3127ae9e435ca22e8fa80e14e6dc3ad3998f3c70
[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 int      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 struct nlm_block *       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 **bp, *b;
61
62         dprintk("lockd: nlmsvc_insert_block(%p, %ld)\n", block, when);
63         kref_get(&block->b_count);
64         if (block->b_queued)
65                 nlmsvc_remove_block(block);
66         bp = &nlm_blocked;
67         if (when != NLM_NEVER) {
68                 if ((when += jiffies) == NLM_NEVER)
69                         when ++;
70                 while ((b = *bp) && time_before_eq(b->b_when,when) && b->b_when != NLM_NEVER)
71                         bp = &b->b_next;
72         } else
73                 while ((b = *bp) != 0)
74                         bp = &b->b_next;
75
76         block->b_queued = 1;
77         block->b_when = when;
78         block->b_next = b;
79         *bp = block;
80 }
81
82 /*
83  * Remove a block from the global list
84  */
85 static int
86 nlmsvc_remove_block(struct nlm_block *block)
87 {
88         struct nlm_block **bp, *b;
89
90         if (!block->b_queued)
91                 return 1;
92         for (bp = &nlm_blocked; (b = *bp) != 0; bp = &b->b_next) {
93                 if (b == block) {
94                         *bp = block->b_next;
95                         block->b_queued = 0;
96                         nlmsvc_release_block(block);
97                         return 1;
98                 }
99         }
100
101         return 0;
102 }
103
104 /*
105  * Find a block for a given lock
106  */
107 static struct nlm_block *
108 nlmsvc_lookup_block(struct nlm_file *file, struct nlm_lock *lock)
109 {
110         struct nlm_block        **head, *block;
111         struct file_lock        *fl;
112
113         dprintk("lockd: nlmsvc_lookup_block f=%p pd=%d %Ld-%Ld ty=%d\n",
114                                 file, lock->fl.fl_pid,
115                                 (long long)lock->fl.fl_start,
116                                 (long long)lock->fl.fl_end, lock->fl.fl_type);
117         for (head = &nlm_blocked; (block = *head) != 0; head = &block->b_next) {
118                 fl = &block->b_call->a_args.lock.fl;
119                 dprintk("lockd: check f=%p pd=%d %Ld-%Ld ty=%d cookie=%s\n",
120                                 block->b_file, fl->fl_pid,
121                                 (long long)fl->fl_start,
122                                 (long long)fl->fl_end, fl->fl_type,
123                                 nlmdbg_cookie2a(&block->b_call->a_args.cookie));
124                 if (block->b_file == file && nlm_compare_locks(fl, &lock->fl)) {
125                         kref_get(&block->b_count);
126                         return block;
127                 }
128         }
129
130         return NULL;
131 }
132
133 static inline int nlm_cookie_match(struct nlm_cookie *a, struct nlm_cookie *b)
134 {
135         if(a->len != b->len)
136                 return 0;
137         if(memcmp(a->data,b->data,a->len))
138                 return 0;
139         return 1;
140 }
141
142 /*
143  * Find a block with a given NLM cookie.
144  */
145 static inline struct nlm_block *
146 nlmsvc_find_block(struct nlm_cookie *cookie,  struct sockaddr_in *sin)
147 {
148         struct nlm_block *block;
149
150         for (block = nlm_blocked; block; block = block->b_next) {
151                 dprintk("cookie: head of blocked queue %p, block %p\n", 
152                         nlm_blocked, block);
153                 if (nlm_cookie_match(&block->b_call->a_args.cookie,cookie)
154                                 && nlm_cmp_addr(sin, &block->b_host->h_addr))
155                         break;
156         }
157
158         if (block != NULL)
159                 kref_get(&block->b_count);
160         return block;
161 }
162
163 /*
164  * Create a block and initialize it.
165  *
166  * Note: we explicitly set the cookie of the grant reply to that of
167  * the blocked lock request. The spec explicitly mentions that the client
168  * should _not_ rely on the callback containing the same cookie as the
169  * request, but (as I found out later) that's because some implementations
170  * do just this. Never mind the standards comittees, they support our
171  * logging industries.
172  */
173 static inline struct nlm_block *
174 nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_file *file,
175                                 struct nlm_lock *lock, struct nlm_cookie *cookie)
176 {
177         struct nlm_block        *block;
178         struct nlm_host         *host;
179         struct nlm_rqst         *call = NULL;
180
181         /* Create host handle for callback */
182         host = nlmsvc_lookup_host(rqstp, lock->caller, lock->len);
183         if (host == NULL)
184                 return NULL;
185
186         call = nlm_alloc_call(host);
187         if (call == NULL)
188                 return NULL;
189
190         /* Allocate memory for block, and initialize arguments */
191         block = kzalloc(sizeof(*block), GFP_KERNEL);
192         if (block == NULL)
193                 goto failed;
194         kref_init(&block->b_count);
195
196         if (!nlmsvc_setgrantargs(call, lock))
197                 goto failed_free;
198
199         /* Set notifier function for VFS, and init args */
200         call->a_args.lock.fl.fl_flags |= FL_SLEEP;
201         call->a_args.lock.fl.fl_lmops = &nlmsvc_lock_operations;
202         call->a_args.cookie = *cookie;  /* see above */
203
204         dprintk("lockd: created block %p...\n", block);
205
206         /* Create and initialize the block */
207         block->b_daemon = rqstp->rq_server;
208         block->b_host   = host;
209         block->b_file   = file;
210         file->f_count++;
211
212         /* Add to file's list of blocks */
213         block->b_fnext  = file->f_blocks;
214         file->f_blocks  = block;
215
216         /* Set up RPC arguments for callback */
217         block->b_call = call;
218         call->a_flags   = RPC_TASK_ASYNC;
219         call->a_block = block;
220
221         return block;
222
223 failed_free:
224         kfree(block);
225 failed:
226         nlm_release_call(call);
227         return NULL;
228 }
229
230 /*
231  * Delete a block. If the lock was cancelled or the grant callback
232  * failed, unlock is set to 1.
233  * It is the caller's responsibility to check whether the file
234  * can be closed hereafter.
235  */
236 static int nlmsvc_unlink_block(struct nlm_block *block)
237 {
238         int status;
239         dprintk("lockd: unlinking block %p...\n", block);
240
241         /* Remove block from list */
242         status = posix_unblock_lock(block->b_file->f_file, &block->b_call->a_args.lock.fl);
243         nlmsvc_remove_block(block);
244         return status;
245 }
246
247 static void nlmsvc_free_block(struct kref *kref)
248 {
249         struct nlm_block *block = container_of(kref, struct nlm_block, b_count);
250         struct nlm_file         *file = block->b_file;
251         struct nlm_block        **bp;
252
253         dprintk("lockd: freeing block %p...\n", block);
254
255         down(&file->f_sema);
256         /* Remove block from file's list of blocks */
257         for (bp = &file->f_blocks; *bp; bp = &(*bp)->b_fnext) {
258                 if (*bp == block) {
259                         *bp = block->b_fnext;
260                         break;
261                 }
262         }
263         up(&file->f_sema);
264
265         nlmsvc_freegrantargs(block->b_call);
266         nlm_release_call(block->b_call);
267         nlm_release_file(block->b_file);
268         kfree(block);
269 }
270
271 static void nlmsvc_release_block(struct nlm_block *block)
272 {
273         if (block != NULL)
274                 kref_put(&block->b_count, nlmsvc_free_block);
275 }
276
277 static void nlmsvc_act_mark(struct nlm_host *host, struct nlm_file *file)
278 {
279         struct nlm_block *block;
280
281         down(&file->f_sema);
282         for (block = file->f_blocks; block != NULL; block = block->b_fnext)
283                 block->b_host->h_inuse = 1;
284         up(&file->f_sema);
285 }
286
287 static void nlmsvc_act_unlock(struct nlm_host *host, struct nlm_file *file)
288 {
289         struct nlm_block *block;
290
291 restart:
292         down(&file->f_sema);
293         for (block = file->f_blocks; block != NULL; block = block->b_fnext) {
294                 if (host != NULL && host != block->b_host)
295                         continue;
296                 if (!block->b_queued)
297                         continue;
298                 kref_get(&block->b_count);
299                 up(&file->f_sema);
300                 nlmsvc_unlink_block(block);
301                 nlmsvc_release_block(block);
302                 goto restart;
303         }
304         up(&file->f_sema);
305 }
306
307 /*
308  * Loop over all blocks and perform the action specified.
309  * (NLM_ACT_CHECK handled by nlmsvc_inspect_file).
310  */
311 void
312 nlmsvc_traverse_blocks(struct nlm_host *host, struct nlm_file *file, int action)
313 {
314         if (action == NLM_ACT_MARK)
315                 nlmsvc_act_mark(host, file);
316         else
317                 nlmsvc_act_unlock(host, file);
318 }
319
320 /*
321  * Initialize arguments for GRANTED call. The nlm_rqst structure
322  * has been cleared already.
323  */
324 static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock)
325 {
326         locks_copy_lock(&call->a_args.lock.fl, &lock->fl);
327         memcpy(&call->a_args.lock.fh, &lock->fh, sizeof(call->a_args.lock.fh));
328         call->a_args.lock.caller = utsname()->nodename;
329         call->a_args.lock.oh.len = lock->oh.len;
330
331         /* set default data area */
332         call->a_args.lock.oh.data = call->a_owner;
333         call->a_args.lock.svid = lock->fl.fl_pid;
334
335         if (lock->oh.len > NLMCLNT_OHSIZE) {
336                 void *data = kmalloc(lock->oh.len, GFP_KERNEL);
337                 if (!data)
338                         return 0;
339                 call->a_args.lock.oh.data = (u8 *) data;
340         }
341
342         memcpy(call->a_args.lock.oh.data, lock->oh.data, lock->oh.len);
343         return 1;
344 }
345
346 static void nlmsvc_freegrantargs(struct nlm_rqst *call)
347 {
348         if (call->a_args.lock.oh.data != call->a_owner)
349                 kfree(call->a_args.lock.oh.data);
350 }
351
352 /*
353  * Attempt to establish a lock, and if it can't be granted, block it
354  * if required.
355  */
356 u32
357 nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
358                         struct nlm_lock *lock, int wait, struct nlm_cookie *cookie)
359 {
360         struct nlm_block        *block, *newblock = NULL;
361         int                     error;
362         u32                     ret;
363
364         dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
365                                 file->f_file->f_dentry->d_inode->i_sb->s_id,
366                                 file->f_file->f_dentry->d_inode->i_ino,
367                                 lock->fl.fl_type, lock->fl.fl_pid,
368                                 (long long)lock->fl.fl_start,
369                                 (long long)lock->fl.fl_end,
370                                 wait);
371
372
373         lock->fl.fl_flags &= ~FL_SLEEP;
374 again:
375         /* Lock file against concurrent access */
376         down(&file->f_sema);
377         /* Get existing block (in case client is busy-waiting) */
378         block = nlmsvc_lookup_block(file, lock);
379         if (block == NULL) {
380                 if (newblock != NULL)
381                         lock = &newblock->b_call->a_args.lock;
382         } else
383                 lock = &block->b_call->a_args.lock;
384
385         error = posix_lock_file(file->f_file, &lock->fl);
386         lock->fl.fl_flags &= ~FL_SLEEP;
387
388         dprintk("lockd: posix_lock_file returned %d\n", error);
389
390         switch(error) {
391                 case 0:
392                         ret = nlm_granted;
393                         goto out;
394                 case -EAGAIN:
395                         break;
396                 case -EDEADLK:
397                         ret = nlm_deadlock;
398                         goto out;
399                 default:                        /* includes ENOLCK */
400                         ret = nlm_lck_denied_nolocks;
401                         goto out;
402         }
403
404         ret = nlm_lck_denied;
405         if (!wait)
406                 goto out;
407
408         ret = nlm_lck_blocked;
409         if (block != NULL)
410                 goto out;
411
412         /* If we don't have a block, create and initialize it. Then
413          * retry because we may have slept in kmalloc. */
414         /* We have to release f_sema as nlmsvc_create_block may try to
415          * to claim it while doing host garbage collection */
416         if (newblock == NULL) {
417                 up(&file->f_sema);
418                 dprintk("lockd: blocking on this lock (allocating).\n");
419                 if (!(newblock = nlmsvc_create_block(rqstp, file, lock, cookie)))
420                         return nlm_lck_denied_nolocks;
421                 goto again;
422         }
423
424         /* Append to list of blocked */
425         nlmsvc_insert_block(newblock, NLM_NEVER);
426 out:
427         up(&file->f_sema);
428         nlmsvc_release_block(newblock);
429         nlmsvc_release_block(block);
430         dprintk("lockd: nlmsvc_lock returned %u\n", ret);
431         return ret;
432 }
433
434 /*
435  * Test for presence of a conflicting lock.
436  */
437 u32
438 nlmsvc_testlock(struct nlm_file *file, struct nlm_lock *lock,
439                                        struct nlm_lock *conflock)
440 {
441         dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
442                                 file->f_file->f_dentry->d_inode->i_sb->s_id,
443                                 file->f_file->f_dentry->d_inode->i_ino,
444                                 lock->fl.fl_type,
445                                 (long long)lock->fl.fl_start,
446                                 (long long)lock->fl.fl_end);
447
448         if (posix_test_lock(file->f_file, &lock->fl, &conflock->fl)) {
449                 dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n",
450                                 conflock->fl.fl_type,
451                                 (long long)conflock->fl.fl_start,
452                                 (long long)conflock->fl.fl_end);
453                 conflock->caller = "somehost";  /* FIXME */
454                 conflock->len = strlen(conflock->caller);
455                 conflock->oh.len = 0;           /* don't return OH info */
456                 conflock->svid = conflock->fl.fl_pid;
457                 return nlm_lck_denied;
458         }
459
460         return nlm_granted;
461 }
462
463 /*
464  * Remove a lock.
465  * This implies a CANCEL call: We send a GRANT_MSG, the client replies
466  * with a GRANT_RES call which gets lost, and calls UNLOCK immediately
467  * afterwards. In this case the block will still be there, and hence
468  * must be removed.
469  */
470 u32
471 nlmsvc_unlock(struct nlm_file *file, struct nlm_lock *lock)
472 {
473         int     error;
474
475         dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
476                                 file->f_file->f_dentry->d_inode->i_sb->s_id,
477                                 file->f_file->f_dentry->d_inode->i_ino,
478                                 lock->fl.fl_pid,
479                                 (long long)lock->fl.fl_start,
480                                 (long long)lock->fl.fl_end);
481
482         /* First, cancel any lock that might be there */
483         nlmsvc_cancel_blocked(file, lock);
484
485         lock->fl.fl_type = F_UNLCK;
486         error = posix_lock_file(file->f_file, &lock->fl);
487
488         return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
489 }
490
491 /*
492  * Cancel a previously blocked request.
493  *
494  * A cancel request always overrides any grant that may currently
495  * be in progress.
496  * The calling procedure must check whether the file can be closed.
497  */
498 u32
499 nlmsvc_cancel_blocked(struct nlm_file *file, struct nlm_lock *lock)
500 {
501         struct nlm_block        *block;
502         int status = 0;
503
504         dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n",
505                                 file->f_file->f_dentry->d_inode->i_sb->s_id,
506                                 file->f_file->f_dentry->d_inode->i_ino,
507                                 lock->fl.fl_pid,
508                                 (long long)lock->fl.fl_start,
509                                 (long long)lock->fl.fl_end);
510
511         down(&file->f_sema);
512         block = nlmsvc_lookup_block(file, lock);
513         up(&file->f_sema);
514         if (block != NULL) {
515                 status = nlmsvc_unlink_block(block);
516                 nlmsvc_release_block(block);
517         }
518         return status ? nlm_lck_denied : nlm_granted;
519 }
520
521 /*
522  * Unblock a blocked lock request. This is a callback invoked from the
523  * VFS layer when a lock on which we blocked is removed.
524  *
525  * This function doesn't grant the blocked lock instantly, but rather moves
526  * the block to the head of nlm_blocked where it can be picked up by lockd.
527  */
528 static void
529 nlmsvc_notify_blocked(struct file_lock *fl)
530 {
531         struct nlm_block        **bp, *block;
532
533         dprintk("lockd: VFS unblock notification for block %p\n", fl);
534         for (bp = &nlm_blocked; (block = *bp) != 0; bp = &block->b_next) {
535                 if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
536                         nlmsvc_insert_block(block, 0);
537                         svc_wake_up(block->b_daemon);
538                         return;
539                 }
540         }
541
542         printk(KERN_WARNING "lockd: notification for unknown block!\n");
543 }
544
545 static int nlmsvc_same_owner(struct file_lock *fl1, struct file_lock *fl2)
546 {
547         return fl1->fl_owner == fl2->fl_owner && fl1->fl_pid == fl2->fl_pid;
548 }
549
550 struct lock_manager_operations nlmsvc_lock_operations = {
551         .fl_compare_owner = nlmsvc_same_owner,
552         .fl_notify = nlmsvc_notify_blocked,
553 };
554
555 /*
556  * Try to claim a lock that was previously blocked.
557  *
558  * Note that we use both the RPC_GRANTED_MSG call _and_ an async
559  * RPC thread when notifying the client. This seems like overkill...
560  * Here's why:
561  *  -   we don't want to use a synchronous RPC thread, otherwise
562  *      we might find ourselves hanging on a dead portmapper.
563  *  -   Some lockd implementations (e.g. HP) don't react to
564  *      RPC_GRANTED calls; they seem to insist on RPC_GRANTED_MSG calls.
565  */
566 static void
567 nlmsvc_grant_blocked(struct nlm_block *block)
568 {
569         struct nlm_file         *file = block->b_file;
570         struct nlm_lock         *lock = &block->b_call->a_args.lock;
571         int                     error;
572
573         dprintk("lockd: grant blocked lock %p\n", block);
574
575         /* Unlink block request from list */
576         nlmsvc_unlink_block(block);
577
578         /* If b_granted is true this means we've been here before.
579          * Just retry the grant callback, possibly refreshing the RPC
580          * binding */
581         if (block->b_granted) {
582                 nlm_rebind_host(block->b_host);
583                 goto callback;
584         }
585
586         /* Try the lock operation again */
587         lock->fl.fl_flags |= FL_SLEEP;
588         error = posix_lock_file(file->f_file, &lock->fl);
589         lock->fl.fl_flags &= ~FL_SLEEP;
590
591         switch (error) {
592         case 0:
593                 break;
594         case -EAGAIN:
595                 dprintk("lockd: lock still blocked\n");
596                 nlmsvc_insert_block(block, NLM_NEVER);
597                 return;
598         default:
599                 printk(KERN_WARNING "lockd: unexpected error %d in %s!\n",
600                                 -error, __FUNCTION__);
601                 nlmsvc_insert_block(block, 10 * HZ);
602                 return;
603         }
604
605 callback:
606         /* Lock was granted by VFS. */
607         dprintk("lockd: GRANTing blocked lock.\n");
608         block->b_granted = 1;
609
610         /* Schedule next grant callback in 30 seconds */
611         nlmsvc_insert_block(block, 30 * HZ);
612
613         /* Call the client */
614         kref_get(&block->b_count);
615         if (nlm_async_call(block->b_call, NLMPROC_GRANTED_MSG,
616                                                 &nlmsvc_grant_ops) < 0)
617                 nlmsvc_release_block(block);
618 }
619
620 /*
621  * This is the callback from the RPC layer when the NLM_GRANTED_MSG
622  * RPC call has succeeded or timed out.
623  * Like all RPC callbacks, it is invoked by the rpciod process, so it
624  * better not sleep. Therefore, we put the blocked lock on the nlm_blocked
625  * chain once more in order to have it removed by lockd itself (which can
626  * then sleep on the file semaphore without disrupting e.g. the nfs client).
627  */
628 static void nlmsvc_grant_callback(struct rpc_task *task, void *data)
629 {
630         struct nlm_rqst         *call = data;
631         struct nlm_block        *block = call->a_block;
632         unsigned long           timeout;
633
634         dprintk("lockd: GRANT_MSG RPC callback\n");
635
636         /* Technically, we should down the file semaphore here. Since we
637          * move the block towards the head of the queue only, no harm
638          * can be done, though. */
639         if (task->tk_status < 0) {
640                 /* RPC error: Re-insert for retransmission */
641                 timeout = 10 * HZ;
642         } else {
643                 /* Call was successful, now wait for client callback */
644                 timeout = 60 * HZ;
645         }
646         nlmsvc_insert_block(block, timeout);
647         svc_wake_up(block->b_daemon);
648 }
649
650 static void nlmsvc_grant_release(void *data)
651 {
652         struct nlm_rqst         *call = data;
653
654         nlmsvc_release_block(call->a_block);
655 }
656
657 static const struct rpc_call_ops nlmsvc_grant_ops = {
658         .rpc_call_done = nlmsvc_grant_callback,
659         .rpc_release = nlmsvc_grant_release,
660 };
661
662 /*
663  * We received a GRANT_RES callback. Try to find the corresponding
664  * block.
665  */
666 void
667 nlmsvc_grant_reply(struct svc_rqst *rqstp, struct nlm_cookie *cookie, u32 status)
668 {
669         struct nlm_block        *block;
670         struct nlm_file         *file;
671
672         dprintk("grant_reply: looking for cookie %x, host (%08x), s=%d \n", 
673                 *(unsigned int *)(cookie->data), 
674                 ntohl(rqstp->rq_addr.sin_addr.s_addr), status);
675         if (!(block = nlmsvc_find_block(cookie, &rqstp->rq_addr)))
676                 return;
677         file = block->b_file;
678
679         if (block) {
680                 if (status == NLM_LCK_DENIED_GRACE_PERIOD) {
681                         /* Try again in a couple of seconds */
682                         nlmsvc_insert_block(block, 10 * HZ);
683                 } else {
684                         /* Lock is now held by client, or has been rejected.
685                          * In both cases, the block should be removed. */
686                         nlmsvc_unlink_block(block);
687                 }
688         }
689         nlmsvc_release_block(block);
690 }
691
692 /*
693  * Retry all blocked locks that have been notified. This is where lockd
694  * picks up locks that can be granted, or grant notifications that must
695  * be retransmitted.
696  */
697 unsigned long
698 nlmsvc_retry_blocked(void)
699 {
700         struct nlm_block        *block;
701
702         dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n",
703                         nlm_blocked,
704                         nlm_blocked? nlm_blocked->b_when : 0);
705         while ((block = nlm_blocked) != 0) {
706                 if (block->b_when == NLM_NEVER)
707                         break;
708                 if (time_after(block->b_when,jiffies))
709                         break;
710                 dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n",
711                         block, block->b_when);
712                 kref_get(&block->b_count);
713                 nlmsvc_grant_blocked(block);
714                 nlmsvc_release_block(block);
715         }
716
717         if ((block = nlm_blocked) && block->b_when != NLM_NEVER)
718                 return (block->b_when - jiffies);
719
720         return MAX_SCHEDULE_TIMEOUT;
721 }