NBD: make nbd default to deadline I/O scheduler
[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 #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;
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 error = req->errors ? -EIO : 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, error ? "failed" : "done");
109
110         spin_lock_irqsave(q->queue_lock, flags);
111         __blk_end_request(req, error, req->nr_sectors << 9);
112         spin_unlock_irqrestore(q->queue_lock, flags);
113 }
114
115 static void sock_shutdown(struct nbd_device *lo, int lock)
116 {
117         /* Forcibly shutdown the socket causing all listeners
118          * to error
119          *
120          * FIXME: This code is duplicated from sys_shutdown, but
121          * there should be a more generic interface rather than
122          * calling socket ops directly here */
123         if (lock)
124                 mutex_lock(&lo->tx_lock);
125         if (lo->sock) {
126                 printk(KERN_WARNING "%s: shutting down socket\n",
127                         lo->disk->disk_name);
128                 kernel_sock_shutdown(lo->sock, SHUT_RDWR);
129                 lo->sock = NULL;
130         }
131         if (lock)
132                 mutex_unlock(&lo->tx_lock);
133 }
134
135 static void nbd_xmit_timeout(unsigned long arg)
136 {
137         struct task_struct *task = (struct task_struct *)arg;
138
139         printk(KERN_WARNING "nbd: killing hung xmit (%s, pid: %d)\n",
140                 task->comm, task->pid);
141         force_sig(SIGKILL, task);
142 }
143
144 /*
145  *  Send or receive packet.
146  */
147 static int sock_xmit(struct nbd_device *lo, int send, void *buf, int size,
148                 int msg_flags)
149 {
150         struct socket *sock = lo->sock;
151         int result;
152         struct msghdr msg;
153         struct kvec iov;
154         sigset_t blocked, oldset;
155
156         /* Allow interception of SIGKILL only
157          * Don't allow other signals to interrupt the transmission */
158         siginitsetinv(&blocked, sigmask(SIGKILL));
159         sigprocmask(SIG_SETMASK, &blocked, &oldset);
160
161         do {
162                 sock->sk->sk_allocation = GFP_NOIO;
163                 iov.iov_base = buf;
164                 iov.iov_len = size;
165                 msg.msg_name = NULL;
166                 msg.msg_namelen = 0;
167                 msg.msg_control = NULL;
168                 msg.msg_controllen = 0;
169                 msg.msg_flags = msg_flags | MSG_NOSIGNAL;
170
171                 if (send) {
172                         struct timer_list ti;
173
174                         if (lo->xmit_timeout) {
175                                 init_timer(&ti);
176                                 ti.function = nbd_xmit_timeout;
177                                 ti.data = (unsigned long)current;
178                                 ti.expires = jiffies + lo->xmit_timeout;
179                                 add_timer(&ti);
180                         }
181                         result = kernel_sendmsg(sock, &msg, &iov, 1, size);
182                         if (lo->xmit_timeout)
183                                 del_timer_sync(&ti);
184                 } else
185                         result = kernel_recvmsg(sock, &msg, &iov, 1, size, 0);
186
187                 if (signal_pending(current)) {
188                         siginfo_t info;
189                         printk(KERN_WARNING "nbd (pid %d: %s) got signal %d\n",
190                                 task_pid_nr(current), current->comm,
191                                 dequeue_signal_lock(current, &current->blocked, &info));
192                         result = -EINTR;
193                         sock_shutdown(lo, !send);
194                         break;
195                 }
196
197                 if (result <= 0) {
198                         if (result == 0)
199                                 result = -EPIPE; /* short read */
200                         break;
201                 }
202                 size -= result;
203                 buf += result;
204         } while (size > 0);
205
206         sigprocmask(SIG_SETMASK, &oldset, NULL);
207
208         return result;
209 }
210
211 static inline int sock_send_bvec(struct nbd_device *lo, struct bio_vec *bvec,
212                 int flags)
213 {
214         int result;
215         void *kaddr = kmap(bvec->bv_page);
216         result = sock_xmit(lo, 1, kaddr + bvec->bv_offset, bvec->bv_len, flags);
217         kunmap(bvec->bv_page);
218         return result;
219 }
220
221 /* always call with the tx_lock held */
222 static int nbd_send_req(struct nbd_device *lo, struct request *req)
223 {
224         int result, flags;
225         struct nbd_request request;
226         unsigned long size = req->nr_sectors << 9;
227
228         request.magic = htonl(NBD_REQUEST_MAGIC);
229         request.type = htonl(nbd_cmd(req));
230         request.from = cpu_to_be64((u64) req->sector << 9);
231         request.len = htonl(size);
232         memcpy(request.handle, &req, sizeof(req));
233
234         dprintk(DBG_TX, "%s: request %p: sending control (%s@%llu,%luB)\n",
235                         lo->disk->disk_name, req,
236                         nbdcmd_to_ascii(nbd_cmd(req)),
237                         (unsigned long long)req->sector << 9,
238                         req->nr_sectors << 9);
239         result = sock_xmit(lo, 1, &request, sizeof(request),
240                         (nbd_cmd(req) == NBD_CMD_WRITE) ? MSG_MORE : 0);
241         if (result <= 0) {
242                 printk(KERN_ERR "%s: Send control failed (result %d)\n",
243                                 lo->disk->disk_name, result);
244                 goto error_out;
245         }
246
247         if (nbd_cmd(req) == NBD_CMD_WRITE) {
248                 struct req_iterator iter;
249                 struct bio_vec *bvec;
250                 /*
251                  * we are really probing at internals to determine
252                  * whether to set MSG_MORE or not...
253                  */
254                 rq_for_each_segment(bvec, req, iter) {
255                         flags = 0;
256                         if (!rq_iter_last(req, iter))
257                                 flags = MSG_MORE;
258                         dprintk(DBG_TX, "%s: request %p: sending %d bytes data\n",
259                                         lo->disk->disk_name, req, bvec->bv_len);
260                         result = sock_send_bvec(lo, bvec, flags);
261                         if (result <= 0) {
262                                 printk(KERN_ERR "%s: Send data failed (result %d)\n",
263                                                 lo->disk->disk_name, result);
264                                 goto error_out;
265                         }
266                 }
267         }
268         return 0;
269
270 error_out:
271         return 1;
272 }
273
274 static struct request *nbd_find_request(struct nbd_device *lo,
275                                         struct request *xreq)
276 {
277         struct request *req, *tmp;
278         int err;
279
280         err = wait_event_interruptible(lo->active_wq, lo->active_req != xreq);
281         if (unlikely(err))
282                 goto out;
283
284         spin_lock(&lo->queue_lock);
285         list_for_each_entry_safe(req, tmp, &lo->queue_head, queuelist) {
286                 if (req != xreq)
287                         continue;
288                 list_del_init(&req->queuelist);
289                 spin_unlock(&lo->queue_lock);
290                 return req;
291         }
292         spin_unlock(&lo->queue_lock);
293
294         err = -ENOENT;
295
296 out:
297         return ERR_PTR(err);
298 }
299
300 static inline int sock_recv_bvec(struct nbd_device *lo, struct bio_vec *bvec)
301 {
302         int result;
303         void *kaddr = kmap(bvec->bv_page);
304         result = sock_xmit(lo, 0, kaddr + bvec->bv_offset, bvec->bv_len,
305                         MSG_WAITALL);
306         kunmap(bvec->bv_page);
307         return result;
308 }
309
310 /* NULL returned = something went wrong, inform userspace */
311 static struct request *nbd_read_stat(struct nbd_device *lo)
312 {
313         int result;
314         struct nbd_reply reply;
315         struct request *req;
316
317         reply.magic = 0;
318         result = sock_xmit(lo, 0, &reply, sizeof(reply), MSG_WAITALL);
319         if (result <= 0) {
320                 printk(KERN_ERR "%s: Receive control failed (result %d)\n",
321                                 lo->disk->disk_name, result);
322                 goto harderror;
323         }
324
325         if (ntohl(reply.magic) != NBD_REPLY_MAGIC) {
326                 printk(KERN_ERR "%s: Wrong magic (0x%lx)\n",
327                                 lo->disk->disk_name,
328                                 (unsigned long)ntohl(reply.magic));
329                 result = -EPROTO;
330                 goto harderror;
331         }
332
333         req = nbd_find_request(lo, *(struct request **)reply.handle);
334         if (unlikely(IS_ERR(req))) {
335                 result = PTR_ERR(req);
336                 if (result != -ENOENT)
337                         goto harderror;
338
339                 printk(KERN_ERR "%s: Unexpected reply (%p)\n",
340                                 lo->disk->disk_name, reply.handle);
341                 result = -EBADR;
342                 goto harderror;
343         }
344
345         if (ntohl(reply.error)) {
346                 printk(KERN_ERR "%s: Other side returned error (%d)\n",
347                                 lo->disk->disk_name, ntohl(reply.error));
348                 req->errors++;
349                 return req;
350         }
351
352         dprintk(DBG_RX, "%s: request %p: got reply\n",
353                         lo->disk->disk_name, req);
354         if (nbd_cmd(req) == NBD_CMD_READ) {
355                 struct req_iterator iter;
356                 struct bio_vec *bvec;
357
358                 rq_for_each_segment(bvec, req, iter) {
359                         result = sock_recv_bvec(lo, bvec);
360                         if (result <= 0) {
361                                 printk(KERN_ERR "%s: Receive data failed (result %d)\n",
362                                                 lo->disk->disk_name, result);
363                                 req->errors++;
364                                 return req;
365                         }
366                         dprintk(DBG_RX, "%s: request %p: got %d bytes data\n",
367                                 lo->disk->disk_name, req, bvec->bv_len);
368                 }
369         }
370         return req;
371 harderror:
372         lo->harderror = result;
373         return NULL;
374 }
375
376 static ssize_t pid_show(struct device *dev,
377                         struct device_attribute *attr, char *buf)
378 {
379         struct gendisk *disk = dev_to_disk(dev);
380
381         return sprintf(buf, "%ld\n",
382                 (long) ((struct nbd_device *)disk->private_data)->pid);
383 }
384
385 static struct device_attribute pid_attr = {
386         .attr = { .name = "pid", .mode = S_IRUGO, .owner = THIS_MODULE },
387         .show = pid_show,
388 };
389
390 static int nbd_do_it(struct nbd_device *lo)
391 {
392         struct request *req;
393         int ret;
394
395         BUG_ON(lo->magic != LO_MAGIC);
396
397         lo->pid = current->pid;
398         ret = sysfs_create_file(&lo->disk->dev.kobj, &pid_attr.attr);
399         if (ret) {
400                 printk(KERN_ERR "nbd: sysfs_create_file failed!");
401                 return ret;
402         }
403
404         while ((req = nbd_read_stat(lo)) != NULL)
405                 nbd_end_request(req);
406
407         sysfs_remove_file(&lo->disk->dev.kobj, &pid_attr.attr);
408         return 0;
409 }
410
411 static void nbd_clear_que(struct nbd_device *lo)
412 {
413         struct request *req;
414
415         BUG_ON(lo->magic != LO_MAGIC);
416
417         /*
418          * Because we have set lo->sock to NULL under the tx_lock, all
419          * modifications to the list must have completed by now.  For
420          * the same reason, the active_req must be NULL.
421          *
422          * As a consequence, we don't need to take the spin lock while
423          * purging the list here.
424          */
425         BUG_ON(lo->sock);
426         BUG_ON(lo->active_req);
427
428         while (!list_empty(&lo->queue_head)) {
429                 req = list_entry(lo->queue_head.next, struct request,
430                                  queuelist);
431                 list_del_init(&req->queuelist);
432                 req->errors++;
433                 nbd_end_request(req);
434         }
435 }
436
437
438 /*
439  * We always wait for result of write, for now. It would be nice to make it optional
440  * in future
441  * if ((rq_data_dir(req) == WRITE) && (lo->flags & NBD_WRITE_NOCHK))
442  *   { printk( "Warning: Ignoring result!\n"); nbd_end_request( req ); }
443  */
444
445 static void do_nbd_request(struct request_queue * q)
446 {
447         struct request *req;
448         
449         while ((req = elv_next_request(q)) != NULL) {
450                 struct nbd_device *lo;
451
452                 blkdev_dequeue_request(req);
453                 dprintk(DBG_BLKDEV, "%s: request %p: dequeued (flags=%x)\n",
454                                 req->rq_disk->disk_name, req, req->cmd_type);
455
456                 if (!blk_fs_request(req))
457                         goto error_out;
458
459                 lo = req->rq_disk->private_data;
460
461                 BUG_ON(lo->magic != LO_MAGIC);
462
463                 nbd_cmd(req) = NBD_CMD_READ;
464                 if (rq_data_dir(req) == WRITE) {
465                         nbd_cmd(req) = NBD_CMD_WRITE;
466                         if (lo->flags & NBD_READ_ONLY) {
467                                 printk(KERN_ERR "%s: Write on read-only\n",
468                                                 lo->disk->disk_name);
469                                 goto error_out;
470                         }
471                 }
472
473                 req->errors = 0;
474                 spin_unlock_irq(q->queue_lock);
475
476                 mutex_lock(&lo->tx_lock);
477                 if (unlikely(!lo->sock)) {
478                         mutex_unlock(&lo->tx_lock);
479                         printk(KERN_ERR "%s: Attempted send on closed socket\n",
480                                lo->disk->disk_name);
481                         req->errors++;
482                         nbd_end_request(req);
483                         spin_lock_irq(q->queue_lock);
484                         continue;
485                 }
486
487                 lo->active_req = req;
488
489                 if (nbd_send_req(lo, req) != 0) {
490                         printk(KERN_ERR "%s: Request send failed\n",
491                                         lo->disk->disk_name);
492                         req->errors++;
493                         nbd_end_request(req);
494                 } else {
495                         spin_lock(&lo->queue_lock);
496                         list_add(&req->queuelist, &lo->queue_head);
497                         spin_unlock(&lo->queue_lock);
498                 }
499
500                 lo->active_req = NULL;
501                 mutex_unlock(&lo->tx_lock);
502                 wake_up_all(&lo->active_wq);
503
504                 spin_lock_irq(q->queue_lock);
505                 continue;
506
507 error_out:
508                 req->errors++;
509                 spin_unlock(q->queue_lock);
510                 nbd_end_request(req);
511                 spin_lock(q->queue_lock);
512         }
513 }
514
515 static int nbd_ioctl(struct inode *inode, struct file *file,
516                      unsigned int cmd, unsigned long arg)
517 {
518         struct nbd_device *lo = inode->i_bdev->bd_disk->private_data;
519         int error;
520         struct request sreq ;
521
522         if (!capable(CAP_SYS_ADMIN))
523                 return -EPERM;
524
525         BUG_ON(lo->magic != LO_MAGIC);
526
527         /* Anyone capable of this syscall can do *real bad* things */
528         dprintk(DBG_IOCTL, "%s: nbd_ioctl cmd=%s(0x%x) arg=%lu\n",
529                         lo->disk->disk_name, ioctl_cmd_to_ascii(cmd), cmd, arg);
530
531         switch (cmd) {
532         case NBD_DISCONNECT:
533                 printk(KERN_INFO "%s: NBD_DISCONNECT\n", lo->disk->disk_name);
534                 sreq.cmd_type = REQ_TYPE_SPECIAL;
535                 nbd_cmd(&sreq) = NBD_CMD_DISC;
536                 /*
537                  * Set these to sane values in case server implementation
538                  * fails to check the request type first and also to keep
539                  * debugging output cleaner.
540                  */
541                 sreq.sector = 0;
542                 sreq.nr_sectors = 0;
543                 if (!lo->sock)
544                         return -EINVAL;
545                 mutex_lock(&lo->tx_lock);
546                 nbd_send_req(lo, &sreq);
547                 mutex_unlock(&lo->tx_lock);
548                 return 0;
549  
550         case NBD_CLEAR_SOCK:
551                 error = 0;
552                 mutex_lock(&lo->tx_lock);
553                 lo->sock = NULL;
554                 mutex_unlock(&lo->tx_lock);
555                 file = lo->file;
556                 lo->file = NULL;
557                 nbd_clear_que(lo);
558                 BUG_ON(!list_empty(&lo->queue_head));
559                 if (file)
560                         fput(file);
561                 return error;
562         case NBD_SET_SOCK:
563                 if (lo->file)
564                         return -EBUSY;
565                 error = -EINVAL;
566                 file = fget(arg);
567                 if (file) {
568                         inode = file->f_path.dentry->d_inode;
569                         if (S_ISSOCK(inode->i_mode)) {
570                                 lo->file = file;
571                                 lo->sock = SOCKET_I(inode);
572                                 error = 0;
573                         } else {
574                                 fput(file);
575                         }
576                 }
577                 return error;
578         case NBD_SET_BLKSIZE:
579                 lo->blksize = arg;
580                 lo->bytesize &= ~(lo->blksize-1);
581                 inode->i_bdev->bd_inode->i_size = lo->bytesize;
582                 set_blocksize(inode->i_bdev, lo->blksize);
583                 set_capacity(lo->disk, lo->bytesize >> 9);
584                 return 0;
585         case NBD_SET_SIZE:
586                 lo->bytesize = arg & ~(lo->blksize-1);
587                 inode->i_bdev->bd_inode->i_size = lo->bytesize;
588                 set_blocksize(inode->i_bdev, lo->blksize);
589                 set_capacity(lo->disk, lo->bytesize >> 9);
590                 return 0;
591         case NBD_SET_TIMEOUT:
592                 lo->xmit_timeout = arg * HZ;
593                 return 0;
594         case NBD_SET_SIZE_BLOCKS:
595                 lo->bytesize = ((u64) arg) * lo->blksize;
596                 inode->i_bdev->bd_inode->i_size = lo->bytesize;
597                 set_blocksize(inode->i_bdev, lo->blksize);
598                 set_capacity(lo->disk, lo->bytesize >> 9);
599                 return 0;
600         case NBD_DO_IT:
601                 if (!lo->file)
602                         return -EINVAL;
603                 error = nbd_do_it(lo);
604                 if (error)
605                         return error;
606                 sock_shutdown(lo, 1);
607                 file = lo->file;
608                 lo->file = NULL;
609                 nbd_clear_que(lo);
610                 printk(KERN_WARNING "%s: queue cleared\n", lo->disk->disk_name);
611                 if (file)
612                         fput(file);
613                 lo->bytesize = 0;
614                 inode->i_bdev->bd_inode->i_size = 0;
615                 set_capacity(lo->disk, 0);
616                 return lo->harderror;
617         case NBD_CLEAR_QUE:
618                 /*
619                  * This is for compatibility only.  The queue is always cleared
620                  * by NBD_DO_IT or NBD_CLEAR_SOCK.
621                  */
622                 BUG_ON(!lo->sock && !list_empty(&lo->queue_head));
623                 return 0;
624         case NBD_PRINT_DEBUG:
625                 printk(KERN_INFO "%s: next = %p, prev = %p, head = %p\n",
626                         inode->i_bdev->bd_disk->disk_name,
627                         lo->queue_head.next, lo->queue_head.prev,
628                         &lo->queue_head);
629                 return 0;
630         }
631         return -EINVAL;
632 }
633
634 static struct block_device_operations nbd_fops =
635 {
636         .owner =        THIS_MODULE,
637         .ioctl =        nbd_ioctl,
638 };
639
640 /*
641  * And here should be modules and kernel interface 
642  *  (Just smiley confuses emacs :-)
643  */
644
645 static int __init nbd_init(void)
646 {
647         int err = -ENOMEM;
648         int i;
649
650         BUILD_BUG_ON(sizeof(struct nbd_request) != 28);
651
652         nbd_dev = kcalloc(nbds_max, sizeof(*nbd_dev), GFP_KERNEL);
653         if (!nbd_dev)
654                 return -ENOMEM;
655
656         for (i = 0; i < nbds_max; i++) {
657                 struct gendisk *disk = alloc_disk(1);
658                 elevator_t *old_e;
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                 old_e = disk->queue->elevator;
673                 if (elevator_init(disk->queue, "deadline") == 0 ||
674                         elevator_init(disk->queue, "noop") == 0) {
675                                 elevator_exit(old_e);
676                 }
677         }
678
679         if (register_blkdev(NBD_MAJOR, "nbd")) {
680                 err = -EIO;
681                 goto out;
682         }
683
684         printk(KERN_INFO "nbd: registered device at major %d\n", NBD_MAJOR);
685         dprintk(DBG_INIT, "nbd: debugflags=0x%x\n", debugflags);
686
687         for (i = 0; i < nbds_max; i++) {
688                 struct gendisk *disk = nbd_dev[i].disk;
689                 nbd_dev[i].file = NULL;
690                 nbd_dev[i].magic = LO_MAGIC;
691                 nbd_dev[i].flags = 0;
692                 spin_lock_init(&nbd_dev[i].queue_lock);
693                 INIT_LIST_HEAD(&nbd_dev[i].queue_head);
694                 mutex_init(&nbd_dev[i].tx_lock);
695                 init_waitqueue_head(&nbd_dev[i].active_wq);
696                 nbd_dev[i].blksize = 1024;
697                 nbd_dev[i].bytesize = 0;
698                 disk->major = NBD_MAJOR;
699                 disk->first_minor = i;
700                 disk->fops = &nbd_fops;
701                 disk->private_data = &nbd_dev[i];
702                 disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO;
703                 sprintf(disk->disk_name, "nbd%d", i);
704                 set_capacity(disk, 0);
705                 add_disk(disk);
706         }
707
708         return 0;
709 out:
710         while (i--) {
711                 blk_cleanup_queue(nbd_dev[i].disk->queue);
712                 put_disk(nbd_dev[i].disk);
713         }
714         return err;
715 }
716
717 static void __exit nbd_cleanup(void)
718 {
719         int i;
720         for (i = 0; i < nbds_max; i++) {
721                 struct gendisk *disk = nbd_dev[i].disk;
722                 nbd_dev[i].magic = 0;
723                 if (disk) {
724                         del_gendisk(disk);
725                         blk_cleanup_queue(disk->queue);
726                         put_disk(disk);
727                 }
728         }
729         unregister_blkdev(NBD_MAJOR, "nbd");
730         printk(KERN_INFO "nbd: unregistered device at major %d\n", NBD_MAJOR);
731 }
732
733 module_init(nbd_init);
734 module_exit(nbd_cleanup);
735
736 MODULE_DESCRIPTION("Network Block Device");
737 MODULE_LICENSE("GPL");
738
739 module_param(nbds_max, int, 0444);
740 MODULE_PARM_DESC(nbds_max, "How many network block devices to initialize.");
741 #ifndef NDEBUG
742 module_param(debugflags, int, 0644);
743 MODULE_PARM_DESC(debugflags, "flags for controlling debug output");
744 #endif