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Linux/fs/lockd/svclock.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * linux/fs/lockd/svclock.c
  4  *
  5  * Handling of server-side locks, mostly of the blocked variety.
  6  * This is the ugliest part of lockd because we tread on very thin ice.
  7  * GRANT and CANCEL calls may get stuck, meet in mid-flight, etc.
  8  * IMNSHO introducing the grant callback into the NLM protocol was one
  9  * of the worst ideas Sun ever had. Except maybe for the idea of doing
 10  * NFS file locking at all.
 11  *
 12  * I'm trying hard to avoid race conditions by protecting most accesses
 13  * to a file's list of blocked locks through a semaphore. The global
 14  * list of blocked locks is not protected in this fashion however.
 15  * Therefore, some functions (such as the RPC callback for the async grant
 16  * call) move blocked locks towards the head of the list *while some other
 17  * process might be traversing it*. This should not be a problem in
 18  * practice, because this will only cause functions traversing the list
 19  * to visit some blocks twice.
 20  *
 21  * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
 22  */
 23 
 24 #include <linux/types.h>
 25 #include <linux/slab.h>
 26 #include <linux/errno.h>
 27 #include <linux/kernel.h>
 28 #include <linux/sched.h>
 29 #include <linux/sunrpc/clnt.h>
 30 #include <linux/sunrpc/svc_xprt.h>
 31 #include <linux/lockd/nlm.h>
 32 #include <linux/lockd/lockd.h>
 33 #include <linux/kthread.h>
 34 
 35 #define NLMDBG_FACILITY         NLMDBG_SVCLOCK
 36 
 37 #ifdef CONFIG_LOCKD_V4
 38 #define nlm_deadlock    nlm4_deadlock
 39 #else
 40 #define nlm_deadlock    nlm_lck_denied
 41 #endif
 42 
 43 static void nlmsvc_release_block(struct nlm_block *block);
 44 static void     nlmsvc_insert_block(struct nlm_block *block, unsigned long);
 45 static void     nlmsvc_remove_block(struct nlm_block *block);
 46 
 47 static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock);
 48 static void nlmsvc_freegrantargs(struct nlm_rqst *call);
 49 static const struct rpc_call_ops nlmsvc_grant_ops;
 50 
 51 /*
 52  * The list of blocked locks to retry
 53  */
 54 static LIST_HEAD(nlm_blocked);
 55 static DEFINE_SPINLOCK(nlm_blocked_lock);
 56 
 57 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 58 static const char *nlmdbg_cookie2a(const struct nlm_cookie *cookie)
 59 {
 60         /*
 61          * We can get away with a static buffer because this is only called
 62          * from lockd, which is single-threaded.
 63          */
 64         static char buf[2*NLM_MAXCOOKIELEN+1];
 65         unsigned int i, len = sizeof(buf);
 66         char *p = buf;
 67 
 68         len--;  /* allow for trailing \0 */
 69         if (len < 3)
 70                 return "???";
 71         for (i = 0 ; i < cookie->len ; i++) {
 72                 if (len < 2) {
 73                         strcpy(p-3, "...");
 74                         break;
 75                 }
 76                 sprintf(p, "%02x", cookie->data[i]);
 77                 p += 2;
 78                 len -= 2;
 79         }
 80         *p = '\0';
 81 
 82         return buf;
 83 }
 84 #endif
 85 
 86 /*
 87  * Insert a blocked lock into the global list
 88  */
 89 static void
 90 nlmsvc_insert_block_locked(struct nlm_block *block, unsigned long when)
 91 {
 92         struct nlm_block *b;
 93         struct list_head *pos;
 94 
 95         dprintk("lockd: nlmsvc_insert_block(%p, %ld)\n", block, when);
 96         if (list_empty(&block->b_list)) {
 97                 kref_get(&block->b_count);
 98         } else {
 99                 list_del_init(&block->b_list);
100         }
101 
102         pos = &nlm_blocked;
103         if (when != NLM_NEVER) {
104                 if ((when += jiffies) == NLM_NEVER)
105                         when ++;
106                 list_for_each(pos, &nlm_blocked) {
107                         b = list_entry(pos, struct nlm_block, b_list);
108                         if (time_after(b->b_when,when) || b->b_when == NLM_NEVER)
109                                 break;
110                 }
111                 /* On normal exit from the loop, pos == &nlm_blocked,
112                  * so we will be adding to the end of the list - good
113                  */
114         }
115 
116         list_add_tail(&block->b_list, pos);
117         block->b_when = when;
118 }
119 
120 static void nlmsvc_insert_block(struct nlm_block *block, unsigned long when)
121 {
122         spin_lock(&nlm_blocked_lock);
123         nlmsvc_insert_block_locked(block, when);
124         spin_unlock(&nlm_blocked_lock);
125 }
126 
127 /*
128  * Remove a block from the global list
129  */
130 static inline void
131 nlmsvc_remove_block(struct nlm_block *block)
132 {
133         if (!list_empty(&block->b_list)) {
134                 spin_lock(&nlm_blocked_lock);
135                 list_del_init(&block->b_list);
136                 spin_unlock(&nlm_blocked_lock);
137                 nlmsvc_release_block(block);
138         }
139 }
140 
141 /*
142  * Find a block for a given lock
143  */
144 static struct nlm_block *
145 nlmsvc_lookup_block(struct nlm_file *file, struct nlm_lock *lock)
146 {
147         struct nlm_block        *block;
148         struct file_lock        *fl;
149 
150         dprintk("lockd: nlmsvc_lookup_block f=%p pd=%d %Ld-%Ld ty=%d\n",
151                                 file, lock->fl.fl_pid,
152                                 (long long)lock->fl.fl_start,
153                                 (long long)lock->fl.fl_end, lock->fl.fl_type);
154         list_for_each_entry(block, &nlm_blocked, b_list) {
155                 fl = &block->b_call->a_args.lock.fl;
156                 dprintk("lockd: check f=%p pd=%d %Ld-%Ld ty=%d cookie=%s\n",
157                                 block->b_file, fl->fl_pid,
158                                 (long long)fl->fl_start,
159                                 (long long)fl->fl_end, fl->fl_type,
160                                 nlmdbg_cookie2a(&block->b_call->a_args.cookie));
161                 if (block->b_file == file && nlm_compare_locks(fl, &lock->fl)) {
162                         kref_get(&block->b_count);
163                         return block;
164                 }
165         }
166 
167         return NULL;
168 }
169 
170 static inline int nlm_cookie_match(struct nlm_cookie *a, struct nlm_cookie *b)
171 {
172         if (a->len != b->len)
173                 return 0;
174         if (memcmp(a->data, b->data, a->len))
175                 return 0;
176         return 1;
177 }
178 
179 /*
180  * Find a block with a given NLM cookie.
181  */
182 static inline struct nlm_block *
183 nlmsvc_find_block(struct nlm_cookie *cookie)
184 {
185         struct nlm_block *block;
186 
187         list_for_each_entry(block, &nlm_blocked, b_list) {
188                 if (nlm_cookie_match(&block->b_call->a_args.cookie,cookie))
189                         goto found;
190         }
191 
192         return NULL;
193 
194 found:
195         dprintk("nlmsvc_find_block(%s): block=%p\n", nlmdbg_cookie2a(cookie), block);
196         kref_get(&block->b_count);
197         return block;
198 }
199 
200 /*
201  * Create a block and initialize it.
202  *
203  * Note: we explicitly set the cookie of the grant reply to that of
204  * the blocked lock request. The spec explicitly mentions that the client
205  * should _not_ rely on the callback containing the same cookie as the
206  * request, but (as I found out later) that's because some implementations
207  * do just this. Never mind the standards comittees, they support our
208  * logging industries.
209  *
210  * 10 years later: I hope we can safely ignore these old and broken
211  * clients by now. Let's fix this so we can uniquely identify an incoming
212  * GRANTED_RES message by cookie, without having to rely on the client's IP
213  * address. --okir
214  */
215 static struct nlm_block *
216 nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_host *host,
217                     struct nlm_file *file, struct nlm_lock *lock,
218                     struct nlm_cookie *cookie)
219 {
220         struct nlm_block        *block;
221         struct nlm_rqst         *call = NULL;
222 
223         call = nlm_alloc_call(host);
224         if (call == NULL)
225                 return NULL;
226 
227         /* Allocate memory for block, and initialize arguments */
228         block = kzalloc(sizeof(*block), GFP_KERNEL);
229         if (block == NULL)
230                 goto failed;
231         kref_init(&block->b_count);
232         INIT_LIST_HEAD(&block->b_list);
233         INIT_LIST_HEAD(&block->b_flist);
234 
235         if (!nlmsvc_setgrantargs(call, lock))
236                 goto failed_free;
237 
238         /* Set notifier function for VFS, and init args */
239         call->a_args.lock.fl.fl_flags |= FL_SLEEP;
240         call->a_args.lock.fl.fl_lmops = &nlmsvc_lock_operations;
241         nlmclnt_next_cookie(&call->a_args.cookie);
242 
243         dprintk("lockd: created block %p...\n", block);
244 
245         /* Create and initialize the block */
246         block->b_daemon = rqstp->rq_server;
247         block->b_host   = host;
248         block->b_file   = file;
249         file->f_count++;
250 
251         /* Add to file's list of blocks */
252         list_add(&block->b_flist, &file->f_blocks);
253 
254         /* Set up RPC arguments for callback */
255         block->b_call = call;
256         call->a_flags   = RPC_TASK_ASYNC;
257         call->a_block = block;
258 
259         return block;
260 
261 failed_free:
262         kfree(block);
263 failed:
264         nlmsvc_release_call(call);
265         return NULL;
266 }
267 
268 /*
269  * Delete a block.
270  * It is the caller's responsibility to check whether the file
271  * can be closed hereafter.
272  */
273 static int nlmsvc_unlink_block(struct nlm_block *block)
274 {
275         int status;
276         dprintk("lockd: unlinking block %p...\n", block);
277 
278         /* Remove block from list */
279         status = locks_delete_block(&block->b_call->a_args.lock.fl);
280         nlmsvc_remove_block(block);
281         return status;
282 }
283 
284 static void nlmsvc_free_block(struct kref *kref)
285 {
286         struct nlm_block *block = container_of(kref, struct nlm_block, b_count);
287         struct nlm_file         *file = block->b_file;
288 
289         dprintk("lockd: freeing block %p...\n", block);
290 
291         /* Remove block from file's list of blocks */
292         list_del_init(&block->b_flist);
293         mutex_unlock(&file->f_mutex);
294 
295         nlmsvc_freegrantargs(block->b_call);
296         nlmsvc_release_call(block->b_call);
297         nlm_release_file(block->b_file);
298         kfree(block);
299 }
300 
301 static void nlmsvc_release_block(struct nlm_block *block)
302 {
303         if (block != NULL)
304                 kref_put_mutex(&block->b_count, nlmsvc_free_block, &block->b_file->f_mutex);
305 }
306 
307 /*
308  * Loop over all blocks and delete blocks held by
309  * a matching host.
310  */
311 void nlmsvc_traverse_blocks(struct nlm_host *host,
312                         struct nlm_file *file,
313                         nlm_host_match_fn_t match)
314 {
315         struct nlm_block *block, *next;
316 
317 restart:
318         mutex_lock(&file->f_mutex);
319         list_for_each_entry_safe(block, next, &file->f_blocks, b_flist) {
320                 if (!match(block->b_host, host))
321                         continue;
322                 /* Do not destroy blocks that are not on
323                  * the global retry list - why? */
324                 if (list_empty(&block->b_list))
325                         continue;
326                 kref_get(&block->b_count);
327                 mutex_unlock(&file->f_mutex);
328                 nlmsvc_unlink_block(block);
329                 nlmsvc_release_block(block);
330                 goto restart;
331         }
332         mutex_unlock(&file->f_mutex);
333 }
334 
335 static struct nlm_lockowner *
336 nlmsvc_get_lockowner(struct nlm_lockowner *lockowner)
337 {
338         refcount_inc(&lockowner->count);
339         return lockowner;
340 }
341 
342 static void nlmsvc_put_lockowner(struct nlm_lockowner *lockowner)
343 {
344         if (!refcount_dec_and_lock(&lockowner->count, &lockowner->host->h_lock))
345                 return;
346         list_del(&lockowner->list);
347         spin_unlock(&lockowner->host->h_lock);
348         nlmsvc_release_host(lockowner->host);
349         kfree(lockowner);
350 }
351 
352 static struct nlm_lockowner *__nlmsvc_find_lockowner(struct nlm_host *host, pid_t pid)
353 {
354         struct nlm_lockowner *lockowner;
355         list_for_each_entry(lockowner, &host->h_lockowners, list) {
356                 if (lockowner->pid != pid)
357                         continue;
358                 return nlmsvc_get_lockowner(lockowner);
359         }
360         return NULL;
361 }
362 
363 static struct nlm_lockowner *nlmsvc_find_lockowner(struct nlm_host *host, pid_t pid)
364 {
365         struct nlm_lockowner *res, *new = NULL;
366 
367         spin_lock(&host->h_lock);
368         res = __nlmsvc_find_lockowner(host, pid);
369 
370         if (res == NULL) {
371                 spin_unlock(&host->h_lock);
372                 new = kmalloc(sizeof(*res), GFP_KERNEL);
373                 spin_lock(&host->h_lock);
374                 res = __nlmsvc_find_lockowner(host, pid);
375                 if (res == NULL && new != NULL) {
376                         res = new;
377                         /* fs/locks.c will manage the refcount through lock_ops */
378                         refcount_set(&new->count, 1);
379                         new->pid = pid;
380                         new->host = nlm_get_host(host);
381                         list_add(&new->list, &host->h_lockowners);
382                         new = NULL;
383                 }
384         }
385 
386         spin_unlock(&host->h_lock);
387         kfree(new);
388         return res;
389 }
390 
391 void
392 nlmsvc_release_lockowner(struct nlm_lock *lock)
393 {
394         if (lock->fl.fl_owner)
395                 nlmsvc_put_lockowner(lock->fl.fl_owner);
396 }
397 
398 static void nlmsvc_locks_copy_lock(struct file_lock *new, struct file_lock *fl)
399 {
400         struct nlm_lockowner *nlm_lo = (struct nlm_lockowner *)fl->fl_owner;
401         new->fl_owner = nlmsvc_get_lockowner(nlm_lo);
402 }
403 
404 static void nlmsvc_locks_release_private(struct file_lock *fl)
405 {
406         nlmsvc_put_lockowner((struct nlm_lockowner *)fl->fl_owner);
407 }
408 
409 static const struct file_lock_operations nlmsvc_lock_ops = {
410         .fl_copy_lock = nlmsvc_locks_copy_lock,
411         .fl_release_private = nlmsvc_locks_release_private,
412 };
413 
414 void nlmsvc_locks_init_private(struct file_lock *fl, struct nlm_host *host,
415                                                 pid_t pid)
416 {
417         fl->fl_owner = nlmsvc_find_lockowner(host, pid);
418         if (fl->fl_owner != NULL)
419                 fl->fl_ops = &nlmsvc_lock_ops;
420 }
421 
422 /*
423  * Initialize arguments for GRANTED call. The nlm_rqst structure
424  * has been cleared already.
425  */
426 static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock)
427 {
428         locks_copy_lock(&call->a_args.lock.fl, &lock->fl);
429         memcpy(&call->a_args.lock.fh, &lock->fh, sizeof(call->a_args.lock.fh));
430         call->a_args.lock.caller = utsname()->nodename;
431         call->a_args.lock.oh.len = lock->oh.len;
432 
433         /* set default data area */
434         call->a_args.lock.oh.data = call->a_owner;
435         call->a_args.lock.svid = ((struct nlm_lockowner *)lock->fl.fl_owner)->pid;
436 
437         if (lock->oh.len > NLMCLNT_OHSIZE) {
438                 void *data = kmalloc(lock->oh.len, GFP_KERNEL);
439                 if (!data)
440                         return 0;
441                 call->a_args.lock.oh.data = (u8 *) data;
442         }
443 
444         memcpy(call->a_args.lock.oh.data, lock->oh.data, lock->oh.len);
445         return 1;
446 }
447 
448 static void nlmsvc_freegrantargs(struct nlm_rqst *call)
449 {
450         if (call->a_args.lock.oh.data != call->a_owner)
451                 kfree(call->a_args.lock.oh.data);
452 
453         locks_release_private(&call->a_args.lock.fl);
454 }
455 
456 /*
457  * Deferred lock request handling for non-blocking lock
458  */
459 static __be32
460 nlmsvc_defer_lock_rqst(struct svc_rqst *rqstp, struct nlm_block *block)
461 {
462         __be32 status = nlm_lck_denied_nolocks;
463 
464         block->b_flags |= B_QUEUED;
465 
466         nlmsvc_insert_block(block, NLM_TIMEOUT);
467 
468         block->b_cache_req = &rqstp->rq_chandle;
469         if (rqstp->rq_chandle.defer) {
470                 block->b_deferred_req =
471                         rqstp->rq_chandle.defer(block->b_cache_req);
472                 if (block->b_deferred_req != NULL)
473                         status = nlm_drop_reply;
474         }
475         dprintk("lockd: nlmsvc_defer_lock_rqst block %p flags %d status %d\n",
476                 block, block->b_flags, ntohl(status));
477 
478         return status;
479 }
480 
481 /*
482  * Attempt to establish a lock, and if it can't be granted, block it
483  * if required.
484  */
485 __be32
486 nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
487             struct nlm_host *host, struct nlm_lock *lock, int wait,
488             struct nlm_cookie *cookie, int reclaim)
489 {
490         struct nlm_block        *block = NULL;
491         int                     error;
492         __be32                  ret;
493 
494         dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
495                                 locks_inode(file->f_file)->i_sb->s_id,
496                                 locks_inode(file->f_file)->i_ino,
497                                 lock->fl.fl_type, lock->fl.fl_pid,
498                                 (long long)lock->fl.fl_start,
499                                 (long long)lock->fl.fl_end,
500                                 wait);
501 
502         /* Lock file against concurrent access */
503         mutex_lock(&file->f_mutex);
504         /* Get existing block (in case client is busy-waiting)
505          * or create new block
506          */
507         block = nlmsvc_lookup_block(file, lock);
508         if (block == NULL) {
509                 block = nlmsvc_create_block(rqstp, host, file, lock, cookie);
510                 ret = nlm_lck_denied_nolocks;
511                 if (block == NULL)
512                         goto out;
513                 lock = &block->b_call->a_args.lock;
514         } else
515                 lock->fl.fl_flags &= ~FL_SLEEP;
516 
517         if (block->b_flags & B_QUEUED) {
518                 dprintk("lockd: nlmsvc_lock deferred block %p flags %d\n",
519                                                         block, block->b_flags);
520                 if (block->b_granted) {
521                         nlmsvc_unlink_block(block);
522                         ret = nlm_granted;
523                         goto out;
524                 }
525                 if (block->b_flags & B_TIMED_OUT) {
526                         nlmsvc_unlink_block(block);
527                         ret = nlm_lck_denied;
528                         goto out;
529                 }
530                 ret = nlm_drop_reply;
531                 goto out;
532         }
533 
534         if (locks_in_grace(SVC_NET(rqstp)) && !reclaim) {
535                 ret = nlm_lck_denied_grace_period;
536                 goto out;
537         }
538         if (reclaim && !locks_in_grace(SVC_NET(rqstp))) {
539                 ret = nlm_lck_denied_grace_period;
540                 goto out;
541         }
542 
543         if (!wait)
544                 lock->fl.fl_flags &= ~FL_SLEEP;
545         error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
546         lock->fl.fl_flags &= ~FL_SLEEP;
547 
548         dprintk("lockd: vfs_lock_file returned %d\n", error);
549         switch (error) {
550                 case 0:
551                         ret = nlm_granted;
552                         goto out;
553                 case -EAGAIN:
554                         /*
555                          * If this is a blocking request for an
556                          * already pending lock request then we need
557                          * to put it back on lockd's block list
558                          */
559                         if (wait)
560                                 break;
561                         ret = nlm_lck_denied;
562                         goto out;
563                 case FILE_LOCK_DEFERRED:
564                         if (wait)
565                                 break;
566                         /* Filesystem lock operation is in progress
567                            Add it to the queue waiting for callback */
568                         ret = nlmsvc_defer_lock_rqst(rqstp, block);
569                         goto out;
570                 case -EDEADLK:
571                         ret = nlm_deadlock;
572                         goto out;
573                 default:                        /* includes ENOLCK */
574                         ret = nlm_lck_denied_nolocks;
575                         goto out;
576         }
577 
578         ret = nlm_lck_blocked;
579 
580         /* Append to list of blocked */
581         nlmsvc_insert_block(block, NLM_NEVER);
582 out:
583         mutex_unlock(&file->f_mutex);
584         nlmsvc_release_block(block);
585         dprintk("lockd: nlmsvc_lock returned %u\n", ret);
586         return ret;
587 }
588 
589 /*
590  * Test for presence of a conflicting lock.
591  */
592 __be32
593 nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
594                 struct nlm_host *host, struct nlm_lock *lock,
595                 struct nlm_lock *conflock, struct nlm_cookie *cookie)
596 {
597         int                     error;
598         __be32                  ret;
599         struct nlm_lockowner    *test_owner;
600 
601         dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
602                                 locks_inode(file->f_file)->i_sb->s_id,
603                                 locks_inode(file->f_file)->i_ino,
604                                 lock->fl.fl_type,
605                                 (long long)lock->fl.fl_start,
606                                 (long long)lock->fl.fl_end);
607 
608         if (locks_in_grace(SVC_NET(rqstp))) {
609                 ret = nlm_lck_denied_grace_period;
610                 goto out;
611         }
612 
613         /* If there's a conflicting lock, remember to clean up the test lock */
614         test_owner = (struct nlm_lockowner *)lock->fl.fl_owner;
615 
616         error = vfs_test_lock(file->f_file, &lock->fl);
617         if (error) {
618                 /* We can't currently deal with deferred test requests */
619                 if (error == FILE_LOCK_DEFERRED)
620                         WARN_ON_ONCE(1);
621 
622                 ret = nlm_lck_denied_nolocks;
623                 goto out;
624         }
625 
626         if (lock->fl.fl_type == F_UNLCK) {
627                 ret = nlm_granted;
628                 goto out;
629         }
630 
631         dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n",
632                 lock->fl.fl_type, (long long)lock->fl.fl_start,
633                 (long long)lock->fl.fl_end);
634         conflock->caller = "somehost";  /* FIXME */
635         conflock->len = strlen(conflock->caller);
636         conflock->oh.len = 0;           /* don't return OH info */
637         conflock->svid = ((struct nlm_lockowner *)lock->fl.fl_owner)->pid;
638         conflock->fl.fl_type = lock->fl.fl_type;
639         conflock->fl.fl_start = lock->fl.fl_start;
640         conflock->fl.fl_end = lock->fl.fl_end;
641         locks_release_private(&lock->fl);
642 
643         /* Clean up the test lock */
644         lock->fl.fl_owner = NULL;
645         nlmsvc_put_lockowner(test_owner);
646 
647         ret = nlm_lck_denied;
648 out:
649         return ret;
650 }
651 
652 /*
653  * Remove a lock.
654  * This implies a CANCEL call: We send a GRANT_MSG, the client replies
655  * with a GRANT_RES call which gets lost, and calls UNLOCK immediately
656  * afterwards. In this case the block will still be there, and hence
657  * must be removed.
658  */
659 __be32
660 nlmsvc_unlock(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
661 {
662         int     error;
663 
664         dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
665                                 locks_inode(file->f_file)->i_sb->s_id,
666                                 locks_inode(file->f_file)->i_ino,
667                                 lock->fl.fl_pid,
668                                 (long long)lock->fl.fl_start,
669                                 (long long)lock->fl.fl_end);
670 
671         /* First, cancel any lock that might be there */
672         nlmsvc_cancel_blocked(net, file, lock);
673 
674         lock->fl.fl_type = F_UNLCK;
675         error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
676 
677         return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
678 }
679 
680 /*
681  * Cancel a previously blocked request.
682  *
683  * A cancel request always overrides any grant that may currently
684  * be in progress.
685  * The calling procedure must check whether the file can be closed.
686  */
687 __be32
688 nlmsvc_cancel_blocked(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
689 {
690         struct nlm_block        *block;
691         int status = 0;
692 
693         dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n",
694                                 locks_inode(file->f_file)->i_sb->s_id,
695                                 locks_inode(file->f_file)->i_ino,
696                                 lock->fl.fl_pid,
697                                 (long long)lock->fl.fl_start,
698                                 (long long)lock->fl.fl_end);
699 
700         if (locks_in_grace(net))
701                 return nlm_lck_denied_grace_period;
702 
703         mutex_lock(&file->f_mutex);
704         block = nlmsvc_lookup_block(file, lock);
705         mutex_unlock(&file->f_mutex);
706         if (block != NULL) {
707                 vfs_cancel_lock(block->b_file->f_file,
708                                 &block->b_call->a_args.lock.fl);
709                 status = nlmsvc_unlink_block(block);
710                 nlmsvc_release_block(block);
711         }
712         return status ? nlm_lck_denied : nlm_granted;
713 }
714 
715 /*
716  * This is a callback from the filesystem for VFS file lock requests.
717  * It will be used if lm_grant is defined and the filesystem can not
718  * respond to the request immediately.
719  * For SETLK or SETLKW request it will get the local posix lock.
720  * In all cases it will move the block to the head of nlm_blocked q where
721  * nlmsvc_retry_blocked() can send back a reply for SETLKW or revisit the
722  * deferred rpc for GETLK and SETLK.
723  */
724 static void
725 nlmsvc_update_deferred_block(struct nlm_block *block, int result)
726 {
727         block->b_flags |= B_GOT_CALLBACK;
728         if (result == 0)
729                 block->b_granted = 1;
730         else
731                 block->b_flags |= B_TIMED_OUT;
732 }
733 
734 static int nlmsvc_grant_deferred(struct file_lock *fl, int result)
735 {
736         struct nlm_block *block;
737         int rc = -ENOENT;
738 
739         spin_lock(&nlm_blocked_lock);
740         list_for_each_entry(block, &nlm_blocked, b_list) {
741                 if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
742                         dprintk("lockd: nlmsvc_notify_blocked block %p flags %d\n",
743                                                         block, block->b_flags);
744                         if (block->b_flags & B_QUEUED) {
745                                 if (block->b_flags & B_TIMED_OUT) {
746                                         rc = -ENOLCK;
747                                         break;
748                                 }
749                                 nlmsvc_update_deferred_block(block, result);
750                         } else if (result == 0)
751                                 block->b_granted = 1;
752 
753                         nlmsvc_insert_block_locked(block, 0);
754                         svc_wake_up(block->b_daemon);
755                         rc = 0;
756                         break;
757                 }
758         }
759         spin_unlock(&nlm_blocked_lock);
760         if (rc == -ENOENT)
761                 printk(KERN_WARNING "lockd: grant for unknown block\n");
762         return rc;
763 }
764 
765 /*
766  * Unblock a blocked lock request. This is a callback invoked from the
767  * VFS layer when a lock on which we blocked is removed.
768  *
769  * This function doesn't grant the blocked lock instantly, but rather moves
770  * the block to the head of nlm_blocked where it can be picked up by lockd.
771  */
772 static void
773 nlmsvc_notify_blocked(struct file_lock *fl)
774 {
775         struct nlm_block        *block;
776 
777         dprintk("lockd: VFS unblock notification for block %p\n", fl);
778         spin_lock(&nlm_blocked_lock);
779         list_for_each_entry(block, &nlm_blocked, b_list) {
780                 if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
781                         nlmsvc_insert_block_locked(block, 0);
782                         spin_unlock(&nlm_blocked_lock);
783                         svc_wake_up(block->b_daemon);
784                         return;
785                 }
786         }
787         spin_unlock(&nlm_blocked_lock);
788         printk(KERN_WARNING "lockd: notification for unknown block!\n");
789 }
790 
791 const struct lock_manager_operations nlmsvc_lock_operations = {
792         .lm_notify = nlmsvc_notify_blocked,
793         .lm_grant = nlmsvc_grant_deferred,
794 };
795 
796 /*
797  * Try to claim a lock that was previously blocked.
798  *
799  * Note that we use both the RPC_GRANTED_MSG call _and_ an async
800  * RPC thread when notifying the client. This seems like overkill...
801  * Here's why:
802  *  -   we don't want to use a synchronous RPC thread, otherwise
803  *      we might find ourselves hanging on a dead portmapper.
804  *  -   Some lockd implementations (e.g. HP) don't react to
805  *      RPC_GRANTED calls; they seem to insist on RPC_GRANTED_MSG calls.
806  */
807 static void
808 nlmsvc_grant_blocked(struct nlm_block *block)
809 {
810         struct nlm_file         *file = block->b_file;
811         struct nlm_lock         *lock = &block->b_call->a_args.lock;
812         int                     error;
813         loff_t                  fl_start, fl_end;
814 
815         dprintk("lockd: grant blocked lock %p\n", block);
816 
817         kref_get(&block->b_count);
818 
819         /* Unlink block request from list */
820         nlmsvc_unlink_block(block);
821 
822         /* If b_granted is true this means we've been here before.
823          * Just retry the grant callback, possibly refreshing the RPC
824          * binding */
825         if (block->b_granted) {
826                 nlm_rebind_host(block->b_host);
827                 goto callback;
828         }
829 
830         /* Try the lock operation again */
831         /* vfs_lock_file() can mangle fl_start and fl_end, but we need
832          * them unchanged for the GRANT_MSG
833          */
834         lock->fl.fl_flags |= FL_SLEEP;
835         fl_start = lock->fl.fl_start;
836         fl_end = lock->fl.fl_end;
837         error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
838         lock->fl.fl_flags &= ~FL_SLEEP;
839         lock->fl.fl_start = fl_start;
840         lock->fl.fl_end = fl_end;
841 
842         switch (error) {
843         case 0:
844                 break;
845         case FILE_LOCK_DEFERRED:
846                 dprintk("lockd: lock still blocked error %d\n", error);
847                 nlmsvc_insert_block(block, NLM_NEVER);
848                 nlmsvc_release_block(block);
849                 return;
850         default:
851                 printk(KERN_WARNING "lockd: unexpected error %d in %s!\n",
852                                 -error, __func__);
853                 nlmsvc_insert_block(block, 10 * HZ);
854                 nlmsvc_release_block(block);
855                 return;
856         }
857 
858 callback:
859         /* Lock was granted by VFS. */
860         dprintk("lockd: GRANTing blocked lock.\n");
861         block->b_granted = 1;
862 
863         /* keep block on the list, but don't reattempt until the RPC
864          * completes or the submission fails
865          */
866         nlmsvc_insert_block(block, NLM_NEVER);
867 
868         /* Call the client -- use a soft RPC task since nlmsvc_retry_blocked
869          * will queue up a new one if this one times out
870          */
871         error = nlm_async_call(block->b_call, NLMPROC_GRANTED_MSG,
872                                 &nlmsvc_grant_ops);
873 
874         /* RPC submission failed, wait a bit and retry */
875         if (error < 0)
876                 nlmsvc_insert_block(block, 10 * HZ);
877 }
878 
879 /*
880  * This is the callback from the RPC layer when the NLM_GRANTED_MSG
881  * RPC call has succeeded or timed out.
882  * Like all RPC callbacks, it is invoked by the rpciod process, so it
883  * better not sleep. Therefore, we put the blocked lock on the nlm_blocked
884  * chain once more in order to have it removed by lockd itself (which can
885  * then sleep on the file semaphore without disrupting e.g. the nfs client).
886  */
887 static void nlmsvc_grant_callback(struct rpc_task *task, void *data)
888 {
889         struct nlm_rqst         *call = data;
890         struct nlm_block        *block = call->a_block;
891         unsigned long           timeout;
892 
893         dprintk("lockd: GRANT_MSG RPC callback\n");
894 
895         spin_lock(&nlm_blocked_lock);
896         /* if the block is not on a list at this point then it has
897          * been invalidated. Don't try to requeue it.
898          *
899          * FIXME: it's possible that the block is removed from the list
900          * after this check but before the nlmsvc_insert_block. In that
901          * case it will be added back. Perhaps we need better locking
902          * for nlm_blocked?
903          */
904         if (list_empty(&block->b_list))
905                 goto out;
906 
907         /* Technically, we should down the file semaphore here. Since we
908          * move the block towards the head of the queue only, no harm
909          * can be done, though. */
910         if (task->tk_status < 0) {
911                 /* RPC error: Re-insert for retransmission */
912                 timeout = 10 * HZ;
913         } else {
914                 /* Call was successful, now wait for client callback */
915                 timeout = 60 * HZ;
916         }
917         nlmsvc_insert_block_locked(block, timeout);
918         svc_wake_up(block->b_daemon);
919 out:
920         spin_unlock(&nlm_blocked_lock);
921 }
922 
923 /*
924  * FIXME: nlmsvc_release_block() grabs a mutex.  This is not allowed for an
925  * .rpc_release rpc_call_op
926  */
927 static void nlmsvc_grant_release(void *data)
928 {
929         struct nlm_rqst         *call = data;
930         nlmsvc_release_block(call->a_block);
931 }
932 
933 static const struct rpc_call_ops nlmsvc_grant_ops = {
934         .rpc_call_done = nlmsvc_grant_callback,
935         .rpc_release = nlmsvc_grant_release,
936 };
937 
938 /*
939  * We received a GRANT_RES callback. Try to find the corresponding
940  * block.
941  */
942 void
943 nlmsvc_grant_reply(struct nlm_cookie *cookie, __be32 status)
944 {
945         struct nlm_block        *block;
946 
947         dprintk("grant_reply: looking for cookie %x, s=%d \n",
948                 *(unsigned int *)(cookie->data), status);
949         if (!(block = nlmsvc_find_block(cookie)))
950                 return;
951 
952         if (status == nlm_lck_denied_grace_period) {
953                 /* Try again in a couple of seconds */
954                 nlmsvc_insert_block(block, 10 * HZ);
955         } else {
956                 /*
957                  * Lock is now held by client, or has been rejected.
958                  * In both cases, the block should be removed.
959                  */
960                 nlmsvc_unlink_block(block);
961         }
962         nlmsvc_release_block(block);
963 }
964 
965 /* Helper function to handle retry of a deferred block.
966  * If it is a blocking lock, call grant_blocked.
967  * For a non-blocking lock or test lock, revisit the request.
968  */
969 static void
970 retry_deferred_block(struct nlm_block *block)
971 {
972         if (!(block->b_flags & B_GOT_CALLBACK))
973                 block->b_flags |= B_TIMED_OUT;
974         nlmsvc_insert_block(block, NLM_TIMEOUT);
975         dprintk("revisit block %p flags %d\n",  block, block->b_flags);
976         if (block->b_deferred_req) {
977                 block->b_deferred_req->revisit(block->b_deferred_req, 0);
978                 block->b_deferred_req = NULL;
979         }
980 }
981 
982 /*
983  * Retry all blocked locks that have been notified. This is where lockd
984  * picks up locks that can be granted, or grant notifications that must
985  * be retransmitted.
986  */
987 unsigned long
988 nlmsvc_retry_blocked(void)
989 {
990         unsigned long   timeout = MAX_SCHEDULE_TIMEOUT;
991         struct nlm_block *block;
992 
993         spin_lock(&nlm_blocked_lock);
994         while (!list_empty(&nlm_blocked) && !kthread_should_stop()) {
995                 block = list_entry(nlm_blocked.next, struct nlm_block, b_list);
996 
997                 if (block->b_when == NLM_NEVER)
998                         break;
999                 if (time_after(block->b_when, jiffies)) {
1000                         timeout = block->b_when - jiffies;
1001                         break;
1002                 }
1003                 spin_unlock(&nlm_blocked_lock);
1004 
1005                 dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n",
1006                         block, block->b_when);
1007                 if (block->b_flags & B_QUEUED) {
1008                         dprintk("nlmsvc_retry_blocked delete block (%p, granted=%d, flags=%d)\n",
1009                                 block, block->b_granted, block->b_flags);
1010                         retry_deferred_block(block);
1011                 } else
1012                         nlmsvc_grant_blocked(block);
1013                 spin_lock(&nlm_blocked_lock);
1014         }
1015         spin_unlock(&nlm_blocked_lock);
1016 
1017         return timeout;
1018 }
1019 

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