[SPARC64]: arch/sparc64/kernel/trampoline.S needs asm/cpudata.h
[linux-2.6] / 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  * (part of code stolen from loop.c)
11  *
12  * 97-3-25 compiled 0-th version, not yet tested it 
13  *   (it did not work, BTW) (later that day) HEY! it works!
14  *   (bit later) hmm, not that much... 2:00am next day:
15  *   yes, it works, but it gives something like 50kB/sec
16  * 97-4-01 complete rewrite to make it possible for many requests at 
17  *   once to be processed
18  * 97-4-11 Making protocol independent of endianity etc.
19  * 97-9-13 Cosmetic changes
20  * 98-5-13 Attempt to make 64-bit-clean on 64-bit machines
21  * 99-1-11 Attempt to make 64-bit-clean on 32-bit machines <ankry@mif.pg.gda.pl>
22  * 01-2-27 Fix to store proper blockcount for kernel (calculated using
23  *   BLOCK_SIZE_BITS, not device blocksize) <aga@permonline.ru>
24  * 01-3-11 Make nbd work with new Linux block layer code. It now supports
25  *   plugging like all the other block devices. Also added in MSG_MORE to
26  *   reduce number of partial TCP segments sent. <steve@chygwyn.com>
27  * 01-12-6 Fix deadlock condition by making queue locks independent of
28  *   the transmit lock. <steve@chygwyn.com>
29  * 02-10-11 Allow hung xmit to be aborted via SIGKILL & various fixes.
30  *   <Paul.Clements@SteelEye.com> <James.Bottomley@SteelEye.com>
31  * 03-06-22 Make nbd work with new linux 2.5 block layer design. This fixes
32  *   memory corruption from module removal and possible memory corruption
33  *   from sending/receiving disk data. <ldl@aros.net>
34  * 03-06-23 Cosmetic changes. <ldl@aros.net>
35  * 03-06-23 Enhance diagnostics support. <ldl@aros.net>
36  * 03-06-24 Remove unneeded blksize_bits field from nbd_device struct.
37  *   <ldl@aros.net>
38  * 03-06-24 Cleanup PARANOIA usage & code. <ldl@aros.net>
39  * 04-02-19 Remove PARANOIA, plus various cleanups (Paul Clements)
40  * possible FIXME: make set_sock / set_blksize / set_size / do_it one syscall
41  * why not: would need access_ok and friends, would share yet another
42  *          structure with userland
43  */
44
45 #include <linux/major.h>
46
47 #include <linux/blkdev.h>
48 #include <linux/module.h>
49 #include <linux/init.h>
50 #include <linux/sched.h>
51 #include <linux/fs.h>
52 #include <linux/bio.h>
53 #include <linux/stat.h>
54 #include <linux/errno.h>
55 #include <linux/file.h>
56 #include <linux/ioctl.h>
57 #include <linux/compiler.h>
58 #include <linux/err.h>
59 #include <linux/kernel.h>
60 #include <net/sock.h>
61
62 #include <linux/devfs_fs_kernel.h>
63
64 #include <asm/uaccess.h>
65 #include <asm/system.h>
66 #include <asm/types.h>
67
68 #include <linux/nbd.h>
69
70 #define LO_MAGIC 0x68797548
71
72 #ifdef NDEBUG
73 #define dprintk(flags, fmt...)
74 #else /* NDEBUG */
75 #define dprintk(flags, fmt...) do { \
76         if (debugflags & (flags)) printk(KERN_DEBUG fmt); \
77 } while (0)
78 #define DBG_IOCTL       0x0004
79 #define DBG_INIT        0x0010
80 #define DBG_EXIT        0x0020
81 #define DBG_BLKDEV      0x0100
82 #define DBG_RX          0x0200
83 #define DBG_TX          0x0400
84 static unsigned int debugflags;
85 static unsigned int nbds_max = 16;
86 #endif /* NDEBUG */
87
88 static struct nbd_device nbd_dev[MAX_NBD];
89
90 /*
91  * Use just one lock (or at most 1 per NIC). Two arguments for this:
92  * 1. Each NIC is essentially a synchronization point for all servers
93  *    accessed through that NIC so there's no need to have more locks
94  *    than NICs anyway.
95  * 2. More locks lead to more "Dirty cache line bouncing" which will slow
96  *    down each lock to the point where they're actually slower than just
97  *    a single lock.
98  * Thanks go to Jens Axboe and Al Viro for their LKML emails explaining this!
99  */
100 static DEFINE_SPINLOCK(nbd_lock);
101
102 #ifndef NDEBUG
103 static const char *ioctl_cmd_to_ascii(int cmd)
104 {
105         switch (cmd) {
106         case NBD_SET_SOCK: return "set-sock";
107         case NBD_SET_BLKSIZE: return "set-blksize";
108         case NBD_SET_SIZE: return "set-size";
109         case NBD_DO_IT: return "do-it";
110         case NBD_CLEAR_SOCK: return "clear-sock";
111         case NBD_CLEAR_QUE: return "clear-que";
112         case NBD_PRINT_DEBUG: return "print-debug";
113         case NBD_SET_SIZE_BLOCKS: return "set-size-blocks";
114         case NBD_DISCONNECT: return "disconnect";
115         case BLKROSET: return "set-read-only";
116         case BLKFLSBUF: return "flush-buffer-cache";
117         }
118         return "unknown";
119 }
120
121 static const char *nbdcmd_to_ascii(int cmd)
122 {
123         switch (cmd) {
124         case  NBD_CMD_READ: return "read";
125         case NBD_CMD_WRITE: return "write";
126         case  NBD_CMD_DISC: return "disconnect";
127         }
128         return "invalid";
129 }
130 #endif /* NDEBUG */
131
132 static void nbd_end_request(struct request *req)
133 {
134         int uptodate = (req->errors == 0) ? 1 : 0;
135         request_queue_t *q = req->q;
136         unsigned long flags;
137
138         dprintk(DBG_BLKDEV, "%s: request %p: %s\n", req->rq_disk->disk_name,
139                         req, uptodate? "done": "failed");
140
141         spin_lock_irqsave(q->queue_lock, flags);
142         if (!end_that_request_first(req, uptodate, req->nr_sectors)) {
143                 end_that_request_last(req, uptodate);
144         }
145         spin_unlock_irqrestore(q->queue_lock, flags);
146 }
147
148 /*
149  *  Send or receive packet.
150  */
151 static int sock_xmit(struct socket *sock, int send, void *buf, int size,
152                 int msg_flags)
153 {
154         int result;
155         struct msghdr msg;
156         struct kvec iov;
157         unsigned long flags;
158         sigset_t oldset;
159
160         /* Allow interception of SIGKILL only
161          * Don't allow other signals to interrupt the transmission */
162         spin_lock_irqsave(&current->sighand->siglock, flags);
163         oldset = current->blocked;
164         sigfillset(&current->blocked);
165         sigdelsetmask(&current->blocked, sigmask(SIGKILL));
166         recalc_sigpending();
167         spin_unlock_irqrestore(&current->sighand->siglock, flags);
168
169         do {
170                 sock->sk->sk_allocation = GFP_NOIO;
171                 iov.iov_base = buf;
172                 iov.iov_len = size;
173                 msg.msg_name = NULL;
174                 msg.msg_namelen = 0;
175                 msg.msg_control = NULL;
176                 msg.msg_controllen = 0;
177                 msg.msg_flags = msg_flags | MSG_NOSIGNAL;
178
179                 if (send)
180                         result = kernel_sendmsg(sock, &msg, &iov, 1, size);
181                 else
182                         result = kernel_recvmsg(sock, &msg, &iov, 1, size, 0);
183
184                 if (signal_pending(current)) {
185                         siginfo_t info;
186                         spin_lock_irqsave(&current->sighand->siglock, flags);
187                         printk(KERN_WARNING "nbd (pid %d: %s) got signal %d\n",
188                                 current->pid, current->comm, 
189                                 dequeue_signal(current, &current->blocked, &info));
190                         spin_unlock_irqrestore(&current->sighand->siglock, flags);
191                         result = -EINTR;
192                         break;
193                 }
194
195                 if (result <= 0) {
196                         if (result == 0)
197                                 result = -EPIPE; /* short read */
198                         break;
199                 }
200                 size -= result;
201                 buf += result;
202         } while (size > 0);
203
204         spin_lock_irqsave(&current->sighand->siglock, flags);
205         current->blocked = oldset;
206         recalc_sigpending();
207         spin_unlock_irqrestore(&current->sighand->siglock, flags);
208
209         return result;
210 }
211
212 static inline int sock_send_bvec(struct socket *sock, struct bio_vec *bvec,
213                 int flags)
214 {
215         int result;
216         void *kaddr = kmap(bvec->bv_page);
217         result = sock_xmit(sock, 1, kaddr + bvec->bv_offset, bvec->bv_len,
218                         flags);
219         kunmap(bvec->bv_page);
220         return result;
221 }
222
223 static int nbd_send_req(struct nbd_device *lo, struct request *req)
224 {
225         int result, i, flags;
226         struct nbd_request request;
227         unsigned long size = req->nr_sectors << 9;
228         struct socket *sock = lo->sock;
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(sock, 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 bio *bio;
251                 /*
252                  * we are really probing at internals to determine
253                  * whether to set MSG_MORE or not...
254                  */
255                 rq_for_each_bio(bio, req) {
256                         struct bio_vec *bvec;
257                         bio_for_each_segment(bvec, bio, i) {
258                                 flags = 0;
259                                 if ((i < (bio->bi_vcnt - 1)) || bio->bi_next)
260                                         flags = MSG_MORE;
261                                 dprintk(DBG_TX, "%s: request %p: sending %d bytes data\n",
262                                                 lo->disk->disk_name, req,
263                                                 bvec->bv_len);
264                                 result = sock_send_bvec(sock, bvec, flags);
265                                 if (result <= 0) {
266                                         printk(KERN_ERR "%s: Send data failed (result %d)\n",
267                                                         lo->disk->disk_name,
268                                                         result);
269                                         goto error_out;
270                                 }
271                         }
272                 }
273         }
274         return 0;
275
276 error_out:
277         return 1;
278 }
279
280 static struct request *nbd_find_request(struct nbd_device *lo, char *handle)
281 {
282         struct request *req;
283         struct list_head *tmp;
284         struct request *xreq;
285         int err;
286
287         memcpy(&xreq, handle, sizeof(xreq));
288
289         err = wait_event_interruptible(lo->active_wq, lo->active_req != xreq);
290         if (unlikely(err))
291                 goto out;
292
293         spin_lock(&lo->queue_lock);
294         list_for_each(tmp, &lo->queue_head) {
295                 req = list_entry(tmp, struct request, queuelist);
296                 if (req != xreq)
297                         continue;
298                 list_del_init(&req->queuelist);
299                 spin_unlock(&lo->queue_lock);
300                 return req;
301         }
302         spin_unlock(&lo->queue_lock);
303
304         err = -ENOENT;
305
306 out:
307         return ERR_PTR(err);
308 }
309
310 static inline int sock_recv_bvec(struct socket *sock, struct bio_vec *bvec)
311 {
312         int result;
313         void *kaddr = kmap(bvec->bv_page);
314         result = sock_xmit(sock, 0, kaddr + bvec->bv_offset, bvec->bv_len,
315                         MSG_WAITALL);
316         kunmap(bvec->bv_page);
317         return result;
318 }
319
320 /* NULL returned = something went wrong, inform userspace */
321 static struct request *nbd_read_stat(struct nbd_device *lo)
322 {
323         int result;
324         struct nbd_reply reply;
325         struct request *req;
326         struct socket *sock = lo->sock;
327
328         reply.magic = 0;
329         result = sock_xmit(sock, 0, &reply, sizeof(reply), MSG_WAITALL);
330         if (result <= 0) {
331                 printk(KERN_ERR "%s: Receive control failed (result %d)\n",
332                                 lo->disk->disk_name, result);
333                 goto harderror;
334         }
335         req = nbd_find_request(lo, 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.magic) != NBD_REPLY_MAGIC) {
348                 printk(KERN_ERR "%s: Wrong magic (0x%lx)\n",
349                                 lo->disk->disk_name,
350                                 (unsigned long)ntohl(reply.magic));
351                 result = -EPROTO;
352                 goto harderror;
353         }
354         if (ntohl(reply.error)) {
355                 printk(KERN_ERR "%s: Other side returned error (%d)\n",
356                                 lo->disk->disk_name, ntohl(reply.error));
357                 req->errors++;
358                 return req;
359         }
360
361         dprintk(DBG_RX, "%s: request %p: got reply\n",
362                         lo->disk->disk_name, req);
363         if (nbd_cmd(req) == NBD_CMD_READ) {
364                 int i;
365                 struct bio *bio;
366                 rq_for_each_bio(bio, req) {
367                         struct bio_vec *bvec;
368                         bio_for_each_segment(bvec, bio, i) {
369                                 result = sock_recv_bvec(sock, bvec);
370                                 if (result <= 0) {
371                                         printk(KERN_ERR "%s: Receive data failed (result %d)\n",
372                                                         lo->disk->disk_name,
373                                                         result);
374                                         goto harderror;
375                                 }
376                                 dprintk(DBG_RX, "%s: request %p: got %d bytes data\n",
377                                         lo->disk->disk_name, req, bvec->bv_len);
378                         }
379                 }
380         }
381         return req;
382 harderror:
383         lo->harderror = result;
384         return NULL;
385 }
386
387 static void nbd_do_it(struct nbd_device *lo)
388 {
389         struct request *req;
390
391         BUG_ON(lo->magic != LO_MAGIC);
392
393         while ((req = nbd_read_stat(lo)) != NULL)
394                 nbd_end_request(req);
395         return;
396 }
397
398 static void nbd_clear_que(struct nbd_device *lo)
399 {
400         struct request *req;
401
402         BUG_ON(lo->magic != LO_MAGIC);
403
404         /*
405          * Because we have set lo->sock to NULL under the tx_lock, all
406          * modifications to the list must have completed by now.  For
407          * the same reason, the active_req must be NULL.
408          *
409          * As a consequence, we don't need to take the spin lock while
410          * purging the list here.
411          */
412         BUG_ON(lo->sock);
413         BUG_ON(lo->active_req);
414
415         while (!list_empty(&lo->queue_head)) {
416                 req = list_entry(lo->queue_head.next, struct request,
417                                  queuelist);
418                 list_del_init(&req->queuelist);
419                 req->errors++;
420                 nbd_end_request(req);
421         }
422 }
423
424 /*
425  * We always wait for result of write, for now. It would be nice to make it optional
426  * in future
427  * if ((req->cmd == WRITE) && (lo->flags & NBD_WRITE_NOCHK)) 
428  *   { printk( "Warning: Ignoring result!\n"); nbd_end_request( req ); }
429  */
430
431 static void do_nbd_request(request_queue_t * q)
432 {
433         struct request *req;
434         
435         while ((req = elv_next_request(q)) != NULL) {
436                 struct nbd_device *lo;
437
438                 blkdev_dequeue_request(req);
439                 dprintk(DBG_BLKDEV, "%s: request %p: dequeued (flags=%lx)\n",
440                                 req->rq_disk->disk_name, req, req->flags);
441
442                 if (!(req->flags & REQ_CMD))
443                         goto error_out;
444
445                 lo = req->rq_disk->private_data;
446
447                 BUG_ON(lo->magic != LO_MAGIC);
448
449                 nbd_cmd(req) = NBD_CMD_READ;
450                 if (rq_data_dir(req) == WRITE) {
451                         nbd_cmd(req) = NBD_CMD_WRITE;
452                         if (lo->flags & NBD_READ_ONLY) {
453                                 printk(KERN_ERR "%s: Write on read-only\n",
454                                                 lo->disk->disk_name);
455                                 goto error_out;
456                         }
457                 }
458
459                 req->errors = 0;
460                 spin_unlock_irq(q->queue_lock);
461
462                 down(&lo->tx_lock);
463                 if (unlikely(!lo->sock)) {
464                         up(&lo->tx_lock);
465                         printk(KERN_ERR "%s: Attempted send on closed socket\n",
466                                lo->disk->disk_name);
467                         req->errors++;
468                         nbd_end_request(req);
469                         spin_lock_irq(q->queue_lock);
470                         continue;
471                 }
472
473                 lo->active_req = req;
474
475                 if (nbd_send_req(lo, req) != 0) {
476                         printk(KERN_ERR "%s: Request send failed\n",
477                                         lo->disk->disk_name);
478                         req->errors++;
479                         nbd_end_request(req);
480                 } else {
481                         spin_lock(&lo->queue_lock);
482                         list_add(&req->queuelist, &lo->queue_head);
483                         spin_unlock(&lo->queue_lock);
484                 }
485
486                 lo->active_req = NULL;
487                 up(&lo->tx_lock);
488                 wake_up_all(&lo->active_wq);
489
490                 spin_lock_irq(q->queue_lock);
491                 continue;
492
493 error_out:
494                 req->errors++;
495                 spin_unlock(q->queue_lock);
496                 nbd_end_request(req);
497                 spin_lock(q->queue_lock);
498         }
499         return;
500 }
501
502 static int nbd_ioctl(struct inode *inode, struct file *file,
503                      unsigned int cmd, unsigned long arg)
504 {
505         struct nbd_device *lo = inode->i_bdev->bd_disk->private_data;
506         int error;
507         struct request sreq ;
508
509         if (!capable(CAP_SYS_ADMIN))
510                 return -EPERM;
511
512         BUG_ON(lo->magic != LO_MAGIC);
513
514         /* Anyone capable of this syscall can do *real bad* things */
515         dprintk(DBG_IOCTL, "%s: nbd_ioctl cmd=%s(0x%x) arg=%lu\n",
516                         lo->disk->disk_name, ioctl_cmd_to_ascii(cmd), cmd, arg);
517
518         switch (cmd) {
519         case NBD_DISCONNECT:
520                 printk(KERN_INFO "%s: NBD_DISCONNECT\n", lo->disk->disk_name);
521                 sreq.flags = REQ_SPECIAL;
522                 nbd_cmd(&sreq) = NBD_CMD_DISC;
523                 /*
524                  * Set these to sane values in case server implementation
525                  * fails to check the request type first and also to keep
526                  * debugging output cleaner.
527                  */
528                 sreq.sector = 0;
529                 sreq.nr_sectors = 0;
530                 if (!lo->sock)
531                         return -EINVAL;
532                 nbd_send_req(lo, &sreq);
533                 return 0;
534  
535         case NBD_CLEAR_SOCK:
536                 error = 0;
537                 down(&lo->tx_lock);
538                 lo->sock = NULL;
539                 up(&lo->tx_lock);
540                 file = lo->file;
541                 lo->file = NULL;
542                 nbd_clear_que(lo);
543                 BUG_ON(!list_empty(&lo->queue_head));
544                 if (file)
545                         fput(file);
546                 return error;
547         case NBD_SET_SOCK:
548                 if (lo->file)
549                         return -EBUSY;
550                 error = -EINVAL;
551                 file = fget(arg);
552                 if (file) {
553                         inode = file->f_dentry->d_inode;
554                         if (S_ISSOCK(inode->i_mode)) {
555                                 lo->file = file;
556                                 lo->sock = SOCKET_I(inode);
557                                 error = 0;
558                         } else {
559                                 fput(file);
560                         }
561                 }
562                 return error;
563         case NBD_SET_BLKSIZE:
564                 lo->blksize = arg;
565                 lo->bytesize &= ~(lo->blksize-1);
566                 inode->i_bdev->bd_inode->i_size = lo->bytesize;
567                 set_blocksize(inode->i_bdev, lo->blksize);
568                 set_capacity(lo->disk, lo->bytesize >> 9);
569                 return 0;
570         case NBD_SET_SIZE:
571                 lo->bytesize = arg & ~(lo->blksize-1);
572                 inode->i_bdev->bd_inode->i_size = lo->bytesize;
573                 set_blocksize(inode->i_bdev, lo->blksize);
574                 set_capacity(lo->disk, lo->bytesize >> 9);
575                 return 0;
576         case NBD_SET_SIZE_BLOCKS:
577                 lo->bytesize = ((u64) arg) * lo->blksize;
578                 inode->i_bdev->bd_inode->i_size = lo->bytesize;
579                 set_blocksize(inode->i_bdev, lo->blksize);
580                 set_capacity(lo->disk, lo->bytesize >> 9);
581                 return 0;
582         case NBD_DO_IT:
583                 if (!lo->file)
584                         return -EINVAL;
585                 nbd_do_it(lo);
586                 /* on return tidy up in case we have a signal */
587                 /* Forcibly shutdown the socket causing all listeners
588                  * to error
589                  *
590                  * FIXME: This code is duplicated from sys_shutdown, but
591                  * there should be a more generic interface rather than
592                  * calling socket ops directly here */
593                 down(&lo->tx_lock);
594                 if (lo->sock) {
595                         printk(KERN_WARNING "%s: shutting down socket\n",
596                                 lo->disk->disk_name);
597                         lo->sock->ops->shutdown(lo->sock,
598                                 SEND_SHUTDOWN|RCV_SHUTDOWN);
599                         lo->sock = NULL;
600                 }
601                 up(&lo->tx_lock);
602                 file = lo->file;
603                 lo->file = NULL;
604                 nbd_clear_que(lo);
605                 printk(KERN_WARNING "%s: queue cleared\n", lo->disk->disk_name);
606                 if (file)
607                         fput(file);
608                 return lo->harderror;
609         case NBD_CLEAR_QUE:
610                 /*
611                  * This is for compatibility only.  The queue is always cleared
612                  * by NBD_DO_IT or NBD_CLEAR_SOCK.
613                  */
614                 BUG_ON(!lo->sock && !list_empty(&lo->queue_head));
615                 return 0;
616         case NBD_PRINT_DEBUG:
617                 printk(KERN_INFO "%s: next = %p, prev = %p, head = %p\n",
618                         inode->i_bdev->bd_disk->disk_name,
619                         lo->queue_head.next, lo->queue_head.prev,
620                         &lo->queue_head);
621                 return 0;
622         }
623         return -EINVAL;
624 }
625
626 static struct block_device_operations nbd_fops =
627 {
628         .owner =        THIS_MODULE,
629         .ioctl =        nbd_ioctl,
630 };
631
632 /*
633  * And here should be modules and kernel interface 
634  *  (Just smiley confuses emacs :-)
635  */
636
637 static int __init nbd_init(void)
638 {
639         int err = -ENOMEM;
640         int i;
641
642         if (sizeof(struct nbd_request) != 28) {
643                 printk(KERN_CRIT "nbd: sizeof nbd_request needs to be 28 in order to work!\n" );
644                 return -EIO;
645         }
646
647         if (nbds_max > MAX_NBD) {
648                 printk(KERN_CRIT "nbd: cannot allocate more than %u nbds; %u requested.\n", MAX_NBD,
649                                 nbds_max);
650                 return -EINVAL;
651         }
652
653         for (i = 0; i < nbds_max; i++) {
654                 struct gendisk *disk = alloc_disk(1);
655                 if (!disk)
656                         goto out;
657                 nbd_dev[i].disk = disk;
658                 /*
659                  * The new linux 2.5 block layer implementation requires
660                  * every gendisk to have its very own request_queue struct.
661                  * These structs are big so we dynamically allocate them.
662                  */
663                 disk->queue = blk_init_queue(do_nbd_request, &nbd_lock);
664                 if (!disk->queue) {
665                         put_disk(disk);
666                         goto out;
667                 }
668         }
669
670         if (register_blkdev(NBD_MAJOR, "nbd")) {
671                 err = -EIO;
672                 goto out;
673         }
674
675         printk(KERN_INFO "nbd: registered device at major %d\n", NBD_MAJOR);
676         dprintk(DBG_INIT, "nbd: debugflags=0x%x\n", debugflags);
677
678         devfs_mk_dir("nbd");
679         for (i = 0; i < nbds_max; i++) {
680                 struct gendisk *disk = nbd_dev[i].disk;
681                 nbd_dev[i].file = NULL;
682                 nbd_dev[i].magic = LO_MAGIC;
683                 nbd_dev[i].flags = 0;
684                 spin_lock_init(&nbd_dev[i].queue_lock);
685                 INIT_LIST_HEAD(&nbd_dev[i].queue_head);
686                 init_MUTEX(&nbd_dev[i].tx_lock);
687                 init_waitqueue_head(&nbd_dev[i].active_wq);
688                 nbd_dev[i].blksize = 1024;
689                 nbd_dev[i].bytesize = 0x7ffffc00ULL << 10; /* 2TB */
690                 disk->major = NBD_MAJOR;
691                 disk->first_minor = i;
692                 disk->fops = &nbd_fops;
693                 disk->private_data = &nbd_dev[i];
694                 disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO;
695                 sprintf(disk->disk_name, "nbd%d", i);
696                 sprintf(disk->devfs_name, "nbd/%d", i);
697                 set_capacity(disk, 0x7ffffc00ULL << 1); /* 2 TB */
698                 add_disk(disk);
699         }
700
701         return 0;
702 out:
703         while (i--) {
704                 blk_cleanup_queue(nbd_dev[i].disk->queue);
705                 put_disk(nbd_dev[i].disk);
706         }
707         return err;
708 }
709
710 static void __exit nbd_cleanup(void)
711 {
712         int i;
713         for (i = 0; i < nbds_max; i++) {
714                 struct gendisk *disk = nbd_dev[i].disk;
715                 nbd_dev[i].magic = 0;
716                 if (disk) {
717                         del_gendisk(disk);
718                         blk_cleanup_queue(disk->queue);
719                         put_disk(disk);
720                 }
721         }
722         devfs_remove("nbd");
723         unregister_blkdev(NBD_MAJOR, "nbd");
724         printk(KERN_INFO "nbd: unregistered device at major %d\n", NBD_MAJOR);
725 }
726
727 module_init(nbd_init);
728 module_exit(nbd_cleanup);
729
730 MODULE_DESCRIPTION("Network Block Device");
731 MODULE_LICENSE("GPL");
732
733 module_param(nbds_max, int, 0444);
734 MODULE_PARM_DESC(nbds_max, "How many network block devices to initialize.");
735 #ifndef NDEBUG
736 module_param(debugflags, int, 0644);
737 MODULE_PARM_DESC(debugflags, "flags for controlling debug output");
738 #endif