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         call = nlm_alloc_call(host);
 184         if (call == NULL)
 185                 return NULL;
 186
 187         /* Allocate memory for block, and initialize arguments */
 188         block = kzalloc(sizeof(*block), GFP_KERNEL);
 189         if (block == NULL)
 190                 goto failed;
 191         kref_init(&block->b_count);
 192         INIT_LIST_HEAD(&block->b_list);
 193         INIT_LIST_HEAD(&block->b_flist);
 194
 195         if (!nlmsvc_setgrantargs(call, lock))
 196                 goto failed_free;
 197
 198         /* Set notifier function for VFS, and init args */
 199         call->a_args.lock.fl.fl_flags |= FL_SLEEP;
 200         call->a_args.lock.fl.fl_lmops = &nlmsvc_lock_operations;
 201         nlmclnt_next_cookie(&call->a_args.cookie);
 202
 203         dprintk("lockd: created block %p...\n", block);
 204
 205         /* Create and initialize the block */
 206         block->b_daemon = rqstp->rq_server;
 207         block->b_host   = host;
 208         block->b_file   = file;
 209         block->b_fl = NULL;
 210         file->f_count++;
 211
 212         /* Add to file's list of blocks */
 213         list_add(&block->b_flist, &file->f_blocks);
 214
 215         /* Set up RPC arguments for callback */
 216         block->b_call = call;
 217         call->a_flags   = RPC_TASK_ASYNC;
 218         call->a_block = block;
 219
 220         return block;
 221
 222 failed_free:
 223         kfree(block);
 224 failed:
 225         nlm_release_call(call);
 226         return NULL;
 227 }
 228
 229 /*
 230  * Delete a block.
 231  * It is the caller's responsibility to check whether the file
 232  * can be closed hereafter.
 233  */
 234 static int nlmsvc_unlink_block(struct nlm_block *block)
 235 {
 236         int status;
 237         dprintk("lockd: unlinking block %p...\n", block);
 238
 239         /* Remove block from list */
 240         status = posix_unblock_lock(block->b_file->f_file, &block->b_call->a_args.lock.fl);
 241         nlmsvc_remove_block(block);
 242         return status;
 243 }
 244
 245 static void nlmsvc_free_block(struct kref *kref)
 246 {
 247         struct nlm_block *block = container_of(kref, struct nlm_block, b_count);
 248         struct nlm_file         *file = block->b_file;
 249
 250         dprintk("lockd: freeing block %p...\n", block);
 251
 252         /* Remove block from file's list of blocks */
 253         mutex_lock(&file->f_mutex);
 254         list_del_init(&block->b_flist);
 255         mutex_unlock(&file->f_mutex);
 256
 257         nlmsvc_freegrantargs(block->b_call);
 258         nlm_release_call(block->b_call);
 259         nlm_release_file(block->b_file);
 260         kfree(block->b_fl);
 261         kfree(block);
 262 }
 263
 264 static void nlmsvc_release_block(struct nlm_block *block)
 265 {
 266         if (block != NULL)
 267                 kref_put(&block->b_count, nlmsvc_free_block);
 268 }
 269
 270 /*
 271  * Loop over all blocks and delete blocks held by
 272  * a matching host.
 273  */
 274 void nlmsvc_traverse_blocks(struct nlm_host *host,
 275                         struct nlm_file *file,
 276                         nlm_host_match_fn_t match)
 277 {
 278         struct nlm_block *block, *next;
 279
 280 restart:
 281         mutex_lock(&file->f_mutex);
 282         list_for_each_entry_safe(block, next, &file->f_blocks, b_flist) {
 283                 if (!match(block->b_host, host))
 284                         continue;
 285                 /* Do not destroy blocks that are not on
 286                  * the global retry list - why? */
 287                 if (list_empty(&block->b_list))
 288                         continue;
 289                 kref_get(&block->b_count);
 290                 mutex_unlock(&file->f_mutex);
 291                 nlmsvc_unlink_block(block);
 292                 nlmsvc_release_block(block);
 293                 goto restart;
 294         }
 295         mutex_unlock(&file->f_mutex);
 296 }
 297
 298 /*
 299  * Initialize arguments for GRANTED call. The nlm_rqst structure
 300  * has been cleared already.
 301  */
 302 static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock)
 303 {
 304         locks_copy_lock(&call->a_args.lock.fl, &lock->fl);
 305         memcpy(&call->a_args.lock.fh, &lock->fh, sizeof(call->a_args.lock.fh));
 306         call->a_args.lock.caller = utsname()->nodename;
 307         call->a_args.lock.oh.len = lock->oh.len;
 308
 309         /* set default data area */
 310         call->a_args.lock.oh.data = call->a_owner;
 311         call->a_args.lock.svid = lock->fl.fl_pid;
 312
 313         if (lock->oh.len > NLMCLNT_OHSIZE) {
 314                 void *data = kmalloc(lock->oh.len, GFP_KERNEL);
 315                 if (!data)
 316                         return 0;
 317                 call->a_args.lock.oh.data = (u8 *) data;
 318         }
 319
 320         memcpy(call->a_args.lock.oh.data, lock->oh.data, lock->oh.len);
 321         return 1;
 322 }
 323
 324 static void nlmsvc_freegrantargs(struct nlm_rqst *call)
 325 {
 326         if (call->a_args.lock.oh.data != call->a_owner)
 327                 kfree(call->a_args.lock.oh.data);
 328 }
 329
 330 /*
 331  * Deferred lock request handling for non-blocking lock
 332  */
 333 static __be32
 334 nlmsvc_defer_lock_rqst(struct svc_rqst *rqstp, struct nlm_block *block)
 335 {
 336         __be32 status = nlm_lck_denied_nolocks;
 337
 338         block->b_flags |= B_QUEUED;
 339
 340         nlmsvc_insert_block(block, NLM_TIMEOUT);
 341
 342         block->b_cache_req = &rqstp->rq_chandle;
 343         if (rqstp->rq_chandle.defer) {
 344                 block->b_deferred_req =
 345                         rqstp->rq_chandle.defer(block->b_cache_req);
 346                 if (block->b_deferred_req != NULL)
 347                         status = nlm_drop_reply;
 348         }
 349         dprintk("lockd: nlmsvc_defer_lock_rqst block %p flags %d status %d\n",
 350                 block, block->b_flags, ntohl(status));
 351
 352         return status;
 353 }
 354
 355 /*
 356  * Attempt to establish a lock, and if it can't be granted, block it
 357  * if required.
 358  */
 359 __be32
 360 nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
 361                         struct nlm_lock *lock, int wait, struct nlm_cookie *cookie)
 362 {
 363         struct nlm_block        *block = NULL;
 364         struct nlm_host         *host;
 365         int                     error;
 366         __be32                  ret;
 367
 368         dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
 369                                 file->f_file->f_path.dentry->d_inode->i_sb->s_id,
 370                                 file->f_file->f_path.dentry->d_inode->i_ino,
 371                                 lock->fl.fl_type, lock->fl.fl_pid,
 372                                 (long long)lock->fl.fl_start,
 373                                 (long long)lock->fl.fl_end,
 374                                 wait);
 375
 376         /* Create host handle for callback */
 377         host = nlmsvc_lookup_host(rqstp, lock->caller, lock->len);
 378         if (host == NULL)
 379                 return nlm_lck_denied_nolocks;
 380
 381         /* Lock file against concurrent access */
 382         mutex_lock(&file->f_mutex);
 383         /* Get existing block (in case client is busy-waiting)
 384          * or create new block
 385          */
 386         block = nlmsvc_lookup_block(file, lock);
 387         if (block == NULL) {
 388                 block = nlmsvc_create_block(rqstp, nlm_get_host(host), file,
 389                                 lock, cookie);
 390                 ret = nlm_lck_denied_nolocks;
 391                 if (block == NULL)
 392                         goto out;
 393                 lock = &block->b_call->a_args.lock;
 394         } else
 395                 lock->fl.fl_flags &= ~FL_SLEEP;
 396
 397         if (block->b_flags & B_QUEUED) {
 398                 dprintk("lockd: nlmsvc_lock deferred block %p flags %d\n",
 399                                                         block, block->b_flags);
 400                 if (block->b_granted) {
 401                         nlmsvc_unlink_block(block);
 402                         ret = nlm_granted;
 403                         goto out;
 404                 }
 405                 if (block->b_flags & B_TIMED_OUT) {
 406                         nlmsvc_unlink_block(block);
 407                         ret = nlm_lck_denied;
 408                         goto out;
 409                 }
 410                 ret = nlm_drop_reply;
 411                 goto out;
 412         }
 413
 414         if (!wait)
 415                 lock->fl.fl_flags &= ~FL_SLEEP;
 416         error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
 417         lock->fl.fl_flags &= ~FL_SLEEP;
 418
 419         dprintk("lockd: vfs_lock_file returned %d\n", error);
 420         switch(error) {
 421                 case 0:
 422                         ret = nlm_granted;
 423                         goto out;
 424                 case -EAGAIN:
 425                         ret = nlm_lck_denied;
 426                         break;
 427                 case -EINPROGRESS:
 428                         if (wait)
 429                                 break;
 430                         /* Filesystem lock operation is in progress
 431                            Add it to the queue waiting for callback */
 432                         ret = nlmsvc_defer_lock_rqst(rqstp, block);
 433                         goto out;
 434                 case -EDEADLK:
 435                         ret = nlm_deadlock;
 436                         goto out;
 437                 default:                        /* includes ENOLCK */
 438                         ret = nlm_lck_denied_nolocks;
 439                         goto out;
 440         }
 441
 442         ret = nlm_lck_denied;
 443         if (!wait)
 444                 goto out;
 445
 446         ret = nlm_lck_blocked;
 447
 448         /* Append to list of blocked */
 449         nlmsvc_insert_block(block, NLM_NEVER);
 450 out:
 451         mutex_unlock(&file->f_mutex);
 452         nlmsvc_release_block(block);
 453         nlm_release_host(host);
 454         dprintk("lockd: nlmsvc_lock returned %u\n", ret);
 455         return ret;
 456 }
 457
 458 /*
 459  * Test for presence of a conflicting lock.
 460  */
 461 __be32
 462 nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
 463                 struct nlm_host *host, struct nlm_lock *lock,
 464                 struct nlm_lock *conflock, struct nlm_cookie *cookie)
 465 {
 466         struct nlm_block        *block = NULL;
 467         int                     error;
 468         __be32                  ret;
 469
 470         dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
 471                                 file->f_file->f_path.dentry->d_inode->i_sb->s_id,
 472                                 file->f_file->f_path.dentry->d_inode->i_ino,
 473                                 lock->fl.fl_type,
 474                                 (long long)lock->fl.fl_start,
 475                                 (long long)lock->fl.fl_end);
 476
 477         /* Get existing block (in case client is busy-waiting) */
 478         block = nlmsvc_lookup_block(file, lock);
 479
 480         if (block == NULL) {
 481                 struct file_lock *conf = kzalloc(sizeof(*conf), GFP_KERNEL);
 482
 483                 if (conf == NULL)
 484                         return nlm_granted;
 485                 nlm_get_host(host);
 486                 block = nlmsvc_create_block(rqstp, host, file, lock, cookie);
 487                 if (block == NULL) {
 488                         kfree(conf);
 489                         return nlm_granted;
 490                 }
 491                 block->b_fl = conf;
 492         }
 493         if (block->b_flags & B_QUEUED) {
 494                 dprintk("lockd: nlmsvc_testlock deferred block %p flags %d fl %p\n",
 495                         block, block->b_flags, block->b_fl);
 496                 if (block->b_flags & B_TIMED_OUT) {
 497                         nlmsvc_unlink_block(block);
 498                         ret = nlm_lck_denied;
 499                         goto out;
 500                 }
 501                 if (block->b_flags & B_GOT_CALLBACK) {
 502                         nlmsvc_unlink_block(block);
 503                         if (block->b_fl != NULL
 504                                         && block->b_fl->fl_type != F_UNLCK) {
 505                                 lock->fl = *block->b_fl;
 506                                 goto conf_lock;
 507                         } else {
 508                                 ret = nlm_granted;
 509                                 goto out;
 510                         }
 511                 }
 512                 ret = nlm_drop_reply;
 513                 goto out;
 514         }
 515
 516         error = vfs_test_lock(file->f_file, &lock->fl);
 517         if (error == -EINPROGRESS) {
 518                 ret = nlmsvc_defer_lock_rqst(rqstp, block);
 519                 goto out;
 520         }
 521         if (error) {
 522                 ret = nlm_lck_denied_nolocks;
 523                 goto out;
 524         }
 525         if (lock->fl.fl_type == F_UNLCK) {
 526                 ret = nlm_granted;
 527                 goto out;
 528         }
 529
 530 conf_lock:
 531         dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n",
 532                 lock->fl.fl_type, (long long)lock->fl.fl_start,
 533                 (long long)lock->fl.fl_end);
 534         conflock->caller = "somehost";  /* FIXME */
 535         conflock->len = strlen(conflock->caller);
 536         conflock->oh.len = 0;           /* don't return OH info */
 537         conflock->svid = lock->fl.fl_pid;
 538         conflock->fl.fl_type = lock->fl.fl_type;
 539         conflock->fl.fl_start = lock->fl.fl_start;
 540         conflock->fl.fl_end = lock->fl.fl_end;
 541         ret = nlm_lck_denied;
 542 out:
 543         if (block)
 544                 nlmsvc_release_block(block);
 545         return ret;
 546 }
 547
 548 /*
 549  * Remove a lock.
 550  * This implies a CANCEL call: We send a GRANT_MSG, the client replies
 551  * with a GRANT_RES call which gets lost, and calls UNLOCK immediately
 552  * afterwards. In this case the block will still be there, and hence
 553  * must be removed.
 554  */
 555 __be32
 556 nlmsvc_unlock(struct nlm_file *file, struct nlm_lock *lock)
 557 {
 558         int     error;
 559
 560         dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
 561                                 file->f_file->f_path.dentry->d_inode->i_sb->s_id,
 562                                 file->f_file->f_path.dentry->d_inode->i_ino,
 563                                 lock->fl.fl_pid,
 564                                 (long long)lock->fl.fl_start,
 565                                 (long long)lock->fl.fl_end);
 566
 567         /* First, cancel any lock that might be there */
 568         nlmsvc_cancel_blocked(file, lock);
 569
 570         lock->fl.fl_type = F_UNLCK;
 571         error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
 572
 573         return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
 574 }
 575
 576 /*
 577  * Cancel a previously blocked request.
 578  *
 579  * A cancel request always overrides any grant that may currently
 580  * be in progress.
 581  * The calling procedure must check whether the file can be closed.
 582  */
 583 __be32
 584 nlmsvc_cancel_blocked(struct nlm_file *file, struct nlm_lock *lock)
 585 {
 586         struct nlm_block        *block;
 587         int status = 0;
 588
 589         dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n",
 590                                 file->f_file->f_path.dentry->d_inode->i_sb->s_id,
 591                                 file->f_file->f_path.dentry->d_inode->i_ino,
 592                                 lock->fl.fl_pid,
 593                                 (long long)lock->fl.fl_start,
 594                                 (long long)lock->fl.fl_end);
 595
 596         mutex_lock(&file->f_mutex);
 597         block = nlmsvc_lookup_block(file, lock);
 598         mutex_unlock(&file->f_mutex);
 599         if (block != NULL) {
 600                 vfs_cancel_lock(block->b_file->f_file,
 601                                 &block->b_call->a_args.lock.fl);
 602                 status = nlmsvc_unlink_block(block);
 603                 nlmsvc_release_block(block);
 604         }
 605         return status ? nlm_lck_denied : nlm_granted;
 606 }
 607
 608 /*
 609  * This is a callback from the filesystem for VFS file lock requests.
 610  * It will be used if fl_grant is defined and the filesystem can not
 611  * respond to the request immediately.
 612  * For GETLK request it will copy the reply to the nlm_block.
 613  * For SETLK or SETLKW request it will get the local posix lock.
 614  * In all cases it will move the block to the head of nlm_blocked q where
 615  * nlmsvc_retry_blocked() can send back a reply for SETLKW or revisit the
 616  * deferred rpc for GETLK and SETLK.
 617  */
 618 static void
 619 nlmsvc_update_deferred_block(struct nlm_block *block, struct file_lock *conf,
 620                              int result)
 621 {
 622         block->b_flags |= B_GOT_CALLBACK;
 623         if (result == 0)
 624                 block->b_granted = 1;
 625         else
 626                 block->b_flags |= B_TIMED_OUT;
 627         if (conf) {
 628                 if (block->b_fl)
 629                         __locks_copy_lock(block->b_fl, conf);
 630         }
 631 }
 632
 633 static int nlmsvc_grant_deferred(struct file_lock *fl, struct file_lock *conf,
 634                                         int result)
 635 {
 636         struct nlm_block *block;
 637         int rc = -ENOENT;
 638
 639         lock_kernel();
 640         list_for_each_entry(block, &nlm_blocked, b_list) {
 641                 if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
 642                         dprintk("lockd: nlmsvc_notify_blocked block %p flags %d\n",
 643                                                         block, block->b_flags);
 644                         if (block->b_flags & B_QUEUED) {
 645                                 if (block->b_flags & B_TIMED_OUT) {
 646                                         rc = -ENOLCK;
 647                                         break;
 648                                 }
 649                                 nlmsvc_update_deferred_block(block, conf, result);
 650                         } else if (result == 0)
 651                                 block->b_granted = 1;
 652
 653                         nlmsvc_insert_block(block, 0);
 654                         svc_wake_up(block->b_daemon);
 655                         rc = 0;
 656                         break;
 657                 }
 658         }
 659         unlock_kernel();
 660         if (rc == -ENOENT)
 661                 printk(KERN_WARNING "lockd: grant for unknown block\n");
 662         return rc;
 663 }
 664
 665 /*
 666  * Unblock a blocked lock request. This is a callback invoked from the
 667  * VFS layer when a lock on which we blocked is removed.
 668  *
 669  * This function doesn't grant the blocked lock instantly, but rather moves
 670  * the block to the head of nlm_blocked where it can be picked up by lockd.
 671  */
 672 static void
 673 nlmsvc_notify_blocked(struct file_lock *fl)
 674 {
 675         struct nlm_block        *block;
 676
 677         dprintk("lockd: VFS unblock notification for block %p\n", fl);
 678         list_for_each_entry(block, &nlm_blocked, b_list) {
 679                 if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
 680                         nlmsvc_insert_block(block, 0);
 681                         svc_wake_up(block->b_daemon);
 682                         return;
 683                 }
 684         }
 685
 686         printk(KERN_WARNING "lockd: notification for unknown block!\n");
 687 }
 688
 689 static int nlmsvc_same_owner(struct file_lock *fl1, struct file_lock *fl2)
 690 {
 691         return fl1->fl_owner == fl2->fl_owner && fl1->fl_pid == fl2->fl_pid;
 692 }
 693
 694 struct lock_manager_operations nlmsvc_lock_operations = {
 695         .fl_compare_owner = nlmsvc_same_owner,
 696         .fl_notify = nlmsvc_notify_blocked,
 697         .fl_grant = nlmsvc_grant_deferred,
 698 };
 699
 700 /*
 701  * Try to claim a lock that was previously blocked.
 702  *
 703  * Note that we use both the RPC_GRANTED_MSG call _and_ an async
 704  * RPC thread when notifying the client. This seems like overkill...
 705  * Here's why:
 706  *  -   we don't want to use a synchronous RPC thread, otherwise
 707  *      we might find ourselves hanging on a dead portmapper.
 708  *  -   Some lockd implementations (e.g. HP) don't react to
 709  *      RPC_GRANTED calls; they seem to insist on RPC_GRANTED_MSG calls.
 710  */
 711 static void
 712 nlmsvc_grant_blocked(struct nlm_block *block)
 713 {
 714         struct nlm_file         *file = block->b_file;
 715         struct nlm_lock         *lock = &block->b_call->a_args.lock;
 716         int                     error;
 717
 718         dprintk("lockd: grant blocked lock %p\n", block);
 719
 720         kref_get(&block->b_count);
 721
 722         /* Unlink block request from list */
 723         nlmsvc_unlink_block(block);
 724
 725         /* If b_granted is true this means we've been here before.
 726          * Just retry the grant callback, possibly refreshing the RPC
 727          * binding */
 728         if (block->b_granted) {
 729                 nlm_rebind_host(block->b_host);
 730                 goto callback;
 731         }
 732
 733         /* Try the lock operation again */
 734         lock->fl.fl_flags |= FL_SLEEP;
 735         error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
 736         lock->fl.fl_flags &= ~FL_SLEEP;
 737
 738         switch (error) {
 739         case 0:
 740                 break;
 741         case -EAGAIN:
 742         case -EINPROGRESS:
 743                 dprintk("lockd: lock still blocked error %d\n", error);
 744                 nlmsvc_insert_block(block, NLM_NEVER);
 745                 nlmsvc_release_block(block);
 746                 return;
 747         default:
 748                 printk(KERN_WARNING "lockd: unexpected error %d in %s!\n",
 749                                 -error, __func__);
 750                 nlmsvc_insert_block(block, 10 * HZ);
 751                 nlmsvc_release_block(block);
 752                 return;
 753         }
 754
 755 callback:
 756         /* Lock was granted by VFS. */
 757         dprintk("lockd: GRANTing blocked lock.\n");
 758         block->b_granted = 1;
 759
 760         /* keep block on the list, but don't reattempt until the RPC
 761          * completes or the submission fails
 762          */
 763         nlmsvc_insert_block(block, NLM_NEVER);
 764
 765         /* Call the client -- use a soft RPC task since nlmsvc_retry_blocked
 766          * will queue up a new one if this one times out
 767          */
 768         error = nlm_async_call(block->b_call, NLMPROC_GRANTED_MSG,
 769                                 &nlmsvc_grant_ops);
 770
 771         /* RPC submission failed, wait a bit and retry */
 772         if (error < 0)
 773                 nlmsvc_insert_block(block, 10 * HZ);
 774 }
 775
 776 /*
 777  * This is the callback from the RPC layer when the NLM_GRANTED_MSG
 778  * RPC call has succeeded or timed out.
 779  * Like all RPC callbacks, it is invoked by the rpciod process, so it
 780  * better not sleep. Therefore, we put the blocked lock on the nlm_blocked
 781  * chain once more in order to have it removed by lockd itself (which can
 782  * then sleep on the file semaphore without disrupting e.g. the nfs client).
 783  */
 784 static void nlmsvc_grant_callback(struct rpc_task *task, void *data)
 785 {
 786         struct nlm_rqst         *call = data;
 787         struct nlm_block        *block = call->a_block;
 788         unsigned long           timeout;
 789
 790         dprintk("lockd: GRANT_MSG RPC callback\n");
 791
 792         /* if the block is not on a list at this point then it has
 793          * been invalidated. Don't try to requeue it.
 794          *
 795          * FIXME: it's possible that the block is removed from the list
 796          * after this check but before the nlmsvc_insert_block. In that
 797          * case it will be added back. Perhaps we need better locking
 798          * for nlm_blocked?
 799          */
 800         if (list_empty(&block->b_list))
 801                 return;
 802
 803         /* Technically, we should down the file semaphore here. Since we
 804          * move the block towards the head of the queue only, no harm
 805          * can be done, though. */
 806         if (task->tk_status < 0) {
 807                 /* RPC error: Re-insert for retransmission */
 808                 timeout = 10 * HZ;
 809         } else {
 810                 /* Call was successful, now wait for client callback */
 811                 timeout = 60 * HZ;
 812         }
 813         nlmsvc_insert_block(block, timeout);
 814         svc_wake_up(block->b_daemon);
 815 }
 816
 817 static void nlmsvc_grant_release(void *data)
 818 {
 819         struct nlm_rqst         *call = data;
 820
 821         nlmsvc_release_block(call->a_block);
 822 }
 823
 824 static const struct rpc_call_ops nlmsvc_grant_ops = {
 825         .rpc_call_done = nlmsvc_grant_callback,
 826         .rpc_release = nlmsvc_grant_release,
 827 };
 828
 829 /*
 830  * We received a GRANT_RES callback. Try to find the corresponding
 831  * block.
 832  */
 833 void
 834 nlmsvc_grant_reply(struct nlm_cookie *cookie, __be32 status)
 835 {
 836         struct nlm_block        *block;
 837
 838         dprintk("grant_reply: looking for cookie %x, s=%d \n",
 839                 *(unsigned int *)(cookie->data), status);
 840         if (!(block = nlmsvc_find_block(cookie)))
 841                 return;
 842
 843         if (block) {
 844                 if (status == nlm_lck_denied_grace_period) {
 845                         /* Try again in a couple of seconds */
 846                         nlmsvc_insert_block(block, 10 * HZ);
 847                 } else {
 848                         /* Lock is now held by client, or has been rejected.
 849                          * In both cases, the block should be removed. */
 850                         nlmsvc_unlink_block(block);
 851                 }
 852         }
 853         nlmsvc_release_block(block);
 854 }
 855
 856 /* Helper function to handle retry of a deferred block.
 857  * If it is a blocking lock, call grant_blocked.
 858  * For a non-blocking lock or test lock, revisit the request.
 859  */
 860 static void
 861 retry_deferred_block(struct nlm_block *block)
 862 {
 863         if (!(block->b_flags & B_GOT_CALLBACK))
 864                 block->b_flags |= B_TIMED_OUT;
 865         nlmsvc_insert_block(block, NLM_TIMEOUT);
 866         dprintk("revisit block %p flags %d\n",  block, block->b_flags);
 867         if (block->b_deferred_req) {
 868                 block->b_deferred_req->revisit(block->b_deferred_req, 0);
 869                 block->b_deferred_req = NULL;
 870         }
 871 }
 872
 873 /*
 874  * Retry all blocked locks that have been notified. This is where lockd
 875  * picks up locks that can be granted, or grant notifications that must
 876  * be retransmitted.
 877  */
 878 unsigned long
 879 nlmsvc_retry_blocked(void)
 880 {
 881         unsigned long   timeout = MAX_SCHEDULE_TIMEOUT;
 882         struct nlm_block *block;
 883
 884         while (!list_empty(&nlm_blocked) && !kthread_should_stop()) {
 885                 block = list_entry(nlm_blocked.next, struct nlm_block, b_list);
 886
 887                 if (block->b_when == NLM_NEVER)
 888                         break;
 889                 if (time_after(block->b_when,jiffies)) {
 890                         timeout = block->b_when - jiffies;
 891                         break;
 892                 }
 893
 894                 dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n",
 895                         block, block->b_when);
 896                 if (block->b_flags & B_QUEUED) {
 897                         dprintk("nlmsvc_retry_blocked delete block (%p, granted=%d, flags=%d)\n",
 898                                 block, block->b_granted, block->b_flags);
 899                         retry_deferred_block(block);
 900                 } else
 901                         nlmsvc_grant_blocked(block);
 902         }
 903
 904         return timeout;
 905 }