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TOMOYO Linux Cross Reference
Linux/fs/lockd/svclock.c

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  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/slab.h>
 25 #include <linux/errno.h>
 26 #include <linux/kernel.h>
 27 #include <linux/sched.h>
 28 #include <linux/sunrpc/clnt.h>
 29 #include <linux/sunrpc/svc_xprt.h>
 30 #include <linux/lockd/nlm.h>
 31 #include <linux/lockd/lockd.h>
 32 #include <linux/kthread.h>
 33 
 34 #define NLMDBG_FACILITY         NLMDBG_SVCLOCK
 35 
 36 #ifdef CONFIG_LOCKD_V4
 37 #define nlm_deadlock    nlm4_deadlock
 38 #else
 39 #define nlm_deadlock    nlm_lck_denied
 40 #endif
 41 
 42 static void nlmsvc_release_block(struct nlm_block *block);
 43 static void     nlmsvc_insert_block(struct nlm_block *block, unsigned long);
 44 static void     nlmsvc_remove_block(struct nlm_block *block);
 45 
 46 static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock);
 47 static void nlmsvc_freegrantargs(struct nlm_rqst *call);
 48 static const struct rpc_call_ops nlmsvc_grant_ops;
 49 
 50 /*
 51  * The list of blocked locks to retry
 52  */
 53 static LIST_HEAD(nlm_blocked);
 54 static DEFINE_SPINLOCK(nlm_blocked_lock);
 55 
 56 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 57 static const char *nlmdbg_cookie2a(const struct nlm_cookie *cookie)
 58 {
 59         /*
 60          * We can get away with a static buffer because this is only called
 61          * from lockd, which is single-threaded.
 62          */
 63         static char buf[2*NLM_MAXCOOKIELEN+1];
 64         unsigned int i, len = sizeof(buf);
 65         char *p = buf;
 66 
 67         len--;  /* allow for trailing \0 */
 68         if (len < 3)
 69                 return "???";
 70         for (i = 0 ; i < cookie->len ; i++) {
 71                 if (len < 2) {
 72                         strcpy(p-3, "...");
 73                         break;
 74                 }
 75                 sprintf(p, "%02x", cookie->data[i]);
 76                 p += 2;
 77                 len -= 2;
 78         }
 79         *p = '\0';
 80 
 81         return buf;
 82 }
 83 #endif
 84 
 85 /*
 86  * Insert a blocked lock into the global list
 87  */
 88 static void
 89 nlmsvc_insert_block_locked(struct nlm_block *block, unsigned long when)
 90 {
 91         struct nlm_block *b;
 92         struct list_head *pos;
 93 
 94         dprintk("lockd: nlmsvc_insert_block(%p, %ld)\n", block, when);
 95         if (list_empty(&block->b_list)) {
 96                 kref_get(&block->b_count);
 97         } else {
 98                 list_del_init(&block->b_list);
 99         }
100 
101         pos = &nlm_blocked;
102         if (when != NLM_NEVER) {
103                 if ((when += jiffies) == NLM_NEVER)
104                         when ++;
105                 list_for_each(pos, &nlm_blocked) {
106                         b = list_entry(pos, struct nlm_block, b_list);
107                         if (time_after(b->b_when,when) || b->b_when == NLM_NEVER)
108                                 break;
109                 }
110                 /* On normal exit from the loop, pos == &nlm_blocked,
111                  * so we will be adding to the end of the list - good
112                  */
113         }
114 
115         list_add_tail(&block->b_list, pos);
116         block->b_when = when;
117 }
118 
119 static void nlmsvc_insert_block(struct nlm_block *block, unsigned long when)
120 {
121         spin_lock(&nlm_blocked_lock);
122         nlmsvc_insert_block_locked(block, when);
123         spin_unlock(&nlm_blocked_lock);
124 }
125 
126 /*
127  * Remove a block from the global list
128  */
129 static inline void
130 nlmsvc_remove_block(struct nlm_block *block)
131 {
132         if (!list_empty(&block->b_list)) {
133                 spin_lock(&nlm_blocked_lock);
134                 list_del_init(&block->b_list);
135                 spin_unlock(&nlm_blocked_lock);
136                 nlmsvc_release_block(block);
137         }
138 }
139 
140 /*
141  * Find a block for a given lock
142  */
143 static struct nlm_block *
144 nlmsvc_lookup_block(struct nlm_file *file, struct nlm_lock *lock)
145 {
146         struct nlm_block        *block;
147         struct file_lock        *fl;
148 
149         dprintk("lockd: nlmsvc_lookup_block f=%p pd=%d %Ld-%Ld ty=%d\n",
150                                 file, lock->fl.fl_pid,
151                                 (long long)lock->fl.fl_start,
152                                 (long long)lock->fl.fl_end, lock->fl.fl_type);
153         list_for_each_entry(block, &nlm_blocked, b_list) {
154                 fl = &block->b_call->a_args.lock.fl;
155                 dprintk("lockd: check f=%p pd=%d %Ld-%Ld ty=%d cookie=%s\n",
156                                 block->b_file, fl->fl_pid,
157                                 (long long)fl->fl_start,
158                                 (long long)fl->fl_end, fl->fl_type,
159                                 nlmdbg_cookie2a(&block->b_call->a_args.cookie));
160                 if (block->b_file == file && nlm_compare_locks(fl, &lock->fl)) {
161                         kref_get(&block->b_count);
162                         return block;
163                 }
164         }
165 
166         return NULL;
167 }
168 
169 static inline int nlm_cookie_match(struct nlm_cookie *a, struct nlm_cookie *b)
170 {
171         if (a->len != b->len)
172                 return 0;
173         if (memcmp(a->data, b->data, a->len))
174                 return 0;
175         return 1;
176 }
177 
178 /*
179  * Find a block with a given NLM cookie.
180  */
181 static inline struct nlm_block *
182 nlmsvc_find_block(struct nlm_cookie *cookie)
183 {
184         struct nlm_block *block;
185 
186         list_for_each_entry(block, &nlm_blocked, b_list) {
187                 if (nlm_cookie_match(&block->b_call->a_args.cookie,cookie))
188                         goto found;
189         }
190 
191         return NULL;
192 
193 found:
194         dprintk("nlmsvc_find_block(%s): block=%p\n", nlmdbg_cookie2a(cookie), block);
195         kref_get(&block->b_count);
196         return block;
197 }
198 
199 /*
200  * Create a block and initialize it.
201  *
202  * Note: we explicitly set the cookie of the grant reply to that of
203  * the blocked lock request. The spec explicitly mentions that the client
204  * should _not_ rely on the callback containing the same cookie as the
205  * request, but (as I found out later) that's because some implementations
206  * do just this. Never mind the standards comittees, they support our
207  * logging industries.
208  *
209  * 10 years later: I hope we can safely ignore these old and broken
210  * clients by now. Let's fix this so we can uniquely identify an incoming
211  * GRANTED_RES message by cookie, without having to rely on the client's IP
212  * address. --okir
213  */
214 static struct nlm_block *
215 nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_host *host,
216                     struct nlm_file *file, struct nlm_lock *lock,
217                     struct nlm_cookie *cookie)
218 {
219         struct nlm_block        *block;
220         struct nlm_rqst         *call = NULL;
221 
222         call = nlm_alloc_call(host);
223         if (call == NULL)
224                 return NULL;
225 
226         /* Allocate memory for block, and initialize arguments */
227         block = kzalloc(sizeof(*block), GFP_KERNEL);
228         if (block == NULL)
229                 goto failed;
230         kref_init(&block->b_count);
231         INIT_LIST_HEAD(&block->b_list);
232         INIT_LIST_HEAD(&block->b_flist);
233 
234         if (!nlmsvc_setgrantargs(call, lock))
235                 goto failed_free;
236 
237         /* Set notifier function for VFS, and init args */
238         call->a_args.lock.fl.fl_flags |= FL_SLEEP;
239         call->a_args.lock.fl.fl_lmops = &nlmsvc_lock_operations;
240         nlmclnt_next_cookie(&call->a_args.cookie);
241 
242         dprintk("lockd: created block %p...\n", block);
243 
244         /* Create and initialize the block */
245         block->b_daemon = rqstp->rq_server;
246         block->b_host   = host;
247         block->b_file   = file;
248         file->f_count++;
249 
250         /* Add to file's list of blocks */
251         list_add(&block->b_flist, &file->f_blocks);
252 
253         /* Set up RPC arguments for callback */
254         block->b_call = call;
255         call->a_flags   = RPC_TASK_ASYNC;
256         call->a_block = block;
257 
258         return block;
259 
260 failed_free:
261         kfree(block);
262 failed:
263         nlmsvc_release_call(call);
264         return NULL;
265 }
266 
267 /*
268  * Delete a block.
269  * It is the caller's responsibility to check whether the file
270  * can be closed hereafter.
271  */
272 static int nlmsvc_unlink_block(struct nlm_block *block)
273 {
274         int status;
275         dprintk("lockd: unlinking block %p...\n", block);
276 
277         /* Remove block from list */
278         status = posix_unblock_lock(&block->b_call->a_args.lock.fl);
279         nlmsvc_remove_block(block);
280         return status;
281 }
282 
283 static void nlmsvc_free_block(struct kref *kref)
284 {
285         struct nlm_block *block = container_of(kref, struct nlm_block, b_count);
286         struct nlm_file         *file = block->b_file;
287 
288         dprintk("lockd: freeing block %p...\n", block);
289 
290         /* Remove block from file's list of blocks */
291         list_del_init(&block->b_flist);
292         mutex_unlock(&file->f_mutex);
293 
294         nlmsvc_freegrantargs(block->b_call);
295         nlmsvc_release_call(block->b_call);
296         nlm_release_file(block->b_file);
297         kfree(block);
298 }
299 
300 static void nlmsvc_release_block(struct nlm_block *block)
301 {
302         if (block != NULL)
303                 kref_put_mutex(&block->b_count, nlmsvc_free_block, &block->b_file->f_mutex);
304 }
305 
306 /*
307  * Loop over all blocks and delete blocks held by
308  * a matching host.
309  */
310 void nlmsvc_traverse_blocks(struct nlm_host *host,
311                         struct nlm_file *file,
312                         nlm_host_match_fn_t match)
313 {
314         struct nlm_block *block, *next;
315 
316 restart:
317         mutex_lock(&file->f_mutex);
318         list_for_each_entry_safe(block, next, &file->f_blocks, b_flist) {
319                 if (!match(block->b_host, host))
320                         continue;
321                 /* Do not destroy blocks that are not on
322                  * the global retry list - why? */
323                 if (list_empty(&block->b_list))
324                         continue;
325                 kref_get(&block->b_count);
326                 mutex_unlock(&file->f_mutex);
327                 nlmsvc_unlink_block(block);
328                 nlmsvc_release_block(block);
329                 goto restart;
330         }
331         mutex_unlock(&file->f_mutex);
332 }
333 
334 /*
335  * Initialize arguments for GRANTED call. The nlm_rqst structure
336  * has been cleared already.
337  */
338 static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock)
339 {
340         locks_copy_lock(&call->a_args.lock.fl, &lock->fl);
341         memcpy(&call->a_args.lock.fh, &lock->fh, sizeof(call->a_args.lock.fh));
342         call->a_args.lock.caller = utsname()->nodename;
343         call->a_args.lock.oh.len = lock->oh.len;
344 
345         /* set default data area */
346         call->a_args.lock.oh.data = call->a_owner;
347         call->a_args.lock.svid = lock->fl.fl_pid;
348 
349         if (lock->oh.len > NLMCLNT_OHSIZE) {
350                 void *data = kmalloc(lock->oh.len, GFP_KERNEL);
351                 if (!data)
352                         return 0;
353                 call->a_args.lock.oh.data = (u8 *) data;
354         }
355 
356         memcpy(call->a_args.lock.oh.data, lock->oh.data, lock->oh.len);
357         return 1;
358 }
359 
360 static void nlmsvc_freegrantargs(struct nlm_rqst *call)
361 {
362         if (call->a_args.lock.oh.data != call->a_owner)
363                 kfree(call->a_args.lock.oh.data);
364 
365         locks_release_private(&call->a_args.lock.fl);
366 }
367 
368 /*
369  * Deferred lock request handling for non-blocking lock
370  */
371 static __be32
372 nlmsvc_defer_lock_rqst(struct svc_rqst *rqstp, struct nlm_block *block)
373 {
374         __be32 status = nlm_lck_denied_nolocks;
375 
376         block->b_flags |= B_QUEUED;
377 
378         nlmsvc_insert_block(block, NLM_TIMEOUT);
379 
380         block->b_cache_req = &rqstp->rq_chandle;
381         if (rqstp->rq_chandle.defer) {
382                 block->b_deferred_req =
383                         rqstp->rq_chandle.defer(block->b_cache_req);
384                 if (block->b_deferred_req != NULL)
385                         status = nlm_drop_reply;
386         }
387         dprintk("lockd: nlmsvc_defer_lock_rqst block %p flags %d status %d\n",
388                 block, block->b_flags, ntohl(status));
389 
390         return status;
391 }
392 
393 /*
394  * Attempt to establish a lock, and if it can't be granted, block it
395  * if required.
396  */
397 __be32
398 nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
399             struct nlm_host *host, struct nlm_lock *lock, int wait,
400             struct nlm_cookie *cookie, int reclaim)
401 {
402         struct nlm_block        *block = NULL;
403         int                     error;
404         __be32                  ret;
405 
406         dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
407                                 file_inode(file->f_file)->i_sb->s_id,
408                                 file_inode(file->f_file)->i_ino,
409                                 lock->fl.fl_type, lock->fl.fl_pid,
410                                 (long long)lock->fl.fl_start,
411                                 (long long)lock->fl.fl_end,
412                                 wait);
413 
414         /* Lock file against concurrent access */
415         mutex_lock(&file->f_mutex);
416         /* Get existing block (in case client is busy-waiting)
417          * or create new block
418          */
419         block = nlmsvc_lookup_block(file, lock);
420         if (block == NULL) {
421                 block = nlmsvc_create_block(rqstp, host, file, lock, cookie);
422                 ret = nlm_lck_denied_nolocks;
423                 if (block == NULL)
424                         goto out;
425                 lock = &block->b_call->a_args.lock;
426         } else
427                 lock->fl.fl_flags &= ~FL_SLEEP;
428 
429         if (block->b_flags & B_QUEUED) {
430                 dprintk("lockd: nlmsvc_lock deferred block %p flags %d\n",
431                                                         block, block->b_flags);
432                 if (block->b_granted) {
433                         nlmsvc_unlink_block(block);
434                         ret = nlm_granted;
435                         goto out;
436                 }
437                 if (block->b_flags & B_TIMED_OUT) {
438                         nlmsvc_unlink_block(block);
439                         ret = nlm_lck_denied;
440                         goto out;
441                 }
442                 ret = nlm_drop_reply;
443                 goto out;
444         }
445 
446         if (locks_in_grace(SVC_NET(rqstp)) && !reclaim) {
447                 ret = nlm_lck_denied_grace_period;
448                 goto out;
449         }
450         if (reclaim && !locks_in_grace(SVC_NET(rqstp))) {
451                 ret = nlm_lck_denied_grace_period;
452                 goto out;
453         }
454 
455         if (!wait)
456                 lock->fl.fl_flags &= ~FL_SLEEP;
457         error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
458         lock->fl.fl_flags &= ~FL_SLEEP;
459 
460         dprintk("lockd: vfs_lock_file returned %d\n", error);
461         switch (error) {
462                 case 0:
463                         ret = nlm_granted;
464                         goto out;
465                 case -EAGAIN:
466                         /*
467                          * If this is a blocking request for an
468                          * already pending lock request then we need
469                          * to put it back on lockd's block list
470                          */
471                         if (wait)
472                                 break;
473                         ret = nlm_lck_denied;
474                         goto out;
475                 case FILE_LOCK_DEFERRED:
476                         if (wait)
477                                 break;
478                         /* Filesystem lock operation is in progress
479                            Add it to the queue waiting for callback */
480                         ret = nlmsvc_defer_lock_rqst(rqstp, block);
481                         goto out;
482                 case -EDEADLK:
483                         ret = nlm_deadlock;
484                         goto out;
485                 default:                        /* includes ENOLCK */
486                         ret = nlm_lck_denied_nolocks;
487                         goto out;
488         }
489 
490         ret = nlm_lck_blocked;
491 
492         /* Append to list of blocked */
493         nlmsvc_insert_block(block, NLM_NEVER);
494 out:
495         mutex_unlock(&file->f_mutex);
496         nlmsvc_release_block(block);
497         dprintk("lockd: nlmsvc_lock returned %u\n", ret);
498         return ret;
499 }
500 
501 /*
502  * Test for presence of a conflicting lock.
503  */
504 __be32
505 nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
506                 struct nlm_host *host, struct nlm_lock *lock,
507                 struct nlm_lock *conflock, struct nlm_cookie *cookie)
508 {
509         int                     error;
510         __be32                  ret;
511 
512         dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
513                                 file_inode(file->f_file)->i_sb->s_id,
514                                 file_inode(file->f_file)->i_ino,
515                                 lock->fl.fl_type,
516                                 (long long)lock->fl.fl_start,
517                                 (long long)lock->fl.fl_end);
518 
519         if (locks_in_grace(SVC_NET(rqstp))) {
520                 ret = nlm_lck_denied_grace_period;
521                 goto out;
522         }
523 
524         error = vfs_test_lock(file->f_file, &lock->fl);
525         if (error) {
526                 /* We can't currently deal with deferred test requests */
527                 if (error == FILE_LOCK_DEFERRED)
528                         WARN_ON_ONCE(1);
529 
530                 ret = nlm_lck_denied_nolocks;
531                 goto out;
532         }
533 
534         if (lock->fl.fl_type == F_UNLCK) {
535                 ret = nlm_granted;
536                 goto out;
537         }
538 
539         dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n",
540                 lock->fl.fl_type, (long long)lock->fl.fl_start,
541                 (long long)lock->fl.fl_end);
542         conflock->caller = "somehost";  /* FIXME */
543         conflock->len = strlen(conflock->caller);
544         conflock->oh.len = 0;           /* don't return OH info */
545         conflock->svid = lock->fl.fl_pid;
546         conflock->fl.fl_type = lock->fl.fl_type;
547         conflock->fl.fl_start = lock->fl.fl_start;
548         conflock->fl.fl_end = lock->fl.fl_end;
549         locks_release_private(&lock->fl);
550         ret = nlm_lck_denied;
551 out:
552         return ret;
553 }
554 
555 /*
556  * Remove a lock.
557  * This implies a CANCEL call: We send a GRANT_MSG, the client replies
558  * with a GRANT_RES call which gets lost, and calls UNLOCK immediately
559  * afterwards. In this case the block will still be there, and hence
560  * must be removed.
561  */
562 __be32
563 nlmsvc_unlock(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
564 {
565         int     error;
566 
567         dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
568                                 file_inode(file->f_file)->i_sb->s_id,
569                                 file_inode(file->f_file)->i_ino,
570                                 lock->fl.fl_pid,
571                                 (long long)lock->fl.fl_start,
572                                 (long long)lock->fl.fl_end);
573 
574         /* First, cancel any lock that might be there */
575         nlmsvc_cancel_blocked(net, file, lock);
576 
577         lock->fl.fl_type = F_UNLCK;
578         error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
579 
580         return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
581 }
582 
583 /*
584  * Cancel a previously blocked request.
585  *
586  * A cancel request always overrides any grant that may currently
587  * be in progress.
588  * The calling procedure must check whether the file can be closed.
589  */
590 __be32
591 nlmsvc_cancel_blocked(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
592 {
593         struct nlm_block        *block;
594         int status = 0;
595 
596         dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n",
597                                 file_inode(file->f_file)->i_sb->s_id,
598                                 file_inode(file->f_file)->i_ino,
599                                 lock->fl.fl_pid,
600                                 (long long)lock->fl.fl_start,
601                                 (long long)lock->fl.fl_end);
602 
603         if (locks_in_grace(net))
604                 return nlm_lck_denied_grace_period;
605 
606         mutex_lock(&file->f_mutex);
607         block = nlmsvc_lookup_block(file, lock);
608         mutex_unlock(&file->f_mutex);
609         if (block != NULL) {
610                 vfs_cancel_lock(block->b_file->f_file,
611                                 &block->b_call->a_args.lock.fl);
612                 status = nlmsvc_unlink_block(block);
613                 nlmsvc_release_block(block);
614         }
615         return status ? nlm_lck_denied : nlm_granted;
616 }
617 
618 /*
619  * This is a callback from the filesystem for VFS file lock requests.
620  * It will be used if lm_grant is defined and the filesystem can not
621  * respond to the request immediately.
622  * For SETLK or SETLKW request it will get the local posix lock.
623  * In all cases it will move the block to the head of nlm_blocked q where
624  * nlmsvc_retry_blocked() can send back a reply for SETLKW or revisit the
625  * deferred rpc for GETLK and SETLK.
626  */
627 static void
628 nlmsvc_update_deferred_block(struct nlm_block *block, int result)
629 {
630         block->b_flags |= B_GOT_CALLBACK;
631         if (result == 0)
632                 block->b_granted = 1;
633         else
634                 block->b_flags |= B_TIMED_OUT;
635 }
636 
637 static int nlmsvc_grant_deferred(struct file_lock *fl, int result)
638 {
639         struct nlm_block *block;
640         int rc = -ENOENT;
641 
642         spin_lock(&nlm_blocked_lock);
643         list_for_each_entry(block, &nlm_blocked, b_list) {
644                 if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
645                         dprintk("lockd: nlmsvc_notify_blocked block %p flags %d\n",
646                                                         block, block->b_flags);
647                         if (block->b_flags & B_QUEUED) {
648                                 if (block->b_flags & B_TIMED_OUT) {
649                                         rc = -ENOLCK;
650                                         break;
651                                 }
652                                 nlmsvc_update_deferred_block(block, result);
653                         } else if (result == 0)
654                                 block->b_granted = 1;
655 
656                         nlmsvc_insert_block_locked(block, 0);
657                         svc_wake_up(block->b_daemon);
658                         rc = 0;
659                         break;
660                 }
661         }
662         spin_unlock(&nlm_blocked_lock);
663         if (rc == -ENOENT)
664                 printk(KERN_WARNING "lockd: grant for unknown block\n");
665         return rc;
666 }
667 
668 /*
669  * Unblock a blocked lock request. This is a callback invoked from the
670  * VFS layer when a lock on which we blocked is removed.
671  *
672  * This function doesn't grant the blocked lock instantly, but rather moves
673  * the block to the head of nlm_blocked where it can be picked up by lockd.
674  */
675 static void
676 nlmsvc_notify_blocked(struct file_lock *fl)
677 {
678         struct nlm_block        *block;
679 
680         dprintk("lockd: VFS unblock notification for block %p\n", fl);
681         spin_lock(&nlm_blocked_lock);
682         list_for_each_entry(block, &nlm_blocked, b_list) {
683                 if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
684                         nlmsvc_insert_block_locked(block, 0);
685                         spin_unlock(&nlm_blocked_lock);
686                         svc_wake_up(block->b_daemon);
687                         return;
688                 }
689         }
690         spin_unlock(&nlm_blocked_lock);
691         printk(KERN_WARNING "lockd: notification for unknown block!\n");
692 }
693 
694 static int nlmsvc_same_owner(struct file_lock *fl1, struct file_lock *fl2)
695 {
696         return fl1->fl_owner == fl2->fl_owner && fl1->fl_pid == fl2->fl_pid;
697 }
698 
699 /*
700  * Since NLM uses two "keys" for tracking locks, we need to hash them down
701  * to one for the blocked_hash. Here, we're just xor'ing the host address
702  * with the pid in order to create a key value for picking a hash bucket.
703  */
704 static unsigned long
705 nlmsvc_owner_key(struct file_lock *fl)
706 {
707         return (unsigned long)fl->fl_owner ^ (unsigned long)fl->fl_pid;
708 }
709 
710 const struct lock_manager_operations nlmsvc_lock_operations = {
711         .lm_compare_owner = nlmsvc_same_owner,
712         .lm_owner_key = nlmsvc_owner_key,
713         .lm_notify = nlmsvc_notify_blocked,
714         .lm_grant = nlmsvc_grant_deferred,
715 };
716 
717 /*
718  * Try to claim a lock that was previously blocked.
719  *
720  * Note that we use both the RPC_GRANTED_MSG call _and_ an async
721  * RPC thread when notifying the client. This seems like overkill...
722  * Here's why:
723  *  -   we don't want to use a synchronous RPC thread, otherwise
724  *      we might find ourselves hanging on a dead portmapper.
725  *  -   Some lockd implementations (e.g. HP) don't react to
726  *      RPC_GRANTED calls; they seem to insist on RPC_GRANTED_MSG calls.
727  */
728 static void
729 nlmsvc_grant_blocked(struct nlm_block *block)
730 {
731         struct nlm_file         *file = block->b_file;
732         struct nlm_lock         *lock = &block->b_call->a_args.lock;
733         int                     error;
734         loff_t                  fl_start, fl_end;
735 
736         dprintk("lockd: grant blocked lock %p\n", block);
737 
738         kref_get(&block->b_count);
739 
740         /* Unlink block request from list */
741         nlmsvc_unlink_block(block);
742 
743         /* If b_granted is true this means we've been here before.
744          * Just retry the grant callback, possibly refreshing the RPC
745          * binding */
746         if (block->b_granted) {
747                 nlm_rebind_host(block->b_host);
748                 goto callback;
749         }
750 
751         /* Try the lock operation again */
752         /* vfs_lock_file() can mangle fl_start and fl_end, but we need
753          * them unchanged for the GRANT_MSG
754          */
755         lock->fl.fl_flags |= FL_SLEEP;
756         fl_start = lock->fl.fl_start;
757         fl_end = lock->fl.fl_end;
758         error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
759         lock->fl.fl_flags &= ~FL_SLEEP;
760         lock->fl.fl_start = fl_start;
761         lock->fl.fl_end = fl_end;
762 
763         switch (error) {
764         case 0:
765                 break;
766         case FILE_LOCK_DEFERRED:
767                 dprintk("lockd: lock still blocked error %d\n", error);
768                 nlmsvc_insert_block(block, NLM_NEVER);
769                 nlmsvc_release_block(block);
770                 return;
771         default:
772                 printk(KERN_WARNING "lockd: unexpected error %d in %s!\n",
773                                 -error, __func__);
774                 nlmsvc_insert_block(block, 10 * HZ);
775                 nlmsvc_release_block(block);
776                 return;
777         }
778 
779 callback:
780         /* Lock was granted by VFS. */
781         dprintk("lockd: GRANTing blocked lock.\n");
782         block->b_granted = 1;
783 
784         /* keep block on the list, but don't reattempt until the RPC
785          * completes or the submission fails
786          */
787         nlmsvc_insert_block(block, NLM_NEVER);
788 
789         /* Call the client -- use a soft RPC task since nlmsvc_retry_blocked
790          * will queue up a new one if this one times out
791          */
792         error = nlm_async_call(block->b_call, NLMPROC_GRANTED_MSG,
793                                 &nlmsvc_grant_ops);
794 
795         /* RPC submission failed, wait a bit and retry */
796         if (error < 0)
797                 nlmsvc_insert_block(block, 10 * HZ);
798 }
799 
800 /*
801  * This is the callback from the RPC layer when the NLM_GRANTED_MSG
802  * RPC call has succeeded or timed out.
803  * Like all RPC callbacks, it is invoked by the rpciod process, so it
804  * better not sleep. Therefore, we put the blocked lock on the nlm_blocked
805  * chain once more in order to have it removed by lockd itself (which can
806  * then sleep on the file semaphore without disrupting e.g. the nfs client).
807  */
808 static void nlmsvc_grant_callback(struct rpc_task *task, void *data)
809 {
810         struct nlm_rqst         *call = data;
811         struct nlm_block        *block = call->a_block;
812         unsigned long           timeout;
813 
814         dprintk("lockd: GRANT_MSG RPC callback\n");
815 
816         spin_lock(&nlm_blocked_lock);
817         /* if the block is not on a list at this point then it has
818          * been invalidated. Don't try to requeue it.
819          *
820          * FIXME: it's possible that the block is removed from the list
821          * after this check but before the nlmsvc_insert_block. In that
822          * case it will be added back. Perhaps we need better locking
823          * for nlm_blocked?
824          */
825         if (list_empty(&block->b_list))
826                 goto out;
827 
828         /* Technically, we should down the file semaphore here. Since we
829          * move the block towards the head of the queue only, no harm
830          * can be done, though. */
831         if (task->tk_status < 0) {
832                 /* RPC error: Re-insert for retransmission */
833                 timeout = 10 * HZ;
834         } else {
835                 /* Call was successful, now wait for client callback */
836                 timeout = 60 * HZ;
837         }
838         nlmsvc_insert_block_locked(block, timeout);
839         svc_wake_up(block->b_daemon);
840 out:
841         spin_unlock(&nlm_blocked_lock);
842 }
843 
844 /*
845  * FIXME: nlmsvc_release_block() grabs a mutex.  This is not allowed for an
846  * .rpc_release rpc_call_op
847  */
848 static void nlmsvc_grant_release(void *data)
849 {
850         struct nlm_rqst         *call = data;
851         nlmsvc_release_block(call->a_block);
852 }
853 
854 static const struct rpc_call_ops nlmsvc_grant_ops = {
855         .rpc_call_done = nlmsvc_grant_callback,
856         .rpc_release = nlmsvc_grant_release,
857 };
858 
859 /*
860  * We received a GRANT_RES callback. Try to find the corresponding
861  * block.
862  */
863 void
864 nlmsvc_grant_reply(struct nlm_cookie *cookie, __be32 status)
865 {
866         struct nlm_block        *block;
867 
868         dprintk("grant_reply: looking for cookie %x, s=%d \n",
869                 *(unsigned int *)(cookie->data), status);
870         if (!(block = nlmsvc_find_block(cookie)))
871                 return;
872 
873         if (block) {
874                 if (status == nlm_lck_denied_grace_period) {
875                         /* Try again in a couple of seconds */
876                         nlmsvc_insert_block(block, 10 * HZ);
877                 } else {
878                         /* Lock is now held by client, or has been rejected.
879                          * In both cases, the block should be removed. */
880                         nlmsvc_unlink_block(block);
881                 }
882         }
883         nlmsvc_release_block(block);
884 }
885 
886 /* Helper function to handle retry of a deferred block.
887  * If it is a blocking lock, call grant_blocked.
888  * For a non-blocking lock or test lock, revisit the request.
889  */
890 static void
891 retry_deferred_block(struct nlm_block *block)
892 {
893         if (!(block->b_flags & B_GOT_CALLBACK))
894                 block->b_flags |= B_TIMED_OUT;
895         nlmsvc_insert_block(block, NLM_TIMEOUT);
896         dprintk("revisit block %p flags %d\n",  block, block->b_flags);
897         if (block->b_deferred_req) {
898                 block->b_deferred_req->revisit(block->b_deferred_req, 0);
899                 block->b_deferred_req = NULL;
900         }
901 }
902 
903 /*
904  * Retry all blocked locks that have been notified. This is where lockd
905  * picks up locks that can be granted, or grant notifications that must
906  * be retransmitted.
907  */
908 unsigned long
909 nlmsvc_retry_blocked(void)
910 {
911         unsigned long   timeout = MAX_SCHEDULE_TIMEOUT;
912         struct nlm_block *block;
913 
914         spin_lock(&nlm_blocked_lock);
915         while (!list_empty(&nlm_blocked) && !kthread_should_stop()) {
916                 block = list_entry(nlm_blocked.next, struct nlm_block, b_list);
917 
918                 if (block->b_when == NLM_NEVER)
919                         break;
920                 if (time_after(block->b_when, jiffies)) {
921                         timeout = block->b_when - jiffies;
922                         break;
923                 }
924                 spin_unlock(&nlm_blocked_lock);
925 
926                 dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n",
927                         block, block->b_when);
928                 if (block->b_flags & B_QUEUED) {
929                         dprintk("nlmsvc_retry_blocked delete block (%p, granted=%d, flags=%d)\n",
930                                 block, block->b_granted, block->b_flags);
931                         retry_deferred_block(block);
932                 } else
933                         nlmsvc_grant_blocked(block);
934                 spin_lock(&nlm_blocked_lock);
935         }
936         spin_unlock(&nlm_blocked_lock);
937 
938         return timeout;
939 }
940 

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