lockd: handle test_lock deferrals
[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         block->b_fl = NULL;
214         file->f_count++;
215
216         /* Add to file's list of blocks */
217         list_add(&block->b_flist, &file->f_blocks);
218
219         /* Set up RPC arguments for callback */
220         block->b_call = call;
221         call->a_flags   = RPC_TASK_ASYNC;
222         call->a_block = block;
223
224         return block;
225
226 failed_free:
227         kfree(block);
228 failed:
229         nlm_release_call(call);
230         return NULL;
231 }
232
233 /*
234  * Delete a block. If the lock was cancelled or the grant callback
235  * failed, unlock is set to 1.
236  * It is the caller's responsibility to check whether the file
237  * can be closed hereafter.
238  */
239 static int nlmsvc_unlink_block(struct nlm_block *block)
240 {
241         int status;
242         dprintk("lockd: unlinking block %p...\n", block);
243
244         /* Remove block from list */
245         status = posix_unblock_lock(block->b_file->f_file, &block->b_call->a_args.lock.fl);
246         nlmsvc_remove_block(block);
247         return status;
248 }
249
250 static void nlmsvc_free_block(struct kref *kref)
251 {
252         struct nlm_block *block = container_of(kref, struct nlm_block, b_count);
253         struct nlm_file         *file = block->b_file;
254
255         dprintk("lockd: freeing block %p...\n", block);
256
257         /* Remove block from file's list of blocks */
258         mutex_lock(&file->f_mutex);
259         list_del_init(&block->b_flist);
260         mutex_unlock(&file->f_mutex);
261
262         nlmsvc_freegrantargs(block->b_call);
263         nlm_release_call(block->b_call);
264         nlm_release_file(block->b_file);
265         kfree(block->b_fl);
266         kfree(block);
267 }
268
269 static void nlmsvc_release_block(struct nlm_block *block)
270 {
271         if (block != NULL)
272                 kref_put(&block->b_count, nlmsvc_free_block);
273 }
274
275 /*
276  * Loop over all blocks and delete blocks held by
277  * a matching host.
278  */
279 void nlmsvc_traverse_blocks(struct nlm_host *host,
280                         struct nlm_file *file,
281                         nlm_host_match_fn_t match)
282 {
283         struct nlm_block *block, *next;
284
285 restart:
286         mutex_lock(&file->f_mutex);
287         list_for_each_entry_safe(block, next, &file->f_blocks, b_flist) {
288                 if (!match(block->b_host, host))
289                         continue;
290                 /* Do not destroy blocks that are not on
291                  * the global retry list - why? */
292                 if (list_empty(&block->b_list))
293                         continue;
294                 kref_get(&block->b_count);
295                 mutex_unlock(&file->f_mutex);
296                 nlmsvc_unlink_block(block);
297                 nlmsvc_release_block(block);
298                 goto restart;
299         }
300         mutex_unlock(&file->f_mutex);
301 }
302
303 /*
304  * Initialize arguments for GRANTED call. The nlm_rqst structure
305  * has been cleared already.
306  */
307 static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock)
308 {
309         locks_copy_lock(&call->a_args.lock.fl, &lock->fl);
310         memcpy(&call->a_args.lock.fh, &lock->fh, sizeof(call->a_args.lock.fh));
311         call->a_args.lock.caller = utsname()->nodename;
312         call->a_args.lock.oh.len = lock->oh.len;
313
314         /* set default data area */
315         call->a_args.lock.oh.data = call->a_owner;
316         call->a_args.lock.svid = lock->fl.fl_pid;
317
318         if (lock->oh.len > NLMCLNT_OHSIZE) {
319                 void *data = kmalloc(lock->oh.len, GFP_KERNEL);
320                 if (!data)
321                         return 0;
322                 call->a_args.lock.oh.data = (u8 *) data;
323         }
324
325         memcpy(call->a_args.lock.oh.data, lock->oh.data, lock->oh.len);
326         return 1;
327 }
328
329 static void nlmsvc_freegrantargs(struct nlm_rqst *call)
330 {
331         if (call->a_args.lock.oh.data != call->a_owner)
332                 kfree(call->a_args.lock.oh.data);
333 }
334
335 /*
336  * Deferred lock request handling for non-blocking lock
337  */
338 static u32
339 nlmsvc_defer_lock_rqst(struct svc_rqst *rqstp, struct nlm_block *block)
340 {
341         u32 status = nlm_lck_denied_nolocks;
342
343         block->b_flags |= B_QUEUED;
344
345         nlmsvc_insert_block(block, NLM_TIMEOUT);
346
347         block->b_cache_req = &rqstp->rq_chandle;
348         if (rqstp->rq_chandle.defer) {
349                 block->b_deferred_req =
350                         rqstp->rq_chandle.defer(block->b_cache_req);
351                 if (block->b_deferred_req != NULL)
352                         status = nlm_drop_reply;
353         }
354         dprintk("lockd: nlmsvc_defer_lock_rqst block %p flags %d status %d\n",
355                 block, block->b_flags, status);
356
357         return status;
358 }
359
360 /*
361  * Attempt to establish a lock, and if it can't be granted, block it
362  * if required.
363  */
364 __be32
365 nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
366                         struct nlm_lock *lock, int wait, struct nlm_cookie *cookie)
367 {
368         struct nlm_block        *block, *newblock = NULL;
369         int                     error;
370         __be32                  ret;
371
372         dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
373                                 file->f_file->f_path.dentry->d_inode->i_sb->s_id,
374                                 file->f_file->f_path.dentry->d_inode->i_ino,
375                                 lock->fl.fl_type, lock->fl.fl_pid,
376                                 (long long)lock->fl.fl_start,
377                                 (long long)lock->fl.fl_end,
378                                 wait);
379
380
381         lock->fl.fl_flags &= ~FL_SLEEP;
382 again:
383         /* Lock file against concurrent access */
384         mutex_lock(&file->f_mutex);
385         /* Get existing block (in case client is busy-waiting) */
386         block = nlmsvc_lookup_block(file, lock);
387         if (block == NULL) {
388                 if (newblock != NULL)
389                         lock = &newblock->b_call->a_args.lock;
390         } else
391                 lock = &block->b_call->a_args.lock;
392
393         error = posix_lock_file(file->f_file, &lock->fl, NULL);
394         lock->fl.fl_flags &= ~FL_SLEEP;
395
396         dprintk("lockd: posix_lock_file returned %d\n", error);
397
398         switch(error) {
399                 case 0:
400                         ret = nlm_granted;
401                         goto out;
402                 case -EAGAIN:
403                         break;
404                 case -EDEADLK:
405                         ret = nlm_deadlock;
406                         goto out;
407                 default:                        /* includes ENOLCK */
408                         ret = nlm_lck_denied_nolocks;
409                         goto out;
410         }
411
412         ret = nlm_lck_denied;
413         if (!wait)
414                 goto out;
415
416         ret = nlm_lck_blocked;
417         if (block != NULL)
418                 goto out;
419
420         /* If we don't have a block, create and initialize it. Then
421          * retry because we may have slept in kmalloc. */
422         /* We have to release f_mutex as nlmsvc_create_block may try to
423          * to claim it while doing host garbage collection */
424         if (newblock == NULL) {
425                 mutex_unlock(&file->f_mutex);
426                 dprintk("lockd: blocking on this lock (allocating).\n");
427                 if (!(newblock = nlmsvc_create_block(rqstp, file, lock, cookie)))
428                         return nlm_lck_denied_nolocks;
429                 goto again;
430         }
431
432         /* Append to list of blocked */
433         nlmsvc_insert_block(newblock, NLM_NEVER);
434 out:
435         mutex_unlock(&file->f_mutex);
436         nlmsvc_release_block(newblock);
437         nlmsvc_release_block(block);
438         dprintk("lockd: nlmsvc_lock returned %u\n", ret);
439         return ret;
440 }
441
442 /*
443  * Test for presence of a conflicting lock.
444  */
445 __be32
446 nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
447                 struct nlm_lock *lock, struct nlm_lock *conflock,
448                 struct nlm_cookie *cookie)
449 {
450         struct nlm_block        *block = NULL;
451         int                     error;
452         __be32                  ret;
453
454         dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
455                                 file->f_file->f_path.dentry->d_inode->i_sb->s_id,
456                                 file->f_file->f_path.dentry->d_inode->i_ino,
457                                 lock->fl.fl_type,
458                                 (long long)lock->fl.fl_start,
459                                 (long long)lock->fl.fl_end);
460
461         /* Get existing block (in case client is busy-waiting) */
462         block = nlmsvc_lookup_block(file, lock);
463
464         if (block == NULL) {
465                 struct file_lock *conf = kzalloc(sizeof(*conf), GFP_KERNEL);
466
467                 if (conf == NULL)
468                         return nlm_granted;
469                 block = nlmsvc_create_block(rqstp, file, lock, cookie);
470                 if (block == NULL) {
471                         kfree(conf);
472                         return nlm_granted;
473                 }
474                 block->b_fl = conf;
475         }
476         if (block->b_flags & B_QUEUED) {
477                 dprintk("lockd: nlmsvc_testlock deferred block %p flags %d fl %p\n",
478                         block, block->b_flags, block->b_fl);
479                 if (block->b_flags & B_TIMED_OUT) {
480                         nlmsvc_unlink_block(block);
481                         return nlm_lck_denied;
482                 }
483                 if (block->b_flags & B_GOT_CALLBACK) {
484                         if (block->b_fl != NULL
485                                         && block->b_fl->fl_type != F_UNLCK) {
486                                 lock->fl = *block->b_fl;
487                                 goto conf_lock;
488                         }
489                         else {
490                                 nlmsvc_unlink_block(block);
491                                 return nlm_granted;
492                         }
493                 }
494                 return nlm_drop_reply;
495         }
496
497         error = vfs_test_lock(file->f_file, &lock->fl);
498         if (error == -EINPROGRESS)
499                 return nlmsvc_defer_lock_rqst(rqstp, block);
500         if (error) {
501                 ret = nlm_lck_denied_nolocks;
502                 goto out;
503         }
504         if (lock->fl.fl_type == F_UNLCK) {
505                 ret = nlm_granted;
506                 goto out;
507         }
508
509 conf_lock:
510         dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n",
511                 lock->fl.fl_type, (long long)lock->fl.fl_start,
512                 (long long)lock->fl.fl_end);
513         conflock->caller = "somehost";  /* FIXME */
514         conflock->len = strlen(conflock->caller);
515         conflock->oh.len = 0;           /* don't return OH info */
516         conflock->svid = lock->fl.fl_pid;
517         conflock->fl.fl_type = lock->fl.fl_type;
518         conflock->fl.fl_start = lock->fl.fl_start;
519         conflock->fl.fl_end = lock->fl.fl_end;
520         ret = nlm_lck_denied;
521 out:
522         if (block)
523                 nlmsvc_release_block(block);
524         return ret;
525 }
526
527 /*
528  * Remove a lock.
529  * This implies a CANCEL call: We send a GRANT_MSG, the client replies
530  * with a GRANT_RES call which gets lost, and calls UNLOCK immediately
531  * afterwards. In this case the block will still be there, and hence
532  * must be removed.
533  */
534 __be32
535 nlmsvc_unlock(struct nlm_file *file, struct nlm_lock *lock)
536 {
537         int     error;
538
539         dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
540                                 file->f_file->f_path.dentry->d_inode->i_sb->s_id,
541                                 file->f_file->f_path.dentry->d_inode->i_ino,
542                                 lock->fl.fl_pid,
543                                 (long long)lock->fl.fl_start,
544                                 (long long)lock->fl.fl_end);
545
546         /* First, cancel any lock that might be there */
547         nlmsvc_cancel_blocked(file, lock);
548
549         lock->fl.fl_type = F_UNLCK;
550         error = posix_lock_file(file->f_file, &lock->fl, NULL);
551
552         return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
553 }
554
555 /*
556  * Cancel a previously blocked request.
557  *
558  * A cancel request always overrides any grant that may currently
559  * be in progress.
560  * The calling procedure must check whether the file can be closed.
561  */
562 __be32
563 nlmsvc_cancel_blocked(struct nlm_file *file, struct nlm_lock *lock)
564 {
565         struct nlm_block        *block;
566         int status = 0;
567
568         dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n",
569                                 file->f_file->f_path.dentry->d_inode->i_sb->s_id,
570                                 file->f_file->f_path.dentry->d_inode->i_ino,
571                                 lock->fl.fl_pid,
572                                 (long long)lock->fl.fl_start,
573                                 (long long)lock->fl.fl_end);
574
575         mutex_lock(&file->f_mutex);
576         block = nlmsvc_lookup_block(file, lock);
577         mutex_unlock(&file->f_mutex);
578         if (block != NULL) {
579                 status = nlmsvc_unlink_block(block);
580                 nlmsvc_release_block(block);
581         }
582         return status ? nlm_lck_denied : nlm_granted;
583 }
584
585 /*
586  * This is a callback from the filesystem for VFS file lock requests.
587  * It will be used if fl_grant is defined and the filesystem can not
588  * respond to the request immediately.
589  * For GETLK request it will copy the reply to the nlm_block.
590  * For SETLK or SETLKW request it will get the local posix lock.
591  * In all cases it will move the block to the head of nlm_blocked q where
592  * nlmsvc_retry_blocked() can send back a reply for SETLKW or revisit the
593  * deferred rpc for GETLK and SETLK.
594  */
595 static void
596 nlmsvc_update_deferred_block(struct nlm_block *block, struct file_lock *conf,
597                              int result)
598 {
599         block->b_flags |= B_GOT_CALLBACK;
600         if (result == 0)
601                 block->b_granted = 1;
602         else
603                 block->b_flags |= B_TIMED_OUT;
604         if (conf) {
605                 if (block->b_fl)
606                         locks_copy_lock(block->b_fl, conf);
607         }
608 }
609
610 static int nlmsvc_grant_deferred(struct file_lock *fl, struct file_lock *conf,
611                                         int result)
612 {
613         struct nlm_block *block;
614         int rc = -ENOENT;
615
616         lock_kernel();
617         list_for_each_entry(block, &nlm_blocked, b_list) {
618                 if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
619                         dprintk("lockd: nlmsvc_notify_blocked block %p flags %d\n",
620                                                         block, block->b_flags);
621                         if (block->b_flags & B_QUEUED) {
622                                 if (block->b_flags & B_TIMED_OUT) {
623                                         rc = -ENOLCK;
624                                         break;
625                                 }
626                                 nlmsvc_update_deferred_block(block, conf, result);
627                         } else if (result == 0)
628                                 block->b_granted = 1;
629
630                         nlmsvc_insert_block(block, 0);
631                         svc_wake_up(block->b_daemon);
632                         rc = 0;
633                         break;
634                 }
635         }
636         unlock_kernel();
637         if (rc == -ENOENT)
638                 printk(KERN_WARNING "lockd: grant for unknown block\n");
639         return rc;
640 }
641
642 /*
643  * Unblock a blocked lock request. This is a callback invoked from the
644  * VFS layer when a lock on which we blocked is removed.
645  *
646  * This function doesn't grant the blocked lock instantly, but rather moves
647  * the block to the head of nlm_blocked where it can be picked up by lockd.
648  */
649 static void
650 nlmsvc_notify_blocked(struct file_lock *fl)
651 {
652         struct nlm_block        *block;
653
654         dprintk("lockd: VFS unblock notification for block %p\n", fl);
655         list_for_each_entry(block, &nlm_blocked, b_list) {
656                 if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
657                         nlmsvc_insert_block(block, 0);
658                         svc_wake_up(block->b_daemon);
659                         return;
660                 }
661         }
662
663         printk(KERN_WARNING "lockd: notification for unknown block!\n");
664 }
665
666 static int nlmsvc_same_owner(struct file_lock *fl1, struct file_lock *fl2)
667 {
668         return fl1->fl_owner == fl2->fl_owner && fl1->fl_pid == fl2->fl_pid;
669 }
670
671 struct lock_manager_operations nlmsvc_lock_operations = {
672         .fl_compare_owner = nlmsvc_same_owner,
673         .fl_notify = nlmsvc_notify_blocked,
674         .fl_grant = nlmsvc_grant_deferred,
675 };
676
677 /*
678  * Try to claim a lock that was previously blocked.
679  *
680  * Note that we use both the RPC_GRANTED_MSG call _and_ an async
681  * RPC thread when notifying the client. This seems like overkill...
682  * Here's why:
683  *  -   we don't want to use a synchronous RPC thread, otherwise
684  *      we might find ourselves hanging on a dead portmapper.
685  *  -   Some lockd implementations (e.g. HP) don't react to
686  *      RPC_GRANTED calls; they seem to insist on RPC_GRANTED_MSG calls.
687  */
688 static void
689 nlmsvc_grant_blocked(struct nlm_block *block)
690 {
691         struct nlm_file         *file = block->b_file;
692         struct nlm_lock         *lock = &block->b_call->a_args.lock;
693         int                     error;
694
695         dprintk("lockd: grant blocked lock %p\n", block);
696
697         kref_get(&block->b_count);
698
699         /* Unlink block request from list */
700         nlmsvc_unlink_block(block);
701
702         /* If b_granted is true this means we've been here before.
703          * Just retry the grant callback, possibly refreshing the RPC
704          * binding */
705         if (block->b_granted) {
706                 nlm_rebind_host(block->b_host);
707                 goto callback;
708         }
709
710         /* Try the lock operation again */
711         lock->fl.fl_flags |= FL_SLEEP;
712         error = posix_lock_file(file->f_file, &lock->fl, NULL);
713         lock->fl.fl_flags &= ~FL_SLEEP;
714
715         switch (error) {
716         case 0:
717                 break;
718         case -EAGAIN:
719                 dprintk("lockd: lock still blocked\n");
720                 nlmsvc_insert_block(block, NLM_NEVER);
721                 nlmsvc_release_block(block);
722                 return;
723         default:
724                 printk(KERN_WARNING "lockd: unexpected error %d in %s!\n",
725                                 -error, __FUNCTION__);
726                 nlmsvc_insert_block(block, 10 * HZ);
727                 nlmsvc_release_block(block);
728                 return;
729         }
730
731 callback:
732         /* Lock was granted by VFS. */
733         dprintk("lockd: GRANTing blocked lock.\n");
734         block->b_granted = 1;
735
736         /* Schedule next grant callback in 30 seconds */
737         nlmsvc_insert_block(block, 30 * HZ);
738
739         /* Call the client */
740         nlm_async_call(block->b_call, NLMPROC_GRANTED_MSG, &nlmsvc_grant_ops);
741 }
742
743 /*
744  * This is the callback from the RPC layer when the NLM_GRANTED_MSG
745  * RPC call has succeeded or timed out.
746  * Like all RPC callbacks, it is invoked by the rpciod process, so it
747  * better not sleep. Therefore, we put the blocked lock on the nlm_blocked
748  * chain once more in order to have it removed by lockd itself (which can
749  * then sleep on the file semaphore without disrupting e.g. the nfs client).
750  */
751 static void nlmsvc_grant_callback(struct rpc_task *task, void *data)
752 {
753         struct nlm_rqst         *call = data;
754         struct nlm_block        *block = call->a_block;
755         unsigned long           timeout;
756
757         dprintk("lockd: GRANT_MSG RPC callback\n");
758
759         /* Technically, we should down the file semaphore here. Since we
760          * move the block towards the head of the queue only, no harm
761          * can be done, though. */
762         if (task->tk_status < 0) {
763                 /* RPC error: Re-insert for retransmission */
764                 timeout = 10 * HZ;
765         } else {
766                 /* Call was successful, now wait for client callback */
767                 timeout = 60 * HZ;
768         }
769         nlmsvc_insert_block(block, timeout);
770         svc_wake_up(block->b_daemon);
771 }
772
773 static void nlmsvc_grant_release(void *data)
774 {
775         struct nlm_rqst         *call = data;
776
777         nlmsvc_release_block(call->a_block);
778 }
779
780 static const struct rpc_call_ops nlmsvc_grant_ops = {
781         .rpc_call_done = nlmsvc_grant_callback,
782         .rpc_release = nlmsvc_grant_release,
783 };
784
785 /*
786  * We received a GRANT_RES callback. Try to find the corresponding
787  * block.
788  */
789 void
790 nlmsvc_grant_reply(struct nlm_cookie *cookie, __be32 status)
791 {
792         struct nlm_block        *block;
793
794         dprintk("grant_reply: looking for cookie %x, s=%d \n",
795                 *(unsigned int *)(cookie->data), status);
796         if (!(block = nlmsvc_find_block(cookie)))
797                 return;
798
799         if (block) {
800                 if (status == nlm_lck_denied_grace_period) {
801                         /* Try again in a couple of seconds */
802                         nlmsvc_insert_block(block, 10 * HZ);
803                 } else {
804                         /* Lock is now held by client, or has been rejected.
805                          * In both cases, the block should be removed. */
806                         nlmsvc_unlink_block(block);
807                 }
808         }
809         nlmsvc_release_block(block);
810 }
811
812 /* Helper function to handle retry of a deferred block.
813  * If it is a blocking lock, call grant_blocked.
814  * For a non-blocking lock or test lock, revisit the request.
815  */
816 static void
817 retry_deferred_block(struct nlm_block *block)
818 {
819         if (!(block->b_flags & B_GOT_CALLBACK))
820                 block->b_flags |= B_TIMED_OUT;
821         nlmsvc_insert_block(block, NLM_TIMEOUT);
822         dprintk("revisit block %p flags %d\n",  block, block->b_flags);
823         if (block->b_deferred_req) {
824                 block->b_deferred_req->revisit(block->b_deferred_req, 0);
825                 block->b_deferred_req = NULL;
826         }
827 }
828
829 /*
830  * Retry all blocked locks that have been notified. This is where lockd
831  * picks up locks that can be granted, or grant notifications that must
832  * be retransmitted.
833  */
834 unsigned long
835 nlmsvc_retry_blocked(void)
836 {
837         unsigned long   timeout = MAX_SCHEDULE_TIMEOUT;
838         struct nlm_block *block;
839
840         while (!list_empty(&nlm_blocked)) {
841                 block = list_entry(nlm_blocked.next, struct nlm_block, b_list);
842
843                 if (block->b_when == NLM_NEVER)
844                         break;
845                 if (time_after(block->b_when,jiffies)) {
846                         timeout = block->b_when - jiffies;
847                         break;
848                 }
849
850                 dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n",
851                         block, block->b_when);
852                 if (block->b_flags & B_QUEUED) {
853                         dprintk("nlmsvc_retry_blocked delete block (%p, granted=%d, flags=%d)\n",
854                                 block, block->b_granted, block->b_flags);
855                         retry_deferred_block(block);
856                 } else
857                         nlmsvc_grant_blocked(block);
858         }
859
860         return timeout;
861 }