[PATCH] lockd endianness annotations
[linux-2.6.git] / fs / lockd / svclock.c
1 /*
2  * linux/fs/lockd/svclock.c
3  *
4  * Handling of server-side locks, mostly of the blocked variety.
5  * This is the ugliest part of lockd because we tread on very thin ice.
6  * GRANT and CANCEL calls may get stuck, meet in mid-flight, etc.
7  * IMNSHO introducing the grant callback into the NLM protocol was one
8  * of the worst ideas Sun ever had. Except maybe for the idea of doing
9  * NFS file locking at all.
10  *
11  * I'm trying hard to avoid race conditions by protecting most accesses
12  * to a file's list of blocked locks through a semaphore. The global
13  * list of blocked locks is not protected in this fashion however.
14  * Therefore, some functions (such as the RPC callback for the async grant
15  * call) move blocked locks towards the head of the list *while some other
16  * process might be traversing it*. This should not be a problem in
17  * practice, because this will only cause functions traversing the list
18  * to visit some blocks twice.
19  *
20  * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
21  */
22
23 #include <linux/types.h>
24 #include <linux/errno.h>
25 #include <linux/kernel.h>
26 #include <linux/sched.h>
27 #include <linux/smp_lock.h>
28 #include <linux/sunrpc/clnt.h>
29 #include <linux/sunrpc/svc.h>
30 #include <linux/lockd/nlm.h>
31 #include <linux/lockd/lockd.h>
32
33 #define NLMDBG_FACILITY         NLMDBG_SVCLOCK
34
35 #ifdef CONFIG_LOCKD_V4
36 #define nlm_deadlock    nlm4_deadlock
37 #else
38 #define nlm_deadlock    nlm_lck_denied
39 #endif
40
41 static void nlmsvc_release_block(struct nlm_block *block);
42 static void     nlmsvc_insert_block(struct nlm_block *block, unsigned long);
43 static void     nlmsvc_remove_block(struct nlm_block *block);
44
45 static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock);
46 static void nlmsvc_freegrantargs(struct nlm_rqst *call);
47 static const struct rpc_call_ops nlmsvc_grant_ops;
48
49 /*
50  * The list of blocked locks to retry
51  */
52 static LIST_HEAD(nlm_blocked);
53
54 /*
55  * Insert a blocked lock into the global list
56  */
57 static void
58 nlmsvc_insert_block(struct nlm_block *block, unsigned long when)
59 {
60         struct nlm_block *b;
61         struct list_head *pos;
62
63         dprintk("lockd: nlmsvc_insert_block(%p, %ld)\n", block, when);
64         if (list_empty(&block->b_list)) {
65                 kref_get(&block->b_count);
66         } else {
67                 list_del_init(&block->b_list);
68         }
69
70         pos = &nlm_blocked;
71         if (when != NLM_NEVER) {
72                 if ((when += jiffies) == NLM_NEVER)
73                         when ++;
74                 list_for_each(pos, &nlm_blocked) {
75                         b = list_entry(pos, struct nlm_block, b_list);
76                         if (time_after(b->b_when,when) || b->b_when == NLM_NEVER)
77                                 break;
78                 }
79                 /* On normal exit from the loop, pos == &nlm_blocked,
80                  * so we will be adding to the end of the list - good
81                  */
82         }
83
84         list_add_tail(&block->b_list, pos);
85         block->b_when = when;
86 }
87
88 /*
89  * Remove a block from the global list
90  */
91 static inline void
92 nlmsvc_remove_block(struct nlm_block *block)
93 {
94         if (!list_empty(&block->b_list)) {
95                 list_del_init(&block->b_list);
96                 nlmsvc_release_block(block);
97         }
98 }
99
100 /*
101  * Find a block for a given lock
102  */
103 static struct nlm_block *
104 nlmsvc_lookup_block(struct nlm_file *file, struct nlm_lock *lock)
105 {
106         struct nlm_block        *block;
107         struct file_lock        *fl;
108
109         dprintk("lockd: nlmsvc_lookup_block f=%p pd=%d %Ld-%Ld ty=%d\n",
110                                 file, lock->fl.fl_pid,
111                                 (long long)lock->fl.fl_start,
112                                 (long long)lock->fl.fl_end, lock->fl.fl_type);
113         list_for_each_entry(block, &nlm_blocked, b_list) {
114                 fl = &block->b_call->a_args.lock.fl;
115                 dprintk("lockd: check f=%p pd=%d %Ld-%Ld ty=%d cookie=%s\n",
116                                 block->b_file, fl->fl_pid,
117                                 (long long)fl->fl_start,
118                                 (long long)fl->fl_end, fl->fl_type,
119                                 nlmdbg_cookie2a(&block->b_call->a_args.cookie));
120                 if (block->b_file == file && nlm_compare_locks(fl, &lock->fl)) {
121                         kref_get(&block->b_count);
122                         return block;
123                 }
124         }
125
126         return NULL;
127 }
128
129 static inline int nlm_cookie_match(struct nlm_cookie *a, struct nlm_cookie *b)
130 {
131         if(a->len != b->len)
132                 return 0;
133         if(memcmp(a->data,b->data,a->len))
134                 return 0;
135         return 1;
136 }
137
138 /*
139  * Find a block with a given NLM cookie.
140  */
141 static inline struct nlm_block *
142 nlmsvc_find_block(struct nlm_cookie *cookie)
143 {
144         struct nlm_block *block;
145
146         list_for_each_entry(block, &nlm_blocked, b_list) {
147                 if (nlm_cookie_match(&block->b_call->a_args.cookie,cookie))
148                         goto found;
149         }
150
151         return NULL;
152
153 found:
154         dprintk("nlmsvc_find_block(%s): block=%p\n", nlmdbg_cookie2a(cookie), block);
155         kref_get(&block->b_count);
156         return block;
157 }
158
159 /*
160  * Create a block and initialize it.
161  *
162  * Note: we explicitly set the cookie of the grant reply to that of
163  * the blocked lock request. The spec explicitly mentions that the client
164  * should _not_ rely on the callback containing the same cookie as the
165  * request, but (as I found out later) that's because some implementations
166  * do just this. Never mind the standards comittees, they support our
167  * logging industries.
168  *
169  * 10 years later: I hope we can safely ignore these old and broken
170  * clients by now. Let's fix this so we can uniquely identify an incoming
171  * GRANTED_RES message by cookie, without having to rely on the client's IP
172  * address. --okir
173  */
174 static inline struct nlm_block *
175 nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_file *file,
176                                 struct nlm_lock *lock, struct nlm_cookie *cookie)
177 {
178         struct nlm_block        *block;
179         struct nlm_host         *host;
180         struct nlm_rqst         *call = NULL;
181
182         /* Create host handle for callback */
183         host = nlmsvc_lookup_host(rqstp, lock->caller, lock->len);
184         if (host == NULL)
185                 return NULL;
186
187         call = nlm_alloc_call(host);
188         if (call == NULL)
189                 return NULL;
190
191         /* Allocate memory for block, and initialize arguments */
192         block = kzalloc(sizeof(*block), GFP_KERNEL);
193         if (block == NULL)
194                 goto failed;
195         kref_init(&block->b_count);
196         INIT_LIST_HEAD(&block->b_list);
197         INIT_LIST_HEAD(&block->b_flist);
198
199         if (!nlmsvc_setgrantargs(call, lock))
200                 goto failed_free;
201
202         /* Set notifier function for VFS, and init args */
203         call->a_args.lock.fl.fl_flags |= FL_SLEEP;
204         call->a_args.lock.fl.fl_lmops = &nlmsvc_lock_operations;
205         nlmclnt_next_cookie(&call->a_args.cookie);
206
207         dprintk("lockd: created block %p...\n", block);
208
209         /* Create and initialize the block */
210         block->b_daemon = rqstp->rq_server;
211         block->b_host   = host;
212         block->b_file   = file;
213         file->f_count++;
214
215         /* Add to file's list of blocks */
216         list_add(&block->b_flist, &file->f_blocks);
217
218         /* Set up RPC arguments for callback */
219         block->b_call = call;
220         call->a_flags   = RPC_TASK_ASYNC;
221         call->a_block = block;
222
223         return block;
224
225 failed_free:
226         kfree(block);
227 failed:
228         nlm_release_call(call);
229         return NULL;
230 }
231
232 /*
233  * Delete a block. If the lock was cancelled or the grant callback
234  * failed, unlock is set to 1.
235  * It is the caller's responsibility to check whether the file
236  * can be closed hereafter.
237  */
238 static int nlmsvc_unlink_block(struct nlm_block *block)
239 {
240         int status;
241         dprintk("lockd: unlinking block %p...\n", block);
242
243         /* Remove block from list */
244         status = posix_unblock_lock(block->b_file->f_file, &block->b_call->a_args.lock.fl);
245         nlmsvc_remove_block(block);
246         return status;
247 }
248
249 static void nlmsvc_free_block(struct kref *kref)
250 {
251         struct nlm_block *block = container_of(kref, struct nlm_block, b_count);
252         struct nlm_file         *file = block->b_file;
253
254         dprintk("lockd: freeing block %p...\n", block);
255
256         /* Remove block from file's list of blocks */
257         mutex_lock(&file->f_mutex);
258         list_del_init(&block->b_flist);
259         mutex_unlock(&file->f_mutex);
260
261         nlmsvc_freegrantargs(block->b_call);
262         nlm_release_call(block->b_call);
263         nlm_release_file(block->b_file);
264         kfree(block);
265 }
266
267 static void nlmsvc_release_block(struct nlm_block *block)
268 {
269         if (block != NULL)
270                 kref_put(&block->b_count, nlmsvc_free_block);
271 }
272
273 /*
274  * Loop over all blocks and delete blocks held by
275  * a matching host.
276  */
277 void nlmsvc_traverse_blocks(struct nlm_host *host,
278                         struct nlm_file *file,
279                         nlm_host_match_fn_t match)
280 {
281         struct nlm_block *block, *next;
282
283 restart:
284         mutex_lock(&file->f_mutex);
285         list_for_each_entry_safe(block, next, &file->f_blocks, b_flist) {
286                 if (!match(block->b_host, host))
287                         continue;
288                 /* Do not destroy blocks that are not on
289                  * the global retry list - why? */
290                 if (list_empty(&block->b_list))
291                         continue;
292                 kref_get(&block->b_count);
293                 mutex_unlock(&file->f_mutex);
294                 nlmsvc_unlink_block(block);
295                 nlmsvc_release_block(block);
296                 goto restart;
297         }
298         mutex_unlock(&file->f_mutex);
299 }
300
301 /*
302  * Initialize arguments for GRANTED call. The nlm_rqst structure
303  * has been cleared already.
304  */
305 static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock)
306 {
307         locks_copy_lock(&call->a_args.lock.fl, &lock->fl);
308         memcpy(&call->a_args.lock.fh, &lock->fh, sizeof(call->a_args.lock.fh));
309         call->a_args.lock.caller = utsname()->nodename;
310         call->a_args.lock.oh.len = lock->oh.len;
311
312         /* set default data area */
313         call->a_args.lock.oh.data = call->a_owner;
314         call->a_args.lock.svid = lock->fl.fl_pid;
315
316         if (lock->oh.len > NLMCLNT_OHSIZE) {
317                 void *data = kmalloc(lock->oh.len, GFP_KERNEL);
318                 if (!data)
319                         return 0;
320                 call->a_args.lock.oh.data = (u8 *) data;
321         }
322
323         memcpy(call->a_args.lock.oh.data, lock->oh.data, lock->oh.len);
324         return 1;
325 }
326
327 static void nlmsvc_freegrantargs(struct nlm_rqst *call)
328 {
329         if (call->a_args.lock.oh.data != call->a_owner)
330                 kfree(call->a_args.lock.oh.data);
331 }
332
333 /*
334  * Attempt to establish a lock, and if it can't be granted, block it
335  * if required.
336  */
337 __be32
338 nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
339                         struct nlm_lock *lock, int wait, struct nlm_cookie *cookie)
340 {
341         struct nlm_block        *block, *newblock = NULL;
342         int                     error;
343         __be32                  ret;
344
345         dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
346                                 file->f_file->f_dentry->d_inode->i_sb->s_id,
347                                 file->f_file->f_dentry->d_inode->i_ino,
348                                 lock->fl.fl_type, lock->fl.fl_pid,
349                                 (long long)lock->fl.fl_start,
350                                 (long long)lock->fl.fl_end,
351                                 wait);
352
353
354         lock->fl.fl_flags &= ~FL_SLEEP;
355 again:
356         /* Lock file against concurrent access */
357         mutex_lock(&file->f_mutex);
358         /* Get existing block (in case client is busy-waiting) */
359         block = nlmsvc_lookup_block(file, lock);
360         if (block == NULL) {
361                 if (newblock != NULL)
362                         lock = &newblock->b_call->a_args.lock;
363         } else
364                 lock = &block->b_call->a_args.lock;
365
366         error = posix_lock_file(file->f_file, &lock->fl);
367         lock->fl.fl_flags &= ~FL_SLEEP;
368
369         dprintk("lockd: posix_lock_file returned %d\n", error);
370
371         switch(error) {
372                 case 0:
373                         ret = nlm_granted;
374                         goto out;
375                 case -EAGAIN:
376                         break;
377                 case -EDEADLK:
378                         ret = nlm_deadlock;
379                         goto out;
380                 default:                        /* includes ENOLCK */
381                         ret = nlm_lck_denied_nolocks;
382                         goto out;
383         }
384
385         ret = nlm_lck_denied;
386         if (!wait)
387                 goto out;
388
389         ret = nlm_lck_blocked;
390         if (block != NULL)
391                 goto out;
392
393         /* If we don't have a block, create and initialize it. Then
394          * retry because we may have slept in kmalloc. */
395         /* We have to release f_mutex as nlmsvc_create_block may try to
396          * to claim it while doing host garbage collection */
397         if (newblock == NULL) {
398                 mutex_unlock(&file->f_mutex);
399                 dprintk("lockd: blocking on this lock (allocating).\n");
400                 if (!(newblock = nlmsvc_create_block(rqstp, file, lock, cookie)))
401                         return nlm_lck_denied_nolocks;
402                 goto again;
403         }
404
405         /* Append to list of blocked */
406         nlmsvc_insert_block(newblock, NLM_NEVER);
407 out:
408         mutex_unlock(&file->f_mutex);
409         nlmsvc_release_block(newblock);
410         nlmsvc_release_block(block);
411         dprintk("lockd: nlmsvc_lock returned %u\n", ret);
412         return ret;
413 }
414
415 /*
416  * Test for presence of a conflicting lock.
417  */
418 __be32
419 nlmsvc_testlock(struct nlm_file *file, struct nlm_lock *lock,
420                                        struct nlm_lock *conflock)
421 {
422         dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
423                                 file->f_file->f_dentry->d_inode->i_sb->s_id,
424                                 file->f_file->f_dentry->d_inode->i_ino,
425                                 lock->fl.fl_type,
426                                 (long long)lock->fl.fl_start,
427                                 (long long)lock->fl.fl_end);
428
429         if (posix_test_lock(file->f_file, &lock->fl, &conflock->fl)) {
430                 dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n",
431                                 conflock->fl.fl_type,
432                                 (long long)conflock->fl.fl_start,
433                                 (long long)conflock->fl.fl_end);
434                 conflock->caller = "somehost";  /* FIXME */
435                 conflock->len = strlen(conflock->caller);
436                 conflock->oh.len = 0;           /* don't return OH info */
437                 conflock->svid = conflock->fl.fl_pid;
438                 return nlm_lck_denied;
439         }
440
441         return nlm_granted;
442 }
443
444 /*
445  * Remove a lock.
446  * This implies a CANCEL call: We send a GRANT_MSG, the client replies
447  * with a GRANT_RES call which gets lost, and calls UNLOCK immediately
448  * afterwards. In this case the block will still be there, and hence
449  * must be removed.
450  */
451 __be32
452 nlmsvc_unlock(struct nlm_file *file, struct nlm_lock *lock)
453 {
454         int     error;
455
456         dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
457                                 file->f_file->f_dentry->d_inode->i_sb->s_id,
458                                 file->f_file->f_dentry->d_inode->i_ino,
459                                 lock->fl.fl_pid,
460                                 (long long)lock->fl.fl_start,
461                                 (long long)lock->fl.fl_end);
462
463         /* First, cancel any lock that might be there */
464         nlmsvc_cancel_blocked(file, lock);
465
466         lock->fl.fl_type = F_UNLCK;
467         error = posix_lock_file(file->f_file, &lock->fl);
468
469         return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
470 }
471
472 /*
473  * Cancel a previously blocked request.
474  *
475  * A cancel request always overrides any grant that may currently
476  * be in progress.
477  * The calling procedure must check whether the file can be closed.
478  */
479 __be32
480 nlmsvc_cancel_blocked(struct nlm_file *file, struct nlm_lock *lock)
481 {
482         struct nlm_block        *block;
483         int status = 0;
484
485         dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n",
486                                 file->f_file->f_dentry->d_inode->i_sb->s_id,
487                                 file->f_file->f_dentry->d_inode->i_ino,
488                                 lock->fl.fl_pid,
489                                 (long long)lock->fl.fl_start,
490                                 (long long)lock->fl.fl_end);
491
492         mutex_lock(&file->f_mutex);
493         block = nlmsvc_lookup_block(file, lock);
494         mutex_unlock(&file->f_mutex);
495         if (block != NULL) {
496                 status = nlmsvc_unlink_block(block);
497                 nlmsvc_release_block(block);
498         }
499         return status ? nlm_lck_denied : nlm_granted;
500 }
501
502 /*
503  * Unblock a blocked lock request. This is a callback invoked from the
504  * VFS layer when a lock on which we blocked is removed.
505  *
506  * This function doesn't grant the blocked lock instantly, but rather moves
507  * the block to the head of nlm_blocked where it can be picked up by lockd.
508  */
509 static void
510 nlmsvc_notify_blocked(struct file_lock *fl)
511 {
512         struct nlm_block        *block;
513
514         dprintk("lockd: VFS unblock notification for block %p\n", fl);
515         list_for_each_entry(block, &nlm_blocked, b_list) {
516                 if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
517                         nlmsvc_insert_block(block, 0);
518                         svc_wake_up(block->b_daemon);
519                         return;
520                 }
521         }
522
523         printk(KERN_WARNING "lockd: notification for unknown block!\n");
524 }
525
526 static int nlmsvc_same_owner(struct file_lock *fl1, struct file_lock *fl2)
527 {
528         return fl1->fl_owner == fl2->fl_owner && fl1->fl_pid == fl2->fl_pid;
529 }
530
531 struct lock_manager_operations nlmsvc_lock_operations = {
532         .fl_compare_owner = nlmsvc_same_owner,
533         .fl_notify = nlmsvc_notify_blocked,
534 };
535
536 /*
537  * Try to claim a lock that was previously blocked.
538  *
539  * Note that we use both the RPC_GRANTED_MSG call _and_ an async
540  * RPC thread when notifying the client. This seems like overkill...
541  * Here's why:
542  *  -   we don't want to use a synchronous RPC thread, otherwise
543  *      we might find ourselves hanging on a dead portmapper.
544  *  -   Some lockd implementations (e.g. HP) don't react to
545  *      RPC_GRANTED calls; they seem to insist on RPC_GRANTED_MSG calls.
546  */
547 static void
548 nlmsvc_grant_blocked(struct nlm_block *block)
549 {
550         struct nlm_file         *file = block->b_file;
551         struct nlm_lock         *lock = &block->b_call->a_args.lock;
552         int                     error;
553
554         dprintk("lockd: grant blocked lock %p\n", block);
555
556         /* Unlink block request from list */
557         nlmsvc_unlink_block(block);
558
559         /* If b_granted is true this means we've been here before.
560          * Just retry the grant callback, possibly refreshing the RPC
561          * binding */
562         if (block->b_granted) {
563                 nlm_rebind_host(block->b_host);
564                 goto callback;
565         }
566
567         /* Try the lock operation again */
568         lock->fl.fl_flags |= FL_SLEEP;
569         error = posix_lock_file(file->f_file, &lock->fl);
570         lock->fl.fl_flags &= ~FL_SLEEP;
571
572         switch (error) {
573         case 0:
574                 break;
575         case -EAGAIN:
576                 dprintk("lockd: lock still blocked\n");
577                 nlmsvc_insert_block(block, NLM_NEVER);
578                 return;
579         default:
580                 printk(KERN_WARNING "lockd: unexpected error %d in %s!\n",
581                                 -error, __FUNCTION__);
582                 nlmsvc_insert_block(block, 10 * HZ);
583                 return;
584         }
585
586 callback:
587         /* Lock was granted by VFS. */
588         dprintk("lockd: GRANTing blocked lock.\n");
589         block->b_granted = 1;
590
591         /* Schedule next grant callback in 30 seconds */
592         nlmsvc_insert_block(block, 30 * HZ);
593
594         /* Call the client */
595         kref_get(&block->b_count);
596         if (nlm_async_call(block->b_call, NLMPROC_GRANTED_MSG,
597                                                 &nlmsvc_grant_ops) < 0)
598                 nlmsvc_release_block(block);
599 }
600
601 /*
602  * This is the callback from the RPC layer when the NLM_GRANTED_MSG
603  * RPC call has succeeded or timed out.
604  * Like all RPC callbacks, it is invoked by the rpciod process, so it
605  * better not sleep. Therefore, we put the blocked lock on the nlm_blocked
606  * chain once more in order to have it removed by lockd itself (which can
607  * then sleep on the file semaphore without disrupting e.g. the nfs client).
608  */
609 static void nlmsvc_grant_callback(struct rpc_task *task, void *data)
610 {
611         struct nlm_rqst         *call = data;
612         struct nlm_block        *block = call->a_block;
613         unsigned long           timeout;
614
615         dprintk("lockd: GRANT_MSG RPC callback\n");
616
617         /* Technically, we should down the file semaphore here. Since we
618          * move the block towards the head of the queue only, no harm
619          * can be done, though. */
620         if (task->tk_status < 0) {
621                 /* RPC error: Re-insert for retransmission */
622                 timeout = 10 * HZ;
623         } else {
624                 /* Call was successful, now wait for client callback */
625                 timeout = 60 * HZ;
626         }
627         nlmsvc_insert_block(block, timeout);
628         svc_wake_up(block->b_daemon);
629 }
630
631 static void nlmsvc_grant_release(void *data)
632 {
633         struct nlm_rqst         *call = data;
634
635         nlmsvc_release_block(call->a_block);
636 }
637
638 static const struct rpc_call_ops nlmsvc_grant_ops = {
639         .rpc_call_done = nlmsvc_grant_callback,
640         .rpc_release = nlmsvc_grant_release,
641 };
642
643 /*
644  * We received a GRANT_RES callback. Try to find the corresponding
645  * block.
646  */
647 void
648 nlmsvc_grant_reply(struct nlm_cookie *cookie, u32 status)
649 {
650         struct nlm_block        *block;
651
652         dprintk("grant_reply: looking for cookie %x, s=%d \n",
653                 *(unsigned int *)(cookie->data), status);
654         if (!(block = nlmsvc_find_block(cookie)))
655                 return;
656
657         if (block) {
658                 if (status == NLM_LCK_DENIED_GRACE_PERIOD) {
659                         /* Try again in a couple of seconds */
660                         nlmsvc_insert_block(block, 10 * HZ);
661                 } else {
662                         /* Lock is now held by client, or has been rejected.
663                          * In both cases, the block should be removed. */
664                         nlmsvc_unlink_block(block);
665                 }
666         }
667         nlmsvc_release_block(block);
668 }
669
670 /*
671  * Retry all blocked locks that have been notified. This is where lockd
672  * picks up locks that can be granted, or grant notifications that must
673  * be retransmitted.
674  */
675 unsigned long
676 nlmsvc_retry_blocked(void)
677 {
678         unsigned long   timeout = MAX_SCHEDULE_TIMEOUT;
679         struct nlm_block *block;
680
681         while (!list_empty(&nlm_blocked)) {
682                 block = list_entry(nlm_blocked.next, struct nlm_block, b_list);
683
684                 if (block->b_when == NLM_NEVER)
685                         break;
686                 if (time_after(block->b_when,jiffies)) {
687                         timeout = block->b_when - jiffies;
688                         break;
689                 }
690
691                 dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n",
692                         block, block->b_when);
693                 kref_get(&block->b_count);
694                 nlmsvc_grant_blocked(block);
695                 nlmsvc_release_block(block);
696         }
697
698         return timeout;
699 }