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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/fdtable.h> |
120 | #include <linux/fs.h> |
121 | #include <linux/init.h> |
122 | #include <linux/module.h> |
123 | #include <linux/security.h> |
124 | #include <linux/slab.h> |
125 | #include <linux/syscalls.h> |
126 | #include <linux/time.h> |
127 | #include <linux/rcupdate.h> |
128 | #include <linux/pid_namespace.h> |
129 | |
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 | static LIST_HEAD(file_lock_list); |
143 | static LIST_HEAD(blocked_list); |
144 | static DEFINE_SPINLOCK(file_lock_lock); |
145 | |
146 | /* |
147 | * Protects the two list heads above, plus the inode->i_flock list |
148 | * FIXME: should use a spinlock, once lockd and ceph are ready. |
149 | */ |
150 | void lock_flocks(void) |
151 | { |
152 | spin_lock(&file_lock_lock); |
153 | } |
154 | EXPORT_SYMBOL_GPL(lock_flocks); |
155 | |
156 | void unlock_flocks(void) |
157 | { |
158 | spin_unlock(&file_lock_lock); |
159 | } |
160 | EXPORT_SYMBOL_GPL(unlock_flocks); |
161 | |
162 | static struct kmem_cache *filelock_cache __read_mostly; |
163 | |
164 | /* Allocate an empty lock structure. */ |
165 | struct file_lock *locks_alloc_lock(void) |
166 | { |
167 | return kmem_cache_alloc(filelock_cache, GFP_KERNEL); |
168 | } |
169 | EXPORT_SYMBOL_GPL(locks_alloc_lock); |
170 | |
171 | void locks_release_private(struct file_lock *fl) |
172 | { |
173 | if (fl->fl_ops) { |
174 | if (fl->fl_ops->fl_release_private) |
175 | fl->fl_ops->fl_release_private(fl); |
176 | fl->fl_ops = NULL; |
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 | } |
185 | EXPORT_SYMBOL_GPL(locks_release_private); |
186 | |
187 | /* Free a lock which is not in use. */ |
188 | void locks_free_lock(struct file_lock *fl) |
189 | { |
190 | BUG_ON(waitqueue_active(&fl->fl_wait)); |
191 | BUG_ON(!list_empty(&fl->fl_block)); |
192 | BUG_ON(!list_empty(&fl->fl_link)); |
193 | |
194 | locks_release_private(fl); |
195 | kmem_cache_free(filelock_cache, fl); |
196 | } |
197 | EXPORT_SYMBOL(locks_free_lock); |
198 | |
199 | void locks_init_lock(struct file_lock *fl) |
200 | { |
201 | INIT_LIST_HEAD(&fl->fl_link); |
202 | INIT_LIST_HEAD(&fl->fl_block); |
203 | init_waitqueue_head(&fl->fl_wait); |
204 | fl->fl_next = NULL; |
205 | fl->fl_fasync = NULL; |
206 | fl->fl_owner = NULL; |
207 | fl->fl_pid = 0; |
208 | fl->fl_nspid = NULL; |
209 | fl->fl_file = NULL; |
210 | fl->fl_flags = 0; |
211 | fl->fl_type = 0; |
212 | fl->fl_start = fl->fl_end = 0; |
213 | fl->fl_ops = NULL; |
214 | fl->fl_lmops = NULL; |
215 | } |
216 | |
217 | EXPORT_SYMBOL(locks_init_lock); |
218 | |
219 | /* |
220 | * Initialises the fields of the file lock which are invariant for |
221 | * free file_locks. |
222 | */ |
223 | static void init_once(void *foo) |
224 | { |
225 | struct file_lock *lock = (struct file_lock *) foo; |
226 | |
227 | locks_init_lock(lock); |
228 | } |
229 | |
230 | static void locks_copy_private(struct file_lock *new, struct file_lock *fl) |
231 | { |
232 | if (fl->fl_ops) { |
233 | if (fl->fl_ops->fl_copy_lock) |
234 | fl->fl_ops->fl_copy_lock(new, fl); |
235 | new->fl_ops = fl->fl_ops; |
236 | } |
237 | if (fl->fl_lmops) |
238 | new->fl_lmops = fl->fl_lmops; |
239 | } |
240 | |
241 | /* |
242 | * Initialize a new lock from an existing file_lock structure. |
243 | */ |
244 | void __locks_copy_lock(struct file_lock *new, const struct file_lock *fl) |
245 | { |
246 | new->fl_owner = fl->fl_owner; |
247 | new->fl_pid = fl->fl_pid; |
248 | new->fl_file = NULL; |
249 | new->fl_flags = fl->fl_flags; |
250 | new->fl_type = fl->fl_type; |
251 | new->fl_start = fl->fl_start; |
252 | new->fl_end = fl->fl_end; |
253 | new->fl_ops = NULL; |
254 | new->fl_lmops = NULL; |
255 | } |
256 | EXPORT_SYMBOL(__locks_copy_lock); |
257 | |
258 | void locks_copy_lock(struct file_lock *new, struct file_lock *fl) |
259 | { |
260 | locks_release_private(new); |
261 | |
262 | __locks_copy_lock(new, fl); |
263 | new->fl_file = fl->fl_file; |
264 | new->fl_ops = fl->fl_ops; |
265 | new->fl_lmops = fl->fl_lmops; |
266 | |
267 | locks_copy_private(new, fl); |
268 | } |
269 | |
270 | EXPORT_SYMBOL(locks_copy_lock); |
271 | |
272 | static inline int flock_translate_cmd(int cmd) { |
273 | if (cmd & LOCK_MAND) |
274 | return cmd & (LOCK_MAND | LOCK_RW); |
275 | switch (cmd) { |
276 | case LOCK_SH: |
277 | return F_RDLCK; |
278 | case LOCK_EX: |
279 | return F_WRLCK; |
280 | case LOCK_UN: |
281 | return F_UNLCK; |
282 | } |
283 | return -EINVAL; |
284 | } |
285 | |
286 | /* Fill in a file_lock structure with an appropriate FLOCK lock. */ |
287 | static int flock_make_lock(struct file *filp, struct file_lock **lock, |
288 | unsigned int cmd) |
289 | { |
290 | struct file_lock *fl; |
291 | int type = flock_translate_cmd(cmd); |
292 | if (type < 0) |
293 | return type; |
294 | |
295 | fl = locks_alloc_lock(); |
296 | if (fl == NULL) |
297 | return -ENOMEM; |
298 | |
299 | fl->fl_file = filp; |
300 | fl->fl_pid = current->tgid; |
301 | fl->fl_flags = FL_FLOCK; |
302 | fl->fl_type = type; |
303 | fl->fl_end = OFFSET_MAX; |
304 | |
305 | *lock = fl; |
306 | return 0; |
307 | } |
308 | |
309 | static int assign_type(struct file_lock *fl, int type) |
310 | { |
311 | switch (type) { |
312 | case F_RDLCK: |
313 | case F_WRLCK: |
314 | case F_UNLCK: |
315 | fl->fl_type = type; |
316 | break; |
317 | default: |
318 | return -EINVAL; |
319 | } |
320 | return 0; |
321 | } |
322 | |
323 | /* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX |
324 | * style lock. |
325 | */ |
326 | static int flock_to_posix_lock(struct file *filp, struct file_lock *fl, |
327 | struct flock *l) |
328 | { |
329 | off_t start, end; |
330 | |
331 | switch (l->l_whence) { |
332 | case SEEK_SET: |
333 | start = 0; |
334 | break; |
335 | case SEEK_CUR: |
336 | start = filp->f_pos; |
337 | break; |
338 | case SEEK_END: |
339 | start = i_size_read(filp->f_path.dentry->d_inode); |
340 | break; |
341 | default: |
342 | return -EINVAL; |
343 | } |
344 | |
345 | /* POSIX-1996 leaves the case l->l_len < 0 undefined; |
346 | POSIX-2001 defines it. */ |
347 | start += l->l_start; |
348 | if (start < 0) |
349 | return -EINVAL; |
350 | fl->fl_end = OFFSET_MAX; |
351 | if (l->l_len > 0) { |
352 | end = start + l->l_len - 1; |
353 | fl->fl_end = end; |
354 | } else if (l->l_len < 0) { |
355 | end = start - 1; |
356 | fl->fl_end = end; |
357 | start += l->l_len; |
358 | if (start < 0) |
359 | return -EINVAL; |
360 | } |
361 | fl->fl_start = start; /* we record the absolute position */ |
362 | if (fl->fl_end < fl->fl_start) |
363 | return -EOVERFLOW; |
364 | |
365 | fl->fl_owner = current->files; |
366 | fl->fl_pid = current->tgid; |
367 | fl->fl_file = filp; |
368 | fl->fl_flags = FL_POSIX; |
369 | fl->fl_ops = NULL; |
370 | fl->fl_lmops = NULL; |
371 | |
372 | return assign_type(fl, l->l_type); |
373 | } |
374 | |
375 | #if BITS_PER_LONG == 32 |
376 | static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl, |
377 | struct flock64 *l) |
378 | { |
379 | loff_t start; |
380 | |
381 | switch (l->l_whence) { |
382 | case SEEK_SET: |
383 | start = 0; |
384 | break; |
385 | case SEEK_CUR: |
386 | start = filp->f_pos; |
387 | break; |
388 | case SEEK_END: |
389 | start = i_size_read(filp->f_path.dentry->d_inode); |
390 | break; |
391 | default: |
392 | return -EINVAL; |
393 | } |
394 | |
395 | start += l->l_start; |
396 | if (start < 0) |
397 | return -EINVAL; |
398 | fl->fl_end = OFFSET_MAX; |
399 | if (l->l_len > 0) { |
400 | fl->fl_end = start + l->l_len - 1; |
401 | } else if (l->l_len < 0) { |
402 | fl->fl_end = start - 1; |
403 | start += l->l_len; |
404 | if (start < 0) |
405 | return -EINVAL; |
406 | } |
407 | fl->fl_start = start; /* we record the absolute position */ |
408 | if (fl->fl_end < fl->fl_start) |
409 | return -EOVERFLOW; |
410 | |
411 | fl->fl_owner = current->files; |
412 | fl->fl_pid = current->tgid; |
413 | fl->fl_file = filp; |
414 | fl->fl_flags = FL_POSIX; |
415 | fl->fl_ops = NULL; |
416 | fl->fl_lmops = NULL; |
417 | |
418 | switch (l->l_type) { |
419 | case F_RDLCK: |
420 | case F_WRLCK: |
421 | case F_UNLCK: |
422 | fl->fl_type = l->l_type; |
423 | break; |
424 | default: |
425 | return -EINVAL; |
426 | } |
427 | |
428 | return (0); |
429 | } |
430 | #endif |
431 | |
432 | /* default lease lock manager operations */ |
433 | static void lease_break_callback(struct file_lock *fl) |
434 | { |
435 | kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG); |
436 | } |
437 | |
438 | static void lease_release_private_callback(struct file_lock *fl) |
439 | { |
440 | if (!fl->fl_file) |
441 | return; |
442 | |
443 | f_delown(fl->fl_file); |
444 | fl->fl_file->f_owner.signum = 0; |
445 | } |
446 | |
447 | static const struct lock_manager_operations lease_manager_ops = { |
448 | .fl_break = lease_break_callback, |
449 | .fl_release_private = lease_release_private_callback, |
450 | .fl_change = lease_modify, |
451 | }; |
452 | |
453 | /* |
454 | * Initialize a lease, use the default lock manager operations |
455 | */ |
456 | static int lease_init(struct file *filp, int type, struct file_lock *fl) |
457 | { |
458 | if (assign_type(fl, type) != 0) |
459 | return -EINVAL; |
460 | |
461 | fl->fl_owner = current->files; |
462 | fl->fl_pid = current->tgid; |
463 | |
464 | fl->fl_file = filp; |
465 | fl->fl_flags = FL_LEASE; |
466 | fl->fl_start = 0; |
467 | fl->fl_end = OFFSET_MAX; |
468 | fl->fl_ops = NULL; |
469 | fl->fl_lmops = &lease_manager_ops; |
470 | return 0; |
471 | } |
472 | |
473 | /* Allocate a file_lock initialised to this type of lease */ |
474 | static struct file_lock *lease_alloc(struct file *filp, int type) |
475 | { |
476 | struct file_lock *fl = locks_alloc_lock(); |
477 | int error = -ENOMEM; |
478 | |
479 | if (fl == NULL) |
480 | return ERR_PTR(error); |
481 | |
482 | error = lease_init(filp, type, fl); |
483 | if (error) { |
484 | locks_free_lock(fl); |
485 | return ERR_PTR(error); |
486 | } |
487 | return fl; |
488 | } |
489 | |
490 | /* Check if two locks overlap each other. |
491 | */ |
492 | static inline int locks_overlap(struct file_lock *fl1, struct file_lock *fl2) |
493 | { |
494 | return ((fl1->fl_end >= fl2->fl_start) && |
495 | (fl2->fl_end >= fl1->fl_start)); |
496 | } |
497 | |
498 | /* |
499 | * Check whether two locks have the same owner. |
500 | */ |
501 | static int posix_same_owner(struct file_lock *fl1, struct file_lock *fl2) |
502 | { |
503 | if (fl1->fl_lmops && fl1->fl_lmops->fl_compare_owner) |
504 | return fl2->fl_lmops == fl1->fl_lmops && |
505 | fl1->fl_lmops->fl_compare_owner(fl1, fl2); |
506 | return fl1->fl_owner == fl2->fl_owner; |
507 | } |
508 | |
509 | /* Remove waiter from blocker's block list. |
510 | * When blocker ends up pointing to itself then the list is empty. |
511 | */ |
512 | static void __locks_delete_block(struct file_lock *waiter) |
513 | { |
514 | list_del_init(&waiter->fl_block); |
515 | list_del_init(&waiter->fl_link); |
516 | waiter->fl_next = NULL; |
517 | } |
518 | |
519 | /* |
520 | */ |
521 | static void locks_delete_block(struct file_lock *waiter) |
522 | { |
523 | lock_flocks(); |
524 | __locks_delete_block(waiter); |
525 | unlock_flocks(); |
526 | } |
527 | |
528 | /* Insert waiter into blocker's block list. |
529 | * We use a circular list so that processes can be easily woken up in |
530 | * the order they blocked. The documentation doesn't require this but |
531 | * it seems like the reasonable thing to do. |
532 | */ |
533 | static void locks_insert_block(struct file_lock *blocker, |
534 | struct file_lock *waiter) |
535 | { |
536 | BUG_ON(!list_empty(&waiter->fl_block)); |
537 | list_add_tail(&waiter->fl_block, &blocker->fl_block); |
538 | waiter->fl_next = blocker; |
539 | if (IS_POSIX(blocker)) |
540 | list_add(&waiter->fl_link, &blocked_list); |
541 | } |
542 | |
543 | /* Wake up processes blocked waiting for blocker. |
544 | * If told to wait then schedule the processes until the block list |
545 | * is empty, otherwise empty the block list ourselves. |
546 | */ |
547 | static void locks_wake_up_blocks(struct file_lock *blocker) |
548 | { |
549 | while (!list_empty(&blocker->fl_block)) { |
550 | struct file_lock *waiter; |
551 | |
552 | waiter = list_first_entry(&blocker->fl_block, |
553 | struct file_lock, fl_block); |
554 | __locks_delete_block(waiter); |
555 | if (waiter->fl_lmops && waiter->fl_lmops->fl_notify) |
556 | waiter->fl_lmops->fl_notify(waiter); |
557 | else |
558 | wake_up(&waiter->fl_wait); |
559 | } |
560 | } |
561 | |
562 | /* Insert file lock fl into an inode's lock list at the position indicated |
563 | * by pos. At the same time add the lock to the global file lock list. |
564 | */ |
565 | static void locks_insert_lock(struct file_lock **pos, struct file_lock *fl) |
566 | { |
567 | list_add(&fl->fl_link, &file_lock_list); |
568 | |
569 | fl->fl_nspid = get_pid(task_tgid(current)); |
570 | |
571 | /* insert into file's list */ |
572 | fl->fl_next = *pos; |
573 | *pos = fl; |
574 | } |
575 | |
576 | /* |
577 | * Delete a lock and then free it. |
578 | * Wake up processes that are blocked waiting for this lock, |
579 | * notify the FS that the lock has been cleared and |
580 | * finally free the lock. |
581 | */ |
582 | static void locks_delete_lock(struct file_lock **thisfl_p) |
583 | { |
584 | struct file_lock *fl = *thisfl_p; |
585 | |
586 | *thisfl_p = fl->fl_next; |
587 | fl->fl_next = NULL; |
588 | list_del_init(&fl->fl_link); |
589 | |
590 | fasync_helper(0, fl->fl_file, 0, &fl->fl_fasync); |
591 | if (fl->fl_fasync != NULL) { |
592 | printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync); |
593 | fl->fl_fasync = NULL; |
594 | } |
595 | |
596 | if (fl->fl_nspid) { |
597 | put_pid(fl->fl_nspid); |
598 | fl->fl_nspid = NULL; |
599 | } |
600 | |
601 | locks_wake_up_blocks(fl); |
602 | locks_free_lock(fl); |
603 | } |
604 | |
605 | /* Determine if lock sys_fl blocks lock caller_fl. Common functionality |
606 | * checks for shared/exclusive status of overlapping locks. |
607 | */ |
608 | static int locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl) |
609 | { |
610 | if (sys_fl->fl_type == F_WRLCK) |
611 | return 1; |
612 | if (caller_fl->fl_type == F_WRLCK) |
613 | return 1; |
614 | return 0; |
615 | } |
616 | |
617 | /* Determine if lock sys_fl blocks lock caller_fl. POSIX specific |
618 | * checking before calling the locks_conflict(). |
619 | */ |
620 | static int posix_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl) |
621 | { |
622 | /* POSIX locks owned by the same process do not conflict with |
623 | * each other. |
624 | */ |
625 | if (!IS_POSIX(sys_fl) || posix_same_owner(caller_fl, sys_fl)) |
626 | return (0); |
627 | |
628 | /* Check whether they overlap */ |
629 | if (!locks_overlap(caller_fl, sys_fl)) |
630 | return 0; |
631 | |
632 | return (locks_conflict(caller_fl, sys_fl)); |
633 | } |
634 | |
635 | /* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific |
636 | * checking before calling the locks_conflict(). |
637 | */ |
638 | static int flock_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl) |
639 | { |
640 | /* FLOCK locks referring to the same filp do not conflict with |
641 | * each other. |
642 | */ |
643 | if (!IS_FLOCK(sys_fl) || (caller_fl->fl_file == sys_fl->fl_file)) |
644 | return (0); |
645 | if ((caller_fl->fl_type & LOCK_MAND) || (sys_fl->fl_type & LOCK_MAND)) |
646 | return 0; |
647 | |
648 | return (locks_conflict(caller_fl, sys_fl)); |
649 | } |
650 | |
651 | void |
652 | posix_test_lock(struct file *filp, struct file_lock *fl) |
653 | { |
654 | struct file_lock *cfl; |
655 | |
656 | lock_flocks(); |
657 | for (cfl = filp->f_path.dentry->d_inode->i_flock; cfl; cfl = cfl->fl_next) { |
658 | if (!IS_POSIX(cfl)) |
659 | continue; |
660 | if (posix_locks_conflict(fl, cfl)) |
661 | break; |
662 | } |
663 | if (cfl) { |
664 | __locks_copy_lock(fl, cfl); |
665 | if (cfl->fl_nspid) |
666 | fl->fl_pid = pid_vnr(cfl->fl_nspid); |
667 | } else |
668 | fl->fl_type = F_UNLCK; |
669 | unlock_flocks(); |
670 | return; |
671 | } |
672 | EXPORT_SYMBOL(posix_test_lock); |
673 | |
674 | /* |
675 | * Deadlock detection: |
676 | * |
677 | * We attempt to detect deadlocks that are due purely to posix file |
678 | * locks. |
679 | * |
680 | * We assume that a task can be waiting for at most one lock at a time. |
681 | * So for any acquired lock, the process holding that lock may be |
682 | * waiting on at most one other lock. That lock in turns may be held by |
683 | * someone waiting for at most one other lock. Given a requested lock |
684 | * caller_fl which is about to wait for a conflicting lock block_fl, we |
685 | * follow this chain of waiters to ensure we are not about to create a |
686 | * cycle. |
687 | * |
688 | * Since we do this before we ever put a process to sleep on a lock, we |
689 | * are ensured that there is never a cycle; that is what guarantees that |
690 | * the while() loop in posix_locks_deadlock() eventually completes. |
691 | * |
692 | * Note: the above assumption may not be true when handling lock |
693 | * requests from a broken NFS client. It may also fail in the presence |
694 | * of tasks (such as posix threads) sharing the same open file table. |
695 | * |
696 | * To handle those cases, we just bail out after a few iterations. |
697 | */ |
698 | |
699 | #define MAX_DEADLK_ITERATIONS 10 |
700 | |
701 | /* Find a lock that the owner of the given block_fl is blocking on. */ |
702 | static struct file_lock *what_owner_is_waiting_for(struct file_lock *block_fl) |
703 | { |
704 | struct file_lock *fl; |
705 | |
706 | list_for_each_entry(fl, &blocked_list, fl_link) { |
707 | if (posix_same_owner(fl, block_fl)) |
708 | return fl->fl_next; |
709 | } |
710 | return NULL; |
711 | } |
712 | |
713 | static int posix_locks_deadlock(struct file_lock *caller_fl, |
714 | struct file_lock *block_fl) |
715 | { |
716 | int i = 0; |
717 | |
718 | while ((block_fl = what_owner_is_waiting_for(block_fl))) { |
719 | if (i++ > MAX_DEADLK_ITERATIONS) |
720 | return 0; |
721 | if (posix_same_owner(caller_fl, block_fl)) |
722 | return 1; |
723 | } |
724 | return 0; |
725 | } |
726 | |
727 | /* Try to create a FLOCK lock on filp. We always insert new FLOCK locks |
728 | * after any leases, but before any posix locks. |
729 | * |
730 | * Note that if called with an FL_EXISTS argument, the caller may determine |
731 | * whether or not a lock was successfully freed by testing the return |
732 | * value for -ENOENT. |
733 | */ |
734 | static int flock_lock_file(struct file *filp, struct file_lock *request) |
735 | { |
736 | struct file_lock *new_fl = NULL; |
737 | struct file_lock **before; |
738 | struct inode * inode = filp->f_path.dentry->d_inode; |
739 | int error = 0; |
740 | int found = 0; |
741 | |
742 | if (!(request->fl_flags & FL_ACCESS) && (request->fl_type != F_UNLCK)) { |
743 | new_fl = locks_alloc_lock(); |
744 | if (!new_fl) |
745 | return -ENOMEM; |
746 | } |
747 | |
748 | lock_flocks(); |
749 | if (request->fl_flags & FL_ACCESS) |
750 | goto find_conflict; |
751 | |
752 | for_each_lock(inode, before) { |
753 | struct file_lock *fl = *before; |
754 | if (IS_POSIX(fl)) |
755 | break; |
756 | if (IS_LEASE(fl)) |
757 | continue; |
758 | if (filp != fl->fl_file) |
759 | continue; |
760 | if (request->fl_type == fl->fl_type) |
761 | goto out; |
762 | found = 1; |
763 | locks_delete_lock(before); |
764 | break; |
765 | } |
766 | |
767 | if (request->fl_type == F_UNLCK) { |
768 | if ((request->fl_flags & FL_EXISTS) && !found) |
769 | error = -ENOENT; |
770 | goto out; |
771 | } |
772 | |
773 | /* |
774 | * If a higher-priority process was blocked on the old file lock, |
775 | * give it the opportunity to lock the file. |
776 | */ |
777 | if (found) { |
778 | unlock_flocks(); |
779 | cond_resched(); |
780 | lock_flocks(); |
781 | } |
782 | |
783 | find_conflict: |
784 | for_each_lock(inode, before) { |
785 | struct file_lock *fl = *before; |
786 | if (IS_POSIX(fl)) |
787 | break; |
788 | if (IS_LEASE(fl)) |
789 | continue; |
790 | if (!flock_locks_conflict(request, fl)) |
791 | continue; |
792 | error = -EAGAIN; |
793 | if (!(request->fl_flags & FL_SLEEP)) |
794 | goto out; |
795 | error = FILE_LOCK_DEFERRED; |
796 | locks_insert_block(fl, request); |
797 | goto out; |
798 | } |
799 | if (request->fl_flags & FL_ACCESS) |
800 | goto out; |
801 | locks_copy_lock(new_fl, request); |
802 | locks_insert_lock(before, new_fl); |
803 | new_fl = NULL; |
804 | error = 0; |
805 | |
806 | out: |
807 | unlock_flocks(); |
808 | if (new_fl) |
809 | locks_free_lock(new_fl); |
810 | return error; |
811 | } |
812 | |
813 | static int __posix_lock_file(struct inode *inode, struct file_lock *request, struct file_lock *conflock) |
814 | { |
815 | struct file_lock *fl; |
816 | struct file_lock *new_fl = NULL; |
817 | struct file_lock *new_fl2 = NULL; |
818 | struct file_lock *left = NULL; |
819 | struct file_lock *right = NULL; |
820 | struct file_lock **before; |
821 | int error, added = 0; |
822 | |
823 | /* |
824 | * We may need two file_lock structures for this operation, |
825 | * so we get them in advance to avoid races. |
826 | * |
827 | * In some cases we can be sure, that no new locks will be needed |
828 | */ |
829 | if (!(request->fl_flags & FL_ACCESS) && |
830 | (request->fl_type != F_UNLCK || |
831 | request->fl_start != 0 || request->fl_end != OFFSET_MAX)) { |
832 | new_fl = locks_alloc_lock(); |
833 | new_fl2 = locks_alloc_lock(); |
834 | } |
835 | |
836 | lock_flocks(); |
837 | if (request->fl_type != F_UNLCK) { |
838 | for_each_lock(inode, before) { |
839 | fl = *before; |
840 | if (!IS_POSIX(fl)) |
841 | continue; |
842 | if (!posix_locks_conflict(request, fl)) |
843 | continue; |
844 | if (conflock) |
845 | __locks_copy_lock(conflock, fl); |
846 | error = -EAGAIN; |
847 | if (!(request->fl_flags & FL_SLEEP)) |
848 | goto out; |
849 | error = -EDEADLK; |
850 | if (posix_locks_deadlock(request, fl)) |
851 | goto out; |
852 | error = FILE_LOCK_DEFERRED; |
853 | locks_insert_block(fl, request); |
854 | goto out; |
855 | } |
856 | } |
857 | |
858 | /* If we're just looking for a conflict, we're done. */ |
859 | error = 0; |
860 | if (request->fl_flags & FL_ACCESS) |
861 | goto out; |
862 | |
863 | /* |
864 | * Find the first old lock with the same owner as the new lock. |
865 | */ |
866 | |
867 | before = &inode->i_flock; |
868 | |
869 | /* First skip locks owned by other processes. */ |
870 | while ((fl = *before) && (!IS_POSIX(fl) || |
871 | !posix_same_owner(request, fl))) { |
872 | before = &fl->fl_next; |
873 | } |
874 | |
875 | /* Process locks with this owner. */ |
876 | while ((fl = *before) && posix_same_owner(request, fl)) { |
877 | /* Detect adjacent or overlapping regions (if same lock type) |
878 | */ |
879 | if (request->fl_type == fl->fl_type) { |
880 | /* In all comparisons of start vs end, use |
881 | * "start - 1" rather than "end + 1". If end |
882 | * is OFFSET_MAX, end + 1 will become negative. |
883 | */ |
884 | if (fl->fl_end < request->fl_start - 1) |
885 | goto next_lock; |
886 | /* If the next lock in the list has entirely bigger |
887 | * addresses than the new one, insert the lock here. |
888 | */ |
889 | if (fl->fl_start - 1 > request->fl_end) |
890 | break; |
891 | |
892 | /* If we come here, the new and old lock are of the |
893 | * same type and adjacent or overlapping. Make one |
894 | * lock yielding from the lower start address of both |
895 | * locks to the higher end address. |
896 | */ |
897 | if (fl->fl_start > request->fl_start) |
898 | fl->fl_start = request->fl_start; |
899 | else |
900 | request->fl_start = fl->fl_start; |
901 | if (fl->fl_end < request->fl_end) |
902 | fl->fl_end = request->fl_end; |
903 | else |
904 | request->fl_end = fl->fl_end; |
905 | if (added) { |
906 | locks_delete_lock(before); |
907 | continue; |
908 | } |
909 | request = fl; |
910 | added = 1; |
911 | } |
912 | else { |
913 | /* Processing for different lock types is a bit |
914 | * more complex. |
915 | */ |
916 | if (fl->fl_end < request->fl_start) |
917 | goto next_lock; |
918 | if (fl->fl_start > request->fl_end) |
919 | break; |
920 | if (request->fl_type == F_UNLCK) |
921 | added = 1; |
922 | if (fl->fl_start < request->fl_start) |
923 | left = fl; |
924 | /* If the next lock in the list has a higher end |
925 | * address than the new one, insert the new one here. |
926 | */ |
927 | if (fl->fl_end > request->fl_end) { |
928 | right = fl; |
929 | break; |
930 | } |
931 | if (fl->fl_start >= request->fl_start) { |
932 | /* The new lock completely replaces an old |
933 | * one (This may happen several times). |
934 | */ |
935 | if (added) { |
936 | locks_delete_lock(before); |
937 | continue; |
938 | } |
939 | /* Replace the old lock with the new one. |
940 | * Wake up anybody waiting for the old one, |
941 | * as the change in lock type might satisfy |
942 | * their needs. |
943 | */ |
944 | locks_wake_up_blocks(fl); |
945 | fl->fl_start = request->fl_start; |
946 | fl->fl_end = request->fl_end; |
947 | fl->fl_type = request->fl_type; |
948 | locks_release_private(fl); |
949 | locks_copy_private(fl, request); |
950 | request = fl; |
951 | added = 1; |
952 | } |
953 | } |
954 | /* Go on to next lock. |
955 | */ |
956 | next_lock: |
957 | before = &fl->fl_next; |
958 | } |
959 | |
960 | /* |
961 | * The above code only modifies existing locks in case of |
962 | * merging or replacing. If new lock(s) need to be inserted |
963 | * all modifications are done bellow this, so it's safe yet to |
964 | * bail out. |
965 | */ |
966 | error = -ENOLCK; /* "no luck" */ |
967 | if (right && left == right && !new_fl2) |
968 | goto out; |
969 | |
970 | error = 0; |
971 | if (!added) { |
972 | if (request->fl_type == F_UNLCK) { |
973 | if (request->fl_flags & FL_EXISTS) |
974 | error = -ENOENT; |
975 | goto out; |
976 | } |
977 | |
978 | if (!new_fl) { |
979 | error = -ENOLCK; |
980 | goto out; |
981 | } |
982 | locks_copy_lock(new_fl, request); |
983 | locks_insert_lock(before, new_fl); |
984 | new_fl = NULL; |
985 | } |
986 | if (right) { |
987 | if (left == right) { |
988 | /* The new lock breaks the old one in two pieces, |
989 | * so we have to use the second new lock. |
990 | */ |
991 | left = new_fl2; |
992 | new_fl2 = NULL; |
993 | locks_copy_lock(left, right); |
994 | locks_insert_lock(before, left); |
995 | } |
996 | right->fl_start = request->fl_end + 1; |
997 | locks_wake_up_blocks(right); |
998 | } |
999 | if (left) { |
1000 | left->fl_end = request->fl_start - 1; |
1001 | locks_wake_up_blocks(left); |
1002 | } |
1003 | out: |
1004 | unlock_flocks(); |
1005 | /* |
1006 | * Free any unused locks. |
1007 | */ |
1008 | if (new_fl) |
1009 | locks_free_lock(new_fl); |
1010 | if (new_fl2) |
1011 | locks_free_lock(new_fl2); |
1012 | return error; |
1013 | } |
1014 | |
1015 | /** |
1016 | * posix_lock_file - Apply a POSIX-style lock to a file |
1017 | * @filp: The file to apply the lock to |
1018 | * @fl: The lock to be applied |
1019 | * @conflock: Place to return a copy of the conflicting lock, if found. |
1020 | * |
1021 | * Add a POSIX style lock to a file. |
1022 | * We merge adjacent & overlapping locks whenever possible. |
1023 | * POSIX locks are sorted by owner task, then by starting address |
1024 | * |
1025 | * Note that if called with an FL_EXISTS argument, the caller may determine |
1026 | * whether or not a lock was successfully freed by testing the return |
1027 | * value for -ENOENT. |
1028 | */ |
1029 | int posix_lock_file(struct file *filp, struct file_lock *fl, |
1030 | struct file_lock *conflock) |
1031 | { |
1032 | return __posix_lock_file(filp->f_path.dentry->d_inode, fl, conflock); |
1033 | } |
1034 | EXPORT_SYMBOL(posix_lock_file); |
1035 | |
1036 | /** |
1037 | * posix_lock_file_wait - Apply a POSIX-style lock to a file |
1038 | * @filp: The file to apply the lock to |
1039 | * @fl: The lock to be applied |
1040 | * |
1041 | * Add a POSIX style lock to a file. |
1042 | * We merge adjacent & overlapping locks whenever possible. |
1043 | * POSIX locks are sorted by owner task, then by starting address |
1044 | */ |
1045 | int posix_lock_file_wait(struct file *filp, struct file_lock *fl) |
1046 | { |
1047 | int error; |
1048 | might_sleep (); |
1049 | for (;;) { |
1050 | error = posix_lock_file(filp, fl, NULL); |
1051 | if (error != FILE_LOCK_DEFERRED) |
1052 | break; |
1053 | error = wait_event_interruptible(fl->fl_wait, !fl->fl_next); |
1054 | if (!error) |
1055 | continue; |
1056 | |
1057 | locks_delete_block(fl); |
1058 | break; |
1059 | } |
1060 | return error; |
1061 | } |
1062 | EXPORT_SYMBOL(posix_lock_file_wait); |
1063 | |
1064 | /** |
1065 | * locks_mandatory_locked - Check for an active lock |
1066 | * @inode: the file to check |
1067 | * |
1068 | * Searches the inode's list of locks to find any POSIX locks which conflict. |
1069 | * This function is called from locks_verify_locked() only. |
1070 | */ |
1071 | int locks_mandatory_locked(struct inode *inode) |
1072 | { |
1073 | fl_owner_t owner = current->files; |
1074 | struct file_lock *fl; |
1075 | |
1076 | /* |
1077 | * Search the lock list for this inode for any POSIX locks. |
1078 | */ |
1079 | lock_flocks(); |
1080 | for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) { |
1081 | if (!IS_POSIX(fl)) |
1082 | continue; |
1083 | if (fl->fl_owner != owner) |
1084 | break; |
1085 | } |
1086 | unlock_flocks(); |
1087 | return fl ? -EAGAIN : 0; |
1088 | } |
1089 | |
1090 | /** |
1091 | * locks_mandatory_area - Check for a conflicting lock |
1092 | * @read_write: %FLOCK_VERIFY_WRITE for exclusive access, %FLOCK_VERIFY_READ |
1093 | * for shared |
1094 | * @inode: the file to check |
1095 | * @filp: how the file was opened (if it was) |
1096 | * @offset: start of area to check |
1097 | * @count: length of area to check |
1098 | * |
1099 | * Searches the inode's list of locks to find any POSIX locks which conflict. |
1100 | * This function is called from rw_verify_area() and |
1101 | * locks_verify_truncate(). |
1102 | */ |
1103 | int locks_mandatory_area(int read_write, struct inode *inode, |
1104 | struct file *filp, loff_t offset, |
1105 | size_t count) |
1106 | { |
1107 | struct file_lock fl; |
1108 | int error; |
1109 | |
1110 | locks_init_lock(&fl); |
1111 | fl.fl_owner = current->files; |
1112 | fl.fl_pid = current->tgid; |
1113 | fl.fl_file = filp; |
1114 | fl.fl_flags = FL_POSIX | FL_ACCESS; |
1115 | if (filp && !(filp->f_flags & O_NONBLOCK)) |
1116 | fl.fl_flags |= FL_SLEEP; |
1117 | fl.fl_type = (read_write == FLOCK_VERIFY_WRITE) ? F_WRLCK : F_RDLCK; |
1118 | fl.fl_start = offset; |
1119 | fl.fl_end = offset + count - 1; |
1120 | |
1121 | for (;;) { |
1122 | error = __posix_lock_file(inode, &fl, NULL); |
1123 | if (error != FILE_LOCK_DEFERRED) |
1124 | break; |
1125 | error = wait_event_interruptible(fl.fl_wait, !fl.fl_next); |
1126 | if (!error) { |
1127 | /* |
1128 | * If we've been sleeping someone might have |
1129 | * changed the permissions behind our back. |
1130 | */ |
1131 | if (__mandatory_lock(inode)) |
1132 | continue; |
1133 | } |
1134 | |
1135 | locks_delete_block(&fl); |
1136 | break; |
1137 | } |
1138 | |
1139 | return error; |
1140 | } |
1141 | |
1142 | EXPORT_SYMBOL(locks_mandatory_area); |
1143 | |
1144 | /* We already had a lease on this file; just change its type */ |
1145 | int lease_modify(struct file_lock **before, int arg) |
1146 | { |
1147 | struct file_lock *fl = *before; |
1148 | int error = assign_type(fl, arg); |
1149 | |
1150 | if (error) |
1151 | return error; |
1152 | locks_wake_up_blocks(fl); |
1153 | if (arg == F_UNLCK) |
1154 | locks_delete_lock(before); |
1155 | return 0; |
1156 | } |
1157 | |
1158 | EXPORT_SYMBOL(lease_modify); |
1159 | |
1160 | static void time_out_leases(struct inode *inode) |
1161 | { |
1162 | struct file_lock **before; |
1163 | struct file_lock *fl; |
1164 | |
1165 | before = &inode->i_flock; |
1166 | while ((fl = *before) && IS_LEASE(fl) && (fl->fl_type & F_INPROGRESS)) { |
1167 | if ((fl->fl_break_time == 0) |
1168 | || time_before(jiffies, fl->fl_break_time)) { |
1169 | before = &fl->fl_next; |
1170 | continue; |
1171 | } |
1172 | lease_modify(before, fl->fl_type & ~F_INPROGRESS); |
1173 | if (fl == *before) /* lease_modify may have freed fl */ |
1174 | before = &fl->fl_next; |
1175 | } |
1176 | } |
1177 | |
1178 | /** |
1179 | * __break_lease - revoke all outstanding leases on file |
1180 | * @inode: the inode of the file to return |
1181 | * @mode: the open mode (read or write) |
1182 | * |
1183 | * break_lease (inlined for speed) has checked there already is at least |
1184 | * some kind of lock (maybe a lease) on this file. Leases are broken on |
1185 | * a call to open() or truncate(). This function can sleep unless you |
1186 | * specified %O_NONBLOCK to your open(). |
1187 | */ |
1188 | int __break_lease(struct inode *inode, unsigned int mode) |
1189 | { |
1190 | int error = 0, future; |
1191 | struct file_lock *new_fl, *flock; |
1192 | struct file_lock *fl; |
1193 | unsigned long break_time; |
1194 | int i_have_this_lease = 0; |
1195 | int want_write = (mode & O_ACCMODE) != O_RDONLY; |
1196 | |
1197 | new_fl = lease_alloc(NULL, want_write ? F_WRLCK : F_RDLCK); |
1198 | |
1199 | lock_flocks(); |
1200 | |
1201 | time_out_leases(inode); |
1202 | |
1203 | flock = inode->i_flock; |
1204 | if ((flock == NULL) || !IS_LEASE(flock)) |
1205 | goto out; |
1206 | |
1207 | for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next) |
1208 | if (fl->fl_owner == current->files) |
1209 | i_have_this_lease = 1; |
1210 | |
1211 | if (want_write) { |
1212 | /* If we want write access, we have to revoke any lease. */ |
1213 | future = F_UNLCK | F_INPROGRESS; |
1214 | } else if (flock->fl_type & F_INPROGRESS) { |
1215 | /* If the lease is already being broken, we just leave it */ |
1216 | future = flock->fl_type; |
1217 | } else if (flock->fl_type & F_WRLCK) { |
1218 | /* Downgrade the exclusive lease to a read-only lease. */ |
1219 | future = F_RDLCK | F_INPROGRESS; |
1220 | } else { |
1221 | /* the existing lease was read-only, so we can read too. */ |
1222 | goto out; |
1223 | } |
1224 | |
1225 | if (IS_ERR(new_fl) && !i_have_this_lease |
1226 | && ((mode & O_NONBLOCK) == 0)) { |
1227 | error = PTR_ERR(new_fl); |
1228 | goto out; |
1229 | } |
1230 | |
1231 | break_time = 0; |
1232 | if (lease_break_time > 0) { |
1233 | break_time = jiffies + lease_break_time * HZ; |
1234 | if (break_time == 0) |
1235 | break_time++; /* so that 0 means no break time */ |
1236 | } |
1237 | |
1238 | for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next) { |
1239 | if (fl->fl_type != future) { |
1240 | fl->fl_type = future; |
1241 | fl->fl_break_time = break_time; |
1242 | /* lease must have lmops break callback */ |
1243 | fl->fl_lmops->fl_break(fl); |
1244 | } |
1245 | } |
1246 | |
1247 | if (i_have_this_lease || (mode & O_NONBLOCK)) { |
1248 | error = -EWOULDBLOCK; |
1249 | goto out; |
1250 | } |
1251 | |
1252 | restart: |
1253 | break_time = flock->fl_break_time; |
1254 | if (break_time != 0) { |
1255 | break_time -= jiffies; |
1256 | if (break_time == 0) |
1257 | break_time++; |
1258 | } |
1259 | locks_insert_block(flock, new_fl); |
1260 | unlock_flocks(); |
1261 | error = wait_event_interruptible_timeout(new_fl->fl_wait, |
1262 | !new_fl->fl_next, break_time); |
1263 | lock_flocks(); |
1264 | __locks_delete_block(new_fl); |
1265 | if (error >= 0) { |
1266 | if (error == 0) |
1267 | time_out_leases(inode); |
1268 | /* Wait for the next lease that has not been broken yet */ |
1269 | for (flock = inode->i_flock; flock && IS_LEASE(flock); |
1270 | flock = flock->fl_next) { |
1271 | if (flock->fl_type & F_INPROGRESS) |
1272 | goto restart; |
1273 | } |
1274 | error = 0; |
1275 | } |
1276 | |
1277 | out: |
1278 | unlock_flocks(); |
1279 | if (!IS_ERR(new_fl)) |
1280 | locks_free_lock(new_fl); |
1281 | return error; |
1282 | } |
1283 | |
1284 | EXPORT_SYMBOL(__break_lease); |
1285 | |
1286 | /** |
1287 | * lease_get_mtime - get the last modified time of an inode |
1288 | * @inode: the inode |
1289 | * @time: pointer to a timespec which will contain the last modified time |
1290 | * |
1291 | * This is to force NFS clients to flush their caches for files with |
1292 | * exclusive leases. The justification is that if someone has an |
1293 | * exclusive lease, then they could be modifying it. |
1294 | */ |
1295 | void lease_get_mtime(struct inode *inode, struct timespec *time) |
1296 | { |
1297 | struct file_lock *flock = inode->i_flock; |
1298 | if (flock && IS_LEASE(flock) && (flock->fl_type & F_WRLCK)) |
1299 | *time = current_fs_time(inode->i_sb); |
1300 | else |
1301 | *time = inode->i_mtime; |
1302 | } |
1303 | |
1304 | EXPORT_SYMBOL(lease_get_mtime); |
1305 | |
1306 | /** |
1307 | * fcntl_getlease - Enquire what lease is currently active |
1308 | * @filp: the file |
1309 | * |
1310 | * The value returned by this function will be one of |
1311 | * (if no lease break is pending): |
1312 | * |
1313 | * %F_RDLCK to indicate a shared lease is held. |
1314 | * |
1315 | * %F_WRLCK to indicate an exclusive lease is held. |
1316 | * |
1317 | * %F_UNLCK to indicate no lease is held. |
1318 | * |
1319 | * (if a lease break is pending): |
1320 | * |
1321 | * %F_RDLCK to indicate an exclusive lease needs to be |
1322 | * changed to a shared lease (or removed). |
1323 | * |
1324 | * %F_UNLCK to indicate the lease needs to be removed. |
1325 | * |
1326 | * XXX: sfr & willy disagree over whether F_INPROGRESS |
1327 | * should be returned to userspace. |
1328 | */ |
1329 | int fcntl_getlease(struct file *filp) |
1330 | { |
1331 | struct file_lock *fl; |
1332 | int type = F_UNLCK; |
1333 | |
1334 | lock_flocks(); |
1335 | time_out_leases(filp->f_path.dentry->d_inode); |
1336 | for (fl = filp->f_path.dentry->d_inode->i_flock; fl && IS_LEASE(fl); |
1337 | fl = fl->fl_next) { |
1338 | if (fl->fl_file == filp) { |
1339 | type = fl->fl_type & ~F_INPROGRESS; |
1340 | break; |
1341 | } |
1342 | } |
1343 | unlock_flocks(); |
1344 | return type; |
1345 | } |
1346 | |
1347 | /** |
1348 | * generic_setlease - sets a lease on an open file |
1349 | * @filp: file pointer |
1350 | * @arg: type of lease to obtain |
1351 | * @flp: input - file_lock to use, output - file_lock inserted |
1352 | * |
1353 | * The (input) flp->fl_lmops->fl_break function is required |
1354 | * by break_lease(). |
1355 | * |
1356 | * Called with file_lock_lock held. |
1357 | */ |
1358 | int generic_setlease(struct file *filp, long arg, struct file_lock **flp) |
1359 | { |
1360 | struct file_lock *fl, **before, **my_before = NULL, *lease; |
1361 | struct dentry *dentry = filp->f_path.dentry; |
1362 | struct inode *inode = dentry->d_inode; |
1363 | int error, rdlease_count = 0, wrlease_count = 0; |
1364 | |
1365 | lease = *flp; |
1366 | |
1367 | error = -EACCES; |
1368 | if ((current_fsuid() != inode->i_uid) && !capable(CAP_LEASE)) |
1369 | goto out; |
1370 | error = -EINVAL; |
1371 | if (!S_ISREG(inode->i_mode)) |
1372 | goto out; |
1373 | error = security_file_lock(filp, arg); |
1374 | if (error) |
1375 | goto out; |
1376 | |
1377 | time_out_leases(inode); |
1378 | |
1379 | BUG_ON(!(*flp)->fl_lmops->fl_break); |
1380 | |
1381 | if (arg != F_UNLCK) { |
1382 | error = -EAGAIN; |
1383 | if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0)) |
1384 | goto out; |
1385 | if ((arg == F_WRLCK) |
1386 | && ((dentry->d_count > 1) |
1387 | || (atomic_read(&inode->i_count) > 1))) |
1388 | goto out; |
1389 | } |
1390 | |
1391 | /* |
1392 | * At this point, we know that if there is an exclusive |
1393 | * lease on this file, then we hold it on this filp |
1394 | * (otherwise our open of this file would have blocked). |
1395 | * And if we are trying to acquire an exclusive lease, |
1396 | * then the file is not open by anyone (including us) |
1397 | * except for this filp. |
1398 | */ |
1399 | for (before = &inode->i_flock; |
1400 | ((fl = *before) != NULL) && IS_LEASE(fl); |
1401 | before = &fl->fl_next) { |
1402 | if (fl->fl_file == filp) |
1403 | my_before = before; |
1404 | else if (fl->fl_type == (F_INPROGRESS | F_UNLCK)) |
1405 | /* |
1406 | * Someone is in the process of opening this |
1407 | * file for writing so we may not take an |
1408 | * exclusive lease on it. |
1409 | */ |
1410 | wrlease_count++; |
1411 | else |
1412 | rdlease_count++; |
1413 | } |
1414 | |
1415 | error = -EAGAIN; |
1416 | if ((arg == F_RDLCK && (wrlease_count > 0)) || |
1417 | (arg == F_WRLCK && ((rdlease_count + wrlease_count) > 0))) |
1418 | goto out; |
1419 | |
1420 | if (my_before != NULL) { |
1421 | error = lease->fl_lmops->fl_change(my_before, arg); |
1422 | if (!error) |
1423 | *flp = *my_before; |
1424 | goto out; |
1425 | } |
1426 | |
1427 | if (arg == F_UNLCK) |
1428 | goto out; |
1429 | |
1430 | error = -EINVAL; |
1431 | if (!leases_enable) |
1432 | goto out; |
1433 | |
1434 | locks_insert_lock(before, lease); |
1435 | return 0; |
1436 | |
1437 | out: |
1438 | return error; |
1439 | } |
1440 | EXPORT_SYMBOL(generic_setlease); |
1441 | |
1442 | static int __vfs_setlease(struct file *filp, long arg, struct file_lock **lease) |
1443 | { |
1444 | if (filp->f_op && filp->f_op->setlease) |
1445 | return filp->f_op->setlease(filp, arg, lease); |
1446 | else |
1447 | return generic_setlease(filp, arg, lease); |
1448 | } |
1449 | |
1450 | /** |
1451 | * vfs_setlease - sets a lease on an open file |
1452 | * @filp: file pointer |
1453 | * @arg: type of lease to obtain |
1454 | * @lease: file_lock to use |
1455 | * |
1456 | * Call this to establish a lease on the file. |
1457 | * The (*lease)->fl_lmops->fl_break operation must be set; if not, |
1458 | * break_lease will oops! |
1459 | * |
1460 | * This will call the filesystem's setlease file method, if |
1461 | * defined. Note that there is no getlease method; instead, the |
1462 | * filesystem setlease method should call back to setlease() to |
1463 | * add a lease to the inode's lease list, where fcntl_getlease() can |
1464 | * find it. Since fcntl_getlease() only reports whether the current |
1465 | * task holds a lease, a cluster filesystem need only do this for |
1466 | * leases held by processes on this node. |
1467 | * |
1468 | * There is also no break_lease method; filesystems that |
1469 | * handle their own leases should break leases themselves from the |
1470 | * filesystem's open, create, and (on truncate) setattr methods. |
1471 | * |
1472 | * Warning: the only current setlease methods exist only to disable |
1473 | * leases in certain cases. More vfs changes may be required to |
1474 | * allow a full filesystem lease implementation. |
1475 | */ |
1476 | |
1477 | int vfs_setlease(struct file *filp, long arg, struct file_lock **lease) |
1478 | { |
1479 | int error; |
1480 | |
1481 | lock_flocks(); |
1482 | error = __vfs_setlease(filp, arg, lease); |
1483 | unlock_flocks(); |
1484 | |
1485 | return error; |
1486 | } |
1487 | EXPORT_SYMBOL_GPL(vfs_setlease); |
1488 | |
1489 | static int do_fcntl_delete_lease(struct file *filp) |
1490 | { |
1491 | struct file_lock fl, *flp = &fl; |
1492 | |
1493 | lease_init(filp, F_UNLCK, flp); |
1494 | |
1495 | return vfs_setlease(filp, F_UNLCK, &flp); |
1496 | } |
1497 | |
1498 | static int do_fcntl_add_lease(unsigned int fd, struct file *filp, long arg) |
1499 | { |
1500 | struct file_lock *fl, *ret; |
1501 | struct fasync_struct *new; |
1502 | int error; |
1503 | |
1504 | fl = lease_alloc(filp, arg); |
1505 | if (IS_ERR(fl)) |
1506 | return PTR_ERR(fl); |
1507 | |
1508 | new = fasync_alloc(); |
1509 | if (!new) { |
1510 | locks_free_lock(fl); |
1511 | return -ENOMEM; |
1512 | } |
1513 | ret = fl; |
1514 | lock_flocks(); |
1515 | error = __vfs_setlease(filp, arg, &ret); |
1516 | if (error) { |
1517 | unlock_flocks(); |
1518 | locks_free_lock(fl); |
1519 | goto out_free_fasync; |
1520 | } |
1521 | if (ret != fl) |
1522 | locks_free_lock(fl); |
1523 | |
1524 | /* |
1525 | * fasync_insert_entry() returns the old entry if any. |
1526 | * If there was no old entry, then it used 'new' and |
1527 | * inserted it into the fasync list. Clear new so that |
1528 | * we don't release it here. |
1529 | */ |
1530 | if (!fasync_insert_entry(fd, filp, &ret->fl_fasync, new)) |
1531 | new = NULL; |
1532 | |
1533 | error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0); |
1534 | unlock_flocks(); |
1535 | |
1536 | out_free_fasync: |
1537 | if (new) |
1538 | fasync_free(new); |
1539 | return error; |
1540 | } |
1541 | |
1542 | /** |
1543 | * fcntl_setlease - sets a lease on an open file |
1544 | * @fd: open file descriptor |
1545 | * @filp: file pointer |
1546 | * @arg: type of lease to obtain |
1547 | * |
1548 | * Call this fcntl to establish a lease on the file. |
1549 | * Note that you also need to call %F_SETSIG to |
1550 | * receive a signal when the lease is broken. |
1551 | */ |
1552 | int fcntl_setlease(unsigned int fd, struct file *filp, long arg) |
1553 | { |
1554 | if (arg == F_UNLCK) |
1555 | return do_fcntl_delete_lease(filp); |
1556 | return do_fcntl_add_lease(fd, filp, arg); |
1557 | } |
1558 | |
1559 | /** |
1560 | * flock_lock_file_wait - Apply a FLOCK-style lock to a file |
1561 | * @filp: The file to apply the lock to |
1562 | * @fl: The lock to be applied |
1563 | * |
1564 | * Add a FLOCK style lock to a file. |
1565 | */ |
1566 | int flock_lock_file_wait(struct file *filp, struct file_lock *fl) |
1567 | { |
1568 | int error; |
1569 | might_sleep(); |
1570 | for (;;) { |
1571 | error = flock_lock_file(filp, fl); |
1572 | if (error != FILE_LOCK_DEFERRED) |
1573 | break; |
1574 | error = wait_event_interruptible(fl->fl_wait, !fl->fl_next); |
1575 | if (!error) |
1576 | continue; |
1577 | |
1578 | locks_delete_block(fl); |
1579 | break; |
1580 | } |
1581 | return error; |
1582 | } |
1583 | |
1584 | EXPORT_SYMBOL(flock_lock_file_wait); |
1585 | |
1586 | /** |
1587 | * sys_flock: - flock() system call. |
1588 | * @fd: the file descriptor to lock. |
1589 | * @cmd: the type of lock to apply. |
1590 | * |
1591 | * Apply a %FL_FLOCK style lock to an open file descriptor. |
1592 | * The @cmd can be one of |
1593 | * |
1594 | * %LOCK_SH -- a shared lock. |
1595 | * |
1596 | * %LOCK_EX -- an exclusive lock. |
1597 | * |
1598 | * %LOCK_UN -- remove an existing lock. |
1599 | * |
1600 | * %LOCK_MAND -- a `mandatory' flock. This exists to emulate Windows Share Modes. |
1601 | * |
1602 | * %LOCK_MAND can be combined with %LOCK_READ or %LOCK_WRITE to allow other |
1603 | * processes read and write access respectively. |
1604 | */ |
1605 | SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd) |
1606 | { |
1607 | struct file *filp; |
1608 | struct file_lock *lock; |
1609 | int can_sleep, unlock; |
1610 | int error; |
1611 | |
1612 | error = -EBADF; |
1613 | filp = fget(fd); |
1614 | if (!filp) |
1615 | goto out; |
1616 | |
1617 | can_sleep = !(cmd & LOCK_NB); |
1618 | cmd &= ~LOCK_NB; |
1619 | unlock = (cmd == LOCK_UN); |
1620 | |
1621 | if (!unlock && !(cmd & LOCK_MAND) && |
1622 | !(filp->f_mode & (FMODE_READ|FMODE_WRITE))) |
1623 | goto out_putf; |
1624 | |
1625 | error = flock_make_lock(filp, &lock, cmd); |
1626 | if (error) |
1627 | goto out_putf; |
1628 | if (can_sleep) |
1629 | lock->fl_flags |= FL_SLEEP; |
1630 | |
1631 | error = security_file_lock(filp, lock->fl_type); |
1632 | if (error) |
1633 | goto out_free; |
1634 | |
1635 | if (filp->f_op && filp->f_op->flock) |
1636 | error = filp->f_op->flock(filp, |
1637 | (can_sleep) ? F_SETLKW : F_SETLK, |
1638 | lock); |
1639 | else |
1640 | error = flock_lock_file_wait(filp, lock); |
1641 | |
1642 | out_free: |
1643 | locks_free_lock(lock); |
1644 | |
1645 | out_putf: |
1646 | fput(filp); |
1647 | out: |
1648 | return error; |
1649 | } |
1650 | |
1651 | /** |
1652 | * vfs_test_lock - test file byte range lock |
1653 | * @filp: The file to test lock for |
1654 | * @fl: The lock to test; also used to hold result |
1655 | * |
1656 | * Returns -ERRNO on failure. Indicates presence of conflicting lock by |
1657 | * setting conf->fl_type to something other than F_UNLCK. |
1658 | */ |
1659 | int vfs_test_lock(struct file *filp, struct file_lock *fl) |
1660 | { |
1661 | if (filp->f_op && filp->f_op->lock) |
1662 | return filp->f_op->lock(filp, F_GETLK, fl); |
1663 | posix_test_lock(filp, fl); |
1664 | return 0; |
1665 | } |
1666 | EXPORT_SYMBOL_GPL(vfs_test_lock); |
1667 | |
1668 | static int posix_lock_to_flock(struct flock *flock, struct file_lock *fl) |
1669 | { |
1670 | flock->l_pid = fl->fl_pid; |
1671 | #if BITS_PER_LONG == 32 |
1672 | /* |
1673 | * Make sure we can represent the posix lock via |
1674 | * legacy 32bit flock. |
1675 | */ |
1676 | if (fl->fl_start > OFFT_OFFSET_MAX) |
1677 | return -EOVERFLOW; |
1678 | if (fl->fl_end != OFFSET_MAX && fl->fl_end > OFFT_OFFSET_MAX) |
1679 | return -EOVERFLOW; |
1680 | #endif |
1681 | flock->l_start = fl->fl_start; |
1682 | flock->l_len = fl->fl_end == OFFSET_MAX ? 0 : |
1683 | fl->fl_end - fl->fl_start + 1; |
1684 | flock->l_whence = 0; |
1685 | flock->l_type = fl->fl_type; |
1686 | return 0; |
1687 | } |
1688 | |
1689 | #if BITS_PER_LONG == 32 |
1690 | static void posix_lock_to_flock64(struct flock64 *flock, struct file_lock *fl) |
1691 | { |
1692 | flock->l_pid = fl->fl_pid; |
1693 | flock->l_start = fl->fl_start; |
1694 | flock->l_len = fl->fl_end == OFFSET_MAX ? 0 : |
1695 | fl->fl_end - fl->fl_start + 1; |
1696 | flock->l_whence = 0; |
1697 | flock->l_type = fl->fl_type; |
1698 | } |
1699 | #endif |
1700 | |
1701 | /* Report the first existing lock that would conflict with l. |
1702 | * This implements the F_GETLK command of fcntl(). |
1703 | */ |
1704 | int fcntl_getlk(struct file *filp, struct flock __user *l) |
1705 | { |
1706 | struct file_lock file_lock; |
1707 | struct flock flock; |
1708 | int error; |
1709 | |
1710 | error = -EFAULT; |
1711 | if (copy_from_user(&flock, l, sizeof(flock))) |
1712 | goto out; |
1713 | error = -EINVAL; |
1714 | if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK)) |
1715 | goto out; |
1716 | |
1717 | error = flock_to_posix_lock(filp, &file_lock, &flock); |
1718 | if (error) |
1719 | goto out; |
1720 | |
1721 | error = vfs_test_lock(filp, &file_lock); |
1722 | if (error) |
1723 | goto out; |
1724 | |
1725 | flock.l_type = file_lock.fl_type; |
1726 | if (file_lock.fl_type != F_UNLCK) { |
1727 | error = posix_lock_to_flock(&flock, &file_lock); |
1728 | if (error) |
1729 | goto out; |
1730 | } |
1731 | error = -EFAULT; |
1732 | if (!copy_to_user(l, &flock, sizeof(flock))) |
1733 | error = 0; |
1734 | out: |
1735 | return error; |
1736 | } |
1737 | |
1738 | /** |
1739 | * vfs_lock_file - file byte range lock |
1740 | * @filp: The file to apply the lock to |
1741 | * @cmd: type of locking operation (F_SETLK, F_GETLK, etc.) |
1742 | * @fl: The lock to be applied |
1743 | * @conf: Place to return a copy of the conflicting lock, if found. |
1744 | * |
1745 | * A caller that doesn't care about the conflicting lock may pass NULL |
1746 | * as the final argument. |
1747 | * |
1748 | * If the filesystem defines a private ->lock() method, then @conf will |
1749 | * be left unchanged; so a caller that cares should initialize it to |
1750 | * some acceptable default. |
1751 | * |
1752 | * To avoid blocking kernel daemons, such as lockd, that need to acquire POSIX |
1753 | * locks, the ->lock() interface may return asynchronously, before the lock has |
1754 | * been granted or denied by the underlying filesystem, if (and only if) |
1755 | * fl_grant is set. Callers expecting ->lock() to return asynchronously |
1756 | * will only use F_SETLK, not F_SETLKW; they will set FL_SLEEP if (and only if) |
1757 | * the request is for a blocking lock. When ->lock() does return asynchronously, |
1758 | * it must return FILE_LOCK_DEFERRED, and call ->fl_grant() when the lock |
1759 | * request completes. |
1760 | * If the request is for non-blocking lock the file system should return |
1761 | * FILE_LOCK_DEFERRED then try to get the lock and call the callback routine |
1762 | * with the result. If the request timed out the callback routine will return a |
1763 | * nonzero return code and the file system should release the lock. The file |
1764 | * system is also responsible to keep a corresponding posix lock when it |
1765 | * grants a lock so the VFS can find out which locks are locally held and do |
1766 | * the correct lock cleanup when required. |
1767 | * The underlying filesystem must not drop the kernel lock or call |
1768 | * ->fl_grant() before returning to the caller with a FILE_LOCK_DEFERRED |
1769 | * return code. |
1770 | */ |
1771 | int vfs_lock_file(struct file *filp, unsigned int cmd, struct file_lock *fl, struct file_lock *conf) |
1772 | { |
1773 | if (filp->f_op && filp->f_op->lock) |
1774 | return filp->f_op->lock(filp, cmd, fl); |
1775 | else |
1776 | return posix_lock_file(filp, fl, conf); |
1777 | } |
1778 | EXPORT_SYMBOL_GPL(vfs_lock_file); |
1779 | |
1780 | static int do_lock_file_wait(struct file *filp, unsigned int cmd, |
1781 | struct file_lock *fl) |
1782 | { |
1783 | int error; |
1784 | |
1785 | error = security_file_lock(filp, fl->fl_type); |
1786 | if (error) |
1787 | return error; |
1788 | |
1789 | for (;;) { |
1790 | error = vfs_lock_file(filp, cmd, fl, NULL); |
1791 | if (error != FILE_LOCK_DEFERRED) |
1792 | break; |
1793 | error = wait_event_interruptible(fl->fl_wait, !fl->fl_next); |
1794 | if (!error) |
1795 | continue; |
1796 | |
1797 | locks_delete_block(fl); |
1798 | break; |
1799 | } |
1800 | |
1801 | return error; |
1802 | } |
1803 | |
1804 | /* Apply the lock described by l to an open file descriptor. |
1805 | * This implements both the F_SETLK and F_SETLKW commands of fcntl(). |
1806 | */ |
1807 | int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd, |
1808 | struct flock __user *l) |
1809 | { |
1810 | struct file_lock *file_lock = locks_alloc_lock(); |
1811 | struct flock flock; |
1812 | struct inode *inode; |
1813 | struct file *f; |
1814 | int error; |
1815 | |
1816 | if (file_lock == NULL) |
1817 | return -ENOLCK; |
1818 | |
1819 | /* |
1820 | * This might block, so we do it before checking the inode. |
1821 | */ |
1822 | error = -EFAULT; |
1823 | if (copy_from_user(&flock, l, sizeof(flock))) |
1824 | goto out; |
1825 | |
1826 | inode = filp->f_path.dentry->d_inode; |
1827 | |
1828 | /* Don't allow mandatory locks on files that may be memory mapped |
1829 | * and shared. |
1830 | */ |
1831 | if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) { |
1832 | error = -EAGAIN; |
1833 | goto out; |
1834 | } |
1835 | |
1836 | again: |
1837 | error = flock_to_posix_lock(filp, file_lock, &flock); |
1838 | if (error) |
1839 | goto out; |
1840 | if (cmd == F_SETLKW) { |
1841 | file_lock->fl_flags |= FL_SLEEP; |
1842 | } |
1843 | |
1844 | error = -EBADF; |
1845 | switch (flock.l_type) { |
1846 | case F_RDLCK: |
1847 | if (!(filp->f_mode & FMODE_READ)) |
1848 | goto out; |
1849 | break; |
1850 | case F_WRLCK: |
1851 | if (!(filp->f_mode & FMODE_WRITE)) |
1852 | goto out; |
1853 | break; |
1854 | case F_UNLCK: |
1855 | break; |
1856 | default: |
1857 | error = -EINVAL; |
1858 | goto out; |
1859 | } |
1860 | |
1861 | error = do_lock_file_wait(filp, cmd, file_lock); |
1862 | |
1863 | /* |
1864 | * Attempt to detect a close/fcntl race and recover by |
1865 | * releasing the lock that was just acquired. |
1866 | */ |
1867 | /* |
1868 | * we need that spin_lock here - it prevents reordering between |
1869 | * update of inode->i_flock and check for it done in close(). |
1870 | * rcu_read_lock() wouldn't do. |
1871 | */ |
1872 | spin_lock(¤t->files->file_lock); |
1873 | f = fcheck(fd); |
1874 | spin_unlock(¤t->files->file_lock); |
1875 | if (!error && f != filp && flock.l_type != F_UNLCK) { |
1876 | flock.l_type = F_UNLCK; |
1877 | goto again; |
1878 | } |
1879 | |
1880 | out: |
1881 | locks_free_lock(file_lock); |
1882 | return error; |
1883 | } |
1884 | |
1885 | #if BITS_PER_LONG == 32 |
1886 | /* Report the first existing lock that would conflict with l. |
1887 | * This implements the F_GETLK command of fcntl(). |
1888 | */ |
1889 | int fcntl_getlk64(struct file *filp, struct flock64 __user *l) |
1890 | { |
1891 | struct file_lock file_lock; |
1892 | struct flock64 flock; |
1893 | int error; |
1894 | |
1895 | error = -EFAULT; |
1896 | if (copy_from_user(&flock, l, sizeof(flock))) |
1897 | goto out; |
1898 | error = -EINVAL; |
1899 | if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK)) |
1900 | goto out; |
1901 | |
1902 | error = flock64_to_posix_lock(filp, &file_lock, &flock); |
1903 | if (error) |
1904 | goto out; |
1905 | |
1906 | error = vfs_test_lock(filp, &file_lock); |
1907 | if (error) |
1908 | goto out; |
1909 | |
1910 | flock.l_type = file_lock.fl_type; |
1911 | if (file_lock.fl_type != F_UNLCK) |
1912 | posix_lock_to_flock64(&flock, &file_lock); |
1913 | |
1914 | error = -EFAULT; |
1915 | if (!copy_to_user(l, &flock, sizeof(flock))) |
1916 | error = 0; |
1917 | |
1918 | out: |
1919 | return error; |
1920 | } |
1921 | |
1922 | /* Apply the lock described by l to an open file descriptor. |
1923 | * This implements both the F_SETLK and F_SETLKW commands of fcntl(). |
1924 | */ |
1925 | int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd, |
1926 | struct flock64 __user *l) |
1927 | { |
1928 | struct file_lock *file_lock = locks_alloc_lock(); |
1929 | struct flock64 flock; |
1930 | struct inode *inode; |
1931 | struct file *f; |
1932 | int error; |
1933 | |
1934 | if (file_lock == NULL) |
1935 | return -ENOLCK; |
1936 | |
1937 | /* |
1938 | * This might block, so we do it before checking the inode. |
1939 | */ |
1940 | error = -EFAULT; |
1941 | if (copy_from_user(&flock, l, sizeof(flock))) |
1942 | goto out; |
1943 | |
1944 | inode = filp->f_path.dentry->d_inode; |
1945 | |
1946 | /* Don't allow mandatory locks on files that may be memory mapped |
1947 | * and shared. |
1948 | */ |
1949 | if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) { |
1950 | error = -EAGAIN; |
1951 | goto out; |
1952 | } |
1953 | |
1954 | again: |
1955 | error = flock64_to_posix_lock(filp, file_lock, &flock); |
1956 | if (error) |
1957 | goto out; |
1958 | if (cmd == F_SETLKW64) { |
1959 | file_lock->fl_flags |= FL_SLEEP; |
1960 | } |
1961 | |
1962 | error = -EBADF; |
1963 | switch (flock.l_type) { |
1964 | case F_RDLCK: |
1965 | if (!(filp->f_mode & FMODE_READ)) |
1966 | goto out; |
1967 | break; |
1968 | case F_WRLCK: |
1969 | if (!(filp->f_mode & FMODE_WRITE)) |
1970 | goto out; |
1971 | break; |
1972 | case F_UNLCK: |
1973 | break; |
1974 | default: |
1975 | error = -EINVAL; |
1976 | goto out; |
1977 | } |
1978 | |
1979 | error = do_lock_file_wait(filp, cmd, file_lock); |
1980 | |
1981 | /* |
1982 | * Attempt to detect a close/fcntl race and recover by |
1983 | * releasing the lock that was just acquired. |
1984 | */ |
1985 | spin_lock(¤t->files->file_lock); |
1986 | f = fcheck(fd); |
1987 | spin_unlock(¤t->files->file_lock); |
1988 | if (!error && f != filp && flock.l_type != F_UNLCK) { |
1989 | flock.l_type = F_UNLCK; |
1990 | goto again; |
1991 | } |
1992 | |
1993 | out: |
1994 | locks_free_lock(file_lock); |
1995 | return error; |
1996 | } |
1997 | #endif /* BITS_PER_LONG == 32 */ |
1998 | |
1999 | /* |
2000 | * This function is called when the file is being removed |
2001 | * from the task's fd array. POSIX locks belonging to this task |
2002 | * are deleted at this time. |
2003 | */ |
2004 | void locks_remove_posix(struct file *filp, fl_owner_t owner) |
2005 | { |
2006 | struct file_lock lock; |
2007 | |
2008 | /* |
2009 | * If there are no locks held on this file, we don't need to call |
2010 | * posix_lock_file(). Another process could be setting a lock on this |
2011 | * file at the same time, but we wouldn't remove that lock anyway. |
2012 | */ |
2013 | if (!filp->f_path.dentry->d_inode->i_flock) |
2014 | return; |
2015 | |
2016 | lock.fl_type = F_UNLCK; |
2017 | lock.fl_flags = FL_POSIX | FL_CLOSE; |
2018 | lock.fl_start = 0; |
2019 | lock.fl_end = OFFSET_MAX; |
2020 | lock.fl_owner = owner; |
2021 | lock.fl_pid = current->tgid; |
2022 | lock.fl_file = filp; |
2023 | lock.fl_ops = NULL; |
2024 | lock.fl_lmops = NULL; |
2025 | |
2026 | vfs_lock_file(filp, F_SETLK, &lock, NULL); |
2027 | |
2028 | if (lock.fl_ops && lock.fl_ops->fl_release_private) |
2029 | lock.fl_ops->fl_release_private(&lock); |
2030 | } |
2031 | |
2032 | EXPORT_SYMBOL(locks_remove_posix); |
2033 | |
2034 | /* |
2035 | * This function is called on the last close of an open file. |
2036 | */ |
2037 | void locks_remove_flock(struct file *filp) |
2038 | { |
2039 | struct inode * inode = filp->f_path.dentry->d_inode; |
2040 | struct file_lock *fl; |
2041 | struct file_lock **before; |
2042 | |
2043 | if (!inode->i_flock) |
2044 | return; |
2045 | |
2046 | if (filp->f_op && filp->f_op->flock) { |
2047 | struct file_lock fl = { |
2048 | .fl_pid = current->tgid, |
2049 | .fl_file = filp, |
2050 | .fl_flags = FL_FLOCK, |
2051 | .fl_type = F_UNLCK, |
2052 | .fl_end = OFFSET_MAX, |
2053 | }; |
2054 | filp->f_op->flock(filp, F_SETLKW, &fl); |
2055 | if (fl.fl_ops && fl.fl_ops->fl_release_private) |
2056 | fl.fl_ops->fl_release_private(&fl); |
2057 | } |
2058 | |
2059 | lock_flocks(); |
2060 | before = &inode->i_flock; |
2061 | |
2062 | while ((fl = *before) != NULL) { |
2063 | if (fl->fl_file == filp) { |
2064 | if (IS_FLOCK(fl)) { |
2065 | locks_delete_lock(before); |
2066 | continue; |
2067 | } |
2068 | if (IS_LEASE(fl)) { |
2069 | lease_modify(before, F_UNLCK); |
2070 | continue; |
2071 | } |
2072 | /* What? */ |
2073 | BUG(); |
2074 | } |
2075 | before = &fl->fl_next; |
2076 | } |
2077 | unlock_flocks(); |
2078 | } |
2079 | |
2080 | /** |
2081 | * posix_unblock_lock - stop waiting for a file lock |
2082 | * @filp: how the file was opened |
2083 | * @waiter: the lock which was waiting |
2084 | * |
2085 | * lockd needs to block waiting for locks. |
2086 | */ |
2087 | int |
2088 | posix_unblock_lock(struct file *filp, struct file_lock *waiter) |
2089 | { |
2090 | int status = 0; |
2091 | |
2092 | lock_flocks(); |
2093 | if (waiter->fl_next) |
2094 | __locks_delete_block(waiter); |
2095 | else |
2096 | status = -ENOENT; |
2097 | unlock_flocks(); |
2098 | return status; |
2099 | } |
2100 | |
2101 | EXPORT_SYMBOL(posix_unblock_lock); |
2102 | |
2103 | /** |
2104 | * vfs_cancel_lock - file byte range unblock lock |
2105 | * @filp: The file to apply the unblock to |
2106 | * @fl: The lock to be unblocked |
2107 | * |
2108 | * Used by lock managers to cancel blocked requests |
2109 | */ |
2110 | int vfs_cancel_lock(struct file *filp, struct file_lock *fl) |
2111 | { |
2112 | if (filp->f_op && filp->f_op->lock) |
2113 | return filp->f_op->lock(filp, F_CANCELLK, fl); |
2114 | return 0; |
2115 | } |
2116 | |
2117 | EXPORT_SYMBOL_GPL(vfs_cancel_lock); |
2118 | |
2119 | #ifdef CONFIG_PROC_FS |
2120 | #include <linux/proc_fs.h> |
2121 | #include <linux/seq_file.h> |
2122 | |
2123 | static void lock_get_status(struct seq_file *f, struct file_lock *fl, |
2124 | loff_t id, char *pfx) |
2125 | { |
2126 | struct inode *inode = NULL; |
2127 | unsigned int fl_pid; |
2128 | |
2129 | if (fl->fl_nspid) |
2130 | fl_pid = pid_vnr(fl->fl_nspid); |
2131 | else |
2132 | fl_pid = fl->fl_pid; |
2133 | |
2134 | if (fl->fl_file != NULL) |
2135 | inode = fl->fl_file->f_path.dentry->d_inode; |
2136 | |
2137 | seq_printf(f, "%lld:%s ", id, pfx); |
2138 | if (IS_POSIX(fl)) { |
2139 | seq_printf(f, "%6s %s ", |
2140 | (fl->fl_flags & FL_ACCESS) ? "ACCESS" : "POSIX ", |
2141 | (inode == NULL) ? "*NOINODE*" : |
2142 | mandatory_lock(inode) ? "MANDATORY" : "ADVISORY "); |
2143 | } else if (IS_FLOCK(fl)) { |
2144 | if (fl->fl_type & LOCK_MAND) { |
2145 | seq_printf(f, "FLOCK MSNFS "); |
2146 | } else { |
2147 | seq_printf(f, "FLOCK ADVISORY "); |
2148 | } |
2149 | } else if (IS_LEASE(fl)) { |
2150 | seq_printf(f, "LEASE "); |
2151 | if (fl->fl_type & F_INPROGRESS) |
2152 | seq_printf(f, "BREAKING "); |
2153 | else if (fl->fl_file) |
2154 | seq_printf(f, "ACTIVE "); |
2155 | else |
2156 | seq_printf(f, "BREAKER "); |
2157 | } else { |
2158 | seq_printf(f, "UNKNOWN UNKNOWN "); |
2159 | } |
2160 | if (fl->fl_type & LOCK_MAND) { |
2161 | seq_printf(f, "%s ", |
2162 | (fl->fl_type & LOCK_READ) |
2163 | ? (fl->fl_type & LOCK_WRITE) ? "RW " : "READ " |
2164 | : (fl->fl_type & LOCK_WRITE) ? "WRITE" : "NONE "); |
2165 | } else { |
2166 | seq_printf(f, "%s ", |
2167 | (fl->fl_type & F_INPROGRESS) |
2168 | ? (fl->fl_type & F_UNLCK) ? "UNLCK" : "READ " |
2169 | : (fl->fl_type & F_WRLCK) ? "WRITE" : "READ "); |
2170 | } |
2171 | if (inode) { |
2172 | #ifdef WE_CAN_BREAK_LSLK_NOW |
2173 | seq_printf(f, "%d %s:%ld ", fl_pid, |
2174 | inode->i_sb->s_id, inode->i_ino); |
2175 | #else |
2176 | /* userspace relies on this representation of dev_t ;-( */ |
2177 | seq_printf(f, "%d %02x:%02x:%ld ", fl_pid, |
2178 | MAJOR(inode->i_sb->s_dev), |
2179 | MINOR(inode->i_sb->s_dev), inode->i_ino); |
2180 | #endif |
2181 | } else { |
2182 | seq_printf(f, "%d <none>:0 ", fl_pid); |
2183 | } |
2184 | if (IS_POSIX(fl)) { |
2185 | if (fl->fl_end == OFFSET_MAX) |
2186 | seq_printf(f, "%Ld EOF\n", fl->fl_start); |
2187 | else |
2188 | seq_printf(f, "%Ld %Ld\n", fl->fl_start, fl->fl_end); |
2189 | } else { |
2190 | seq_printf(f, "0 EOF\n"); |
2191 | } |
2192 | } |
2193 | |
2194 | static int locks_show(struct seq_file *f, void *v) |
2195 | { |
2196 | struct file_lock *fl, *bfl; |
2197 | |
2198 | fl = list_entry(v, struct file_lock, fl_link); |
2199 | |
2200 | lock_get_status(f, fl, *((loff_t *)f->private), ""); |
2201 | |
2202 | list_for_each_entry(bfl, &fl->fl_block, fl_block) |
2203 | lock_get_status(f, bfl, *((loff_t *)f->private), " ->"); |
2204 | |
2205 | return 0; |
2206 | } |
2207 | |
2208 | static void *locks_start(struct seq_file *f, loff_t *pos) |
2209 | { |
2210 | loff_t *p = f->private; |
2211 | |
2212 | lock_flocks(); |
2213 | *p = (*pos + 1); |
2214 | return seq_list_start(&file_lock_list, *pos); |
2215 | } |
2216 | |
2217 | static void *locks_next(struct seq_file *f, void *v, loff_t *pos) |
2218 | { |
2219 | loff_t *p = f->private; |
2220 | ++*p; |
2221 | return seq_list_next(v, &file_lock_list, pos); |
2222 | } |
2223 | |
2224 | static void locks_stop(struct seq_file *f, void *v) |
2225 | { |
2226 | unlock_flocks(); |
2227 | } |
2228 | |
2229 | static const struct seq_operations locks_seq_operations = { |
2230 | .start = locks_start, |
2231 | .next = locks_next, |
2232 | .stop = locks_stop, |
2233 | .show = locks_show, |
2234 | }; |
2235 | |
2236 | static int locks_open(struct inode *inode, struct file *filp) |
2237 | { |
2238 | return seq_open_private(filp, &locks_seq_operations, sizeof(loff_t)); |
2239 | } |
2240 | |
2241 | static const struct file_operations proc_locks_operations = { |
2242 | .open = locks_open, |
2243 | .read = seq_read, |
2244 | .llseek = seq_lseek, |
2245 | .release = seq_release_private, |
2246 | }; |
2247 | |
2248 | static int __init proc_locks_init(void) |
2249 | { |
2250 | proc_create("locks", 0, NULL, &proc_locks_operations); |
2251 | return 0; |
2252 | } |
2253 | module_init(proc_locks_init); |
2254 | #endif |
2255 | |
2256 | /** |
2257 | * lock_may_read - checks that the region is free of locks |
2258 | * @inode: the inode that is being read |
2259 | * @start: the first byte to read |
2260 | * @len: the number of bytes to read |
2261 | * |
2262 | * Emulates Windows locking requirements. Whole-file |
2263 | * mandatory locks (share modes) can prohibit a read and |
2264 | * byte-range POSIX locks can prohibit a read if they overlap. |
2265 | * |
2266 | * N.B. this function is only ever called |
2267 | * from knfsd and ownership of locks is never checked. |
2268 | */ |
2269 | int lock_may_read(struct inode *inode, loff_t start, unsigned long len) |
2270 | { |
2271 | struct file_lock *fl; |
2272 | int result = 1; |
2273 | lock_flocks(); |
2274 | for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) { |
2275 | if (IS_POSIX(fl)) { |
2276 | if (fl->fl_type == F_RDLCK) |
2277 | continue; |
2278 | if ((fl->fl_end < start) || (fl->fl_start > (start + len))) |
2279 | continue; |
2280 | } else if (IS_FLOCK(fl)) { |
2281 | if (!(fl->fl_type & LOCK_MAND)) |
2282 | continue; |
2283 | if (fl->fl_type & LOCK_READ) |
2284 | continue; |
2285 | } else |
2286 | continue; |
2287 | result = 0; |
2288 | break; |
2289 | } |
2290 | unlock_flocks(); |
2291 | return result; |
2292 | } |
2293 | |
2294 | EXPORT_SYMBOL(lock_may_read); |
2295 | |
2296 | /** |
2297 | * lock_may_write - checks that the region is free of locks |
2298 | * @inode: the inode that is being written |
2299 | * @start: the first byte to write |
2300 | * @len: the number of bytes to write |
2301 | * |
2302 | * Emulates Windows locking requirements. Whole-file |
2303 | * mandatory locks (share modes) can prohibit a write and |
2304 | * byte-range POSIX locks can prohibit a write if they overlap. |
2305 | * |
2306 | * N.B. this function is only ever called |
2307 | * from knfsd and ownership of locks is never checked. |
2308 | */ |
2309 | int lock_may_write(struct inode *inode, loff_t start, unsigned long len) |
2310 | { |
2311 | struct file_lock *fl; |
2312 | int result = 1; |
2313 | lock_flocks(); |
2314 | for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) { |
2315 | if (IS_POSIX(fl)) { |
2316 | if ((fl->fl_end < start) || (fl->fl_start > (start + len))) |
2317 | continue; |
2318 | } else if (IS_FLOCK(fl)) { |
2319 | if (!(fl->fl_type & LOCK_MAND)) |
2320 | continue; |
2321 | if (fl->fl_type & LOCK_WRITE) |
2322 | continue; |
2323 | } else |
2324 | continue; |
2325 | result = 0; |
2326 | break; |
2327 | } |
2328 | unlock_flocks(); |
2329 | return result; |
2330 | } |
2331 | |
2332 | EXPORT_SYMBOL(lock_may_write); |
2333 | |
2334 | static int __init filelock_init(void) |
2335 | { |
2336 | filelock_cache = kmem_cache_create("file_lock_cache", |
2337 | sizeof(struct file_lock), 0, SLAB_PANIC, |
2338 | init_once); |
2339 | return 0; |
2340 | } |
2341 | |
2342 | core_initcall(filelock_init); |
2343 |
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