1 /* 2 * linux/fs/locks.c 3 * 4 * Provide support for fcntl()'s F_GETLK, F_SETLK, and F_SETLKW calls. 5 * Doug Evans (dje@spiff.uucp), August 07, 1992 6 * 7 * Deadlock detection added. 8 * FIXME: one thing isn't handled yet: 9 * - mandatory locks (requires lots of changes elsewhere) 10 * Kelly Carmichael (kelly@[142.24.8.65]), September 17, 1994. 11 * 12 * Miscellaneous edits, and a total rewrite of posix_lock_file() code. 13 * Kai Petzke (wpp@marie.physik.tu-berlin.de), 1994 14 * 15 * Converted file_lock_table to a linked list from an array, which eliminates 16 * the limits on how many active file locks are open. 17 * Chad Page (pageone@netcom.com), November 27, 1994 18 * 19 * Removed dependency on file descriptors. dup()'ed file descriptors now 20 * get the same locks as the original file descriptors, and a close() on 21 * any file descriptor removes ALL the locks on the file for the current 22 * process. Since locks still depend on the process id, locks are inherited 23 * after an exec() but not after a fork(). This agrees with POSIX, and both 24 * BSD and SVR4 practice. 25 * Andy Walker (andy@lysaker.kvaerner.no), February 14, 1995 26 * 27 * Scrapped free list which is redundant now that we allocate locks 28 * dynamically with kmalloc()/kfree(). 29 * Andy Walker (andy@lysaker.kvaerner.no), February 21, 1995 30 * 31 * Implemented two lock personalities - FL_FLOCK and FL_POSIX. 32 * 33 * FL_POSIX locks are created with calls to fcntl() and lockf() through the 34 * fcntl() system call. They have the semantics described above. 35 * 36 * FL_FLOCK locks are created with calls to flock(), through the flock() 37 * system call, which is new. Old C libraries implement flock() via fcntl() 38 * and will continue to use the old, broken implementation. 39 * 40 * FL_FLOCK locks follow the 4.4 BSD flock() semantics. They are associated 41 * with a file pointer (filp). As a result they can be shared by a parent 42 * process and its children after a fork(). They are removed when the last 43 * file descriptor referring to the file pointer is closed (unless explicitly 44 * unlocked). 45 * 46 * FL_FLOCK locks never deadlock, an existing lock is always removed before 47 * upgrading from shared to exclusive (or vice versa). When this happens 48 * any processes blocked by the current lock are woken up and allowed to 49 * run before the new lock is applied. 50 * Andy Walker (andy@lysaker.kvaerner.no), June 09, 1995 51 * 52 * Removed some race conditions in flock_lock_file(), marked other possible 53 * races. Just grep for FIXME to see them. 54 * Dmitry Gorodchanin (pgmdsg@ibi.com), February 09, 1996. 55 * 56 * Addressed Dmitry's concerns. Deadlock checking no longer recursive. 57 * Lock allocation changed to GFP_ATOMIC as we can't afford to sleep 58 * once we've checked for blocking and deadlocking. 59 * Andy Walker (andy@lysaker.kvaerner.no), April 03, 1996. 60 * 61 * Initial implementation of mandatory locks. SunOS turned out to be 62 * a rotten model, so I implemented the "obvious" semantics. 63 * See 'Documentation/mandatory.txt' for details. 64 * Andy Walker (andy@lysaker.kvaerner.no), April 06, 1996. 65 * 66 * Don't allow mandatory locks on mmap()'ed files. Added simple functions to 67 * check if a file has mandatory locks, used by mmap(), open() and creat() to 68 * see if system call should be rejected. Ref. HP-UX/SunOS/Solaris Reference 69 * Manual, Section 2. 70 * Andy Walker (andy@lysaker.kvaerner.no), April 09, 1996. 71 * 72 * Tidied up block list handling. Added '/proc/locks' interface. 73 * Andy Walker (andy@lysaker.kvaerner.no), April 24, 1996. 74 * 75 * Fixed deadlock condition for pathological code that mixes calls to 76 * flock() and fcntl(). 77 * Andy Walker (andy@lysaker.kvaerner.no), April 29, 1996. 78 * 79 * Allow only one type of locking scheme (FL_POSIX or FL_FLOCK) to be in use 80 * for a given file at a time. Changed the CONFIG_LOCK_MANDATORY scheme to 81 * guarantee sensible behaviour in the case where file system modules might 82 * be compiled with different options than the kernel itself. 83 * Andy Walker (andy@lysaker.kvaerner.no), May 15, 1996. 84 * 85 * Added a couple of missing wake_up() calls. Thanks to Thomas Meckel 86 * (Thomas.Meckel@mni.fh-giessen.de) for spotting this. 87 * Andy Walker (andy@lysaker.kvaerner.no), May 15, 1996. 88 * 89 * Changed FL_POSIX locks to use the block list in the same way as FL_FLOCK 90 * locks. Changed process synchronisation to avoid dereferencing locks that 91 * have already been freed. 92 * Andy Walker (andy@lysaker.kvaerner.no), Sep 21, 1996. 93 * 94 * Made the block list a circular list to minimise searching in the list. 95 * Andy Walker (andy@lysaker.kvaerner.no), Sep 25, 1996. 96 * 97 * Made mandatory locking a mount option. Default is not to allow mandatory 98 * locking. 99 * Andy Walker (andy@lysaker.kvaerner.no), Oct 04, 1996. 100 * 101 * Some adaptations for NFS support. 102 * Olaf Kirch (okir@monad.swb.de), Dec 1996, 103 * 104 * Fixed /proc/locks interface so that we can't overrun the buffer we are handed. 105 * Andy Walker (andy@lysaker.kvaerner.no), May 12, 1997. 106 * 107 * Use slab allocator instead of kmalloc/kfree. 108 * Use generic list implementation from <linux/list.h>. 109 * Sped up posix_locks_deadlock by only considering blocked locks. 110 * Matthew Wilcox <willy@debian.org>, March, 2000. 111 * 112 * Leases and LOCK_MAND 113 * Matthew Wilcox <willy@debian.org>, June, 2000. 114 * Stephen Rothwell <sfr@canb.auug.org.au>, June, 2000. 115 */ 116 117 #include <linux/capability.h> 118 #include <linux/file.h> 119 #include <linux/fs.h> 120 #include <linux/init.h> 121 #include <linux/module.h> 122 #include <linux/security.h> 123 #include <linux/slab.h> 124 #include <linux/smp_lock.h> 125 #include <linux/syscalls.h> 126 #include <linux/time.h> 127 #include <linux/rcupdate.h> 128 129 #include <asm/semaphore.h> 130 #include <asm/uaccess.h> 131 132 #define IS_POSIX(fl) (fl->fl_flags & FL_POSIX) 133 #define IS_FLOCK(fl) (fl->fl_flags & FL_FLOCK) 134 #define IS_LEASE(fl) (fl->fl_flags & FL_LEASE) 135 136 int leases_enable = 1; 137 int lease_break_time = 45; 138 139 #define for_each_lock(inode, lockp) \ 140 for (lockp = &inode->i_flock; *lockp != NULL; lockp = &(*lockp)->fl_next) 141 142 LIST_HEAD(file_lock_list); 143 144 EXPORT_SYMBOL(file_lock_list); 145 146 static LIST_HEAD(blocked_list); 147 148 static kmem_cache_t *filelock_cache; 149 150 /* Allocate an empty lock structure. */ 151 static struct file_lock *locks_alloc_lock(void) 152 { 153 return kmem_cache_alloc(filelock_cache, SLAB_KERNEL); 154 } 155 156 /* Free a lock which is not in use. */ 157 static inline void locks_free_lock(struct file_lock *fl) 158 { 159 if (fl == NULL) { 160 BUG(); 161 return; 162 } 163 if (waitqueue_active(&fl->fl_wait)) 164 panic("Attempting to free lock with active wait queue"); 165 166 if (!list_empty(&fl->fl_block)) 167 panic("Attempting to free lock with active block list"); 168 169 if (!list_empty(&fl->fl_link)) 170 panic("Attempting to free lock on active lock list"); 171 172 if (fl->fl_ops) { 173 if (fl->fl_ops->fl_release_private) 174 fl->fl_ops->fl_release_private(fl); 175 fl->fl_ops = NULL; 176 } 177 178 if (fl->fl_lmops) { 179 if (fl->fl_lmops->fl_release_private) 180 fl->fl_lmops->fl_release_private(fl); 181 fl->fl_lmops = NULL; 182 } 183 184 kmem_cache_free(filelock_cache, fl); 185 } 186 187 void locks_init_lock(struct file_lock *fl) 188 { 189 INIT_LIST_HEAD(&fl->fl_link); 190 INIT_LIST_HEAD(&fl->fl_block); 191 init_waitqueue_head(&fl->fl_wait); 192 fl->fl_next = NULL; 193 fl->fl_fasync = NULL; 194 fl->fl_owner = NULL; 195 fl->fl_pid = 0; 196 fl->fl_file = NULL; 197 fl->fl_flags = 0; 198 fl->fl_type = 0; 199 fl->fl_start = fl->fl_end = 0; 200 fl->fl_ops = NULL; 201 fl->fl_lmops = NULL; 202 } 203 204 EXPORT_SYMBOL(locks_init_lock); 205 206 /* 207 * Initialises the fields of the file lock which are invariant for 208 * free file_locks. 209 */ 210 static void init_once(void *foo, kmem_cache_t *cache, unsigned long flags) 211 { 212 struct file_lock *lock = (struct file_lock *) foo; 213 214 if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) != 215 SLAB_CTOR_CONSTRUCTOR) 216 return; 217 218 locks_init_lock(lock); 219 } 220 221 /* 222 * Initialize a new lock from an existing file_lock structure. 223 */ 224 void locks_copy_lock(struct file_lock *new, struct file_lock *fl) 225 { 226 new->fl_owner = fl->fl_owner; 227 new->fl_pid = fl->fl_pid; 228 new->fl_file = fl->fl_file; 229 new->fl_flags = fl->fl_flags; 230 new->fl_type = fl->fl_type; 231 new->fl_start = fl->fl_start; 232 new->fl_end = fl->fl_end; 233 new->fl_ops = fl->fl_ops; 234 new->fl_lmops = fl->fl_lmops; 235 if (fl->fl_ops && fl->fl_ops->fl_copy_lock) 236 fl->fl_ops->fl_copy_lock(new, fl); 237 if (fl->fl_lmops && fl->fl_lmops->fl_copy_lock) 238 fl->fl_lmops->fl_copy_lock(new, fl); 239 } 240 241 EXPORT_SYMBOL(locks_copy_lock); 242 243 static inline int flock_translate_cmd(int cmd) { 244 if (cmd & LOCK_MAND) 245 return cmd & (LOCK_MAND | LOCK_RW); 246 switch (cmd) { 247 case LOCK_SH: 248 return F_RDLCK; 249 case LOCK_EX: 250 return F_WRLCK; 251 case LOCK_UN: 252 return F_UNLCK; 253 } 254 return -EINVAL; 255 } 256 257 /* Fill in a file_lock structure with an appropriate FLOCK lock. */ 258 static int flock_make_lock(struct file *filp, struct file_lock **lock, 259 unsigned int cmd) 260 { 261 struct file_lock *fl; 262 int type = flock_translate_cmd(cmd); 263 if (type < 0) 264 return type; 265 266 fl = locks_alloc_lock(); 267 if (fl == NULL) 268 return -ENOMEM; 269 270 fl->fl_file = filp; 271 fl->fl_pid = current->tgid; 272 fl->fl_flags = FL_FLOCK; 273 fl->fl_type = type; 274 fl->fl_end = OFFSET_MAX; 275 276 *lock = fl; 277 return 0; 278 } 279 280 static int assign_type(struct file_lock *fl, int type) 281 { 282 switch (type) { 283 case F_RDLCK: 284 case F_WRLCK: 285 case F_UNLCK: 286 fl->fl_type = type; 287 break; 288 default: 289 return -EINVAL; 290 } 291 return 0; 292 } 293 294 /* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX 295 * style lock. 296 */ 297 static int flock_to_posix_lock(struct file *filp, struct file_lock *fl, 298 struct flock *l) 299 { 300 off_t start, end; 301 302 switch (l->l_whence) { 303 case 0: /*SEEK_SET*/ 304 start = 0; 305 break; 306 case 1: /*SEEK_CUR*/ 307 start = filp->f_pos; 308 break; 309 case 2: /*SEEK_END*/ 310 start = i_size_read(filp->f_dentry->d_inode); 311 break; 312 default: 313 return -EINVAL; 314 } 315 316 /* POSIX-1996 leaves the case l->l_len < 0 undefined; 317 POSIX-2001 defines it. */ 318 start += l->l_start; 319 if (start < 0) 320 return -EINVAL; 321 fl->fl_end = OFFSET_MAX; 322 if (l->l_len > 0) { 323 end = start + l->l_len - 1; 324 fl->fl_end = end; 325 } else if (l->l_len < 0) { 326 end = start - 1; 327 fl->fl_end = end; 328 start += l->l_len; 329 if (start < 0) 330 return -EINVAL; 331 } 332 fl->fl_start = start; /* we record the absolute position */ 333 if (fl->fl_end < fl->fl_start) 334 return -EOVERFLOW; 335 336 fl->fl_owner = current->files; 337 fl->fl_pid = current->tgid; 338 fl->fl_file = filp; 339 fl->fl_flags = FL_POSIX; 340 fl->fl_ops = NULL; 341 fl->fl_lmops = NULL; 342 343 return assign_type(fl, l->l_type); 344 } 345 346 #if BITS_PER_LONG == 32 347 static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl, 348 struct flock64 *l) 349 { 350 loff_t start; 351 352 switch (l->l_whence) { 353 case 0: /*SEEK_SET*/ 354 start = 0; 355 break; 356 case 1: /*SEEK_CUR*/ 357 start = filp->f_pos; 358 break; 359 case 2: /*SEEK_END*/ 360 start = i_size_read(filp->f_dentry->d_inode); 361 break; 362 default: 363 return -EINVAL; 364 } 365 366 start += l->l_start; 367 if (start < 0) 368 return -EINVAL; 369 fl->fl_end = OFFSET_MAX; 370 if (l->l_len > 0) { 371 fl->fl_end = start + l->l_len - 1; 372 } else if (l->l_len < 0) { 373 fl->fl_end = start - 1; 374 start += l->l_len; 375 if (start < 0) 376 return -EINVAL; 377 } 378 fl->fl_start = start; /* we record the absolute position */ 379 if (fl->fl_end < fl->fl_start) 380 return -EOVERFLOW; 381 382 fl->fl_owner = current->files; 383 fl->fl_pid = current->tgid; 384 fl->fl_file = filp; 385 fl->fl_flags = FL_POSIX; 386 fl->fl_ops = NULL; 387 fl->fl_lmops = NULL; 388 389 switch (l->l_type) { 390 case F_RDLCK: 391 case F_WRLCK: 392 case F_UNLCK: 393 fl->fl_type = l->l_type; 394 break; 395 default: 396 return -EINVAL; 397 } 398 399 return (0); 400 } 401 #endif 402 403 /* default lease lock manager operations */ 404 static void lease_break_callback(struct file_lock *fl) 405 { 406 kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG); 407 } 408 409 static void lease_release_private_callback(struct file_lock *fl) 410 { 411 if (!fl->fl_file) 412 return; 413 414 f_delown(fl->fl_file); 415 fl->fl_file->f_owner.signum = 0; 416 } 417 418 static int lease_mylease_callback(struct file_lock *fl, struct file_lock *try) 419 { 420 return fl->fl_file == try->fl_file; 421 } 422 423 static struct lock_manager_operations lease_manager_ops = { 424 .fl_break = lease_break_callback, 425 .fl_release_private = lease_release_private_callback, 426 .fl_mylease = lease_mylease_callback, 427 .fl_change = lease_modify, 428 }; 429 430 /* 431 * Initialize a lease, use the default lock manager operations 432 */ 433 static int lease_init(struct file *filp, int type, struct file_lock *fl) 434 { 435 fl->fl_owner = current->files; 436 fl->fl_pid = current->tgid; 437 438 fl->fl_file = filp; 439 fl->fl_flags = FL_LEASE; 440 if (assign_type(fl, type) != 0) { 441 locks_free_lock(fl); 442 return -EINVAL; 443 } 444 fl->fl_start = 0; 445 fl->fl_end = OFFSET_MAX; 446 fl->fl_ops = NULL; 447 fl->fl_lmops = &lease_manager_ops; 448 return 0; 449 } 450 451 /* Allocate a file_lock initialised to this type of lease */ 452 static int lease_alloc(struct file *filp, int type, struct file_lock **flp) 453 { 454 struct file_lock *fl = locks_alloc_lock(); 455 int error; 456 457 if (fl == NULL) 458 return -ENOMEM; 459 460 error = lease_init(filp, type, fl); 461 if (error) 462 return error; 463 *flp = fl; 464 return 0; 465 } 466 467 /* Check if two locks overlap each other. 468 */ 469 static inline int locks_overlap(struct file_lock *fl1, struct file_lock *fl2) 470 { 471 return ((fl1->fl_end >= fl2->fl_start) && 472 (fl2->fl_end >= fl1->fl_start)); 473 } 474 475 /* 476 * Check whether two locks have the same owner. 477 */ 478 static inline int 479 posix_same_owner(struct file_lock *fl1, struct file_lock *fl2) 480 { 481 if (fl1->fl_lmops && fl1->fl_lmops->fl_compare_owner) 482 return fl2->fl_lmops == fl1->fl_lmops && 483 fl1->fl_lmops->fl_compare_owner(fl1, fl2); 484 return fl1->fl_owner == fl2->fl_owner; 485 } 486 487 /* Remove waiter from blocker's block list. 488 * When blocker ends up pointing to itself then the list is empty. 489 */ 490 static inline void __locks_delete_block(struct file_lock *waiter) 491 { 492 list_del_init(&waiter->fl_block); 493 list_del_init(&waiter->fl_link); 494 waiter->fl_next = NULL; 495 } 496 497 /* 498 */ 499 static void locks_delete_block(struct file_lock *waiter) 500 { 501 lock_kernel(); 502 __locks_delete_block(waiter); 503 unlock_kernel(); 504 } 505 506 /* Insert waiter into blocker's block list. 507 * We use a circular list so that processes can be easily woken up in 508 * the order they blocked. The documentation doesn't require this but 509 * it seems like the reasonable thing to do. 510 */ 511 static void locks_insert_block(struct file_lock *blocker, 512 struct file_lock *waiter) 513 { 514 if (!list_empty(&waiter->fl_block)) { 515 printk(KERN_ERR "locks_insert_block: removing duplicated lock " 516 "(pid=%d %Ld-%Ld type=%d)\n", waiter->fl_pid, 517 waiter->fl_start, waiter->fl_end, waiter->fl_type); 518 __locks_delete_block(waiter); 519 } 520 list_add_tail(&waiter->fl_block, &blocker->fl_block); 521 waiter->fl_next = blocker; 522 if (IS_POSIX(blocker)) 523 list_add(&waiter->fl_link, &blocked_list); 524 } 525 526 /* Wake up processes blocked waiting for blocker. 527 * If told to wait then schedule the processes until the block list 528 * is empty, otherwise empty the block list ourselves. 529 */ 530 static void locks_wake_up_blocks(struct file_lock *blocker) 531 { 532 while (!list_empty(&blocker->fl_block)) { 533 struct file_lock *waiter = list_entry(blocker->fl_block.next, 534 struct file_lock, fl_block); 535 __locks_delete_block(waiter); 536 if (waiter->fl_lmops && waiter->fl_lmops->fl_notify) 537 waiter->fl_lmops->fl_notify(waiter); 538 else 539 wake_up(&waiter->fl_wait); 540 } 541 } 542 543 /* Insert file lock fl into an inode's lock list at the position indicated 544 * by pos. At the same time add the lock to the global file lock list. 545 */ 546 static void locks_insert_lock(struct file_lock **pos, struct file_lock *fl) 547 { 548 list_add(&fl->fl_link, &file_lock_list); 549 550 /* insert into file's list */ 551 fl->fl_next = *pos; 552 *pos = fl; 553 554 if (fl->fl_ops && fl->fl_ops->fl_insert) 555 fl->fl_ops->fl_insert(fl); 556 } 557 558 /* 559 * Delete a lock and then free it. 560 * Wake up processes that are blocked waiting for this lock, 561 * notify the FS that the lock has been cleared and 562 * finally free the lock. 563 */ 564 static void locks_delete_lock(struct file_lock **thisfl_p) 565 { 566 struct file_lock *fl = *thisfl_p; 567 568 *thisfl_p = fl->fl_next; 569 fl->fl_next = NULL; 570 list_del_init(&fl->fl_link); 571 572 fasync_helper(0, fl->fl_file, 0, &fl->fl_fasync); 573 if (fl->fl_fasync != NULL) { 574 printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync); 575 fl->fl_fasync = NULL; 576 } 577 578 if (fl->fl_ops && fl->fl_ops->fl_remove) 579 fl->fl_ops->fl_remove(fl); 580 581 locks_wake_up_blocks(fl); 582 locks_free_lock(fl); 583 } 584 585 /* Determine if lock sys_fl blocks lock caller_fl. Common functionality 586 * checks for shared/exclusive status of overlapping locks. 587 */ 588 static int locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl) 589 { 590 if (sys_fl->fl_type == F_WRLCK) 591 return 1; 592 if (caller_fl->fl_type == F_WRLCK) 593 return 1; 594 return 0; 595 } 596 597 /* Determine if lock sys_fl blocks lock caller_fl. POSIX specific 598 * checking before calling the locks_conflict(). 599 */ 600 static int posix_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl) 601 { 602 /* POSIX locks owned by the same process do not conflict with 603 * each other. 604 */ 605 if (!IS_POSIX(sys_fl) || posix_same_owner(caller_fl, sys_fl)) 606 return (0); 607 608 /* Check whether they overlap */ 609 if (!locks_overlap(caller_fl, sys_fl)) 610 return 0; 611 612 return (locks_conflict(caller_fl, sys_fl)); 613 } 614 615 /* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific 616 * checking before calling the locks_conflict(). 617 */ 618 static int flock_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl) 619 { 620 /* FLOCK locks referring to the same filp do not conflict with 621 * each other. 622 */ 623 if (!IS_FLOCK(sys_fl) || (caller_fl->fl_file == sys_fl->fl_file)) 624 return (0); 625 if ((caller_fl->fl_type & LOCK_MAND) || (sys_fl->fl_type & LOCK_MAND)) 626 return 0; 627 628 return (locks_conflict(caller_fl, sys_fl)); 629 } 630 631 static int interruptible_sleep_on_locked(wait_queue_head_t *fl_wait, int timeout) 632 { 633 int result = 0; 634 DECLARE_WAITQUEUE(wait, current); 635 636 __set_current_state(TASK_INTERRUPTIBLE); 637 add_wait_queue(fl_wait, &wait); 638 if (timeout == 0) 639 schedule(); 640 else 641 result = schedule_timeout(timeout); 642 if (signal_pending(current)) 643 result = -ERESTARTSYS; 644 remove_wait_queue(fl_wait, &wait); 645 __set_current_state(TASK_RUNNING); 646 return result; 647 } 648 649 static int locks_block_on_timeout(struct file_lock *blocker, struct file_lock *waiter, int time) 650 { 651 int result; 652 locks_insert_block(blocker, waiter); 653 result = interruptible_sleep_on_locked(&waiter->fl_wait, time); 654 __locks_delete_block(waiter); 655 return result; 656 } 657 658 struct file_lock * 659 posix_test_lock(struct file *filp, struct file_lock *fl) 660 { 661 struct file_lock *cfl; 662 663 lock_kernel(); 664 for (cfl = filp->f_dentry->d_inode->i_flock; cfl; cfl = cfl->fl_next) { 665 if (!IS_POSIX(cfl)) 666 continue; 667 if (posix_locks_conflict(cfl, fl)) 668 break; 669 } 670 unlock_kernel(); 671 672 return (cfl); 673 } 674 675 EXPORT_SYMBOL(posix_test_lock); 676 677 /* This function tests for deadlock condition before putting a process to 678 * sleep. The detection scheme is no longer recursive. Recursive was neat, 679 * but dangerous - we risked stack corruption if the lock data was bad, or 680 * if the recursion was too deep for any other reason. 681 * 682 * We rely on the fact that a task can only be on one lock's wait queue 683 * at a time. When we find blocked_task on a wait queue we can re-search 684 * with blocked_task equal to that queue's owner, until either blocked_task 685 * isn't found, or blocked_task is found on a queue owned by my_task. 686 * 687 * Note: the above assumption may not be true when handling lock requests 688 * from a broken NFS client. But broken NFS clients have a lot more to 689 * worry about than proper deadlock detection anyway... --okir 690 */ 691 int posix_locks_deadlock(struct file_lock *caller_fl, 692 struct file_lock *block_fl) 693 { 694 struct list_head *tmp; 695 696 next_task: 697 if (posix_same_owner(caller_fl, block_fl)) 698 return 1; 699 list_for_each(tmp, &blocked_list) { 700 struct file_lock *fl = list_entry(tmp, struct file_lock, fl_link); 701 if (posix_same_owner(fl, block_fl)) { 702 fl = fl->fl_next; 703 block_fl = fl; 704 goto next_task; 705 } 706 } 707 return 0; 708 } 709 710 EXPORT_SYMBOL(posix_locks_deadlock); 711 712 /* Try to create a FLOCK lock on filp. We always insert new FLOCK locks 713 * at the head of the list, but that's secret knowledge known only to 714 * flock_lock_file and posix_lock_file. 715 */ 716 static int flock_lock_file(struct file *filp, struct file_lock *new_fl) 717 { 718 struct file_lock **before; 719 struct inode * inode = filp->f_dentry->d_inode; 720 int error = 0; 721 int found = 0; 722 723 lock_kernel(); 724 for_each_lock(inode, before) { 725 struct file_lock *fl = *before; 726 if (IS_POSIX(fl)) 727 break; 728 if (IS_LEASE(fl)) 729 continue; 730 if (filp != fl->fl_file) 731 continue; 732 if (new_fl->fl_type == fl->fl_type) 733 goto out; 734 found = 1; 735 locks_delete_lock(before); 736 break; 737 } 738 unlock_kernel(); 739 740 if (new_fl->fl_type == F_UNLCK) 741 return 0; 742 743 /* 744 * If a higher-priority process was blocked on the old file lock, 745 * give it the opportunity to lock the file. 746 */ 747 if (found) 748 cond_resched(); 749 750 lock_kernel(); 751 for_each_lock(inode, before) { 752 struct file_lock *fl = *before; 753 if (IS_POSIX(fl)) 754 break; 755 if (IS_LEASE(fl)) 756 continue; 757 if (!flock_locks_conflict(new_fl, fl)) 758 continue; 759 error = -EAGAIN; 760 if (new_fl->fl_flags & FL_SLEEP) { 761 locks_insert_block(fl, new_fl); 762 } 763 goto out; 764 } 765 locks_insert_lock(&inode->i_flock, new_fl); 766 error = 0; 767 768 out: 769 unlock_kernel(); 770 return error; 771 } 772 773 EXPORT_SYMBOL(posix_lock_file); 774 775 static int __posix_lock_file(struct inode *inode, struct file_lock *request) 776 { 777 struct file_lock *fl; 778 struct file_lock *new_fl, *new_fl2; 779 struct file_lock *left = NULL; 780 struct file_lock *right = NULL; 781 struct file_lock **before; 782 int error, added = 0; 783 784 /* 785 * We may need two file_lock structures for this operation, 786 * so we get them in advance to avoid races. 787 */ 788 new_fl = locks_alloc_lock(); 789 new_fl2 = locks_alloc_lock(); 790 791 lock_kernel(); 792 if (request->fl_type != F_UNLCK) { 793 for_each_lock(inode, before) { 794 struct file_lock *fl = *before; 795 if (!IS_POSIX(fl)) 796 continue; 797 if (!posix_locks_conflict(request, fl)) 798 continue; 799 error = -EAGAIN; 800 if (!(request->fl_flags & FL_SLEEP)) 801 goto out; 802 error = -EDEADLK; 803 if (posix_locks_deadlock(request, fl)) 804 goto out; 805 error = -EAGAIN; 806 locks_insert_block(fl, request); 807 goto out; 808 } 809 } 810 811 /* If we're just looking for a conflict, we're done. */ 812 error = 0; 813 if (request->fl_flags & FL_ACCESS) 814 goto out; 815 816 error = -ENOLCK; /* "no luck" */ 817 if (!(new_fl && new_fl2)) 818 goto out; 819 820 /* 821 * We've allocated the new locks in advance, so there are no 822 * errors possible (and no blocking operations) from here on. 823 * 824 * Find the first old lock with the same owner as the new lock. 825 */ 826 827 before = &inode->i_flock; 828 829 /* First skip locks owned by other processes. */ 830 while ((fl = *before) && (!IS_POSIX(fl) || 831 !posix_same_owner(request, fl))) { 832 before = &fl->fl_next; 833 } 834 835 /* Process locks with this owner. */ 836 while ((fl = *before) && posix_same_owner(request, fl)) { 837 /* Detect adjacent or overlapping regions (if same lock type) 838 */ 839 if (request->fl_type == fl->fl_type) { 840 /* In all comparisons of start vs end, use 841 * "start - 1" rather than "end + 1". If end 842 * is OFFSET_MAX, end + 1 will become negative. 843 */ 844 if (fl->fl_end < request->fl_start - 1) 845 goto next_lock; 846 /* If the next lock in the list has entirely bigger 847 * addresses than the new one, insert the lock here. 848 */ 849 if (fl->fl_start - 1 > request->fl_end) 850 break; 851 852 /* If we come here, the new and old lock are of the 853 * same type and adjacent or overlapping. Make one 854 * lock yielding from the lower start address of both 855 * locks to the higher end address. 856 */ 857 if (fl->fl_start > request->fl_start) 858 fl->fl_start = request->fl_start; 859 else 860 request->fl_start = fl->fl_start; 861 if (fl->fl_end < request->fl_end) 862 fl->fl_end = request->fl_end; 863 else 864 request->fl_end = fl->fl_end; 865 if (added) { 866 locks_delete_lock(before); 867 continue; 868 } 869 request = fl; 870 added = 1; 871 } 872 else { 873 /* Processing for different lock types is a bit 874 * more complex. 875 */ 876 if (fl->fl_end < request->fl_start) 877 goto next_lock; 878 if (fl->fl_start > request->fl_end) 879 break; 880 if (request->fl_type == F_UNLCK) 881 added = 1; 882 if (fl->fl_start < request->fl_start) 883 left = fl; 884 /* If the next lock in the list has a higher end 885 * address than the new one, insert the new one here. 886 */ 887 if (fl->fl_end > request->fl_end) { 888 right = fl; 889 break; 890 } 891 if (fl->fl_start >= request->fl_start) { 892 /* The new lock completely replaces an old 893 * one (This may happen several times). 894 */ 895 if (added) { 896 locks_delete_lock(before); 897 continue; 898 } 899 /* Replace the old lock with the new one. 900 * Wake up anybody waiting for the old one, 901 * as the change in lock type might satisfy 902 * their needs. 903 */ 904 locks_wake_up_blocks(fl); 905 fl->fl_start = request->fl_start; 906 fl->fl_end = request->fl_end; 907 fl->fl_type = request->fl_type; 908 fl->fl_u = request->fl_u; 909 request = fl; 910 added = 1; 911 } 912 } 913 /* Go on to next lock. 914 */ 915 next_lock: 916 before = &fl->fl_next; 917 } 918 919 error = 0; 920 if (!added) { 921 if (request->fl_type == F_UNLCK) 922 goto out; 923 locks_copy_lock(new_fl, request); 924 locks_insert_lock(before, new_fl); 925 new_fl = NULL; 926 } 927 if (right) { 928 if (left == right) { 929 /* The new lock breaks the old one in two pieces, 930 * so we have to use the second new lock. 931 */ 932 left = new_fl2; 933 new_fl2 = NULL; 934 locks_copy_lock(left, right); 935 locks_insert_lock(before, left); 936 } 937 right->fl_start = request->fl_end + 1; 938 locks_wake_up_blocks(right); 939 } 940 if (left) { 941 left->fl_end = request->fl_start - 1; 942 locks_wake_up_blocks(left); 943 } 944 out: 945 unlock_kernel(); 946 /* 947 * Free any unused locks. 948 */ 949 if (new_fl) 950 locks_free_lock(new_fl); 951 if (new_fl2) 952 locks_free_lock(new_fl2); 953 return error; 954 } 955 956 /** 957 * posix_lock_file - Apply a POSIX-style lock to a file 958 * @filp: The file to apply the lock to 959 * @fl: The lock to be applied 960 * 961 * Add a POSIX style lock to a file. 962 * We merge adjacent & overlapping locks whenever possible. 963 * POSIX locks are sorted by owner task, then by starting address 964 */ 965 int posix_lock_file(struct file *filp, struct file_lock *fl) 966 { 967 return __posix_lock_file(filp->f_dentry->d_inode, fl); 968 } 969 970 /** 971 * posix_lock_file_wait - Apply a POSIX-style lock to a file 972 * @filp: The file to apply the lock to 973 * @fl: The lock to be applied 974 * 975 * Add a POSIX style lock to a file. 976 * We merge adjacent & overlapping locks whenever possible. 977 * POSIX locks are sorted by owner task, then by starting address 978 */ 979 int posix_lock_file_wait(struct file *filp, struct file_lock *fl) 980 { 981 int error; 982 might_sleep (); 983 for (;;) { 984 error = __posix_lock_file(filp->f_dentry->d_inode, fl); 985 if ((error != -EAGAIN) || !(fl->fl_flags & FL_SLEEP)) 986 break; 987 error = wait_event_interruptible(fl->fl_wait, !fl->fl_next); 988 if (!error) 989 continue; 990 991 locks_delete_block(fl); 992 break; 993 } 994 return error; 995 } 996 EXPORT_SYMBOL(posix_lock_file_wait); 997 998 /** 999 * locks_mandatory_locked - Check for an active lock 1000 * @inode: the file to check 1001 * 1002 * Searches the inode's list of locks to find any POSIX locks which conflict. 1003 * This function is called from locks_verify_locked() only. 1004 */ 1005 int locks_mandatory_locked(struct inode *inode) 1006 { 1007 fl_owner_t owner = current->files; 1008 struct file_lock *fl; 1009 1010 /* 1011 * Search the lock list for this inode for any POSIX locks. 1012 */ 1013 lock_kernel(); 1014 for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) { 1015 if (!IS_POSIX(fl)) 1016 continue; 1017 if (fl->fl_owner != owner) 1018 break; 1019 } 1020 unlock_kernel(); 1021 return fl ? -EAGAIN : 0; 1022 } 1023 1024 /** 1025 * locks_mandatory_area - Check for a conflicting lock 1026 * @read_write: %FLOCK_VERIFY_WRITE for exclusive access, %FLOCK_VERIFY_READ 1027 * for shared 1028 * @inode: the file to check 1029 * @filp: how the file was opened (if it was) 1030 * @offset: start of area to check 1031 * @count: length of area to check 1032 * 1033 * Searches the inode's list of locks to find any POSIX locks which conflict. 1034 * This function is called from rw_verify_area() and 1035 * locks_verify_truncate(). 1036 */ 1037 int locks_mandatory_area(int read_write, struct inode *inode, 1038 struct file *filp, loff_t offset, 1039 size_t count) 1040 { 1041 struct file_lock fl; 1042 int error; 1043 1044 locks_init_lock(&fl); 1045 fl.fl_owner = current->files; 1046 fl.fl_pid = current->tgid; 1047 fl.fl_file = filp; 1048 fl.fl_flags = FL_POSIX | FL_ACCESS; 1049 if (filp && !(filp->f_flags & O_NONBLOCK)) 1050 fl.fl_flags |= FL_SLEEP; 1051 fl.fl_type = (read_write == FLOCK_VERIFY_WRITE) ? F_WRLCK : F_RDLCK; 1052 fl.fl_start = offset; 1053 fl.fl_end = offset + count - 1; 1054 1055 for (;;) { 1056 error = __posix_lock_file(inode, &fl); 1057 if (error != -EAGAIN) 1058 break; 1059 if (!(fl.fl_flags & FL_SLEEP)) 1060 break; 1061 error = wait_event_interruptible(fl.fl_wait, !fl.fl_next); 1062 if (!error) { 1063 /* 1064 * If we've been sleeping someone might have 1065 * changed the permissions behind our back. 1066 */ 1067 if ((inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID) 1068 continue; 1069 } 1070 1071 locks_delete_block(&fl); 1072 break; 1073 } 1074 1075 return error; 1076 } 1077 1078 EXPORT_SYMBOL(locks_mandatory_area); 1079 1080 /* We already had a lease on this file; just change its type */ 1081 int lease_modify(struct file_lock **before, int arg) 1082 { 1083 struct file_lock *fl = *before; 1084 int error = assign_type(fl, arg); 1085 1086 if (error) 1087 return error; 1088 locks_wake_up_blocks(fl); 1089 if (arg == F_UNLCK) 1090 locks_delete_lock(before); 1091 return 0; 1092 } 1093 1094 EXPORT_SYMBOL(lease_modify); 1095 1096 static void time_out_leases(struct inode *inode) 1097 { 1098 struct file_lock **before; 1099 struct file_lock *fl; 1100 1101 before = &inode->i_flock; 1102 while ((fl = *before) && IS_LEASE(fl) && (fl->fl_type & F_INPROGRESS)) { 1103 if ((fl->fl_break_time == 0) 1104 || time_before(jiffies, fl->fl_break_time)) { 1105 before = &fl->fl_next; 1106 continue; 1107 } 1108 printk(KERN_INFO "lease broken - owner pid = %d\n", fl->fl_pid); 1109 lease_modify(before, fl->fl_type & ~F_INPROGRESS); 1110 if (fl == *before) /* lease_modify may have freed fl */ 1111 before = &fl->fl_next; 1112 } 1113 } 1114 1115 /** 1116 * __break_lease - revoke all outstanding leases on file 1117 * @inode: the inode of the file to return 1118 * @mode: the open mode (read or write) 1119 * 1120 * break_lease (inlined for speed) has checked there already 1121 * is a lease on this file. Leases are broken on a call to open() 1122 * or truncate(). This function can sleep unless you 1123 * specified %O_NONBLOCK to your open(). 1124 */ 1125 int __break_lease(struct inode *inode, unsigned int mode) 1126 { 1127 int error = 0, future; 1128 struct file_lock *new_fl, *flock; 1129 struct file_lock *fl; 1130 int alloc_err; 1131 unsigned long break_time; 1132 int i_have_this_lease = 0; 1133 1134 alloc_err = lease_alloc(NULL, mode & FMODE_WRITE ? F_WRLCK : F_RDLCK, 1135 &new_fl); 1136 1137 lock_kernel(); 1138 1139 time_out_leases(inode); 1140 1141 flock = inode->i_flock; 1142 if ((flock == NULL) || !IS_LEASE(flock)) 1143 goto out; 1144 1145 for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next) 1146 if (fl->fl_owner == current->files) 1147 i_have_this_lease = 1; 1148 1149 if (mode & FMODE_WRITE) { 1150 /* If we want write access, we have to revoke any lease. */ 1151 future = F_UNLCK | F_INPROGRESS; 1152 } else if (flock->fl_type & F_INPROGRESS) { 1153 /* If the lease is already being broken, we just leave it */ 1154 future = flock->fl_type; 1155 } else if (flock->fl_type & F_WRLCK) { 1156 /* Downgrade the exclusive lease to a read-only lease. */ 1157 future = F_RDLCK | F_INPROGRESS; 1158 } else { 1159 /* the existing lease was read-only, so we can read too. */ 1160 goto out; 1161 } 1162 1163 if (alloc_err && !i_have_this_lease && ((mode & O_NONBLOCK) == 0)) { 1164 error = alloc_err; 1165 goto out; 1166 } 1167 1168 break_time = 0; 1169 if (lease_break_time > 0) { 1170 break_time = jiffies + lease_break_time * HZ; 1171 if (break_time == 0) 1172 break_time++; /* so that 0 means no break time */ 1173 } 1174 1175 for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next) { 1176 if (fl->fl_type != future) { 1177 fl->fl_type = future; 1178 fl->fl_break_time = break_time; 1179 /* lease must have lmops break callback */ 1180 fl->fl_lmops->fl_break(fl); 1181 } 1182 } 1183 1184 if (i_have_this_lease || (mode & O_NONBLOCK)) { 1185 error = -EWOULDBLOCK; 1186 goto out; 1187 } 1188 1189 restart: 1190 break_time = flock->fl_break_time; 1191 if (break_time != 0) { 1192 break_time -= jiffies; 1193 if (break_time == 0) 1194 break_time++; 1195 } 1196 error = locks_block_on_timeout(flock, new_fl, break_time); 1197 if (error >= 0) { 1198 if (error == 0) 1199 time_out_leases(inode); 1200 /* Wait for the next lease that has not been broken yet */ 1201 for (flock = inode->i_flock; flock && IS_LEASE(flock); 1202 flock = flock->fl_next) { 1203 if (flock->fl_type & F_INPROGRESS) 1204 goto restart; 1205 } 1206 error = 0; 1207 } 1208 1209 out: 1210 unlock_kernel(); 1211 if (!alloc_err) 1212 locks_free_lock(new_fl); 1213 return error; 1214 } 1215 1216 EXPORT_SYMBOL(__break_lease); 1217 1218 /** 1219 * lease_get_mtime 1220 * @inode: the inode 1221 * @time: pointer to a timespec which will contain the last modified time 1222 * 1223 * This is to force NFS clients to flush their caches for files with 1224 * exclusive leases. The justification is that if someone has an 1225 * exclusive lease, then they could be modifiying it. 1226 */ 1227 void lease_get_mtime(struct inode *inode, struct timespec *time) 1228 { 1229 struct file_lock *flock = inode->i_flock; 1230 if (flock && IS_LEASE(flock) && (flock->fl_type & F_WRLCK)) 1231 *time = current_fs_time(inode->i_sb); 1232 else 1233 *time = inode->i_mtime; 1234 } 1235 1236 EXPORT_SYMBOL(lease_get_mtime); 1237 1238 /** 1239 * fcntl_getlease - Enquire what lease is currently active 1240 * @filp: the file 1241 * 1242 * The value returned by this function will be one of 1243 * (if no lease break is pending): 1244 * 1245 * %F_RDLCK to indicate a shared lease is held. 1246 * 1247 * %F_WRLCK to indicate an exclusive lease is held. 1248 * 1249 * %F_UNLCK to indicate no lease is held. 1250 * 1251 * (if a lease break is pending): 1252 * 1253 * %F_RDLCK to indicate an exclusive lease needs to be 1254 * changed to a shared lease (or removed). 1255 * 1256 * %F_UNLCK to indicate the lease needs to be removed. 1257 * 1258 * XXX: sfr & willy disagree over whether F_INPROGRESS 1259 * should be returned to userspace. 1260 */ 1261 int fcntl_getlease(struct file *filp) 1262 { 1263 struct file_lock *fl; 1264 int type = F_UNLCK; 1265 1266 lock_kernel(); 1267 time_out_leases(filp->f_dentry->d_inode); 1268 for (fl = filp->f_dentry->d_inode->i_flock; fl && IS_LEASE(fl); 1269 fl = fl->fl_next) { 1270 if (fl->fl_file == filp) { 1271 type = fl->fl_type & ~F_INPROGRESS; 1272 break; 1273 } 1274 } 1275 unlock_kernel(); 1276 return type; 1277 } 1278 1279 /** 1280 * __setlease - sets a lease on an open file 1281 * @filp: file pointer 1282 * @arg: type of lease to obtain 1283 * @flp: input - file_lock to use, output - file_lock inserted 1284 * 1285 * The (input) flp->fl_lmops->fl_break function is required 1286 * by break_lease(). 1287 * 1288 * Called with kernel lock held. 1289 */ 1290 static int __setlease(struct file *filp, long arg, struct file_lock **flp) 1291 { 1292 struct file_lock *fl, **before, **my_before = NULL, *lease; 1293 struct dentry *dentry = filp->f_dentry; 1294 struct inode *inode = dentry->d_inode; 1295 int error, rdlease_count = 0, wrlease_count = 0; 1296 1297 time_out_leases(inode); 1298 1299 error = -EINVAL; 1300 if (!flp || !(*flp) || !(*flp)->fl_lmops || !(*flp)->fl_lmops->fl_break) 1301 goto out; 1302 1303 lease = *flp; 1304 1305 error = -EAGAIN; 1306 if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0)) 1307 goto out; 1308 if ((arg == F_WRLCK) 1309 && ((atomic_read(&dentry->d_count) > 1) 1310 || (atomic_read(&inode->i_count) > 1))) 1311 goto out; 1312 1313 /* 1314 * At this point, we know that if there is an exclusive 1315 * lease on this file, then we hold it on this filp 1316 * (otherwise our open of this file would have blocked). 1317 * And if we are trying to acquire an exclusive lease, 1318 * then the file is not open by anyone (including us) 1319 * except for this filp. 1320 */ 1321 for (before = &inode->i_flock; 1322 ((fl = *before) != NULL) && IS_LEASE(fl); 1323 before = &fl->fl_next) { 1324 if (lease->fl_lmops->fl_mylease(fl, lease)) 1325 my_before = before; 1326 else if (fl->fl_type == (F_INPROGRESS | F_UNLCK)) 1327 /* 1328 * Someone is in the process of opening this 1329 * file for writing so we may not take an 1330 * exclusive lease on it. 1331 */ 1332 wrlease_count++; 1333 else 1334 rdlease_count++; 1335 } 1336 1337 if ((arg == F_RDLCK && (wrlease_count > 0)) || 1338 (arg == F_WRLCK && ((rdlease_count + wrlease_count) > 0))) 1339 goto out; 1340 1341 if (my_before != NULL) { 1342 error = lease->fl_lmops->fl_change(my_before, arg); 1343 goto out; 1344 } 1345 1346 error = 0; 1347 if (arg == F_UNLCK) 1348 goto out; 1349 1350 error = -EINVAL; 1351 if (!leases_enable) 1352 goto out; 1353 1354 error = lease_alloc(filp, arg, &fl); 1355 if (error) 1356 goto out; 1357 1358 locks_copy_lock(fl, lease); 1359 1360 locks_insert_lock(before, fl); 1361 1362 *flp = fl; 1363 out: 1364 return error; 1365 } 1366 1367 /** 1368 * setlease - sets a lease on an open file 1369 * @filp: file pointer 1370 * @arg: type of lease to obtain 1371 * @lease: file_lock to use 1372 * 1373 * Call this to establish a lease on the file. 1374 * The fl_lmops fl_break function is required by break_lease 1375 */ 1376 1377 int setlease(struct file *filp, long arg, struct file_lock **lease) 1378 { 1379 struct dentry *dentry = filp->f_dentry; 1380 struct inode *inode = dentry->d_inode; 1381 int error; 1382 1383 if ((current->fsuid != inode->i_uid) && !capable(CAP_LEASE)) 1384 return -EACCES; 1385 if (!S_ISREG(inode->i_mode)) 1386 return -EINVAL; 1387 error = security_file_lock(filp, arg); 1388 if (error) 1389 return error; 1390 1391 lock_kernel(); 1392 error = __setlease(filp, arg, lease); 1393 unlock_kernel(); 1394 1395 return error; 1396 } 1397 1398 EXPORT_SYMBOL(setlease); 1399 1400 /** 1401 * fcntl_setlease - sets a lease on an open file 1402 * @fd: open file descriptor 1403 * @filp: file pointer 1404 * @arg: type of lease to obtain 1405 * 1406 * Call this fcntl to establish a lease on the file. 1407 * Note that you also need to call %F_SETSIG to 1408 * receive a signal when the lease is broken. 1409 */ 1410 int fcntl_setlease(unsigned int fd, struct file *filp, long arg) 1411 { 1412 struct file_lock fl, *flp = &fl; 1413 struct dentry *dentry = filp->f_dentry; 1414 struct inode *inode = dentry->d_inode; 1415 int error; 1416 1417 if ((current->fsuid != inode->i_uid) && !capable(CAP_LEASE)) 1418 return -EACCES; 1419 if (!S_ISREG(inode->i_mode)) 1420 return -EINVAL; 1421 error = security_file_lock(filp, arg); 1422 if (error) 1423 return error; 1424 1425 locks_init_lock(&fl); 1426 error = lease_init(filp, arg, &fl); 1427 if (error) 1428 return error; 1429 1430 lock_kernel(); 1431 1432 error = __setlease(filp, arg, &flp); 1433 if (error) 1434 goto out_unlock; 1435 1436 error = fasync_helper(fd, filp, 1, &flp->fl_fasync); 1437 if (error < 0) { 1438 /* remove lease just inserted by __setlease */ 1439 flp->fl_type = F_UNLCK | F_INPROGRESS; 1440 flp->fl_break_time = jiffies- 10; 1441 time_out_leases(inode); 1442 goto out_unlock; 1443 } 1444 1445 error = f_setown(filp, current->pid, 0); 1446 out_unlock: 1447 unlock_kernel(); 1448 return error; 1449 } 1450 1451 /** 1452 * flock_lock_file_wait - Apply a FLOCK-style lock to a file 1453 * @filp: The file to apply the lock to 1454 * @fl: The lock to be applied 1455 * 1456 * Add a FLOCK style lock to a file. 1457 */ 1458 int flock_lock_file_wait(struct file *filp, struct file_lock *fl) 1459 { 1460 int error; 1461 might_sleep(); 1462 for (;;) { 1463 error = flock_lock_file(filp, fl); 1464 if ((error != -EAGAIN) || !(fl->fl_flags & FL_SLEEP)) 1465 break; 1466 error = wait_event_interruptible(fl->fl_wait, !fl->fl_next); 1467 if (!error) 1468 continue; 1469 1470 locks_delete_block(fl); 1471 break; 1472 } 1473 return error; 1474 } 1475 1476 EXPORT_SYMBOL(flock_lock_file_wait); 1477 1478 /** 1479 * sys_flock: - flock() system call. 1480 * @fd: the file descriptor to lock. 1481 * @cmd: the type of lock to apply. 1482 * 1483 * Apply a %FL_FLOCK style lock to an open file descriptor. 1484 * The @cmd can be one of 1485 * 1486 * %LOCK_SH -- a shared lock. 1487 * 1488 * %LOCK_EX -- an exclusive lock. 1489 * 1490 * %LOCK_UN -- remove an existing lock. 1491 * 1492 * %LOCK_MAND -- a `mandatory' flock. This exists to emulate Windows Share Modes. 1493 * 1494 * %LOCK_MAND can be combined with %LOCK_READ or %LOCK_WRITE to allow other 1495 * processes read and write access respectively. 1496 */ 1497 asmlinkage long sys_flock(unsigned int fd, unsigned int cmd) 1498 { 1499 struct file *filp; 1500 struct file_lock *lock; 1501 int can_sleep, unlock; 1502 int error; 1503 1504 error = -EBADF; 1505 filp = fget(fd); 1506 if (!filp) 1507 goto out; 1508 1509 can_sleep = !(cmd & LOCK_NB); 1510 cmd &= ~LOCK_NB; 1511 unlock = (cmd == LOCK_UN); 1512 1513 if (!unlock && !(cmd & LOCK_MAND) && !(filp->f_mode & 3)) 1514 goto out_putf; 1515 1516 error = flock_make_lock(filp, &lock, cmd); 1517 if (error) 1518 goto out_putf; 1519 if (can_sleep) 1520 lock->fl_flags |= FL_SLEEP; 1521 1522 error = security_file_lock(filp, cmd); 1523 if (error) 1524 goto out_free; 1525 1526 if (filp->f_op && filp->f_op->flock) 1527 error = filp->f_op->flock(filp, 1528 (can_sleep) ? F_SETLKW : F_SETLK, 1529 lock); 1530 else 1531 error = flock_lock_file_wait(filp, lock); 1532 1533 out_free: 1534 if (list_empty(&lock->fl_link)) { 1535 locks_free_lock(lock); 1536 } 1537 1538 out_putf: 1539 fput(filp); 1540 out: 1541 return error; 1542 } 1543 1544 /* Report the first existing lock that would conflict with l. 1545 * This implements the F_GETLK command of fcntl(). 1546 */ 1547 int fcntl_getlk(struct file *filp, struct flock __user *l) 1548 { 1549 struct file_lock *fl, file_lock; 1550 struct flock flock; 1551 int error; 1552 1553 error = -EFAULT; 1554 if (copy_from_user(&flock, l, sizeof(flock))) 1555 goto out; 1556 error = -EINVAL; 1557 if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK)) 1558 goto out; 1559 1560 error = flock_to_posix_lock(filp, &file_lock, &flock); 1561 if (error) 1562 goto out; 1563 1564 if (filp->f_op && filp->f_op->lock) { 1565 error = filp->f_op->lock(filp, F_GETLK, &file_lock); 1566 if (file_lock.fl_ops && file_lock.fl_ops->fl_release_private) 1567 file_lock.fl_ops->fl_release_private(&file_lock); 1568 if (error < 0) 1569 goto out; 1570 else 1571 fl = (file_lock.fl_type == F_UNLCK ? NULL : &file_lock); 1572 } else { 1573 fl = posix_test_lock(filp, &file_lock); 1574 } 1575 1576 flock.l_type = F_UNLCK; 1577 if (fl != NULL) { 1578 flock.l_pid = fl->fl_pid; 1579 #if BITS_PER_LONG == 32 1580 /* 1581 * Make sure we can represent the posix lock via 1582 * legacy 32bit flock. 1583 */ 1584 error = -EOVERFLOW; 1585 if (fl->fl_start > OFFT_OFFSET_MAX) 1586 goto out; 1587 if ((fl->fl_end != OFFSET_MAX) 1588 && (fl->fl_end > OFFT_OFFSET_MAX)) 1589 goto out; 1590 #endif 1591 flock.l_start = fl->fl_start; 1592 flock.l_len = fl->fl_end == OFFSET_MAX ? 0 : 1593 fl->fl_end - fl->fl_start + 1; 1594 flock.l_whence = 0; 1595 flock.l_type = fl->fl_type; 1596 } 1597 error = -EFAULT; 1598 if (!copy_to_user(l, &flock, sizeof(flock))) 1599 error = 0; 1600 out: 1601 return error; 1602 } 1603 1604 /* Apply the lock described by l to an open file descriptor. 1605 * This implements both the F_SETLK and F_SETLKW commands of fcntl(). 1606 */ 1607 int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd, 1608 struct flock __user *l) 1609 { 1610 struct file_lock *file_lock = locks_alloc_lock(); 1611 struct flock flock; 1612 struct inode *inode; 1613 int error; 1614 1615 if (file_lock == NULL) 1616 return -ENOLCK; 1617 1618 /* 1619 * This might block, so we do it before checking the inode. 1620 */ 1621 error = -EFAULT; 1622 if (copy_from_user(&flock, l, sizeof(flock))) 1623 goto out; 1624 1625 inode = filp->f_dentry->d_inode; 1626 1627 /* Don't allow mandatory locks on files that may be memory mapped 1628 * and shared. 1629 */ 1630 if (IS_MANDLOCK(inode) && 1631 (inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID && 1632 mapping_writably_mapped(filp->f_mapping)) { 1633 error = -EAGAIN; 1634 goto out; 1635 } 1636 1637 again: 1638 error = flock_to_posix_lock(filp, file_lock, &flock); 1639 if (error) 1640 goto out; 1641 if (cmd == F_SETLKW) { 1642 file_lock->fl_flags |= FL_SLEEP; 1643 } 1644 1645 error = -EBADF; 1646 switch (flock.l_type) { 1647 case F_RDLCK: 1648 if (!(filp->f_mode & FMODE_READ)) 1649 goto out; 1650 break; 1651 case F_WRLCK: 1652 if (!(filp->f_mode & FMODE_WRITE)) 1653 goto out; 1654 break; 1655 case F_UNLCK: 1656 break; 1657 default: 1658 error = -EINVAL; 1659 goto out; 1660 } 1661 1662 error = security_file_lock(filp, file_lock->fl_type); 1663 if (error) 1664 goto out; 1665 1666 if (filp->f_op && filp->f_op->lock != NULL) 1667 error = filp->f_op->lock(filp, cmd, file_lock); 1668 else { 1669 for (;;) { 1670 error = __posix_lock_file(inode, file_lock); 1671 if ((error != -EAGAIN) || (cmd == F_SETLK)) 1672 break; 1673 error = wait_event_interruptible(file_lock->fl_wait, 1674 !file_lock->fl_next); 1675 if (!error) 1676 continue; 1677 1678 locks_delete_block(file_lock); 1679 break; 1680 } 1681 } 1682 1683 /* 1684 * Attempt to detect a close/fcntl race and recover by 1685 * releasing the lock that was just acquired. 1686 */ 1687 if (!error && fcheck(fd) != filp && flock.l_type != F_UNLCK) { 1688 flock.l_type = F_UNLCK; 1689 goto again; 1690 } 1691 1692 out: 1693 locks_free_lock(file_lock); 1694 return error; 1695 } 1696 1697 #if BITS_PER_LONG == 32 1698 /* Report the first existing lock that would conflict with l. 1699 * This implements the F_GETLK command of fcntl(). 1700 */ 1701 int fcntl_getlk64(struct file *filp, struct flock64 __user *l) 1702 { 1703 struct file_lock *fl, file_lock; 1704 struct flock64 flock; 1705 int error; 1706 1707 error = -EFAULT; 1708 if (copy_from_user(&flock, l, sizeof(flock))) 1709 goto out; 1710 error = -EINVAL; 1711 if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK)) 1712 goto out; 1713 1714 error = flock64_to_posix_lock(filp, &file_lock, &flock); 1715 if (error) 1716 goto out; 1717 1718 if (filp->f_op && filp->f_op->lock) { 1719 error = filp->f_op->lock(filp, F_GETLK, &file_lock); 1720 if (file_lock.fl_ops && file_lock.fl_ops->fl_release_private) 1721 file_lock.fl_ops->fl_release_private(&file_lock); 1722 if (error < 0) 1723 goto out; 1724 else 1725 fl = (file_lock.fl_type == F_UNLCK ? NULL : &file_lock); 1726 } else { 1727 fl = posix_test_lock(filp, &file_lock); 1728 } 1729 1730 flock.l_type = F_UNLCK; 1731 if (fl != NULL) { 1732 flock.l_pid = fl->fl_pid; 1733 flock.l_start = fl->fl_start; 1734 flock.l_len = fl->fl_end == OFFSET_MAX ? 0 : 1735 fl->fl_end - fl->fl_start + 1; 1736 flock.l_whence = 0; 1737 flock.l_type = fl->fl_type; 1738 } 1739 error = -EFAULT; 1740 if (!copy_to_user(l, &flock, sizeof(flock))) 1741 error = 0; 1742 1743 out: 1744 return error; 1745 } 1746 1747 /* Apply the lock described by l to an open file descriptor. 1748 * This implements both the F_SETLK and F_SETLKW commands of fcntl(). 1749 */ 1750 int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd, 1751 struct flock64 __user *l) 1752 { 1753 struct file_lock *file_lock = locks_alloc_lock(); 1754 struct flock64 flock; 1755 struct inode *inode; 1756 int error; 1757 1758 if (file_lock == NULL) 1759 return -ENOLCK; 1760 1761 /* 1762 * This might block, so we do it before checking the inode. 1763 */ 1764 error = -EFAULT; 1765 if (copy_from_user(&flock, l, sizeof(flock))) 1766 goto out; 1767 1768 inode = filp->f_dentry->d_inode; 1769 1770 /* Don't allow mandatory locks on files that may be memory mapped 1771 * and shared. 1772 */ 1773 if (IS_MANDLOCK(inode) && 1774 (inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID && 1775 mapping_writably_mapped(filp->f_mapping)) { 1776 error = -EAGAIN; 1777 goto out; 1778 } 1779 1780 again: 1781 error = flock64_to_posix_lock(filp, file_lock, &flock); 1782 if (error) 1783 goto out; 1784 if (cmd == F_SETLKW64) { 1785 file_lock->fl_flags |= FL_SLEEP; 1786 } 1787 1788 error = -EBADF; 1789 switch (flock.l_type) { 1790 case F_RDLCK: 1791 if (!(filp->f_mode & FMODE_READ)) 1792 goto out; 1793 break; 1794 case F_WRLCK: 1795 if (!(filp->f_mode & FMODE_WRITE)) 1796 goto out; 1797 break; 1798 case F_UNLCK: 1799 break; 1800 default: 1801 error = -EINVAL; 1802 goto out; 1803 } 1804 1805 error = security_file_lock(filp, file_lock->fl_type); 1806 if (error) 1807 goto out; 1808 1809 if (filp->f_op && filp->f_op->lock != NULL) 1810 error = filp->f_op->lock(filp, cmd, file_lock); 1811 else { 1812 for (;;) { 1813 error = __posix_lock_file(inode, file_lock); 1814 if ((error != -EAGAIN) || (cmd == F_SETLK64)) 1815 break; 1816 error = wait_event_interruptible(file_lock->fl_wait, 1817 !file_lock->fl_next); 1818 if (!error) 1819 continue; 1820 1821 locks_delete_block(file_lock); 1822 break; 1823 } 1824 } 1825 1826 /* 1827 * Attempt to detect a close/fcntl race and recover by 1828 * releasing the lock that was just acquired. 1829 */ 1830 if (!error && fcheck(fd) != filp && flock.l_type != F_UNLCK) { 1831 flock.l_type = F_UNLCK; 1832 goto again; 1833 } 1834 1835 out: 1836 locks_free_lock(file_lock); 1837 return error; 1838 } 1839 #endif /* BITS_PER_LONG == 32 */ 1840 1841 /* 1842 * This function is called when the file is being removed 1843 * from the task's fd array. POSIX locks belonging to this task 1844 * are deleted at this time. 1845 */ 1846 void locks_remove_posix(struct file *filp, fl_owner_t owner) 1847 { 1848 struct file_lock lock, **before; 1849 1850 /* 1851 * If there are no locks held on this file, we don't need to call 1852 * posix_lock_file(). Another process could be setting a lock on this 1853 * file at the same time, but we wouldn't remove that lock anyway. 1854 */ 1855 before = &filp->f_dentry->d_inode->i_flock; 1856 if (*before == NULL) 1857 return; 1858 1859 lock.fl_type = F_UNLCK; 1860 lock.fl_flags = FL_POSIX; 1861 lock.fl_start = 0; 1862 lock.fl_end = OFFSET_MAX; 1863 lock.fl_owner = owner; 1864 lock.fl_pid = current->tgid; 1865 lock.fl_file = filp; 1866 lock.fl_ops = NULL; 1867 lock.fl_lmops = NULL; 1868 1869 if (filp->f_op && filp->f_op->lock != NULL) { 1870 filp->f_op->lock(filp, F_SETLK, &lock); 1871 goto out; 1872 } 1873 1874 /* Can't use posix_lock_file here; we need to remove it no matter 1875 * which pid we have. 1876 */ 1877 lock_kernel(); 1878 while (*before != NULL) { 1879 struct file_lock *fl = *before; 1880 if (IS_POSIX(fl) && posix_same_owner(fl, &lock)) { 1881 locks_delete_lock(before); 1882 continue; 1883 } 1884 before = &fl->fl_next; 1885 } 1886 unlock_kernel(); 1887 out: 1888 if (lock.fl_ops && lock.fl_ops->fl_release_private) 1889 lock.fl_ops->fl_release_private(&lock); 1890 } 1891 1892 EXPORT_SYMBOL(locks_remove_posix); 1893 1894 /* 1895 * This function is called on the last close of an open file. 1896 */ 1897 void locks_remove_flock(struct file *filp) 1898 { 1899 struct inode * inode = filp->f_dentry->d_inode; 1900 struct file_lock *fl; 1901 struct file_lock **before; 1902 1903 if (!inode->i_flock) 1904 return; 1905 1906 if (filp->f_op && filp->f_op->flock) { 1907 struct file_lock fl = { 1908 .fl_pid = current->tgid, 1909 .fl_file = filp, 1910 .fl_flags = FL_FLOCK, 1911 .fl_type = F_UNLCK, 1912 .fl_end = OFFSET_MAX, 1913 }; 1914 filp->f_op->flock(filp, F_SETLKW, &fl); 1915 if (fl.fl_ops && fl.fl_ops->fl_release_private) 1916 fl.fl_ops->fl_release_private(&fl); 1917 } 1918 1919 lock_kernel(); 1920 before = &inode->i_flock; 1921 1922 while ((fl = *before) != NULL) { 1923 if (fl->fl_file == filp) { 1924 if (IS_FLOCK(fl)) { 1925 locks_delete_lock(before); 1926 continue; 1927 } 1928 if (IS_LEASE(fl)) { 1929 lease_modify(before, F_UNLCK); 1930 continue; 1931 } 1932 /* What? */ 1933 BUG(); 1934 } 1935 before = &fl->fl_next; 1936 } 1937 unlock_kernel(); 1938 } 1939 1940 /** 1941 * posix_block_lock - blocks waiting for a file lock 1942 * @blocker: the lock which is blocking 1943 * @waiter: the lock which conflicts and has to wait 1944 * 1945 * lockd needs to block waiting for locks. 1946 */ 1947 void 1948 posix_block_lock(struct file_lock *blocker, struct file_lock *waiter) 1949 { 1950 locks_insert_block(blocker, waiter); 1951 } 1952 1953 EXPORT_SYMBOL(posix_block_lock); 1954 1955 /** 1956 * posix_unblock_lock - stop waiting for a file lock 1957 * @filp: how the file was opened 1958 * @waiter: the lock which was waiting 1959 * 1960 * lockd needs to block waiting for locks. 1961 */ 1962 void 1963 posix_unblock_lock(struct file *filp, struct file_lock *waiter) 1964 { 1965 /* 1966 * A remote machine may cancel the lock request after it's been 1967 * granted locally. If that happens, we need to delete the lock. 1968 */ 1969 lock_kernel(); 1970 if (waiter->fl_next) { 1971 __locks_delete_block(waiter); 1972 unlock_kernel(); 1973 } else { 1974 unlock_kernel(); 1975 waiter->fl_type = F_UNLCK; 1976 posix_lock_file(filp, waiter); 1977 } 1978 } 1979 1980 EXPORT_SYMBOL(posix_unblock_lock); 1981 1982 static void lock_get_status(char* out, struct file_lock *fl, int id, char *pfx) 1983 { 1984 struct inode *inode = NULL; 1985 1986 if (fl->fl_file != NULL) 1987 inode = fl->fl_file->f_dentry->d_inode; 1988 1989 out += sprintf(out, "%d:%s ", id, pfx); 1990 if (IS_POSIX(fl)) { 1991 out += sprintf(out, "%6s %s ", 1992 (fl->fl_flags & FL_ACCESS) ? "ACCESS" : "POSIX ", 1993 (inode == NULL) ? "*NOINODE*" : 1994 (IS_MANDLOCK(inode) && 1995 (inode->i_mode & (S_IXGRP | S_ISGID)) == S_ISGID) ? 1996 "MANDATORY" : "ADVISORY "); 1997 } else if (IS_FLOCK(fl)) { 1998 if (fl->fl_type & LOCK_MAND) { 1999 out += sprintf(out, "FLOCK MSNFS "); 2000 } else { 2001 out += sprintf(out, "FLOCK ADVISORY "); 2002 } 2003 } else if (IS_LEASE(fl)) { 2004 out += sprintf(out, "LEASE "); 2005 if (fl->fl_type & F_INPROGRESS) 2006 out += sprintf(out, "BREAKING "); 2007 else if (fl->fl_file) 2008 out += sprintf(out, "ACTIVE "); 2009 else 2010 out += sprintf(out, "BREAKER "); 2011 } else { 2012 out += sprintf(out, "UNKNOWN UNKNOWN "); 2013 } 2014 if (fl->fl_type & LOCK_MAND) { 2015 out += sprintf(out, "%s ", 2016 (fl->fl_type & LOCK_READ) 2017 ? (fl->fl_type & LOCK_WRITE) ? "RW " : "READ " 2018 : (fl->fl_type & LOCK_WRITE) ? "WRITE" : "NONE "); 2019 } else { 2020 out += sprintf(out, "%s ", 2021 (fl->fl_type & F_INPROGRESS) 2022 ? (fl->fl_type & F_UNLCK) ? "UNLCK" : "READ " 2023 : (fl->fl_type & F_WRLCK) ? "WRITE" : "READ "); 2024 } 2025 if (inode) { 2026 #ifdef WE_CAN_BREAK_LSLK_NOW 2027 out += sprintf(out, "%d %s:%ld ", fl->fl_pid, 2028 inode->i_sb->s_id, inode->i_ino); 2029 #else 2030 /* userspace relies on this representation of dev_t ;-( */ 2031 out += sprintf(out, "%d %02x:%02x:%ld ", fl->fl_pid, 2032 MAJOR(inode->i_sb->s_dev), 2033 MINOR(inode->i_sb->s_dev), inode->i_ino); 2034 #endif 2035 } else { 2036 out += sprintf(out, "%d <none>:0 ", fl->fl_pid); 2037 } 2038 if (IS_POSIX(fl)) { 2039 if (fl->fl_end == OFFSET_MAX) 2040 out += sprintf(out, "%Ld EOF\n", fl->fl_start); 2041 else 2042 out += sprintf(out, "%Ld %Ld\n", fl->fl_start, 2043 fl->fl_end); 2044 } else { 2045 out += sprintf(out, "0 EOF\n"); 2046 } 2047 } 2048 2049 static void move_lock_status(char **p, off_t* pos, off_t offset) 2050 { 2051 int len; 2052 len = strlen(*p); 2053 if(*pos >= offset) { 2054 /* the complete line is valid */ 2055 *p += len; 2056 *pos += len; 2057 return; 2058 } 2059 if(*pos+len > offset) { 2060 /* use the second part of the line */ 2061 int i = offset-*pos; 2062 memmove(*p,*p+i,len-i); 2063 *p += len-i; 2064 *pos += len; 2065 return; 2066 } 2067 /* discard the complete line */ 2068 *pos += len; 2069 } 2070 2071 /** 2072 * get_locks_status - reports lock usage in /proc/locks 2073 * @buffer: address in userspace to write into 2074 * @start: ? 2075 * @offset: how far we are through the buffer 2076 * @length: how much to read 2077 */ 2078 2079 int get_locks_status(char *buffer, char **start, off_t offset, int length) 2080 { 2081 struct list_head *tmp; 2082 char *q = buffer; 2083 off_t pos = 0; 2084 int i = 0; 2085 2086 lock_kernel(); 2087 list_for_each(tmp, &file_lock_list) { 2088 struct list_head *btmp; 2089 struct file_lock *fl = list_entry(tmp, struct file_lock, fl_link); 2090 lock_get_status(q, fl, ++i, ""); 2091 move_lock_status(&q, &pos, offset); 2092 2093 if(pos >= offset+length) 2094 goto done; 2095 2096 list_for_each(btmp, &fl->fl_block) { 2097 struct file_lock *bfl = list_entry(btmp, 2098 struct file_lock, fl_block); 2099 lock_get_status(q, bfl, i, " ->"); 2100 move_lock_status(&q, &pos, offset); 2101 2102 if(pos >= offset+length) 2103 goto done; 2104 } 2105 } 2106 done: 2107 unlock_kernel(); 2108 *start = buffer; 2109 if(q-buffer < length) 2110 return (q-buffer); 2111 return length; 2112 } 2113 2114 /** 2115 * lock_may_read - checks that the region is free of locks 2116 * @inode: the inode that is being read 2117 * @start: the first byte to read 2118 * @len: the number of bytes to read 2119 * 2120 * Emulates Windows locking requirements. Whole-file 2121 * mandatory locks (share modes) can prohibit a read and 2122 * byte-range POSIX locks can prohibit a read if they overlap. 2123 * 2124 * N.B. this function is only ever called 2125 * from knfsd and ownership of locks is never checked. 2126 */ 2127 int lock_may_read(struct inode *inode, loff_t start, unsigned long len) 2128 { 2129 struct file_lock *fl; 2130 int result = 1; 2131 lock_kernel(); 2132 for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) { 2133 if (IS_POSIX(fl)) { 2134 if (fl->fl_type == F_RDLCK) 2135 continue; 2136 if ((fl->fl_end < start) || (fl->fl_start > (start + len))) 2137 continue; 2138 } else if (IS_FLOCK(fl)) { 2139 if (!(fl->fl_type & LOCK_MAND)) 2140 continue; 2141 if (fl->fl_type & LOCK_READ) 2142 continue; 2143 } else 2144 continue; 2145 result = 0; 2146 break; 2147 } 2148 unlock_kernel(); 2149 return result; 2150 } 2151 2152 EXPORT_SYMBOL(lock_may_read); 2153 2154 /** 2155 * lock_may_write - checks that the region is free of locks 2156 * @inode: the inode that is being written 2157 * @start: the first byte to write 2158 * @len: the number of bytes to write 2159 * 2160 * Emulates Windows locking requirements. Whole-file 2161 * mandatory locks (share modes) can prohibit a write and 2162 * byte-range POSIX locks can prohibit a write if they overlap. 2163 * 2164 * N.B. this function is only ever called 2165 * from knfsd and ownership of locks is never checked. 2166 */ 2167 int lock_may_write(struct inode *inode, loff_t start, unsigned long len) 2168 { 2169 struct file_lock *fl; 2170 int result = 1; 2171 lock_kernel(); 2172 for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) { 2173 if (IS_POSIX(fl)) { 2174 if ((fl->fl_end < start) || (fl->fl_start > (start + len))) 2175 continue; 2176 } else if (IS_FLOCK(fl)) { 2177 if (!(fl->fl_type & LOCK_MAND)) 2178 continue; 2179 if (fl->fl_type & LOCK_WRITE) 2180 continue; 2181 } else 2182 continue; 2183 result = 0; 2184 break; 2185 } 2186 unlock_kernel(); 2187 return result; 2188 } 2189 2190 EXPORT_SYMBOL(lock_may_write); 2191 2192 static inline void __steal_locks(struct file *file, fl_owner_t from) 2193 { 2194 struct inode *inode = file->f_dentry->d_inode; 2195 struct file_lock *fl = inode->i_flock; 2196 2197 while (fl) { 2198 if (fl->fl_file == file && fl->fl_owner == from) 2199 fl->fl_owner = current->files; 2200 fl = fl->fl_next; 2201 } 2202 } 2203 2204 /* When getting ready for executing a binary, we make sure that current 2205 * has a files_struct on its own. Before dropping the old files_struct, 2206 * we take over ownership of all locks for all file descriptors we own. 2207 * Note that we may accidentally steal a lock for a file that a sibling 2208 * has created since the unshare_files() call. 2209 */ 2210 void steal_locks(fl_owner_t from) 2211 { 2212 struct files_struct *files = current->files; 2213 int i, j; 2214 struct fdtable *fdt; 2215 2216 if (from == files) 2217 return; 2218 2219 lock_kernel(); 2220 j = 0; 2221 rcu_read_lock(); 2222 fdt = files_fdtable(files); 2223 for (;;) { 2224 unsigned long set; 2225 i = j * __NFDBITS; 2226 if (i >= fdt->max_fdset || i >= fdt->max_fds) 2227 break; 2228 set = fdt->open_fds->fds_bits[j++]; 2229 while (set) { 2230 if (set & 1) { 2231 struct file *file = fdt->fd[i]; 2232 if (file) 2233 __steal_locks(file, from); 2234 } 2235 i++; 2236 set >>= 1; 2237 } 2238 } 2239 rcu_read_unlock(); 2240 unlock_kernel(); 2241 } 2242 EXPORT_SYMBOL(steal_locks); 2243 2244 static int __init filelock_init(void) 2245 { 2246 filelock_cache = kmem_cache_create("file_lock_cache", 2247 sizeof(struct file_lock), 0, SLAB_PANIC, 2248 init_once, NULL); 2249 return 0; 2250 } 2251 2252 core_initcall(filelock_init); 2253