fs/lockd/svclock.c

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