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