xref: /openbmc/linux/fs/lockd/svclock.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
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 = 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 file against concurrent access */
382 	mutex_lock(&file->f_mutex);
383 	/* Get existing block (in case client is busy-waiting)
384 	 * or create new block
385 	 */
386 	block = nlmsvc_lookup_block(file, lock);
387 	if (block == NULL) {
388 		block = nlmsvc_create_block(rqstp, file, lock, cookie);
389 		ret = nlm_lck_denied_nolocks;
390 		if (block == NULL)
391 			goto out;
392 		lock = &block->b_call->a_args.lock;
393 	} else
394 		lock->fl.fl_flags &= ~FL_SLEEP;
395 
396 	if (block->b_flags & B_QUEUED) {
397 		dprintk("lockd: nlmsvc_lock deferred block %p flags %d\n",
398 							block, block->b_flags);
399 		if (block->b_granted) {
400 			nlmsvc_unlink_block(block);
401 			ret = nlm_granted;
402 			goto out;
403 		}
404 		if (block->b_flags & B_TIMED_OUT) {
405 			nlmsvc_unlink_block(block);
406 			ret = nlm_lck_denied;
407 			goto out;
408 		}
409 		ret = nlm_drop_reply;
410 		goto out;
411 	}
412 
413 	if (!wait)
414 		lock->fl.fl_flags &= ~FL_SLEEP;
415 	error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
416 	lock->fl.fl_flags &= ~FL_SLEEP;
417 
418 	dprintk("lockd: vfs_lock_file returned %d\n", error);
419 	switch(error) {
420 		case 0:
421 			ret = nlm_granted;
422 			goto out;
423 		case -EAGAIN:
424 			ret = nlm_lck_denied;
425 			break;
426 		case -EINPROGRESS:
427 			if (wait)
428 				break;
429 			/* Filesystem lock operation is in progress
430 			   Add it to the queue waiting for callback */
431 			ret = nlmsvc_defer_lock_rqst(rqstp, block);
432 			goto out;
433 		case -EDEADLK:
434 			ret = nlm_deadlock;
435 			goto out;
436 		default:			/* includes ENOLCK */
437 			ret = nlm_lck_denied_nolocks;
438 			goto out;
439 	}
440 
441 	ret = nlm_lck_denied;
442 	if (!wait)
443 		goto out;
444 
445 	ret = nlm_lck_blocked;
446 
447 	/* Append to list of blocked */
448 	nlmsvc_insert_block(block, NLM_NEVER);
449 out:
450 	mutex_unlock(&file->f_mutex);
451 	nlmsvc_release_block(block);
452 	dprintk("lockd: nlmsvc_lock returned %u\n", ret);
453 	return ret;
454 }
455 
456 /*
457  * Test for presence of a conflicting lock.
458  */
459 __be32
460 nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
461 		struct nlm_lock *lock, struct nlm_lock *conflock,
462 		struct nlm_cookie *cookie)
463 {
464 	struct nlm_block 	*block = NULL;
465 	int			error;
466 	__be32			ret;
467 
468 	dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
469 				file->f_file->f_path.dentry->d_inode->i_sb->s_id,
470 				file->f_file->f_path.dentry->d_inode->i_ino,
471 				lock->fl.fl_type,
472 				(long long)lock->fl.fl_start,
473 				(long long)lock->fl.fl_end);
474 
475 	/* Get existing block (in case client is busy-waiting) */
476 	block = nlmsvc_lookup_block(file, lock);
477 
478 	if (block == NULL) {
479 		struct file_lock *conf = kzalloc(sizeof(*conf), GFP_KERNEL);
480 
481 		if (conf == NULL)
482 			return nlm_granted;
483 		block = nlmsvc_create_block(rqstp, file, lock, cookie);
484 		if (block == NULL) {
485 			kfree(conf);
486 			return nlm_granted;
487 		}
488 		block->b_fl = conf;
489 	}
490 	if (block->b_flags & B_QUEUED) {
491 		dprintk("lockd: nlmsvc_testlock deferred block %p flags %d fl %p\n",
492 			block, block->b_flags, block->b_fl);
493 		if (block->b_flags & B_TIMED_OUT) {
494 			nlmsvc_unlink_block(block);
495 			return nlm_lck_denied;
496 		}
497 		if (block->b_flags & B_GOT_CALLBACK) {
498 			if (block->b_fl != NULL
499 					&& block->b_fl->fl_type != F_UNLCK) {
500 				lock->fl = *block->b_fl;
501 				goto conf_lock;
502 			}
503 			else {
504 				nlmsvc_unlink_block(block);
505 				return nlm_granted;
506 			}
507 		}
508 		return nlm_drop_reply;
509 	}
510 
511 	error = vfs_test_lock(file->f_file, &lock->fl);
512 	if (error == -EINPROGRESS)
513 		return nlmsvc_defer_lock_rqst(rqstp, block);
514 	if (error) {
515 		ret = nlm_lck_denied_nolocks;
516 		goto out;
517 	}
518 	if (lock->fl.fl_type == F_UNLCK) {
519 		ret = nlm_granted;
520 		goto out;
521 	}
522 
523 conf_lock:
524 	dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n",
525 		lock->fl.fl_type, (long long)lock->fl.fl_start,
526 		(long long)lock->fl.fl_end);
527 	conflock->caller = "somehost";	/* FIXME */
528 	conflock->len = strlen(conflock->caller);
529 	conflock->oh.len = 0;		/* don't return OH info */
530 	conflock->svid = lock->fl.fl_pid;
531 	conflock->fl.fl_type = lock->fl.fl_type;
532 	conflock->fl.fl_start = lock->fl.fl_start;
533 	conflock->fl.fl_end = lock->fl.fl_end;
534 	ret = nlm_lck_denied;
535 out:
536 	if (block)
537 		nlmsvc_release_block(block);
538 	return ret;
539 }
540 
541 /*
542  * Remove a lock.
543  * This implies a CANCEL call: We send a GRANT_MSG, the client replies
544  * with a GRANT_RES call which gets lost, and calls UNLOCK immediately
545  * afterwards. In this case the block will still be there, and hence
546  * must be removed.
547  */
548 __be32
549 nlmsvc_unlock(struct nlm_file *file, struct nlm_lock *lock)
550 {
551 	int	error;
552 
553 	dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
554 				file->f_file->f_path.dentry->d_inode->i_sb->s_id,
555 				file->f_file->f_path.dentry->d_inode->i_ino,
556 				lock->fl.fl_pid,
557 				(long long)lock->fl.fl_start,
558 				(long long)lock->fl.fl_end);
559 
560 	/* First, cancel any lock that might be there */
561 	nlmsvc_cancel_blocked(file, lock);
562 
563 	lock->fl.fl_type = F_UNLCK;
564 	error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
565 
566 	return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
567 }
568 
569 /*
570  * Cancel a previously blocked request.
571  *
572  * A cancel request always overrides any grant that may currently
573  * be in progress.
574  * The calling procedure must check whether the file can be closed.
575  */
576 __be32
577 nlmsvc_cancel_blocked(struct nlm_file *file, struct nlm_lock *lock)
578 {
579 	struct nlm_block	*block;
580 	int status = 0;
581 
582 	dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n",
583 				file->f_file->f_path.dentry->d_inode->i_sb->s_id,
584 				file->f_file->f_path.dentry->d_inode->i_ino,
585 				lock->fl.fl_pid,
586 				(long long)lock->fl.fl_start,
587 				(long long)lock->fl.fl_end);
588 
589 	mutex_lock(&file->f_mutex);
590 	block = nlmsvc_lookup_block(file, lock);
591 	mutex_unlock(&file->f_mutex);
592 	if (block != NULL) {
593 		vfs_cancel_lock(block->b_file->f_file,
594 				&block->b_call->a_args.lock.fl);
595 		status = nlmsvc_unlink_block(block);
596 		nlmsvc_release_block(block);
597 	}
598 	return status ? nlm_lck_denied : nlm_granted;
599 }
600 
601 /*
602  * This is a callback from the filesystem for VFS file lock requests.
603  * It will be used if fl_grant is defined and the filesystem can not
604  * respond to the request immediately.
605  * For GETLK request it will copy the reply to the nlm_block.
606  * For SETLK or SETLKW request it will get the local posix lock.
607  * In all cases it will move the block to the head of nlm_blocked q where
608  * nlmsvc_retry_blocked() can send back a reply for SETLKW or revisit the
609  * deferred rpc for GETLK and SETLK.
610  */
611 static void
612 nlmsvc_update_deferred_block(struct nlm_block *block, struct file_lock *conf,
613 			     int result)
614 {
615 	block->b_flags |= B_GOT_CALLBACK;
616 	if (result == 0)
617 		block->b_granted = 1;
618 	else
619 		block->b_flags |= B_TIMED_OUT;
620 	if (conf) {
621 		if (block->b_fl)
622 			locks_copy_lock(block->b_fl, conf);
623 	}
624 }
625 
626 static int nlmsvc_grant_deferred(struct file_lock *fl, struct file_lock *conf,
627 					int result)
628 {
629 	struct nlm_block *block;
630 	int rc = -ENOENT;
631 
632 	lock_kernel();
633 	list_for_each_entry(block, &nlm_blocked, b_list) {
634 		if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
635 			dprintk("lockd: nlmsvc_notify_blocked block %p flags %d\n",
636 							block, block->b_flags);
637 			if (block->b_flags & B_QUEUED) {
638 				if (block->b_flags & B_TIMED_OUT) {
639 					rc = -ENOLCK;
640 					break;
641 				}
642 				nlmsvc_update_deferred_block(block, conf, result);
643 			} else if (result == 0)
644 				block->b_granted = 1;
645 
646 			nlmsvc_insert_block(block, 0);
647 			svc_wake_up(block->b_daemon);
648 			rc = 0;
649 			break;
650 		}
651 	}
652 	unlock_kernel();
653 	if (rc == -ENOENT)
654 		printk(KERN_WARNING "lockd: grant for unknown block\n");
655 	return rc;
656 }
657 
658 /*
659  * Unblock a blocked lock request. This is a callback invoked from the
660  * VFS layer when a lock on which we blocked is removed.
661  *
662  * This function doesn't grant the blocked lock instantly, but rather moves
663  * the block to the head of nlm_blocked where it can be picked up by lockd.
664  */
665 static void
666 nlmsvc_notify_blocked(struct file_lock *fl)
667 {
668 	struct nlm_block	*block;
669 
670 	dprintk("lockd: VFS unblock notification for block %p\n", fl);
671 	list_for_each_entry(block, &nlm_blocked, b_list) {
672 		if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
673 			nlmsvc_insert_block(block, 0);
674 			svc_wake_up(block->b_daemon);
675 			return;
676 		}
677 	}
678 
679 	printk(KERN_WARNING "lockd: notification for unknown block!\n");
680 }
681 
682 static int nlmsvc_same_owner(struct file_lock *fl1, struct file_lock *fl2)
683 {
684 	return fl1->fl_owner == fl2->fl_owner && fl1->fl_pid == fl2->fl_pid;
685 }
686 
687 struct lock_manager_operations nlmsvc_lock_operations = {
688 	.fl_compare_owner = nlmsvc_same_owner,
689 	.fl_notify = nlmsvc_notify_blocked,
690 	.fl_grant = nlmsvc_grant_deferred,
691 };
692 
693 /*
694  * Try to claim a lock that was previously blocked.
695  *
696  * Note that we use both the RPC_GRANTED_MSG call _and_ an async
697  * RPC thread when notifying the client. This seems like overkill...
698  * Here's why:
699  *  -	we don't want to use a synchronous RPC thread, otherwise
700  *	we might find ourselves hanging on a dead portmapper.
701  *  -	Some lockd implementations (e.g. HP) don't react to
702  *	RPC_GRANTED calls; they seem to insist on RPC_GRANTED_MSG calls.
703  */
704 static void
705 nlmsvc_grant_blocked(struct nlm_block *block)
706 {
707 	struct nlm_file		*file = block->b_file;
708 	struct nlm_lock		*lock = &block->b_call->a_args.lock;
709 	int			error;
710 
711 	dprintk("lockd: grant blocked lock %p\n", block);
712 
713 	kref_get(&block->b_count);
714 
715 	/* Unlink block request from list */
716 	nlmsvc_unlink_block(block);
717 
718 	/* If b_granted is true this means we've been here before.
719 	 * Just retry the grant callback, possibly refreshing the RPC
720 	 * binding */
721 	if (block->b_granted) {
722 		nlm_rebind_host(block->b_host);
723 		goto callback;
724 	}
725 
726 	/* Try the lock operation again */
727 	lock->fl.fl_flags |= FL_SLEEP;
728 	error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
729 	lock->fl.fl_flags &= ~FL_SLEEP;
730 
731 	switch (error) {
732 	case 0:
733 		break;
734 	case -EAGAIN:
735 	case -EINPROGRESS:
736 		dprintk("lockd: lock still blocked error %d\n", error);
737 		nlmsvc_insert_block(block, NLM_NEVER);
738 		nlmsvc_release_block(block);
739 		return;
740 	default:
741 		printk(KERN_WARNING "lockd: unexpected error %d in %s!\n",
742 				-error, __FUNCTION__);
743 		nlmsvc_insert_block(block, 10 * HZ);
744 		nlmsvc_release_block(block);
745 		return;
746 	}
747 
748 callback:
749 	/* Lock was granted by VFS. */
750 	dprintk("lockd: GRANTing blocked lock.\n");
751 	block->b_granted = 1;
752 
753 	/* Schedule next grant callback in 30 seconds */
754 	nlmsvc_insert_block(block, 30 * HZ);
755 
756 	/* Call the client */
757 	nlm_async_call(block->b_call, NLMPROC_GRANTED_MSG, &nlmsvc_grant_ops);
758 }
759 
760 /*
761  * This is the callback from the RPC layer when the NLM_GRANTED_MSG
762  * RPC call has succeeded or timed out.
763  * Like all RPC callbacks, it is invoked by the rpciod process, so it
764  * better not sleep. Therefore, we put the blocked lock on the nlm_blocked
765  * chain once more in order to have it removed by lockd itself (which can
766  * then sleep on the file semaphore without disrupting e.g. the nfs client).
767  */
768 static void nlmsvc_grant_callback(struct rpc_task *task, void *data)
769 {
770 	struct nlm_rqst		*call = data;
771 	struct nlm_block	*block = call->a_block;
772 	unsigned long		timeout;
773 
774 	dprintk("lockd: GRANT_MSG RPC callback\n");
775 
776 	/* Technically, we should down the file semaphore here. Since we
777 	 * move the block towards the head of the queue only, no harm
778 	 * can be done, though. */
779 	if (task->tk_status < 0) {
780 		/* RPC error: Re-insert for retransmission */
781 		timeout = 10 * HZ;
782 	} else {
783 		/* Call was successful, now wait for client callback */
784 		timeout = 60 * HZ;
785 	}
786 	nlmsvc_insert_block(block, timeout);
787 	svc_wake_up(block->b_daemon);
788 }
789 
790 static void nlmsvc_grant_release(void *data)
791 {
792 	struct nlm_rqst		*call = data;
793 
794 	nlmsvc_release_block(call->a_block);
795 }
796 
797 static const struct rpc_call_ops nlmsvc_grant_ops = {
798 	.rpc_call_done = nlmsvc_grant_callback,
799 	.rpc_release = nlmsvc_grant_release,
800 };
801 
802 /*
803  * We received a GRANT_RES callback. Try to find the corresponding
804  * block.
805  */
806 void
807 nlmsvc_grant_reply(struct nlm_cookie *cookie, __be32 status)
808 {
809 	struct nlm_block	*block;
810 
811 	dprintk("grant_reply: looking for cookie %x, s=%d \n",
812 		*(unsigned int *)(cookie->data), status);
813 	if (!(block = nlmsvc_find_block(cookie)))
814 		return;
815 
816 	if (block) {
817 		if (status == nlm_lck_denied_grace_period) {
818 			/* Try again in a couple of seconds */
819 			nlmsvc_insert_block(block, 10 * HZ);
820 		} else {
821 			/* Lock is now held by client, or has been rejected.
822 			 * In both cases, the block should be removed. */
823 			nlmsvc_unlink_block(block);
824 		}
825 	}
826 	nlmsvc_release_block(block);
827 }
828 
829 /* Helper function to handle retry of a deferred block.
830  * If it is a blocking lock, call grant_blocked.
831  * For a non-blocking lock or test lock, revisit the request.
832  */
833 static void
834 retry_deferred_block(struct nlm_block *block)
835 {
836 	if (!(block->b_flags & B_GOT_CALLBACK))
837 		block->b_flags |= B_TIMED_OUT;
838 	nlmsvc_insert_block(block, NLM_TIMEOUT);
839 	dprintk("revisit block %p flags %d\n",	block, block->b_flags);
840 	if (block->b_deferred_req) {
841 		block->b_deferred_req->revisit(block->b_deferred_req, 0);
842 		block->b_deferred_req = NULL;
843 	}
844 }
845 
846 /*
847  * Retry all blocked locks that have been notified. This is where lockd
848  * picks up locks that can be granted, or grant notifications that must
849  * be retransmitted.
850  */
851 unsigned long
852 nlmsvc_retry_blocked(void)
853 {
854 	unsigned long	timeout = MAX_SCHEDULE_TIMEOUT;
855 	struct nlm_block *block;
856 
857 	while (!list_empty(&nlm_blocked)) {
858 		block = list_entry(nlm_blocked.next, struct nlm_block, b_list);
859 
860 		if (block->b_when == NLM_NEVER)
861 			break;
862 	        if (time_after(block->b_when,jiffies)) {
863 			timeout = block->b_when - jiffies;
864 			break;
865 		}
866 
867 		dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n",
868 			block, block->b_when);
869 		if (block->b_flags & B_QUEUED) {
870 			dprintk("nlmsvc_retry_blocked delete block (%p, granted=%d, flags=%d)\n",
871 				block, block->b_granted, block->b_flags);
872 			retry_deferred_block(block);
873 		} else
874 			nlmsvc_grant_blocked(block);
875 	}
876 
877 	return timeout;
878 }
879