL       0x0004
48 #define DBG_INIT        0x0010
49 #define DBG_EXIT        0x0020
50 #define DBG_BLKDEV      0x0100
51 #define DBG_RX          0x0200
52 #define DBG_TX          0x0400
53 static unsigned int debugflags;
54 #endif /* NDEBUG */
55
56 static unsigned int nbds_max = 16;
57 static struct nbd_device nbd_dev[MAX_NBD];
58
59 /*
60  * Use just one lock (or at most 1 per NIC). Two arguments for this:
61  * 1. Each NIC is essentially a synchronization point for all servers
62  *    accessed through that NIC so there's no need to have more locks
63  *    than NICs anyway.
64  * 2. More locks lead to more "Dirty cache line bouncing" which will slow
65  *    down each lock to the point where they're actually slower than just
66  *    a single lock.
67  * Thanks go to Jens Axboe and Al Viro for their LKML emails explaining this!
68  */
69 static DEFINE_SPINLOCK(nbd_lock);
70
71 #ifndef NDEBUG
72 static const char *ioctl_cmd_to_ascii(int cmd)
73 {
74         switch (cmd) {
75         case NBD_SET_SOCK: return "set-sock";
76         case NBD_SET_BLKSIZE: return "set-blksize";
77         case NBD_SET_SIZE: return "set-size";
78         case NBD_DO_IT: return "do-it";
79         case NBD_CLEAR_SOCK: return "clear-sock";
80         case NBD_CLEAR_QUE: return "clear-que";
81         case NBD_PRINT_DEBUG: return "print-debug";
82         case NBD_SET_SIZE_BLOCKS: return "set-size-blocks";
83         case NBD_DISCONNECT: return "disconnect";
84         case BLKROSET: return "set-read-only";
85         case BLKFLSBUF: return "flush-buffer-cache";
86         }
87         return "unknown";
88 }
89
90 static const char *nbdcmd_to_ascii(int cmd)
91 {
92         switch (cmd) {
93         case  NBD_CMD_READ: return "read";
94         case NBD_CMD_WRITE: return "write";
95         case  NBD_CMD_DISC: return "disconnect";
96         }
97         return "invalid";
98 }
99 #endif /* NDEBUG */
100
101 static void nbd_end_request(struct request *req)
102 {
103         int uptodate = (req->errors == 0) ? 1 : 0;
104         struct request_queue *q = req->q;
105         unsigned long flags;
106
107         dprintk(DBG_BLKDEV, "%s: request %p: %s\n", req->rq_disk->disk_name,
108                         req, uptodate? "done": "failed");
109
110         spin_lock_irqsave(q->queue_lock, flags);
111         if (!end_that_request_first(req, uptodate, req->nr_sectors)) {
112                 end_that_request_last(req, uptodate);
113         }
114         spin_unlock_irqrestore(q->queue_lock, flags);
115 }
116
117 static void sock_shutdown(struct nbd_device *lo, int lock)
118 {
119         /* Forcibly shutdown the socket causing all listeners
120          * to error
121          *
122          * FIXME: This code is duplicated from sys_shutdown, but
123          * there should be a more generic interface rather than
124          * calling socket ops directly here */
125         if (lock)
126                 mutex_lock(&lo->tx_lock);
127         if (lo->sock) {
128                 printk(KERN_WARNING "%s: shutting down socket\n",
129                         lo->disk->disk_name);
130                 kernel_sock_shutdown(lo->sock, SHUT_RDWR);
131                 lo->sock = NULL;
132         }
133         if (lock)
134                 mutex_unlock(&lo->tx_lock);
135 }
136
137 static void nbd_xmit_timeout(unsigned long arg)
138 {
139         struct task_struct *task = (struct task_struct *)arg;
140
141         printk(KERN_WARNING "nbd: killing hung xmit (%s, pid: %d)\n",
142                 task->comm, task->pid);
143         force_sig(SIGKILL, task);
144 }
145
146 /*
147  *  Send or receive packet.
148  */
149 static int sock_xmit(struct nbd_device *lo, int send, void *buf, int size,
150                 int msg_flags)
151 {
152         struct socket *sock = lo->sock;
153         int result;
154         struct msghdr msg;
155         struct kvec iov;
156         sigset_t blocked, oldset;
157
158         /* Allow interception of SIGKILL only
159          * Don't allow other signals to interrupt the transmission */
160         siginitsetinv(&blocked, sigmask(SIGKILL));
161         sigprocmask(SIG_SETMASK, &blocked, &oldset);
162
163         do {
164                 sock->sk->sk_allocation = GFP_NOIO;
165                 iov.iov_base = buf;
166                 iov.iov_len = size;
167                 msg.msg_name = NULL;
168                 msg.msg_namelen = 0;
169                 msg.msg_control = NULL;
170                 msg.msg_controllen = 0;
171                 msg.msg_flags = msg_flags | MSG_NOSIGNAL;
172
173                 if (send) {
174                         struct timer_list ti;
175
176                         if (lo->xmit_timeout) {
177                                 init_timer(&ti);
178                                 ti.function = nbd_xmit_timeout;
179                                 ti.data = (unsigned long)current;
180                                 ti.expires = jiffies + lo->xmit_timeout;
181                                 add_timer(&ti);
182                         }
183                         result = kernel_sendmsg(sock, &msg, &iov, 1, size);
184                         if (lo->xmit_timeout)
185                                 del_timer_sync(&ti);
186                 } else
187                         result = kernel_recvmsg(sock, &msg, &iov, 1, size, 0);
188
189                 if (signal_pending(current)) {
190                         siginfo_t info;
191                         printk(KERN_WARNING "nbd (pid %d: %s) got signal %d\n",
192                                 task_pid_nr(current), current->comm,
193                                 dequeue_signal_lock(current, &current->blocked, &info));
194                         result = -EINTR;
195                         sock_shutdown(lo, !send);
196                         break;
197                 }
198
199                 if (result <= 0) {
200                         if (result == 0)
201                                 result = -EPIPE; /* short read */
202                         break;
203                 }
204                 size -= result;
205                 buf += result;
206         } while (size > 0);
207
208         sigprocmask(SIG_SETMASK, &oldset, NULL);
209
210         return result;
211 }
212
213 static inline int sock_send_bvec(struct nbd_device *lo, struct bio_vec *bvec,
214                 int flags)
215 {
216         int result;
217         void *kaddr = kmap(bvec->bv_page);
218         result = sock_xmit(lo, 1, kaddr + bvec->bv_offset, bvec->bv_len, flags);
219         kunmap(bvec->bv_page);
220         return result;
221 }
222
223 /* always call with the tx_lock held */
224 static int nbd_send_req(struct nbd_device *lo, struct request *req)
225 {
226         int result, flags;
227         struct nbd_request request;
228         unsigned long size = req->nr_sectors << 9;
229
230         request.magic = htonl(NBD_REQUEST_MAGIC);
231         request.type = htonl(nbd_cmd(req));
232         request.from = cpu_to_be64((u64) req->sector << 9);
233         request.len = htonl(size);
234         memcpy(request.handle, &req, sizeof(req));
235
236         dprintk(DBG_TX, "%s: request %p: sending control (%s@%llu,%luB)\n",
237                         lo->disk->disk_name, req,
238                         nbdcmd_to_ascii(nbd_cmd(req)),
239                         (unsigned long long)req->sector << 9,
240                         req->nr_sectors << 9);
241         result = sock_xmit(lo, 1, &request, sizeof(request),
242                         (nbd_cmd(req) == NBD_CMD_WRITE) ? MSG_MORE : 0);
243         if (result <= 0) {
244                 printk(KERN_ERR "%s: Send control failed (result %d)\n",
245                                 lo->disk->disk_name, result);
246                 goto error_out;
247         }
248
249         if (nbd_cmd(req) == NBD_CMD_WRITE) {
250                 struct req_iterator iter;
251                 struct bio_vec *bvec;
252                 /*
253                  * we are really probing at internals to determine
254                  * whether to set MSG_MORE or not...
255                  */
256                 rq_for_each_segment(bvec, req, iter) {
257                         flags = 0;
258                         if (!rq_iter_last(req, iter))
259                                 flags = MSG_MORE;
260                         dprintk(DBG_TX, "%s: request %p: sending %d bytes data\n",
261                                         lo->disk->disk_name, req, bvec->bv_len);
262                         result = sock_send_bvec(lo, bvec, flags);
263                         if (result <= 0) {
264                                 printk(KERN_ERR "%s: Send data failed (result %d)\n",
265                                                 lo->disk->disk_name, result);
266                                 goto error_out;
267                         }
268                 }
269         }
270         return 0;
271
272 error_out:
273         return 1;
274 }
275
276 static struct request *nbd_find_request(struct nbd_device *lo,
277                                         struct request *xreq)
278 {
279         struct request *req, *tmp;
280         int err;
281
282         err = wait_event_interruptible(lo->active_wq, lo->active_req != xreq);
283         if (unlikely(err))
284                 goto out;
285
286         spin_lock(&lo->queue_lock);
287         list_for_each_entry_safe(req, tmp, &lo->queue_head, queuelist) {
288                 if (req != xreq)
289                         continue;
290                 list_del_init(&req->queuelist);
291                 spin_unlock(&lo->queue_lock);
292                 return req;
293         }
294         spin_unlock(&lo->queue_lock);
295
296         err = -ENOENT;
297
298 out:
299         return ERR_PTR(err);
300 }
301
302 static inline int sock_recv_bvec(struct nbd_device *lo, struct bio_vec *bvec)
303 {
304         int result;
305         void *kaddr = kmap(bvec->bv_page);
306         result = sock_xmit(lo, 0, kaddr + bvec->bv_offset, bvec->bv_len,
307                         MSG_WAITALL);
308         kunmap(bvec->bv_page);
309         return result;
310 }
311
312 /* NULL returned = something went wrong, inform userspace */
313 static struct request *nbd_read_stat(struct nbd_device *lo)
314 {
315         int result;
316         struct nbd_reply reply;
317         struct request *req;
318
319         reply.magic = 0;
320         result = sock_xmit(lo, 0, &reply, sizeof(reply), MSG_WAITALL);
321         if (result <= 0) {
322                 printk(KERN_ERR "%s: Receive control failed (result %d)\n",
323                                 lo->disk->disk_name, result);
324                 goto harderror;
325         }
326
327         if (ntohl(reply.magic) != NBD_REPLY_MAGIC) {
328                 printk(KERN_ERR "%s: Wrong magic (0x%lx)\n",
329                                 lo->disk->disk_name,
330                                 (unsigned long)ntohl(reply.magic));
331                 result = -EPROTO;
332                 goto harderror;
333         }
334
335         req = nbd_find_request(lo, *(struct request **)reply.handle);
336         if (unlikely(IS_ERR(req))) {
337                 result = PTR_ERR(req);
338                 if (result != -ENOENT)
339                         goto harderror;
340
341                 printk(KERN_ERR "%s: Unexpected reply (%p)\n",
342                                 lo->disk->disk_name, reply.handle);
343                 result = -EBADR;
344                 goto harderror;
345         }
346
347         if (ntohl(reply.error)) {
348                 printk(KERN_ERR "%s: Other side returned error (%d)\n",
349                                 lo->disk->disk_name, ntohl(reply.error));
350                 req->errors++;
351                 return req;
352         }
353
354         dprintk(DBG_RX, "%s: request %p: got reply\n",
355                         lo->disk->disk_name, req);
356         if (nbd_cmd(req) == NBD_CMD_READ) {
357                 struct req_iterator iter;
358                 struct bio_vec *bvec;
359
360                 rq_for_each_segment(bvec, req, iter) {
361                         result = sock_recv_bvec(lo, bvec);
362                         if (result <= 0) {
363                                 printk(KERN_ERR "%s: Receive data failed (result %d)\n",
364                                                 lo->disk->disk_name, result);
365                                 req->errors++;
366                                 return req;
367                         }
368                         dprintk(DBG_RX, "%s: request %p: got %d bytes data\n",
369                                 lo->disk->disk_name, req, bvec->bv_len);
370                 }
371         }
372         return req;
373 harderror:
374         lo->harderror = result;
375         return NULL;
376 }
377
378 static ssize_t pid_show(struct gendisk *disk, char *page)
379 {
380         return sprintf(page, "%ld\n",
381                 (long) ((struct nbd_device *)disk->private_data)->pid);
382 }
383
384 static struct disk_attribute pid_attr = {
385         .attr = { .name = "pid", .mode = S_IRUGO },
386         .show = pid_show,
387 };
388
389 static int nbd_do_it(struct nbd_device *lo)
390 {
391         struct request *req;
392         int ret;
393
394         BUG_ON(lo->magic != LO_MAGIC);
395
396         lo->pid = current->pid;
397         ret = sysfs_create_file(&lo->disk->kobj, &pid_attr.attr);
398         if (ret) {
399                 printk(KERN_ERR "nbd: sysfs_create_file failed!");
400                 return ret;
401         }
402
403         while ((req = nbd_read_stat(lo)) != NULL)
404                 nbd_end_request(req);
405
406         sysfs_remove_file(&lo->disk->kobj, &pid_attr.attr);
407         return 0;
408 }
409
410 static void nbd_clear_que(struct nbd_device *lo)
411 {
412         struct request *req;
413
414         BUG_ON(lo->magic != LO_MAGIC);
415
416         /*
417          * Because we have set lo->sock to NULL under the tx_lock, all
418          * modifications to the list must have completed by now.  For
419          * the same reason, the active_req must be NULL.
420          *
421          * As a consequence, we don't need to take the spin lock while
422          * purging the list here.
423          */
424         BUG_ON(lo->sock);
425         BUG_ON(lo->active_req);
426
427         while (!list_empty(&lo->queue_head)) {
428                 req = list_entry(lo->queue_head.next, struct request,
429                                  queuelist);
430                 list_del_init(&req->queuelist);
431                 req->errors++;
432                 nbd_end_request(req);
433         }
434 }
435
436
437 /*
438  * We always wait for result of write, for now. It would be nice to make it optional
439  * in future
440  * if ((rq_data_dir(req) == WRITE) && (lo->flags & NBD_WRITE_NOCHK))
441  *   { printk( "Warning: Ignoring result!\n"); nbd_end_request( req ); }
442  */
443
444 static void do_nbd_request(struct request_queue * q)
445 {
446         struct request *req;
447         
448         while ((req = elv_next_request(q)) != NULL) {
449                 struct nbd_device *lo;
450
451                 blkdev_dequeue_request(req);
452                 dprintk(DBG_BLKDEV, "%s: request %p: dequeued (flags=%x)\n",
453                                 req->rq_disk->disk_name, req, req->cmd_type);
454
455                 if (!blk_fs_request(req))
456                         goto error_out;
457
458                 lo = req->rq_disk->private_data;
459
460                 BUG_ON(lo->magic != LO_MAGIC);
461
462                 nbd_cmd(req) = NBD_CMD_READ;
463                 if (rq_data_dir(req) == WRITE) {
464                         nbd_cmd(req) = NBD_CMD_WRITE;
465                         if (lo->flags & NBD_READ_ONLY) {
466                                 printk(KERN_ERR "%s: Write on read-only\n",
467                                                 lo->disk->disk_name);
468                                 goto error_out;
469                         }
470                 }
471
472                 req->errors = 0;
473                 spin_unlock_irq(q->queue_lock);
474
475                 mutex_lock(&lo->tx_lock);
476                 if (unlikely(!lo->sock)) {
477                         mutex_unlock(&lo->tx_lock);
478                         printk(KERN_ERR "%s: Attempted send on closed socket\n",
479                                lo->disk->disk_name);
480                         req->errors++;
481                         nbd_end_request(req);
482                         spin_lock_irq(q->queue_lock);
483                         continue;
484                 }
485
486                 lo->active_req = req;
487
488                 if (nbd_send_req(lo, req) != 0) {
489                         printk(KERN_ERR "%s: Request send failed\n",
490                                         lo->disk->disk_name);
491                         req->errors++;
492                         nbd_end_request(req);
493                 } else {
494                         spin_lock(&lo->queue_lock);
495                         list_add(&req->queuelist, &lo->queue_head);
496                         spin_unlock(&lo->queue_lock);
497                 }
498
499                 lo->active_req = NULL;
500                 mutex_unlock(&lo->tx_lock);
501                 wake_up_all(&lo->active_wq);
502
503                 spin_lock_irq(q->queue_lock);
504                 continue;
505
506 error_out:
507                 req->errors++;
508                 spin_unlock(q->queue_lock);
509                 nbd_end_request(req);
510                 spin_lock(q->queue_lock);
511         }
512 }
513
514 static int nbd_ioctl(struct inode *inode, struct file *file,
515                      unsigned int cmd, unsigned long arg)
516 {
517         struct nbd_device *lo = inode->i_bdev->bd_disk->private_data;
518         int error;
519         struct request sreq ;
520
521         if (!capable(CAP_SYS_ADMIN))
522                 return -EPERM;
523
524         BUG_ON(lo->magic != LO_MAGIC);
525
526         /* Anyone capable of this syscall can do *real bad* things */
527         dprintk(DBG_IOCTL, "%s: nbd_ioctl cmd=%s(0x%x) arg=%lu\n",
528                         lo->disk->disk_name, ioctl_cmd_to_ascii(cmd), cmd, arg);
529
530         switch (cmd) {
531         case NBD_DISCONNECT:
532                 printk(KERN_INFO "%s: NBD_DISCONNECT\n", lo->disk->disk_name);
533                 sreq.cmd_type = REQ_TYPE_SPECIAL;
534                 nbd_cmd(&sreq) = NBD_CMD_DISC;
535                 /*
536                  * Set these to sane values in case server implementation
537                  * fails to check the request type first and also to keep
538                  * debugging output cleaner.
539                  */
540                 sreq.sector = 0;
541                 sreq.nr_sectors = 0;
542                 if (!lo->sock)
543                         return -EINVAL;
544                 mutex_lock(&lo->tx_lock);
545                 nbd_send_req(lo, &sreq);
546                 mutex_unlock(&lo->tx_lock);
547                 return 0;
548  
549         case NBD_CLEAR_SOCK:
550                 error = 0;
551                 mutex_lock(&lo->tx_lock);
552                 lo->sock = NULL;
553                 mutex_unlock(&lo->tx_lock);
554                 file = lo->file;
555                 lo->file = NULL;
556                 nbd_clear_que(lo);
557                 BUG_ON(!list_empty(&lo->queue_head));
558                 if (file)
559                         fput(file);
560                 return error;
561         case NBD_SET_SOCK:
562                 if (lo->file)
563                         return -EBUSY;
564                 error = -EINVAL;
565                 file = fget(arg);
566                 if (file) {
567                         inode = file->f_path.dentry->d_inode;
568                         if (S_ISSOCK(inode->i_mode)) {
569                                 lo->file = file;
570                                 lo->sock = SOCKET_I(inode);
571                                 error = 0;
572                         } else {
573                                 fput(file);
574                         }
575                 }
576                 return error;
577         case NBD_SET_BLKSIZE:
578                 lo->blksize = arg;
579                 lo->bytesize &= ~(lo->blksize-1);
580                 inode->i_bdev->bd_inode->i_size = lo->bytesize;
581                 set_blocksize(inode->i_bdev, lo->blksize);
582                 set_capacity(lo->disk, lo->bytesize >> 9);
583                 return 0;
584         case NBD_SET_SIZE:
585                 lo->bytesize = arg & ~(lo->blksize-1);
586                 inode->i_bdev->bd_inode->i_size = lo->bytesize;
587                 set_blocksize(inode->i_bdev, lo->blksize);
588                 set_capacity(lo->disk, lo->bytesize >> 9);
589                 return 0;
590         case NBD_SET_TIMEOUT:
591                 lo->xmit_timeout = arg * HZ;
592                 return 0;
593         case NBD_SET_SIZE_BLOCKS:
594                 lo->bytesize = ((u64) arg) * lo->blksize;
595                 inode->i_bdev->bd_inode->i_size = lo->bytesize;
596                 set_blocksize(inode->i_bdev, lo->blksize);
597                 set_capacity(lo->disk, lo->bytesize >> 9);
598                 return 0;
599         case NBD_DO_IT:
600                 if (!lo->file)
601                         return -EINVAL;
602                 error = nbd_do_it(lo);
603                 if (error)
604                         return error;
605                 sock_shutdown(lo, 1);
606                 file = lo->file;
607                 lo->file = NULL;
608                 nbd_clear_que(lo);
609                 printk(KERN_WARNING "%s: queue cleared\n", lo->disk->disk_name);
610                 if (file)
611                         fput(file);
612                 lo->bytesize = 0;
613                 inode->i_bdev->bd_inode->i_size = 0;
614                 set_capacity(lo->disk, 0);
615                 return lo->harderror;
616         case NBD_CLEAR_QUE:
617                 /*
618                  * This is for compatibility only.  The queue is always cleared
619                  * by NBD_DO_IT or NBD_CLEAR_SOCK.
620                  */
621                 BUG_ON(!lo->sock && !list_empty(&lo->queue_head));
622                 return 0;
623         case NBD_PRINT_DEBUG:
624                 printk(KERN_INFO "%s: next = %p, prev = %p, head = %p\n",
625                         inode->i_bdev->bd_disk->disk_name,
626                         lo->queue_head.next, lo->queue_head.prev,
627                         &lo->queue_head);
628                 return 0;
629         }
630         return -EINVAL;
631 }
632
633 static struct block_device_operations nbd_fops =
634 {
635         .owner =        THIS_MODULE,
636         .ioctl =        nbd_ioctl,
637 };
638
639 /*
640  * And here should be modules and kernel interface 
641  *  (Just smiley confuses emacs :-)
642  */
643
644 static int __init nbd_init(void)
645 {
646         int err = -ENOMEM;
647         int i;
648
649         BUILD_BUG_ON(sizeof(struct nbd_request) != 28);
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         for (i = 0; i < nbds_max; i++) {
683                 struct gendisk *disk = nbd_dev[i].disk;
684                 nbd_dev[i].file = NULL;
685                 nbd_dev[i].magic = LO_MAGIC;
686                 nbd_dev[i].flags = 0;
687                 spin_lock_init(&nbd_dev[i].queue_lock);
688                 INIT_LIST_HEAD(&nbd_dev[i].queue_head);
689                 mutex_init(&nbd_dev[i].tx_lock);
690                 init_waitqueue_head(&nbd_dev[i].active_wq);
691                 nbd_dev[i].blksize = 1024;
692                 nbd_dev[i].bytesize = 0;
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                 set_capacity(disk, 0);
700                 add_disk(disk);
701         }
702
703         return 0;
704 out:
705         while (i--) {
706                 blk_cleanup_queue(nbd_dev[i].disk->queue);
707                 put_disk(nbd_dev[i].disk);
708         }
709         return err;
710 }
711
712 static void __exit nbd_cleanup(void)
713 {
714         int i;
715         for (i = 0; i < nbds_max; i++) {
716                 struct gendisk *disk = nbd_dev[i].disk;
717                 nbd_dev[i].magic = 0;
718                 if (disk) {
719                         del_gendisk(disk);
720                         blk_cleanup_queue(disk->queue);
721                         put_disk(disk);
722                 }
723         }
724         unregister_blkdev(NBD_MAJOR, "nbd");
725         printk(KERN_INFO "nbd: unregistered device at major %d\n", NBD_MAJOR);
726 }
727
728 module_init(nbd_init);
729 module_exit(nbd_cleanup);
730
731 MODULE_DESCRIPTION("Network Block Device");
732 MODULE_LICENSE("GPL");
733
734 module_param(nbds_max, int, 0444);
735 MODULE_PARM_DESC(nbds_max, "How many network block devices to initialize.");
736 #ifndef NDEBUG
737 module_param(debugflags, int, 0644);
738 MODULE_PARM_DESC(debugflags, "flags for controlling debug output");
739 #endif