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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/errno.h>
  25 #include <linux/kernel.h>
  26 #include <linux/sched.h>
  27 #include <linux/smp_lock.h>
  28 #include <linux/sunrpc/clnt.h>
  29 #include <linux/sunrpc/svc.h>
  30 #include <linux/lockd/nlm.h>
  31 #include <linux/lockd/lockd.h>
  32
  33 #define NLMDBG_FACILITY         NLMDBG_SVCLOCK
  34
  35 #ifdef CONFIG_LOCKD_V4
  36 #define nlm_deadlock    nlm4_deadlock
  37 #else
  38 #define nlm_deadlock    nlm_lck_denied
  39 #endif
  40
  41 static void nlmsvc_release_block(struct nlm_block *block);
  42 static void     nlmsvc_insert_block(struct nlm_block *block, unsigned long);
  43 static void     nlmsvc_remove_block(struct nlm_block *block);
  44
  45 static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock);
  46 static void nlmsvc_freegrantargs(struct nlm_rqst *call);
  47 static const struct rpc_call_ops nlmsvc_grant_ops;
  48
  49 /*
  50  * The list of blocked locks to retry
  51  */
  52 static LIST_HEAD(nlm_blocked);
  53
  54 /*
  55  * Insert a blocked lock into the global list
  56  */
  57 static void
  58 nlmsvc_insert_block(struct nlm_block *block, unsigned long when)
  59 {
  60         struct nlm_block *b;
  61         struct list_head *pos;
  62
  63         dprintk("lockd: nlmsvc_insert_block(%p, %ld)\n", block, when);
  64         if (list_empty(&block->b_list)) {
  65                 kref_get(&block->b_count);
  66         } else {
  67                 list_del_init(&block->b_list);
  68         }
  69
  70         pos = &nlm_blocked;
  71         if (when != NLM_NEVER) {
  72                 if ((when += jiffies) == NLM_NEVER)
  73                         when ++;
  74                 list_for_each(pos, &nlm_blocked) {
  75                         b = list_entry(pos, struct nlm_block, b_list);
  76                         if (time_after(b->b_when,when) || b->b_when == NLM_NEVER)
  77                                 break;
  78                 }
  79                 /* On normal exit from the loop, pos == &nlm_blocked,
  80                  * so we will be adding to the end of the list - good
  81                  */
  82         }
  83
  84         list_add_tail(&block->b_list, pos);
  85         block->b_when = when;
  86 }
  87
  88 /*
  89  * Remove a block from the global list
  90  */
  91 static inline void
  92 nlmsvc_remove_block(struct nlm_block *block)
  93 {
  94         if (!list_empty(&block->b_list)) {
  95                 list_del_init(&block->b_list);
  96                 nlmsvc_release_block(block);
  97         }
  98 }
  99
 100 /*
 101  * Find a block for a given lock
 102  */
 103 static struct nlm_block *
 104 nlmsvc_lookup_block(struct nlm_file *file, struct nlm_lock *lock)
 105 {
 106         struct nlm_block        *block;
 107         struct file_lock        *fl;
 108
 109         dprintk("lockd: nlmsvc_lookup_block f=%p pd=%d %Ld-%Ld ty=%d\n",
 110                                 file, lock->fl.fl_pid,
 111                                 (long long)lock->fl.fl_start,
 112                                 (long long)lock->fl.fl_end, lock->fl.fl_type);
 113         list_for_each_entry(block, &nlm_blocked, b_list) {
 114                 fl = &block->b_call->a_args.lock.fl;
 115                 dprintk("lockd: check f=%p pd=%d %Ld-%Ld ty=%d cookie=%s\n",
 116                                 block->b_file, fl->fl_pid,
 117                                 (long long)fl->fl_start,
 118                                 (long long)fl->fl_end, fl->fl_type,
 119                                 nlmdbg_cookie2a(&block->b_call->a_args.cookie));
 120                 if (block->b_file == file && nlm_compare_locks(fl, &lock->fl)) {
 121                         kref_get(&block->b_count);
 122                         return block;
 123                 }
 124         }
 125
 126         return NULL;
 127 }
 128
 129 static inline int nlm_cookie_match(struct nlm_cookie *a, struct nlm_cookie *b)
 130 {
 131         if(a->len != b->len)
 132                 return 0;
 133         if(memcmp(a->data,b->data,a->len))
 134                 return 0;
 135         return 1;
 136 }
 137
 138 /*
 139  * Find a block with a given NLM cookie.
 140  */
 141 static inline struct nlm_block *
 142 nlmsvc_find_block(struct nlm_cookie *cookie)
 143 {
 144         struct nlm_block *block;
 145
 146         list_for_each_entry(block, &nlm_blocked, b_list) {
 147                 if (nlm_cookie_match(&block->b_call->a_args.cookie,cookie))
 148                         goto found;
 149         }
 150
 151         return NULL;
 152
 153 found:
 154         dprintk("nlmsvc_find_block(%s): block=%p\n", nlmdbg_cookie2a(cookie), block);
 155         kref_get(&block->b_count);
 156         return block;
 157 }
 158
 159 /*
 160  * Create a block and initialize it.
 161  *
 162  * Note: we explicitly set the cookie of the grant reply to that of
 163  * the blocked lock request. The spec explicitly mentions that the client
 164  * should _not_ rely on the callback containing the same cookie as the
 165  * request, but (as I found out later) that's because some implementations
 166  * do just this. Never mind the standards comittees, they support our
 167  * logging industries.
 168  *
 169  * 10 years later: I hope we can safely ignore these old and broken
 170  * clients by now. Let's fix this so we can uniquely identify an incoming
 171  * GRANTED_RES message by cookie, without having to rely on the client's IP
 172  * address. --okir
 173  */
 174 static inline struct nlm_block *
 175 nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_file *file,
 176                                 struct nlm_lock *lock, struct nlm_cookie *cookie)
 177 {
 178         struct nlm_block        *block;
 179         struct nlm_host         *host;
 180         struct nlm_rqst         *call = NULL;
 181
 182         /* Create host handle for callback */
 183         host = nlmsvc_lookup_host(rqstp, lock->caller, lock->len);
 184         if (host == NULL)
 185                 return NULL;
 186
 187         call = nlm_alloc_call(host);
 188         if (call == NULL)
 189                 return NULL;
 190
 191         /* Allocate memory for block, and initialize arguments */
 192         block = kzalloc(sizeof(*block), GFP_KERNEL);
 193         if (block == NULL)
 194                 goto failed;
 195         kref_init(&block->b_count);
 196         INIT_LIST_HEAD(&block->b_list);
 197         INIT_LIST_HEAD(&block->b_flist);
 198
 199         if (!nlmsvc_setgrantargs(call, lock))
 200                 goto failed_free;
 201
 202         /* Set notifier function for VFS, and init args */
 203         call->a_args.lock.fl.fl_flags |= FL_SLEEP;
 204         call->a_args.lock.fl.fl_lmops = &nlmsvc_lock_operations;
 205         nlmclnt_next_cookie(&call->a_args.cookie);
 206
 207         dprintk("lockd: created block %p...\n", block);
 208
 209         /* Create and initialize the block */
 210         block->b_daemon = rqstp->rq_server;
 211         block->b_host   = host;
 212         block->b_file   = file;
 213         file->f_count++;
 214
 215         /* Add to file's list of blocks */
 216         list_add(&block->b_flist, &file->f_blocks);
 217
 218         /* Set up RPC arguments for callback */
 219         block->b_call = call;
 220         call->a_flags   = RPC_TASK_ASYNC;
 221         call->a_block = block;
 222
 223         return block;
 224
 225 failed_free:
 226         kfree(block);
 227 failed:
 228         nlm_release_call(call);
 229         return NULL;
 230 }
 231
 232 /*
 233  * Delete a block. If the lock was cancelled or the grant callback
 234  * failed, unlock is set to 1.
 235  * It is the caller's responsibility to check whether the file
 236  * can be closed hereafter.
 237  */
 238 static int nlmsvc_unlink_block(struct nlm_block *block)
 239 {
 240         int status;
 241         dprintk("lockd: unlinking block %p...\n", block);
 242
 243         /* Remove block from list */
 244         status = posix_unblock_lock(block->b_file->f_file, &block->b_call->a_args.lock.fl);
 245         nlmsvc_remove_block(block);
 246         return status;
 247 }
 248
 249 static void nlmsvc_free_block(struct kref *kref)
 250 {
 251         struct nlm_block *block = container_of(kref, struct nlm_block, b_count);
 252         struct nlm_file         *file = block->b_file;
 253
 254         dprintk("lockd: freeing block %p...\n", block);
 255
 256         /* Remove block from file's list of blocks */
 257         mutex_lock(&file->f_mutex);
 258         list_del_init(&block->b_flist);
 259         mutex_unlock(&file->f_mutex);
 260
 261         nlmsvc_freegrantargs(block->b_call);
 262         nlm_release_call(block->b_call);
 263         nlm_release_file(block->b_file);
 264         kfree(block);
 265 }
 266
 267 static void nlmsvc_release_block(struct nlm_block *block)
 268 {
 269         if (block != NULL)
 270                 kref_put(&block->b_count, nlmsvc_free_block);
 271 }
 272
 273 /*
 274  * Loop over all blocks and delete blocks held by
 275  * a matching host.
 276  */
 277 void nlmsvc_traverse_blocks(struct nlm_host *host,
 278                         struct nlm_file *file,
 279                         nlm_host_match_fn_t match)
 280 {
 281         struct nlm_block *block, *next;
 282
 283 restart:
 284         mutex_lock(&file->f_mutex);
 285         list_for_each_entry_safe(block, next, &file->f_blocks, b_flist) {
 286                 if (!match(block->b_host, host))
 287                         continue;
 288                 /* Do not destroy blocks that are not on
 289                  * the global retry list - why? */
 290                 if (list_empty(&block->b_list))
 291                         continue;
 292                 kref_get(&block->b_count);
 293                 mutex_unlock(&file->f_mutex);
 294                 nlmsvc_unlink_block(block);
 295                 nlmsvc_release_block(block);
 296                 goto restart;
 297         }
 298         mutex_unlock(&file->f_mutex);
 299 }
 300
 301 /*
 302  * Initialize arguments for GRANTED call. The nlm_rqst structure
 303  * has been cleared already.
 304  */
 305 static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock)
 306 {
 307         locks_copy_lock(&call->a_args.lock.fl, &lock->fl);
 308         memcpy(&call->a_args.lock.fh, &lock->fh, sizeof(call->a_args.lock.fh));
 309         call->a_args.lock.caller = utsname()->nodename;
 310         call->a_args.lock.oh.len = lock->oh.len;
 311
 312         /* set default data area */
 313         call->a_args.lock.oh.data = call->a_owner;
 314         call->a_args.lock.svid = lock->fl.fl_pid;
 315
 316         if (lock->oh.len > NLMCLNT_OHSIZE) {
 317                 void *data = kmalloc(lock->oh.len, GFP_KERNEL);
 318                 if (!data)
 319                         return 0;
 320                 call->a_args.lock.oh.data = (u8 *) data;
 321         }
 322
 323         memcpy(call->a_args.lock.oh.data, lock->oh.data, lock->oh.len);
 324         return 1;
 325 }
 326
 327 static void nlmsvc_freegrantargs(struct nlm_rqst *call)
 328 {
 329         if (call->a_args.lock.oh.data != call->a_owner)
 330                 kfree(call->a_args.lock.oh.data);
 331 }
 332
 333 /*
 334  * Deferred lock request handling for non-blocking lock
 335  */
 336 static u32
 337 nlmsvc_defer_lock_rqst(struct svc_rqst *rqstp, struct nlm_block *block)
 338 {
 339         u32 status = nlm_lck_denied_nolocks;
 340
 341         block->b_flags |= B_QUEUED;
 342
 343         nlmsvc_insert_block(block, NLM_TIMEOUT);
 344
 345         block->b_cache_req = &rqstp->rq_chandle;
 346         if (rqstp->rq_chandle.defer) {
 347                 block->b_deferred_req =
 348                         rqstp->rq_chandle.defer(block->b_cache_req);
 349                 if (block->b_deferred_req != NULL)
 350                         status = nlm_drop_reply;
 351         }
 352         dprintk("lockd: nlmsvc_defer_lock_rqst block %p flags %d status %d\n",
 353                 block, block->b_flags, status);
 354
 355         return status;
 356 }
 357
 358 /*
 359  * Attempt to establish a lock, and if it can't be granted, block it
 360  * if required.
 361  */
 362 __be32
 363 nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
 364                         struct nlm_lock *lock, int wait, struct nlm_cookie *cookie)
 365 {
 366         struct nlm_block        *block, *newblock = NULL;
 367         int                     error;
 368         __be32                  ret;
 369
 370         dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
 371                                 file->f_file->f_path.dentry->d_inode->i_sb->s_id,
 372                                 file->f_file->f_path.dentry->d_inode->i_ino,
 373                                 lock->fl.fl_type, lock->fl.fl_pid,
 374                                 (long long)lock->fl.fl_start,
 375                                 (long long)lock->fl.fl_end,
 376                                 wait);
 377
 378
 379         lock->fl.fl_flags &= ~FL_SLEEP;
 380 again:
 381         /* Lock file against concurrent access */
 382         mutex_lock(&file->f_mutex);
 383         /* Get existing block (in case client is busy-waiting) */
 384         block = nlmsvc_lookup_block(file, lock);
 385         if (block == NULL) {
 386                 if (newblock != NULL)
 387                         lock = &newblock->b_call->a_args.lock;
 388         } else
 389                 lock = &block->b_call->a_args.lock;
 390
 391         error = posix_lock_file(file->f_file, &lock->fl, NULL);
 392         lock->fl.fl_flags &= ~FL_SLEEP;
 393
 394         dprintk("lockd: posix_lock_file returned %d\n", error);
 395
 396         switch(error) {
 397                 case 0:
 398                         ret = nlm_granted;
 399                         goto out;
 400                 case -EAGAIN:
 401                         break;
 402                 case -EDEADLK:
 403                         ret = nlm_deadlock;
 404                         goto out;
 405                 default:                        /* includes ENOLCK */
 406                         ret = nlm_lck_denied_nolocks;
 407                         goto out;
 408         }
 409
 410         ret = nlm_lck_denied;
 411         if (!wait)
 412                 goto out;
 413
 414         ret = nlm_lck_blocked;
 415         if (block != NULL)
 416                 goto out;
 417
 418         /* If we don't have a block, create and initialize it. Then
 419          * retry because we may have slept in kmalloc. */
 420         /* We have to release f_mutex as nlmsvc_create_block may try to
 421          * to claim it while doing host garbage collection */
 422         if (newblock == NULL) {
 423                 mutex_unlock(&file->f_mutex);
 424                 dprintk("lockd: blocking on this lock (allocating).\n");
 425                 if (!(newblock = nlmsvc_create_block(rqstp, file, lock, cookie)))
 426                         return nlm_lck_denied_nolocks;
 427                 goto again;
 428         }
 429
 430         /* Append to list of blocked */
 431         nlmsvc_insert_block(newblock, NLM_NEVER);
 432 out:
 433         mutex_unlock(&file->f_mutex);
 434         nlmsvc_release_block(newblock);
 435         nlmsvc_release_block(block);
 436         dprintk("lockd: nlmsvc_lock returned %u\n", ret);
 437         return ret;
 438 }
 439
 440 /*
 441  * Test for presence of a conflicting lock.
 442  */
 443 __be32
 444 nlmsvc_testlock(struct nlm_file *file, struct nlm_lock *lock,
 445                                        struct nlm_lock *conflock)
 446 {
 447         dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
 448                                 file->f_file->f_path.dentry->d_inode->i_sb->s_id,
 449                                 file->f_file->f_path.dentry->d_inode->i_ino,
 450                                 lock->fl.fl_type,
 451                                 (long long)lock->fl.fl_start,
 452                                 (long long)lock->fl.fl_end);
 453
 454         if (posix_test_lock(file->f_file, &lock->fl)) {
 455                 dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n",
 456                                 lock->fl.fl_type,
 457                                 (long long)lock->fl.fl_start,
 458                                 (long long)lock->fl.fl_end);
 459                 conflock->caller = "somehost";  /* FIXME */
 460                 conflock->len = strlen(conflock->caller);
 461                 conflock->oh.len = 0;           /* don't return OH info */
 462                 conflock->svid = lock->fl.fl_pid;
 463                 conflock->fl.fl_type = lock->fl.fl_type;
 464                 conflock->fl.fl_start = lock->fl.fl_start;
 465                 conflock->fl.fl_end = lock->fl.fl_end;
 466                 return nlm_lck_denied;
 467         }
 468
 469         return nlm_granted;
 470 }
 471
 472 /*
 473  * Remove a lock.
 474  * This implies a CANCEL call: We send a GRANT_MSG, the client replies
 475  * with a GRANT_RES call which gets lost, and calls UNLOCK immediately
 476  * afterwards. In this case the block will still be there, and hence
 477  * must be removed.
 478  */
 479 __be32
 480 nlmsvc_unlock(struct nlm_file *file, struct nlm_lock *lock)
 481 {
 482         int     error;
 483
 484         dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
 485                                 file->f_file->f_path.dentry->d_inode->i_sb->s_id,
 486                                 file->f_file->f_path.dentry->d_inode->i_ino,
 487                                 lock->fl.fl_pid,
 488                                 (long long)lock->fl.fl_start,
 489                                 (long long)lock->fl.fl_end);
 490
 491         /* First, cancel any lock that might be there */
 492         nlmsvc_cancel_blocked(file, lock);
 493
 494         lock->fl.fl_type = F_UNLCK;
 495         error = posix_lock_file(file->f_file, &lock->fl, NULL);
 496
 497         return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
 498 }
 499
 500 /*
 501  * Cancel a previously blocked request.
 502  *
 503  * A cancel request always overrides any grant that may currently
 504  * be in progress.
 505  * The calling procedure must check whether the file can be closed.
 506  */
 507 __be32
 508 nlmsvc_cancel_blocked(struct nlm_file *file, struct nlm_lock *lock)
 509 {
 510         struct nlm_block        *block;
 511         int status = 0;
 512
 513         dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n",
 514                                 file->f_file->f_path.dentry->d_inode->i_sb->s_id,
 515                                 file->f_file->f_path.dentry->d_inode->i_ino,
 516                                 lock->fl.fl_pid,
 517                                 (long long)lock->fl.fl_start,
 518                                 (long long)lock->fl.fl_end);
 519
 520         mutex_lock(&file->f_mutex);
 521         block = nlmsvc_lookup_block(file, lock);
 522         mutex_unlock(&file->f_mutex);
 523         if (block != NULL) {
 524                 status = nlmsvc_unlink_block(block);
 525                 nlmsvc_release_block(block);
 526         }
 527         return status ? nlm_lck_denied : nlm_granted;
 528 }
 529
 530 /*
 531  * Unblock a blocked lock request. This is a callback invoked from the
 532  * VFS layer when a lock on which we blocked is removed.
 533  *
 534  * This function doesn't grant the blocked lock instantly, but rather moves
 535  * the block to the head of nlm_blocked where it can be picked up by lockd.
 536  */
 537 static void
 538 nlmsvc_notify_blocked(struct file_lock *fl)
 539 {
 540         struct nlm_block        *block;
 541
 542         dprintk("lockd: VFS unblock notification for block %p\n", fl);
 543         list_for_each_entry(block, &nlm_blocked, b_list) {
 544                 if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
 545                         nlmsvc_insert_block(block, 0);
 546                         svc_wake_up(block->b_daemon);
 547                         return;
 548                 }
 549         }
 550
 551         printk(KERN_WARNING "lockd: notification for unknown block!\n");
 552 }
 553
 554 static int nlmsvc_same_owner(struct file_lock *fl1, struct file_lock *fl2)
 555 {
 556         return fl1->fl_owner == fl2->fl_owner && fl1->fl_pid == fl2->fl_pid;
 557 }
 558
 559 struct lock_manager_operations nlmsvc_lock_operations = {
 560         .fl_compare_owner = nlmsvc_same_owner,
 561         .fl_notify = nlmsvc_notify_blocked,
 562 };
 563
 564 /*
 565  * Try to claim a lock that was previously blocked.
 566  *
 567  * Note that we use both the RPC_GRANTED_MSG call _and_ an async
 568  * RPC thread when notifying the client. This seems like overkill...
 569  * Here's why:
 570  *  -   we don't want to use a synchronous RPC thread, otherwise
 571  *      we might find ourselves hanging on a dead portmapper.
 572  *  -   Some lockd implementations (e.g. HP) don't react to
 573  *      RPC_GRANTED calls; they seem to insist on RPC_GRANTED_MSG calls.
 574  */
 575 static void
 576 nlmsvc_grant_blocked(struct nlm_block *block)
 577 {
 578         struct nlm_file         *file = block->b_file;
 579         struct nlm_lock         *lock = &block->b_call->a_args.lock;
 580         int                     error;
 581
 582         dprintk("lockd: grant blocked lock %p\n", block);
 583
 584         /* Unlink block request from list */
 585         nlmsvc_unlink_block(block);
 586
 587         /* If b_granted is true this means we've been here before.
 588          * Just retry the grant callback, possibly refreshing the RPC
 589          * binding */
 590         if (block->b_granted) {
 591                 nlm_rebind_host(block->b_host);
 592                 goto callback;
 593         }
 594
 595         /* Try the lock operation again */
 596         lock->fl.fl_flags |= FL_SLEEP;
 597         error = posix_lock_file(file->f_file, &lock->fl, NULL);
 598         lock->fl.fl_flags &= ~FL_SLEEP;
 599
 600         switch (error) {
 601         case 0:
 602                 break;
 603         case -EAGAIN:
 604                 dprintk("lockd: lock still blocked\n");
 605                 nlmsvc_insert_block(block, NLM_NEVER);
 606                 return;
 607         default:
 608                 printk(KERN_WARNING "lockd: unexpected error %d in %s!\n",
 609                                 -error, __FUNCTION__);
 610                 nlmsvc_insert_block(block, 10 * HZ);
 611                 return;
 612         }
 613
 614 callback:
 615         /* Lock was granted by VFS. */
 616         dprintk("lockd: GRANTing blocked lock.\n");
 617         block->b_granted = 1;
 618
 619         /* Schedule next grant callback in 30 seconds */
 620         nlmsvc_insert_block(block, 30 * HZ);
 621
 622         /* Call the client */
 623         kref_get(&block->b_count);
 624         nlm_async_call(block->b_call, NLMPROC_GRANTED_MSG, &nlmsvc_grant_ops);
 625 }
 626
 627 /*
 628  * This is the callback from the RPC layer when the NLM_GRANTED_MSG
 629  * RPC call has succeeded or timed out.
 630  * Like all RPC callbacks, it is invoked by the rpciod process, so it
 631  * better not sleep. Therefore, we put the blocked lock on the nlm_blocked
 632  * chain once more in order to have it removed by lockd itself (which can
 633  * then sleep on the file semaphore without disrupting e.g. the nfs client).
 634  */
 635 static void nlmsvc_grant_callback(struct rpc_task *task, void *data)
 636 {
 637         struct nlm_rqst         *call = data;
 638         struct nlm_block        *block = call->a_block;
 639         unsigned long           timeout;
 640
 641         dprintk("lockd: GRANT_MSG RPC callback\n");
 642
 643         /* Technically, we should down the file semaphore here. Since we
 644          * move the block towards the head of the queue only, no harm
 645          * can be done, though. */
 646         if (task->tk_status < 0) {
 647                 /* RPC error: Re-insert for retransmission */
 648                 timeout = 10 * HZ;
 649         } else {
 650                 /* Call was successful, now wait for client callback */
 651                 timeout = 60 * HZ;
 652         }
 653         nlmsvc_insert_block(block, timeout);
 654         svc_wake_up(block->b_daemon);
 655 }
 656
 657 static void nlmsvc_grant_release(void *data)
 658 {
 659         struct nlm_rqst         *call = data;
 660
 661         nlmsvc_release_block(call->a_block);
 662 }
 663
 664 static const struct rpc_call_ops nlmsvc_grant_ops = {
 665         .rpc_call_done = nlmsvc_grant_callback,
 666         .rpc_release = nlmsvc_grant_release,
 667 };
 668
 669 /*
 670  * We received a GRANT_RES callback. Try to find the corresponding
 671  * block.
 672  */
 673 void
 674 nlmsvc_grant_reply(struct nlm_cookie *cookie, __be32 status)
 675 {
 676         struct nlm_block        *block;
 677
 678         dprintk("grant_reply: looking for cookie %x, s=%d \n",
 679                 *(unsigned int *)(cookie->data), status);
 680         if (!(block = nlmsvc_find_block(cookie)))
 681                 return;
 682
 683         if (block) {
 684                 if (status == nlm_lck_denied_grace_period) {
 685                         /* Try again in a couple of seconds */
 686                         nlmsvc_insert_block(block, 10 * HZ);
 687                 } else {
 688                         /* Lock is now held by client, or has been rejected.
 689                          * In both cases, the block should be removed. */
 690                         nlmsvc_unlink_block(block);
 691                 }
 692         }
 693         nlmsvc_release_block(block);
 694 }
 695
 696 /*
 697  * Retry all blocked locks that have been notified. This is where lockd
 698  * picks up locks that can be granted, or grant notifications that must
 699  * be retransmitted.
 700  */
 701 unsigned long
 702 nlmsvc_retry_blocked(void)
 703 {
 704         unsigned long   timeout = MAX_SCHEDULE_TIMEOUT;
 705         struct nlm_block *block;
 706
 707         while (!list_empty(&nlm_blocked)) {
 708                 block = list_entry(nlm_blocked.next, struct nlm_block, b_list);
 709
 710                 if (block->b_when == NLM_NEVER)
 711                         break;
 712                 if (time_after(block->b_when,jiffies)) {
 713                         timeout = block->b_when - jiffies;
 714                         break;
 715                 }
 716
 717                 dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n",
 718                         block, block->b_when);
 719                 kref_get(&block->b_count);
 720                 nlmsvc_grant_blocked(block);
 721                 nlmsvc_release_block(block);
 722         }
 723
 724         return timeout;
 725 }