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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 = posix_unblock_lock(&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 /*
336  * Initialize arguments for GRANTED call. The nlm_rqst structure
337  * has been cleared already.
338  */
339 static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock)
340 {
341         locks_copy_lock(&call->a_args.lock.fl, &lock->fl);
342         memcpy(&call->a_args.lock.fh, &lock->fh, sizeof(call->a_args.lock.fh));
343         call->a_args.lock.caller = utsname()->nodename;
344         call->a_args.lock.oh.len = lock->oh.len;
345 
346         /* set default data area */
347         call->a_args.lock.oh.data = call->a_owner;
348         call->a_args.lock.svid = lock->fl.fl_pid;
349 
350         if (lock->oh.len > NLMCLNT_OHSIZE) {
351                 void *data = kmalloc(lock->oh.len, GFP_KERNEL);
352                 if (!data)
353                         return 0;
354                 call->a_args.lock.oh.data = (u8 *) data;
355         }
356 
357         memcpy(call->a_args.lock.oh.data, lock->oh.data, lock->oh.len);
358         return 1;
359 }
360 
361 static void nlmsvc_freegrantargs(struct nlm_rqst *call)
362 {
363         if (call->a_args.lock.oh.data != call->a_owner)
364                 kfree(call->a_args.lock.oh.data);
365 
366         locks_release_private(&call->a_args.lock.fl);
367 }
368 
369 /*
370  * Deferred lock request handling for non-blocking lock
371  */
372 static __be32
373 nlmsvc_defer_lock_rqst(struct svc_rqst *rqstp, struct nlm_block *block)
374 {
375         __be32 status = nlm_lck_denied_nolocks;
376 
377         block->b_flags |= B_QUEUED;
378 
379         nlmsvc_insert_block(block, NLM_TIMEOUT);
380 
381         block->b_cache_req = &rqstp->rq_chandle;
382         if (rqstp->rq_chandle.defer) {
383                 block->b_deferred_req =
384                         rqstp->rq_chandle.defer(block->b_cache_req);
385                 if (block->b_deferred_req != NULL)
386                         status = nlm_drop_reply;
387         }
388         dprintk("lockd: nlmsvc_defer_lock_rqst block %p flags %d status %d\n",
389                 block, block->b_flags, ntohl(status));
390 
391         return status;
392 }
393 
394 /*
395  * Attempt to establish a lock, and if it can't be granted, block it
396  * if required.
397  */
398 __be32
399 nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
400             struct nlm_host *host, struct nlm_lock *lock, int wait,
401             struct nlm_cookie *cookie, int reclaim)
402 {
403         struct nlm_block        *block = NULL;
404         int                     error;
405         __be32                  ret;
406 
407         dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
408                                 file_inode(file->f_file)->i_sb->s_id,
409                                 file_inode(file->f_file)->i_ino,
410                                 lock->fl.fl_type, lock->fl.fl_pid,
411                                 (long long)lock->fl.fl_start,
412                                 (long long)lock->fl.fl_end,
413                                 wait);
414 
415         /* Lock file against concurrent access */
416         mutex_lock(&file->f_mutex);
417         /* Get existing block (in case client is busy-waiting)
418          * or create new block
419          */
420         block = nlmsvc_lookup_block(file, lock);
421         if (block == NULL) {
422                 block = nlmsvc_create_block(rqstp, host, file, lock, cookie);
423                 ret = nlm_lck_denied_nolocks;
424                 if (block == NULL)
425                         goto out;
426                 lock = &block->b_call->a_args.lock;
427         } else
428                 lock->fl.fl_flags &= ~FL_SLEEP;
429 
430         if (block->b_flags & B_QUEUED) {
431                 dprintk("lockd: nlmsvc_lock deferred block %p flags %d\n",
432                                                         block, block->b_flags);
433                 if (block->b_granted) {
434                         nlmsvc_unlink_block(block);
435                         ret = nlm_granted;
436                         goto out;
437                 }
438                 if (block->b_flags & B_TIMED_OUT) {
439                         nlmsvc_unlink_block(block);
440                         ret = nlm_lck_denied;
441                         goto out;
442                 }
443                 ret = nlm_drop_reply;
444                 goto out;
445         }
446 
447         if (locks_in_grace(SVC_NET(rqstp)) && !reclaim) {
448                 ret = nlm_lck_denied_grace_period;
449                 goto out;
450         }
451         if (reclaim && !locks_in_grace(SVC_NET(rqstp))) {
452                 ret = nlm_lck_denied_grace_period;
453                 goto out;
454         }
455 
456         if (!wait)
457                 lock->fl.fl_flags &= ~FL_SLEEP;
458         error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
459         lock->fl.fl_flags &= ~FL_SLEEP;
460 
461         dprintk("lockd: vfs_lock_file returned %d\n", error);
462         switch (error) {
463                 case 0:
464                         ret = nlm_granted;
465                         goto out;
466                 case -EAGAIN:
467                         /*
468                          * If this is a blocking request for an
469                          * already pending lock request then we need
470                          * to put it back on lockd's block list
471                          */
472                         if (wait)
473                                 break;
474                         ret = nlm_lck_denied;
475                         goto out;
476                 case FILE_LOCK_DEFERRED:
477                         if (wait)
478                                 break;
479                         /* Filesystem lock operation is in progress
480                            Add it to the queue waiting for callback */
481                         ret = nlmsvc_defer_lock_rqst(rqstp, block);
482                         goto out;
483                 case -EDEADLK:
484                         ret = nlm_deadlock;
485                         goto out;
486                 default:                        /* includes ENOLCK */
487                         ret = nlm_lck_denied_nolocks;
488                         goto out;
489         }
490 
491         ret = nlm_lck_blocked;
492 
493         /* Append to list of blocked */
494         nlmsvc_insert_block(block, NLM_NEVER);
495 out:
496         mutex_unlock(&file->f_mutex);
497         nlmsvc_release_block(block);
498         dprintk("lockd: nlmsvc_lock returned %u\n", ret);
499         return ret;
500 }
501 
502 /*
503  * Test for presence of a conflicting lock.
504  */
505 __be32
506 nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
507                 struct nlm_host *host, struct nlm_lock *lock,
508                 struct nlm_lock *conflock, struct nlm_cookie *cookie)
509 {
510         int                     error;
511         __be32                  ret;
512 
513         dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
514                                 file_inode(file->f_file)->i_sb->s_id,
515                                 file_inode(file->f_file)->i_ino,
516                                 lock->fl.fl_type,
517                                 (long long)lock->fl.fl_start,
518                                 (long long)lock->fl.fl_end);
519 
520         if (locks_in_grace(SVC_NET(rqstp))) {
521                 ret = nlm_lck_denied_grace_period;
522                 goto out;
523         }
524 
525         error = vfs_test_lock(file->f_file, &lock->fl);
526         if (error) {
527                 /* We can't currently deal with deferred test requests */
528                 if (error == FILE_LOCK_DEFERRED)
529                         WARN_ON_ONCE(1);
530 
531                 ret = nlm_lck_denied_nolocks;
532                 goto out;
533         }
534 
535         if (lock->fl.fl_type == F_UNLCK) {
536                 ret = nlm_granted;
537                 goto out;
538         }
539 
540         dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n",
541                 lock->fl.fl_type, (long long)lock->fl.fl_start,
542                 (long long)lock->fl.fl_end);
543         conflock->caller = "somehost";  /* FIXME */
544         conflock->len = strlen(conflock->caller);
545         conflock->oh.len = 0;           /* don't return OH info */
546         conflock->svid = lock->fl.fl_pid;
547         conflock->fl.fl_type = lock->fl.fl_type;
548         conflock->fl.fl_start = lock->fl.fl_start;
549         conflock->fl.fl_end = lock->fl.fl_end;
550         locks_release_private(&lock->fl);
551         ret = nlm_lck_denied;
552 out:
553         return ret;
554 }
555 
556 /*
557  * Remove a lock.
558  * This implies a CANCEL call: We send a GRANT_MSG, the client replies
559  * with a GRANT_RES call which gets lost, and calls UNLOCK immediately
560  * afterwards. In this case the block will still be there, and hence
561  * must be removed.
562  */
563 __be32
564 nlmsvc_unlock(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
565 {
566         int     error;
567 
568         dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
569                                 file_inode(file->f_file)->i_sb->s_id,
570                                 file_inode(file->f_file)->i_ino,
571                                 lock->fl.fl_pid,
572                                 (long long)lock->fl.fl_start,
573                                 (long long)lock->fl.fl_end);
574 
575         /* First, cancel any lock that might be there */
576         nlmsvc_cancel_blocked(net, file, lock);
577 
578         lock->fl.fl_type = F_UNLCK;
579         error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
580 
581         return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
582 }
583 
584 /*
585  * Cancel a previously blocked request.
586  *
587  * A cancel request always overrides any grant that may currently
588  * be in progress.
589  * The calling procedure must check whether the file can be closed.
590  */
591 __be32
592 nlmsvc_cancel_blocked(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
593 {
594         struct nlm_block        *block;
595         int status = 0;
596 
597         dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n",
598                                 file_inode(file->f_file)->i_sb->s_id,
599                                 file_inode(file->f_file)->i_ino,
600                                 lock->fl.fl_pid,
601                                 (long long)lock->fl.fl_start,
602                                 (long long)lock->fl.fl_end);
603 
604         if (locks_in_grace(net))
605                 return nlm_lck_denied_grace_period;
606 
607         mutex_lock(&file->f_mutex);
608         block = nlmsvc_lookup_block(file, lock);
609         mutex_unlock(&file->f_mutex);
610         if (block != NULL) {
611                 vfs_cancel_lock(block->b_file->f_file,
612                                 &block->b_call->a_args.lock.fl);
613                 status = nlmsvc_unlink_block(block);
614                 nlmsvc_release_block(block);
615         }
616         return status ? nlm_lck_denied : nlm_granted;
617 }
618 
619 /*
620  * This is a callback from the filesystem for VFS file lock requests.
621  * It will be used if lm_grant is defined and the filesystem can not
622  * respond to the request immediately.
623  * For SETLK or SETLKW request it will get the local posix lock.
624  * In all cases it will move the block to the head of nlm_blocked q where
625  * nlmsvc_retry_blocked() can send back a reply for SETLKW or revisit the
626  * deferred rpc for GETLK and SETLK.
627  */
628 static void
629 nlmsvc_update_deferred_block(struct nlm_block *block, int result)
630 {
631         block->b_flags |= B_GOT_CALLBACK;
632         if (result == 0)
633                 block->b_granted = 1;
634         else
635                 block->b_flags |= B_TIMED_OUT;
636 }
637 
638 static int nlmsvc_grant_deferred(struct file_lock *fl, int result)
639 {
640         struct nlm_block *block;
641         int rc = -ENOENT;
642 
643         spin_lock(&nlm_blocked_lock);
644         list_for_each_entry(block, &nlm_blocked, b_list) {
645                 if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
646                         dprintk("lockd: nlmsvc_notify_blocked block %p flags %d\n",
647                                                         block, block->b_flags);
648                         if (block->b_flags & B_QUEUED) {
649                                 if (block->b_flags & B_TIMED_OUT) {
650                                         rc = -ENOLCK;
651                                         break;
652                                 }
653                                 nlmsvc_update_deferred_block(block, result);
654                         } else if (result == 0)
655                                 block->b_granted = 1;
656 
657                         nlmsvc_insert_block_locked(block, 0);
658                         svc_wake_up(block->b_daemon);
659                         rc = 0;
660                         break;
661                 }
662         }
663         spin_unlock(&nlm_blocked_lock);
664         if (rc == -ENOENT)
665                 printk(KERN_WARNING "lockd: grant for unknown block\n");
666         return rc;
667 }
668 
669 /*
670  * Unblock a blocked lock request. This is a callback invoked from the
671  * VFS layer when a lock on which we blocked is removed.
672  *
673  * This function doesn't grant the blocked lock instantly, but rather moves
674  * the block to the head of nlm_blocked where it can be picked up by lockd.
675  */
676 static void
677 nlmsvc_notify_blocked(struct file_lock *fl)
678 {
679         struct nlm_block        *block;
680 
681         dprintk("lockd: VFS unblock notification for block %p\n", fl);
682         spin_lock(&nlm_blocked_lock);
683         list_for_each_entry(block, &nlm_blocked, b_list) {
684                 if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
685                         nlmsvc_insert_block_locked(block, 0);
686                         spin_unlock(&nlm_blocked_lock);
687                         svc_wake_up(block->b_daemon);
688                         return;
689                 }
690         }
691         spin_unlock(&nlm_blocked_lock);
692         printk(KERN_WARNING "lockd: notification for unknown block!\n");
693 }
694 
695 static int nlmsvc_same_owner(struct file_lock *fl1, struct file_lock *fl2)
696 {
697         return fl1->fl_owner == fl2->fl_owner && fl1->fl_pid == fl2->fl_pid;
698 }
699 
700 /*
701  * Since NLM uses two "keys" for tracking locks, we need to hash them down
702  * to one for the blocked_hash. Here, we're just xor'ing the host address
703  * with the pid in order to create a key value for picking a hash bucket.
704  */
705 static unsigned long
706 nlmsvc_owner_key(struct file_lock *fl)
707 {
708         return (unsigned long)fl->fl_owner ^ (unsigned long)fl->fl_pid;
709 }
710 
711 const struct lock_manager_operations nlmsvc_lock_operations = {
712         .lm_compare_owner = nlmsvc_same_owner,
713         .lm_owner_key = nlmsvc_owner_key,
714         .lm_notify = nlmsvc_notify_blocked,
715         .lm_grant = nlmsvc_grant_deferred,
716 };
717 
718 /*
719  * Try to claim a lock that was previously blocked.
720  *
721  * Note that we use both the RPC_GRANTED_MSG call _and_ an async
722  * RPC thread when notifying the client. This seems like overkill...
723  * Here's why:
724  *  -   we don't want to use a synchronous RPC thread, otherwise
725  *      we might find ourselves hanging on a dead portmapper.
726  *  -   Some lockd implementations (e.g. HP) don't react to
727  *      RPC_GRANTED calls; they seem to insist on RPC_GRANTED_MSG calls.
728  */
729 static void
730 nlmsvc_grant_blocked(struct nlm_block *block)
731 {
732         struct nlm_file         *file = block->b_file;
733         struct nlm_lock         *lock = &block->b_call->a_args.lock;
734         int                     error;
735         loff_t                  fl_start, fl_end;
736 
737         dprintk("lockd: grant blocked lock %p\n", block);
738 
739         kref_get(&block->b_count);
740 
741         /* Unlink block request from list */
742         nlmsvc_unlink_block(block);
743 
744         /* If b_granted is true this means we've been here before.
745          * Just retry the grant callback, possibly refreshing the RPC
746          * binding */
747         if (block->b_granted) {
748                 nlm_rebind_host(block->b_host);
749                 goto callback;
750         }
751 
752         /* Try the lock operation again */
753         /* vfs_lock_file() can mangle fl_start and fl_end, but we need
754          * them unchanged for the GRANT_MSG
755          */
756         lock->fl.fl_flags |= FL_SLEEP;
757         fl_start = lock->fl.fl_start;
758         fl_end = lock->fl.fl_end;
759         error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
760         lock->fl.fl_flags &= ~FL_SLEEP;
761         lock->fl.fl_start = fl_start;
762         lock->fl.fl_end = fl_end;
763 
764         switch (error) {
765         case 0:
766                 break;
767         case FILE_LOCK_DEFERRED:
768                 dprintk("lockd: lock still blocked error %d\n", error);
769                 nlmsvc_insert_block(block, NLM_NEVER);
770                 nlmsvc_release_block(block);
771                 return;
772         default:
773                 printk(KERN_WARNING "lockd: unexpected error %d in %s!\n",
774                                 -error, __func__);
775                 nlmsvc_insert_block(block, 10 * HZ);
776                 nlmsvc_release_block(block);
777                 return;
778         }
779 
780 callback:
781         /* Lock was granted by VFS. */
782         dprintk("lockd: GRANTing blocked lock.\n");
783         block->b_granted = 1;
784 
785         /* keep block on the list, but don't reattempt until the RPC
786          * completes or the submission fails
787          */
788         nlmsvc_insert_block(block, NLM_NEVER);
789 
790         /* Call the client -- use a soft RPC task since nlmsvc_retry_blocked
791          * will queue up a new one if this one times out
792          */
793         error = nlm_async_call(block->b_call, NLMPROC_GRANTED_MSG,
794                                 &nlmsvc_grant_ops);
795 
796         /* RPC submission failed, wait a bit and retry */
797         if (error < 0)
798                 nlmsvc_insert_block(block, 10 * HZ);
799 }
800 
801 /*
802  * This is the callback from the RPC layer when the NLM_GRANTED_MSG
803  * RPC call has succeeded or timed out.
804  * Like all RPC callbacks, it is invoked by the rpciod process, so it
805  * better not sleep. Therefore, we put the blocked lock on the nlm_blocked
806  * chain once more in order to have it removed by lockd itself (which can
807  * then sleep on the file semaphore without disrupting e.g. the nfs client).
808  */
809 static void nlmsvc_grant_callback(struct rpc_task *task, void *data)
810 {
811         struct nlm_rqst         *call = data;
812         struct nlm_block        *block = call->a_block;
813         unsigned long           timeout;
814 
815         dprintk("lockd: GRANT_MSG RPC callback\n");
816 
817         spin_lock(&nlm_blocked_lock);
818         /* if the block is not on a list at this point then it has
819          * been invalidated. Don't try to requeue it.
820          *
821          * FIXME: it's possible that the block is removed from the list
822          * after this check but before the nlmsvc_insert_block. In that
823          * case it will be added back. Perhaps we need better locking
824          * for nlm_blocked?
825          */
826         if (list_empty(&block->b_list))
827                 goto out;
828 
829         /* Technically, we should down the file semaphore here. Since we
830          * move the block towards the head of the queue only, no harm
831          * can be done, though. */
832         if (task->tk_status < 0) {
833                 /* RPC error: Re-insert for retransmission */
834                 timeout = 10 * HZ;
835         } else {
836                 /* Call was successful, now wait for client callback */
837                 timeout = 60 * HZ;
838         }
839         nlmsvc_insert_block_locked(block, timeout);
840         svc_wake_up(block->b_daemon);
841 out:
842         spin_unlock(&nlm_blocked_lock);
843 }
844 
845 /*
846  * FIXME: nlmsvc_release_block() grabs a mutex.  This is not allowed for an
847  * .rpc_release rpc_call_op
848  */
849 static void nlmsvc_grant_release(void *data)
850 {
851         struct nlm_rqst         *call = data;
852         nlmsvc_release_block(call->a_block);
853 }
854 
855 static const struct rpc_call_ops nlmsvc_grant_ops = {
856         .rpc_call_done = nlmsvc_grant_callback,
857         .rpc_release = nlmsvc_grant_release,
858 };
859 
860 /*
861  * We received a GRANT_RES callback. Try to find the corresponding
862  * block.
863  */
864 void
865 nlmsvc_grant_reply(struct nlm_cookie *cookie, __be32 status)
866 {
867         struct nlm_block        *block;
868 
869         dprintk("grant_reply: looking for cookie %x, s=%d \n",
870                 *(unsigned int *)(cookie->data), status);
871         if (!(block = nlmsvc_find_block(cookie)))
872                 return;
873 
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                 /*
879                  * Lock is now held by client, or has been rejected.
880                  * In both cases, the block should be removed.
881                  */
882                 nlmsvc_unlink_block(block);
883         }
884         nlmsvc_release_block(block);
885 }
886 
887 /* Helper function to handle retry of a deferred block.
888  * If it is a blocking lock, call grant_blocked.
889  * For a non-blocking lock or test lock, revisit the request.
890  */
891 static void
892 retry_deferred_block(struct nlm_block *block)
893 {
894         if (!(block->b_flags & B_GOT_CALLBACK))
895                 block->b_flags |= B_TIMED_OUT;
896         nlmsvc_insert_block(block, NLM_TIMEOUT);
897         dprintk("revisit block %p flags %d\n",  block, block->b_flags);
898         if (block->b_deferred_req) {
899                 block->b_deferred_req->revisit(block->b_deferred_req, 0);
900                 block->b_deferred_req = NULL;
901         }
902 }
903 
904 /*
905  * Retry all blocked locks that have been notified. This is where lockd
906  * picks up locks that can be granted, or grant notifications that must
907  * be retransmitted.
908  */
909 unsigned long
910 nlmsvc_retry_blocked(void)
911 {
912         unsigned long   timeout = MAX_SCHEDULE_TIMEOUT;
913         struct nlm_block *block;
914 
915         spin_lock(&nlm_blocked_lock);
916         while (!list_empty(&nlm_blocked) && !kthread_should_stop()) {
917                 block = list_entry(nlm_blocked.next, struct nlm_block, b_list);
918 
919                 if (block->b_when == NLM_NEVER)
920                         break;
921                 if (time_after(block->b_when, jiffies)) {
922                         timeout = block->b_when - jiffies;
923                         break;
924                 }
925                 spin_unlock(&nlm_blocked_lock);
926 
927                 dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n",
928                         block, block->b_when);
929                 if (block->b_flags & B_QUEUED) {
930                         dprintk("nlmsvc_retry_blocked delete block (%p, granted=%d, flags=%d)\n",
931                                 block, block->b_granted, block->b_flags);
932                         retry_deferred_block(block);
933                 } else
934                         nlmsvc_grant_blocked(block);
935                 spin_lock(&nlm_blocked_lock);
936         }
937         spin_unlock(&nlm_blocked_lock);
938 
939         return timeout;
940 }
941 

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