fs/lockd/svclock.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * linux/fs/lockd/svclock.c
   4  *
   5  * Handling of server-side locks, mostly of the blocked variety.
   6  * This is the ugliest part of lockd because we tread on very thin ice.
   7  * GRANT and CANCEL calls may get stuck, meet in mid-flight, etc.
   8  * IMNSHO introducing the grant callback into the NLM protocol was one
   9  * of the worst ideas Sun ever had. Except maybe for the idea of doing
  10  * NFS file locking at all.
  11  *
  12  * I'm trying hard to avoid race conditions by protecting most accesses
  13  * to a file's list of blocked locks through a semaphore. The global
  14  * list of blocked locks is not protected in this fashion however.
  15  * Therefore, some functions (such as the RPC callback for the async grant
  16  * call) move blocked locks towards the head of the list *while some other
  17  * process might be traversing it*. This should not be a problem in
  18  * practice, because this will only cause functions traversing the list
  19  * to visit some blocks twice.
  20  *
  21  * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
  22  */
  23
  24 #include <linux/types.h>
  25 #include <linux/slab.h>
  26 #include <linux/errno.h>
  27 #include <linux/kernel.h>
  28 #include <linux/sched.h>
  29 #include <linux/sunrpc/clnt.h>
  30 #include <linux/sunrpc/svc_xprt.h>
  31 #include <linux/lockd/nlm.h>
  32 #include <linux/lockd/lockd.h>
  33 #include <linux/kthread.h>
  34
  35 #define NLMDBG_FACILITY         NLMDBG_SVCLOCK
  36
  37 #ifdef CONFIG_LOCKD_V4
  38 #define nlm_deadlock    nlm4_deadlock
  39 #else
  40 #define nlm_deadlock    nlm_lck_denied
  41 #endif
  42
  43 static void nlmsvc_release_block(struct nlm_block *block);
  44 static void     nlmsvc_insert_block(struct nlm_block *block, unsigned long);
  45 static void     nlmsvc_remove_block(struct nlm_block *block);
  46
  47 static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock);
  48 static void nlmsvc_freegrantargs(struct nlm_rqst *call);
  49 static const struct rpc_call_ops nlmsvc_grant_ops;
  50
  51 /*
  52  * The list of blocked locks to retry
  53  */
  54 static LIST_HEAD(nlm_blocked);
  55 static DEFINE_SPINLOCK(nlm_blocked_lock);
  56
  57 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
  58 static const char *nlmdbg_cookie2a(const struct nlm_cookie *cookie)
  59 {
  60         /*
  61          * We can get away with a static buffer because this is only called
  62          * from lockd, which is single-threaded.
  63          */
  64         static char buf[2*NLM_MAXCOOKIELEN+1];
  65         unsigned int i, len = sizeof(buf);
  66         char *p = buf;
  67
  68         len--;  /* allow for trailing \0 */
  69         if (len < 3)
  70                 return "???";
  71         for (i = 0 ; i < cookie->len ; i++) {
  72                 if (len < 2) {
  73                         strcpy(p-3, "...");
  74                         break;
  75                 }
  76                 sprintf(p, "%02x", cookie->data[i]);
  77                 p += 2;
  78                 len -= 2;
  79         }
  80         *p = '\0';
  81
  82         return buf;
  83 }
  84 #endif
  85
  86 /*
  87  * Insert a blocked lock into the global list
  88  */
  89 static void
  90 nlmsvc_insert_block_locked(struct nlm_block *block, unsigned long when)
  91 {
  92         struct nlm_block *b;
  93         struct list_head *pos;
  94
  95         dprintk("lockd: nlmsvc_insert_block(%p, %ld)\n", block, when);
  96         if (list_empty(&block->b_list)) {
  97                 kref_get(&block->b_count);
  98         } else {
  99                 list_del_init(&block->b_list);
 100         }
 101
 102         pos = &nlm_blocked;
 103         if (when != NLM_NEVER) {
 104                 if ((when += jiffies) == NLM_NEVER)
 105                         when ++;
 106                 list_for_each(pos, &nlm_blocked) {
 107                         b = list_entry(pos, struct nlm_block, b_list);
 108                         if (time_after(b->b_when,when) || b->b_when == NLM_NEVER)
 109                                 break;
 110                 }
 111                 /* On normal exit from the loop, pos == &nlm_blocked,
 112                  * so we will be adding to the end of the list - good
 113                  */
 114         }
 115
 116         list_add_tail(&block->b_list, pos);
 117         block->b_when = when;
 118 }
 119
 120 static void nlmsvc_insert_block(struct nlm_block *block, unsigned long when)
 121 {
 122         spin_lock(&nlm_blocked_lock);
 123         nlmsvc_insert_block_locked(block, when);
 124         spin_unlock(&nlm_blocked_lock);
 125 }
 126
 127 /*
 128  * Remove a block from the global list
 129  */
 130 static inline void
 131 nlmsvc_remove_block(struct nlm_block *block)
 132 {
 133         if (!list_empty(&block->b_list)) {
 134                 spin_lock(&nlm_blocked_lock);
 135                 list_del_init(&block->b_list);
 136                 spin_unlock(&nlm_blocked_lock);
 137                 nlmsvc_release_block(block);
 138         }
 139 }
 140
 141 /*
 142  * Find a block for a given lock
 143  */
 144 static struct nlm_block *
 145 nlmsvc_lookup_block(struct nlm_file *file, struct nlm_lock *lock)
 146 {
 147         struct nlm_block        *block;
 148         struct file_lock        *fl;
 149
 150         dprintk("lockd: nlmsvc_lookup_block f=%p pd=%d %Ld-%Ld ty=%d\n",
 151                                 file, lock->fl.fl_pid,
 152                                 (long long)lock->fl.fl_start,
 153                                 (long long)lock->fl.fl_end, lock->fl.fl_type);
 154         list_for_each_entry(block, &nlm_blocked, b_list) {
 155                 fl = &block->b_call->a_args.lock.fl;
 156                 dprintk("lockd: check f=%p pd=%d %Ld-%Ld ty=%d cookie=%s\n",
 157                                 block->b_file, fl->fl_pid,
 158                                 (long long)fl->fl_start,
 159                                 (long long)fl->fl_end, fl->fl_type,
 160                                 nlmdbg_cookie2a(&block->b_call->a_args.cookie));
 161                 if (block->b_file == file && nlm_compare_locks(fl, &lock->fl)) {
 162                         kref_get(&block->b_count);
 163                         return block;
 164                 }
 165         }
 166
 167         return NULL;
 168 }
 169
 170 static inline int nlm_cookie_match(struct nlm_cookie *a, struct nlm_cookie *b)
 171 {
 172         if (a->len != b->len)
 173                 return 0;
 174         if (memcmp(a->data, b->data, a->len))
 175                 return 0;
 176         return 1;
 177 }
 178
 179 /*
 180  * Find a block with a given NLM cookie.
 181  */
 182 static inline struct nlm_block *
 183 nlmsvc_find_block(struct nlm_cookie *cookie)
 184 {
 185         struct nlm_block *block;
 186
 187         list_for_each_entry(block, &nlm_blocked, b_list) {
 188                 if (nlm_cookie_match(&block->b_call->a_args.cookie,cookie))
 189                         goto found;
 190         }
 191
 192         return NULL;
 193
 194 found:
 195         dprintk("nlmsvc_find_block(%s): block=%p\n", nlmdbg_cookie2a(cookie), block);
 196         kref_get(&block->b_count);
 197         return block;
 198 }
 199
 200 /*
 201  * Create a block and initialize it.
 202  *
 203  * Note: we explicitly set the cookie of the grant reply to that of
 204  * the blocked lock request. The spec explicitly mentions that the client
 205  * should _not_ rely on the callback containing the same cookie as the
 206  * request, but (as I found out later) that's because some implementations
 207  * do just this. Never mind the standards comittees, they support our
 208  * logging industries.
 209  *
 210  * 10 years later: I hope we can safely ignore these old and broken
 211  * clients by now. Let's fix this so we can uniquely identify an incoming
 212  * GRANTED_RES message by cookie, without having to rely on the client's IP
 213  * address. --okir
 214  */
 215 static struct nlm_block *
 216 nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_host *host,
 217                     struct nlm_file *file, struct nlm_lock *lock,
 218                     struct nlm_cookie *cookie)
 219 {
 220         struct nlm_block        *block;
 221         struct nlm_rqst         *call = NULL;
 222
 223         call = nlm_alloc_call(host);
 224         if (call == NULL)
 225                 return NULL;
 226
 227         /* Allocate memory for block, and initialize arguments */
 228         block = kzalloc(sizeof(*block), GFP_KERNEL);
 229         if (block == NULL)
 230                 goto failed;
 231         kref_init(&block->b_count);
 232         INIT_LIST_HEAD(&block->b_list);
 233         INIT_LIST_HEAD(&block->b_flist);
 234
 235         if (!nlmsvc_setgrantargs(call, lock))
 236                 goto failed_free;
 237
 238         /* Set notifier function for VFS, and init args */
 239         call->a_args.lock.fl.fl_flags |= FL_SLEEP;
 240         call->a_args.lock.fl.fl_lmops = &nlmsvc_lock_operations;
 241         nlmclnt_next_cookie(&call->a_args.cookie);
 242
 243         dprintk("lockd: created block %p...\n", block);
 244
 245         /* Create and initialize the block */
 246         block->b_daemon = rqstp->rq_server;
 247         block->b_host   = host;
 248         block->b_file   = file;
 249         file->f_count++;
 250
 251         /* Add to file's list of blocks */
 252         list_add(&block->b_flist, &file->f_blocks);
 253
 254         /* Set up RPC arguments for callback */
 255         block->b_call = call;
 256         call->a_flags   = RPC_TASK_ASYNC;
 257         call->a_block = block;
 258
 259         return block;
 260
 261 failed_free:
 262         kfree(block);
 263 failed:
 264         nlmsvc_release_call(call);
 265         return NULL;
 266 }
 267
 268 /*
 269  * Delete a block.
 270  * It is the caller's responsibility to check whether the file
 271  * can be closed hereafter.
 272  */
 273 static int nlmsvc_unlink_block(struct nlm_block *block)
 274 {
 275         int status;
 276         dprintk("lockd: unlinking block %p...\n", block);
 277
 278         /* Remove block from list */
 279         status = posix_unblock_lock(&block->b_call->a_args.lock.fl);
 280         nlmsvc_remove_block(block);
 281         return status;
 282 }
 283
 284 static void nlmsvc_free_block(struct kref *kref)
 285 {
 286         struct nlm_block *block = container_of(kref, struct nlm_block, b_count);
 287         struct nlm_file         *file = block->b_file;
 288
 289         dprintk("lockd: freeing block %p...\n", block);
 290
 291         /* Remove block from file's list of blocks */
 292         list_del_init(&block->b_flist);
 293         mutex_unlock(&file->f_mutex);
 294
 295         nlmsvc_freegrantargs(block->b_call);
 296         nlmsvc_release_call(block->b_call);
 297         nlm_release_file(block->b_file);
 298         kfree(block);
 299 }
 300
 301 static void nlmsvc_release_block(struct nlm_block *block)
 302 {
 303         if (block != NULL)
 304                 kref_put_mutex(&block->b_count, nlmsvc_free_block, &block->b_file->f_mutex);
 305 }
 306
 307 /*
 308  * Loop over all blocks and delete blocks held by
 309  * a matching host.
 310  */
 311 void nlmsvc_traverse_blocks(struct nlm_host *host,
 312                         struct nlm_file *file,
 313                         nlm_host_match_fn_t match)
 314 {
 315         struct nlm_block *block, *next;
 316
 317 restart:
 318         mutex_lock(&file->f_mutex);
 319         list_for_each_entry_safe(block, next, &file->f_blocks, b_flist) {
 320                 if (!match(block->b_host, host))
 321                         continue;
 322                 /* Do not destroy blocks that are not on
 323                  * the global retry list - why? */
 324                 if (list_empty(&block->b_list))
 325                         continue;
 326                 kref_get(&block->b_count);
 327                 mutex_unlock(&file->f_mutex);
 328                 nlmsvc_unlink_block(block);
 329                 nlmsvc_release_block(block);
 330                 goto restart;
 331         }
 332         mutex_unlock(&file->f_mutex);
 333 }
 334
 335 /*
 336  * Initialize arguments for GRANTED call. The nlm_rqst structure
 337  * has been cleared already.
 338  */
 339 static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock)
 340 {
 341         locks_copy_lock(&call->a_args.lock.fl, &lock->fl);
 342         memcpy(&call->a_args.lock.fh, &lock->fh, sizeof(call->a_args.lock.fh));
 343         call->a_args.lock.caller = utsname()->nodename;
 344         call->a_args.lock.oh.len = lock->oh.len;
 345
 346         /* set default data area */
 347         call->a_args.lock.oh.data = call->a_owner;
 348         call->a_args.lock.svid = lock->fl.fl_pid;
 349
 350         if (lock->oh.len > NLMCLNT_OHSIZE) {
 351                 void *data = kmalloc(lock->oh.len, GFP_KERNEL);
 352                 if (!data)
 353                         return 0;
 354                 call->a_args.lock.oh.data = (u8 *) data;
 355         }
 356
 357         memcpy(call->a_args.lock.oh.data, lock->oh.data, lock->oh.len);
 358         return 1;
 359 }
 360
 361 static void nlmsvc_freegrantargs(struct nlm_rqst *call)
 362 {
 363         if (call->a_args.lock.oh.data != call->a_owner)
 364                 kfree(call->a_args.lock.oh.data);
 365
 366         locks_release_private(&call->a_args.lock.fl);
 367 }
 368
 369 /*
 370  * Deferred lock request handling for non-blocking lock
 371  */
 372 static __be32
 373 nlmsvc_defer_lock_rqst(struct svc_rqst *rqstp, struct nlm_block *block)
 374 {
 375         __be32 status = nlm_lck_denied_nolocks;
 376
 377         block->b_flags |= B_QUEUED;
 378
 379         nlmsvc_insert_block(block, NLM_TIMEOUT);
 380
 381         block->b_cache_req = &rqstp->rq_chandle;
 382         if (rqstp->rq_chandle.defer) {
 383                 block->b_deferred_req =
 384                         rqstp->rq_chandle.defer(block->b_cache_req);
 385                 if (block->b_deferred_req != NULL)
 386                         status = nlm_drop_reply;
 387         }
 388         dprintk("lockd: nlmsvc_defer_lock_rqst block %p flags %d status %d\n",
 389                 block, block->b_flags, ntohl(status));
 390
 391         return status;
 392 }
 393
 394 /*
 395  * Attempt to establish a lock, and if it can't be granted, block it
 396  * if required.
 397  */
 398 __be32
 399 nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
 400             struct nlm_host *host, struct nlm_lock *lock, int wait,
 401             struct nlm_cookie *cookie, int reclaim)
 402 {
 403         struct nlm_block        *block = NULL;
 404         int                     error;
 405         __be32                  ret;
 406
 407         dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
 408                                 file_inode(file->f_file)->i_sb->s_id,
 409                                 file_inode(file->f_file)->i_ino,
 410                                 lock->fl.fl_type, lock->fl.fl_pid,
 411                                 (long long)lock->fl.fl_start,
 412                                 (long long)lock->fl.fl_end,
 413                                 wait);
 414
 415         /* Lock file against concurrent access */
 416         mutex_lock(&file->f_mutex);
 417         /* Get existing block (in case client is busy-waiting)
 418          * or create new block
 419          */
 420         block = nlmsvc_lookup_block(file, lock);
 421         if (block == NULL) {
 422                 block = nlmsvc_create_block(rqstp, host, file, lock, cookie);
 423                 ret = nlm_lck_denied_nolocks;
 424                 if (block == NULL)
 425                         goto out;
 426                 lock = &block->b_call->a_args.lock;
 427         } else
 428                 lock->fl.fl_flags &= ~FL_SLEEP;
 429
 430         if (block->b_flags & B_QUEUED) {
 431                 dprintk("lockd: nlmsvc_lock deferred block %p flags %d\n",
 432                                                         block, block->b_flags);
 433                 if (block->b_granted) {
 434                         nlmsvc_unlink_block(block);
 435                         ret = nlm_granted;
 436                         goto out;
 437                 }
 438                 if (block->b_flags & B_TIMED_OUT) {
 439                         nlmsvc_unlink_block(block);
 440                         ret = nlm_lck_denied;
 441                         goto out;
 442                 }
 443                 ret = nlm_drop_reply;
 444                 goto out;
 445         }
 446
 447         if (locks_in_grace(SVC_NET(rqstp)) && !reclaim) {
 448                 ret = nlm_lck_denied_grace_period;
 449                 goto out;
 450         }
 451         if (reclaim && !locks_in_grace(SVC_NET(rqstp))) {
 452                 ret = nlm_lck_denied_grace_period;
 453                 goto out;
 454         }
 455
 456         if (!wait)
 457                 lock->fl.fl_flags &= ~FL_SLEEP;
 458         error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
 459         lock->fl.fl_flags &= ~FL_SLEEP;
 460
 461         dprintk("lockd: vfs_lock_file returned %d\n", error);
 462         switch (error) {
 463                 case 0:
 464                         ret = nlm_granted;
 465                         goto out;
 466                 case -EAGAIN:
 467                         /*
 468                          * If this is a blocking request for an
 469                          * already pending lock request then we need
 470                          * to put it back on lockd's block list
 471                          */
 472                         if (wait)
 473                                 break;
 474                         ret = nlm_lck_denied;
 475                         goto out;
 476                 case FILE_LOCK_DEFERRED:
 477                         if (wait)
 478                                 break;
 479                         /* Filesystem lock operation is in progress
 480                            Add it to the queue waiting for callback */
 481                         ret = nlmsvc_defer_lock_rqst(rqstp, block);
 482                         goto out;
 483                 case -EDEADLK:
 484                         ret = nlm_deadlock;
 485                         goto out;
 486                 default:                        /* includes ENOLCK */
 487                         ret = nlm_lck_denied_nolocks;
 488                         goto out;
 489         }
 490
 491         ret = nlm_lck_blocked;
 492
 493         /* Append to list of blocked */
 494         nlmsvc_insert_block(block, NLM_NEVER);
 495 out:
 496         mutex_unlock(&file->f_mutex);
 497         nlmsvc_release_block(block);
 498         dprintk("lockd: nlmsvc_lock returned %u\n", ret);
 499         return ret;
 500 }
 501
 502 /*
 503  * Test for presence of a conflicting lock.
 504  */
 505 __be32
 506 nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
 507                 struct nlm_host *host, struct nlm_lock *lock,
 508                 struct nlm_lock *conflock, struct nlm_cookie *cookie)
 509 {
 510         int                     error;
 511         __be32                  ret;
 512
 513         dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
 514                                 file_inode(file->f_file)->i_sb->s_id,
 515                                 file_inode(file->f_file)->i_ino,
 516                                 lock->fl.fl_type,
 517                                 (long long)lock->fl.fl_start,
 518                                 (long long)lock->fl.fl_end);
 519
 520         if (locks_in_grace(SVC_NET(rqstp))) {
 521                 ret = nlm_lck_denied_grace_period;
 522                 goto out;
 523         }
 524
 525         error = vfs_test_lock(file->f_file, &lock->fl);
 526         if (error) {
 527                 /* We can't currently deal with deferred test requests */
 528                 if (error == FILE_LOCK_DEFERRED)
 529                         WARN_ON_ONCE(1);
 530
 531                 ret = nlm_lck_denied_nolocks;
 532                 goto out;
 533         }
 534
 535         if (lock->fl.fl_type == F_UNLCK) {
 536                 ret = nlm_granted;
 537                 goto out;
 538         }
 539
 540         dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n",
 541                 lock->fl.fl_type, (long long)lock->fl.fl_start,
 542                 (long long)lock->fl.fl_end);
 543         conflock->caller = "somehost";  /* FIXME */
 544         conflock->len = strlen(conflock->caller);
 545         conflock->oh.len = 0;           /* don't return OH info */
 546         conflock->svid = lock->fl.fl_pid;
 547         conflock->fl.fl_type = lock->fl.fl_type;
 548         conflock->fl.fl_start = lock->fl.fl_start;
 549         conflock->fl.fl_end = lock->fl.fl_end;
 550         locks_release_private(&lock->fl);
 551         ret = nlm_lck_denied;
 552 out:
 553         return ret;
 554 }
 555
 556 /*
 557  * Remove a lock.
 558  * This implies a CANCEL call: We send a GRANT_MSG, the client replies
 559  * with a GRANT_RES call which gets lost, and calls UNLOCK immediately
 560  * afterwards. In this case the block will still be there, and hence
 561  * must be removed.
 562  */
 563 __be32
 564 nlmsvc_unlock(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
 565 {
 566         int     error;
 567
 568         dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
 569                                 file_inode(file->f_file)->i_sb->s_id,
 570                                 file_inode(file->f_file)->i_ino,
 571                                 lock->fl.fl_pid,
 572                                 (long long)lock->fl.fl_start,
 573                                 (long long)lock->fl.fl_end);
 574
 575         /* First, cancel any lock that might be there */
 576         nlmsvc_cancel_blocked(net, file, lock);
 577
 578         lock->fl.fl_type = F_UNLCK;
 579         error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
 580
 581         return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
 582 }
 583
 584 /*
 585  * Cancel a previously blocked request.
 586  *
 587  * A cancel request always overrides any grant that may currently
 588  * be in progress.
 589  * The calling procedure must check whether the file can be closed.
 590  */
 591 __be32
 592 nlmsvc_cancel_blocked(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
 593 {
 594         struct nlm_block        *block;
 595         int status = 0;
 596
 597         dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n",
 598                                 file_inode(file->f_file)->i_sb->s_id,
 599                                 file_inode(file->f_file)->i_ino,
 600                                 lock->fl.fl_pid,
 601                                 (long long)lock->fl.fl_start,
 602                                 (long long)lock->fl.fl_end);
 603
 604         if (locks_in_grace(net))
 605                 return nlm_lck_denied_grace_period;
 606
 607         mutex_lock(&file->f_mutex);
 608         block = nlmsvc_lookup_block(file, lock);
 609         mutex_unlock(&file->f_mutex);
 610         if (block != NULL) {
 611                 vfs_cancel_lock(block->b_file->f_file,
 612                                 &block->b_call->a_args.lock.fl);
 613                 status = nlmsvc_unlink_block(block);
 614                 nlmsvc_release_block(block);
 615         }
 616         return status ? nlm_lck_denied : nlm_granted;
 617 }
 618
 619 /*
 620  * This is a callback from the filesystem for VFS file lock requests.
 621  * It will be used if lm_grant is defined and the filesystem can not
 622  * respond to the request immediately.
 623  * For SETLK or SETLKW request it will get the local posix lock.
 624  * In all cases it will move the block to the head of nlm_blocked q where
 625  * nlmsvc_retry_blocked() can send back a reply for SETLKW or revisit the
 626  * deferred rpc for GETLK and SETLK.
 627  */
 628 static void
 629 nlmsvc_update_deferred_block(struct nlm_block *block, int result)
 630 {
 631         block->b_flags |= B_GOT_CALLBACK;
 632         if (result == 0)
 633                 block->b_granted = 1;
 634         else
 635                 block->b_flags |= B_TIMED_OUT;
 636 }
 637
 638 static int nlmsvc_grant_deferred(struct file_lock *fl, int result)
 639 {
 640         struct nlm_block *block;
 641         int rc = -ENOENT;
 642
 643         spin_lock(&nlm_blocked_lock);
 644         list_for_each_entry(block, &nlm_blocked, b_list) {
 645                 if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
 646                         dprintk("lockd: nlmsvc_notify_blocked block %p flags %d\n",
 647                                                         block, block->b_flags);
 648                         if (block->b_flags & B_QUEUED) {
 649                                 if (block->b_flags & B_TIMED_OUT) {
 650                                         rc = -ENOLCK;
 651                                         break;
 652                                 }
 653                                 nlmsvc_update_deferred_block(block, result);
 654                         } else if (result == 0)
 655                                 block->b_granted = 1;
 656
 657                         nlmsvc_insert_block_locked(block, 0);
 658                         svc_wake_up(block->b_daemon);
 659                         rc = 0;
 660                         break;
 661                 }
 662         }
 663         spin_unlock(&nlm_blocked_lock);
 664         if (rc == -ENOENT)
 665                 printk(KERN_WARNING "lockd: grant for unknown block\n");
 666         return rc;
 667 }
 668
 669 /*
 670  * Unblock a blocked lock request. This is a callback invoked from the
 671  * VFS layer when a lock on which we blocked is removed.
 672  *
 673  * This function doesn't grant the blocked lock instantly, but rather moves
 674  * the block to the head of nlm_blocked where it can be picked up by lockd.
 675  */
 676 static void
 677 nlmsvc_notify_blocked(struct file_lock *fl)
 678 {
 679         struct nlm_block        *block;
 680
 681         dprintk("lockd: VFS unblock notification for block %p\n", fl);
 682         spin_lock(&nlm_blocked_lock);
 683         list_for_each_entry(block, &nlm_blocked, b_list) {
 684                 if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
 685                         nlmsvc_insert_block_locked(block, 0);
 686                         spin_unlock(&nlm_blocked_lock);
 687                         svc_wake_up(block->b_daemon);
 688                         return;
 689                 }
 690         }
 691         spin_unlock(&nlm_blocked_lock);
 692         printk(KERN_WARNING "lockd: notification for unknown block!\n");
 693 }
 694
 695 static int nlmsvc_same_owner(struct file_lock *fl1, struct file_lock *fl2)
 696 {
 697         return fl1->fl_owner == fl2->fl_owner && fl1->fl_pid == fl2->fl_pid;
 698 }
 699
 700 /*
 701  * Since NLM uses two "keys" for tracking locks, we need to hash them down
 702  * to one for the blocked_hash. Here, we're just xor'ing the host address
 703  * with the pid in order to create a key value for picking a hash bucket.
 704  */
 705 static unsigned long
 706 nlmsvc_owner_key(struct file_lock *fl)
 707 {
 708         return (unsigned long)fl->fl_owner ^ (unsigned long)fl->fl_pid;
 709 }
 710
 711 const struct lock_manager_operations nlmsvc_lock_operations = {
 712         .lm_compare_owner = nlmsvc_same_owner,
 713         .lm_owner_key = nlmsvc_owner_key,
 714         .lm_notify = nlmsvc_notify_blocked,
 715         .lm_grant = nlmsvc_grant_deferred,
 716 };
 717
 718 /*
 719  * Try to claim a lock that was previously blocked.
 720  *
 721  * Note that we use both the RPC_GRANTED_MSG call _and_ an async
 722  * RPC thread when notifying the client. This seems like overkill...
 723  * Here's why:
 724  *  -   we don't want to use a synchronous RPC thread, otherwise
 725  *      we might find ourselves hanging on a dead portmapper.
 726  *  -   Some lockd implementations (e.g. HP) don't react to
 727  *      RPC_GRANTED calls; they seem to insist on RPC_GRANTED_MSG calls.
 728  */
 729 static void
 730 nlmsvc_grant_blocked(struct nlm_block *block)
 731 {
 732         struct nlm_file         *file = block->b_file;
 733         struct nlm_lock         *lock = &block->b_call->a_args.lock;
 734         int                     error;
 735         loff_t                  fl_start, fl_end;
 736
 737         dprintk("lockd: grant blocked lock %p\n", block);
 738
 739         kref_get(&block->b_count);
 740
 741         /* Unlink block request from list */
 742         nlmsvc_unlink_block(block);
 743
 744         /* If b_granted is true this means we've been here before.
 745          * Just retry the grant callback, possibly refreshing the RPC
 746          * binding */
 747         if (block->b_granted) {
 748                 nlm_rebind_host(block->b_host);
 749                 goto callback;
 750         }
 751
 752         /* Try the lock operation again */
 753         /* vfs_lock_file() can mangle fl_start and fl_end, but we need
 754          * them unchanged for the GRANT_MSG
 755          */
 756         lock->fl.fl_flags |= FL_SLEEP;
 757         fl_start = lock->fl.fl_start;
 758         fl_end = lock->fl.fl_end;
 759         error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
 760         lock->fl.fl_flags &= ~FL_SLEEP;
 761         lock->fl.fl_start = fl_start;
 762         lock->fl.fl_end = fl_end;
 763
 764         switch (error) {
 765         case 0:
 766                 break;
 767         case FILE_LOCK_DEFERRED:
 768                 dprintk("lockd: lock still blocked error %d\n", error);
 769                 nlmsvc_insert_block(block, NLM_NEVER);
 770                 nlmsvc_release_block(block);
 771                 return;
 772         default:
 773                 printk(KERN_WARNING "lockd: unexpected error %d in %s!\n",
 774                                 -error, __func__);
 775                 nlmsvc_insert_block(block, 10 * HZ);
 776                 nlmsvc_release_block(block);
 777                 return;
 778         }
 779
 780 callback:
 781         /* Lock was granted by VFS. */
 782         dprintk("lockd: GRANTing blocked lock.\n");
 783         block->b_granted = 1;
 784
 785         /* keep block on the list, but don't reattempt until the RPC
 786          * completes or the submission fails
 787          */
 788         nlmsvc_insert_block(block, NLM_NEVER);
 789
 790         /* Call the client -- use a soft RPC task since nlmsvc_retry_blocked
 791          * will queue up a new one if this one times out
 792          */
 793         error = nlm_async_call(block->b_call, NLMPROC_GRANTED_MSG,
 794                                 &nlmsvc_grant_ops);
 795
 796         /* RPC submission failed, wait a bit and retry */
 797         if (error < 0)
 798                 nlmsvc_insert_block(block, 10 * HZ);
 799 }
 800
 801 /*
 802  * This is the callback from the RPC layer when the NLM_GRANTED_MSG
 803  * RPC call has succeeded or timed out.
 804  * Like all RPC callbacks, it is invoked by the rpciod process, so it
 805  * better not sleep. Therefore, we put the blocked lock on the nlm_blocked
 806  * chain once more in order to have it removed by lockd itself (which can
 807  * then sleep on the file semaphore without disrupting e.g. the nfs client).
 808  */
 809 static void nlmsvc_grant_callback(struct rpc_task *task, void *data)
 810 {
 811         struct nlm_rqst         *call = data;
 812         struct nlm_block        *block = call->a_block;
 813         unsigned long           timeout;
 814
 815         dprintk("lockd: GRANT_MSG RPC callback\n");
 816
 817         spin_lock(&nlm_blocked_lock);
 818         /* if the block is not on a list at this point then it has
 819          * been invalidated. Don't try to requeue it.
 820          *
 821          * FIXME: it's possible that the block is removed from the list
 822          * after this check but before the nlmsvc_insert_block. In that
 823          * case it will be added back. Perhaps we need better locking
 824          * for nlm_blocked?
 825          */
 826         if (list_empty(&block->b_list))
 827                 goto out;
 828
 829         /* Technically, we should down the file semaphore here. Since we
 830          * move the block towards the head of the queue only, no harm
 831          * can be done, though. */
 832         if (task->tk_status < 0) {
 833                 /* RPC error: Re-insert for retransmission */
 834                 timeout = 10 * HZ;
 835         } else {
 836                 /* Call was successful, now wait for client callback */
 837                 timeout = 60 * HZ;
 838         }
 839         nlmsvc_insert_block_locked(block, timeout);
 840         svc_wake_up(block->b_daemon);
 841 out:
 842         spin_unlock(&nlm_blocked_lock);
 843 }
 844
 845 /*
 846  * FIXME: nlmsvc_release_block() grabs a mutex.  This is not allowed for an
 847  * .rpc_release rpc_call_op
 848  */
 849 static void nlmsvc_grant_release(void *data)
 850 {
 851         struct nlm_rqst         *call = data;
 852         nlmsvc_release_block(call->a_block);
 853 }
 854
 855 static const struct rpc_call_ops nlmsvc_grant_ops = {
 856         .rpc_call_done = nlmsvc_grant_callback,
 857         .rpc_release = nlmsvc_grant_release,
 858 };
 859
 860 /*
 861  * We received a GRANT_RES callback. Try to find the corresponding
 862  * block.
 863  */
 864 void
 865 nlmsvc_grant_reply(struct nlm_cookie *cookie, __be32 status)
 866 {
 867         struct nlm_block        *block;
 868
 869         dprintk("grant_reply: looking for cookie %x, s=%d \n",
 870                 *(unsigned int *)(cookie->data), status);
 871         if (!(block = nlmsvc_find_block(cookie)))
 872                 return;
 873
 874         if (status == nlm_lck_denied_grace_period) {
 875                 /* Try again in a couple of seconds */
 876                 nlmsvc_insert_block(block, 10 * HZ);
 877         } else {
 878                 /*
 879                  * Lock is now held by client, or has been rejected.
 880                  * In both cases, the block should be removed.
 881                  */
 882                 nlmsvc_unlink_block(block);
 883         }
 884         nlmsvc_release_block(block);
 885 }
 886
 887 /* Helper function to handle retry of a deferred block.
 888  * If it is a blocking lock, call grant_blocked.
 889  * For a non-blocking lock or test lock, revisit the request.
 890  */
 891 static void
 892 retry_deferred_block(struct nlm_block *block)
 893 {
 894         if (!(block->b_flags & B_GOT_CALLBACK))
 895                 block->b_flags |= B_TIMED_OUT;
 896         nlmsvc_insert_block(block, NLM_TIMEOUT);
 897         dprintk("revisit block %p flags %d\n",  block, block->b_flags);
 898         if (block->b_deferred_req) {
 899                 block->b_deferred_req->revisit(block->b_deferred_req, 0);
 900                 block->b_deferred_req = NULL;
 901         }
 902 }
 903
 904 /*
 905  * Retry all blocked locks that have been notified. This is where lockd
 906  * picks up locks that can be granted, or grant notifications that must
 907  * be retransmitted.
 908  */
 909 unsigned long
 910 nlmsvc_retry_blocked(void)
 911 {
 912         unsigned long   timeout = MAX_SCHEDULE_TIMEOUT;
 913         struct nlm_block *block;
 914
 915         spin_lock(&nlm_blocked_lock);
 916         while (!list_empty(&nlm_blocked) && !kthread_should_stop()) {
 917                 block = list_entry(nlm_blocked.next, struct nlm_block, b_list);
 918
 919                 if (block->b_when == NLM_NEVER)
 920                         break;
 921                 if (time_after(block->b_when, jiffies)) {
 922                         timeout = block->b_when - jiffies;
 923                         break;
 924                 }
 925                 spin_unlock(&nlm_blocked_lock);
 926
 927                 dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n",
 928                         block, block->b_when);
 929                 if (block->b_flags & B_QUEUED) {
 930                         dprintk("nlmsvc_retry_blocked delete block (%p, granted=%d, flags=%d)\n",
 931                                 block, block->b_granted, block->b_flags);
 932                         retry_deferred_block(block);
 933                 } else
 934                         nlmsvc_grant_blocked(block);
 935                 spin_lock(&nlm_blocked_lock);
 936         }
 937         spin_unlock(&nlm_blocked_lock);
 938
 939         return timeout;
 940 }