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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 - F_FLOCK and F_POSIX.
32 *
33 * F_POSIX locks are created with calls to fcntl() and lockf() through the
34 * fcntl() system call. They have the semantics described above.
35 *
36 * F_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 * F_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 * F_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 (begemot@bgm.rosprint.net), 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 'linux/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
73 #include <linux/malloc.h>
74 #include <linux/sched.h>
75 #include <linux/kernel.h>
76 #include <linux/errno.h>
77 #include <linux/stat.h>
78 #include <linux/fcntl.h>
79
80 #include <asm/segment.h>
81
82 #define OFFSET_MAX ((off_t)0x7fffffff) /* FIXME: move elsewhere? */
83
84 static int flock_make_lock(struct file *filp, struct file_lock *fl,
85 unsigned int cmd);
86 static int posix_make_lock(struct file *filp, struct file_lock *fl,
87 struct flock *l);
88 static int flock_locks_conflict(struct file_lock *caller_fl,
89 struct file_lock *sys_fl);
90 static int posix_locks_conflict(struct file_lock *caller_fl,
91 struct file_lock *sys_fl);
92 static int locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl);
93 static int flock_lock_file(struct file *filp, struct file_lock *caller,
94 unsigned int wait);
95 static int posix_lock_file(struct file *filp, struct file_lock *caller,
96 unsigned int wait);
97 static int posix_locks_deadlock(struct task_struct *my_task,
98 struct task_struct *blocked_task);
99 static int locks_overlap(struct file_lock *fl1, struct file_lock *fl2);
100
101 static struct file_lock *locks_alloc_lock(struct file_lock *fl);
102 static void locks_insert_lock(struct file_lock **pos, struct file_lock *fl);
103 static void locks_delete_lock(struct file_lock **fl, unsigned int wait);
104
105 static struct file_lock *file_lock_table = NULL;
106
107 /* Free lock not inserted in any queue */
108 static inline void locks_free_lock(struct file_lock **fl)
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*/
109 {
110 kfree(*fl);
111 *fl = NULL; /* Just in case */
112 }
113
114 /* Add lock fl to the blocked list pointed to by block.
115 * We search to the end of the existing list and insert the the new
116 * struct. This ensures processes will be woken up in the order they
117 * blocked.
118 * NOTE: nowhere does the documentation insist that processes be woken
119 * up in this order, but it seems like the reasonable thing to do.
120 * If the blocked list gets long then this search could get expensive,
121 * in which case we could consider waking the processes up in reverse
122 * order, or making the blocked list a doubly linked circular list.
123 *
124 * This functions are called only from one place (flock_lock_file)
125 * so they are inlined now. -- Dmitry Gorodchanin 02/09/96.
126 */
127
128 static inline void locks_insert_block(struct file_lock **block,
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*/
129 struct file_lock *fl)
130 {
131 struct file_lock *bfl;
132
133 while ((bfl = *block) != NULL) {
134 block = &bfl->fl_block;
135 }
136
137 *block = fl;
138 fl->fl_block = NULL;
139
140 return;
141 }
142
143 static inline void locks_delete_block(struct file_lock **block,
/* */
144 struct file_lock *fl)
145 {
146 struct file_lock *bfl;
147
148 while ((bfl = *block) != NULL) {
149 if (bfl == fl) {
150 *block = fl->fl_block;
151 fl->fl_block = NULL;
152 return;
153 }
154 block = &bfl->fl_block;
155 }
156 }
157
158 /* flock() system call entry point. Apply a FLOCK style lock to
159 * an open file descriptor.
160 */
161 asmlinkage int sys_flock(unsigned int fd, unsigned int cmd)
/* */
162 {
163 struct file_lock file_lock;
164 struct file *filp;
165
166 if ((fd >= NR_OPEN) || !(filp = current->files->fd[fd]))
167 return (-EBADF);
168
169 if (!flock_make_lock(filp, &file_lock, cmd))
170 return (-EINVAL);
171
172 if ((file_lock.fl_type != F_UNLCK) && !(filp->f_mode & 3))
173 return (-EBADF);
174
175 return (flock_lock_file(filp, &file_lock, cmd & LOCK_UN ? 0 : cmd & LOCK_NB ? 0 : 1));
176 }
177
178 /* Report the first existing lock that would conflict with l.
179 * This implements the F_GETLK command of fcntl().
180 */
181 int fcntl_getlk(unsigned int fd, struct flock *l)
/* */
182 {
183 int error;
184 struct flock flock;
185 struct file *filp;
186 struct file_lock *fl,file_lock;
187
188 if ((fd >= NR_OPEN) || !(filp = current->files->fd[fd]))
189 return (-EBADF);
190 error = verify_area(VERIFY_WRITE, l, sizeof(*l));
191 if (error)
192 return (error);
193
194 memcpy_fromfs(&flock, l, sizeof(flock));
195 if ((flock.l_type == F_UNLCK) || (flock.l_type == F_EXLCK) ||
196 (flock.l_type == F_SHLCK))
197 return (-EINVAL);
198
199 if (!filp->f_inode || !posix_make_lock(filp, &file_lock, &flock))
200 return (-EINVAL);
201
202 for (fl = filp->f_inode->i_flock; fl != NULL; fl = fl->fl_next) {
203 if (posix_locks_conflict(&file_lock, fl)) {
204 flock.l_pid = fl->fl_owner->pid;
205 flock.l_start = fl->fl_start;
206 flock.l_len = fl->fl_end == OFFSET_MAX ? 0 :
207 fl->fl_end - fl->fl_start + 1;
208 flock.l_whence = 0;
209 flock.l_type = fl->fl_type;
210 memcpy_tofs(l, &flock, sizeof(flock));
211 return (0);
212 }
213 }
214
215 flock.l_type = F_UNLCK; /* no conflict found */
216 memcpy_tofs(l, &flock, sizeof(flock));
217 return (0);
218 }
219
220 /* Apply the lock described by l to an open file descriptor.
221 * This implements both the F_SETLK and F_SETLKW commands of fcntl().
222 * It also emulates flock() in a pretty broken way for older C
223 * libraries.
224 */
225 int fcntl_setlk(unsigned int fd, unsigned int cmd, struct flock *l)
/* */
226 {
227 int error;
228 struct file *filp;
229 struct file_lock file_lock;
230 struct flock flock;
231 struct inode *inode;
232
233 /*
234 * Get arguments and validate them ...
235 */
236
237 if ((fd >= NR_OPEN) || !(filp = current->files->fd[fd]))
238 return (-EBADF);
239
240 error = verify_area(VERIFY_READ, l, sizeof(*l));
241 if (error)
242 return (error);
243
244 if (!(inode = filp->f_inode))
245 return (-EINVAL);
246
247 /* Don't allow mandatory locks on files that may be memory mapped
248 * and shared.
249 */
250 if ((inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID && inode->i_mmap) {
251 struct vm_area_struct *vma = inode->i_mmap;
252 do {
253 if (vma->vm_flags & VM_MAYSHARE)
254 return (-EAGAIN);
255 vma = vma->vm_next_share;
256 } while (vma != inode->i_mmap);
257 }
258
259 memcpy_fromfs(&flock, l, sizeof(flock));
260 if (!posix_make_lock(filp, &file_lock, &flock))
261 return (-EINVAL);
262
263 switch (flock.l_type) {
264 case F_RDLCK :
265 if (!(filp->f_mode & 1))
266 return (-EBADF);
267 break;
268 case F_WRLCK :
269 if (!(filp->f_mode & 2))
270 return (-EBADF);
271 break;
272 case F_SHLCK :
273 case F_EXLCK :
274 if (!(filp->f_mode & 3))
275 return (-EBADF);
276 break;
277 case F_UNLCK :
278 break;
279 }
280
281 return (posix_lock_file(filp, &file_lock, cmd == F_SETLKW));
282 }
283
284 /* This function is called when the file is closed.
285 */
286 void locks_remove_locks(struct task_struct *task, struct file *filp)
/* */
287 {
288 struct file_lock *fl;
289 struct file_lock **before;
290
291 /* For POSIX locks we free all locks on this file for the given task.
292 * For FLOCK we only free locks on this *open* file if it is the last
293 * close on that file.
294 */
295 before = &filp->f_inode->i_flock;
296 while ((fl = *before) != NULL) {
297 if (((fl->fl_flags == F_POSIX) && (fl->fl_owner == task)) ||
298 ((fl->fl_flags == F_FLOCK) && (fl->fl_file == filp) &&
299 (filp->f_count == 1)))
300 locks_delete_lock(before, 0);
301 else
302 before = &fl->fl_next;
303 }
304
305 return;
306 }
307
308 int locks_verify_locked(struct inode *inode)
/* */
309 {
310 /* Candidates for mandatory locking have the setgid bit set
311 * but no group execute bit - an otherwise meaningless combination.
312 */
313 if ((inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID)
314 return (locks_mandatory_locked(inode));
315 return (0);
316 }
317
318 int locks_mandatory_locked(struct inode *inode)
/* */
319 {
320 struct file_lock *fl;
321
322 /* Search the lock list for this inode for any POSIX locks.
323 */
324 for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
325 if (fl->fl_flags == F_POSIX && fl->fl_owner != current)
326 return (-EAGAIN);
327 }
328 return (0);
329 }
330
331 int locks_verify_area(int read_write, struct inode *inode, struct file *filp,
/* */
332 unsigned int offset, unsigned int count)
333 {
334 /* Candidates for mandatory locking have the setgid bit set
335 * but no group execute bit - an otherwise meaningless combination.
336 */
337 if ((inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID)
338 return (locks_mandatory_area(read_write, inode, filp, offset,
339 count));
340 return (0);
341 }
342
343 int locks_mandatory_area(int read_write, struct inode *inode,
/* */
344 struct file *filp, unsigned int offset,
345 unsigned int count)
346 {
347 struct file_lock *fl;
348
349 repeat:
350 /*
351 * Search the lock list for this inode for locks that conflict with
352 * the proposed read/write.
353 */
354 for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
355 if (fl->fl_flags == F_FLOCK ||
356 (fl->fl_flags == F_POSIX && fl->fl_owner == current))
357 continue;
358 if (fl->fl_end < offset ||
359 fl->fl_start >= offset + count)
360 continue;
361 /*
362 * Block for writes against a "read" lock, and both reads and
363 * writes against a "write" lock.
364 */
365 if (read_write == FLOCK_VERIFY_WRITE ||
366 fl->fl_type == F_WRLCK) {
367 if (filp && (filp->f_flags & O_NONBLOCK))
368 return (-EAGAIN);
369 if (current->signal & ~current->blocked)
370 return (-ERESTARTSYS);
371 if (posix_locks_deadlock(current, fl->fl_owner))
372 return (-EDEADLOCK);
373 interruptible_sleep_on(&fl->fl_wait);
374 if (current->signal & ~current->blocked)
375 return (-ERESTARTSYS);
376 /*
377 * If we've been sleeping someone might have changed
378 * the permissions behind our back.
379 */
380 if ((inode->i_mode & (S_ISGID | S_IXGRP)) != S_ISGID)
381 break;
382 goto repeat;
383 }
384 }
385 return (0);
386 }
387
388 /* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX
389 * style lock.
390 */
391 static int posix_make_lock(struct file *filp, struct file_lock *fl,
/* */
392 struct flock *l)
393 {
394 off_t start;
395
396 switch (l->l_type) {
397 case F_RDLCK :
398 case F_WRLCK :
399 case F_UNLCK :
400 fl->fl_type = l->l_type;
401 break;
402 case F_SHLCK :
403 fl->fl_type = F_RDLCK;
404 break;
405 case F_EXLCK :
406 fl->fl_type = F_WRLCK;
407 break;
408 default :
409 return (0);
410 }
411
412 switch (l->l_whence) {
413 case 0 : /*SEEK_SET*/
414 start = 0;
415 break;
416 case 1 : /*SEEK_CUR*/
417 start = filp->f_pos;
418 break;
419 case 2 : /*SEEK_END*/
420 start = filp->f_inode->i_size;
421 break;
422 default :
423 return (0);
424 }
425
426 if (((start += l->l_start) < 0) || (l->l_len < 0))
427 return (0);
428 fl->fl_start = start; /* we record the absolute position */
429 if ((l->l_len == 0) || ((fl->fl_end = start + l->l_len - 1) < 0))
430 fl->fl_end = OFFSET_MAX;
431
432 fl->fl_flags = F_POSIX;
433 fl->fl_file = filp;
434 fl->fl_owner = current;
435 fl->fl_wait = NULL; /* just for cleanliness */
436
437 return (1);
438 }
439
440 /* Verify a call to flock() and fill in a file_lock structure with
441 * an appropriate FLOCK lock.
442 */
443 static int flock_make_lock(struct file *filp, struct file_lock *fl,
/* */
444 unsigned int cmd)
445 {
446 if (!filp->f_inode) /* just in case */
447 return (0);
448
449 switch (cmd & ~LOCK_NB) {
450 case LOCK_SH :
451 fl->fl_type = F_RDLCK;
452 break;
453 case LOCK_EX :
454 fl->fl_type = F_WRLCK;
455 break;
456 case LOCK_UN :
457 fl->fl_type = F_UNLCK;
458 break;
459 default :
460 return (0);
461 }
462
463 fl->fl_flags = F_FLOCK;
464 fl->fl_start = 0;
465 fl->fl_end = OFFSET_MAX;
466 fl->fl_file = filp;
467 fl->fl_owner = current;
468 fl->fl_wait = NULL; /* just for cleanliness */
469
470 return (1);
471 }
472
473 /* Determine if lock sys_fl blocks lock caller_fl. POSIX specific
474 * checking before calling the locks_conflict().
475 */
476 static int posix_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
/* */
477 {
478 /* POSIX locks owned by the same process do not conflict with
479 * each other.
480 */
481 if ((sys_fl->fl_flags == F_POSIX) &&
482 (caller_fl->fl_owner == sys_fl->fl_owner))
483 return (0);
484
485 return (locks_conflict(caller_fl, sys_fl));
486 }
487
488 /* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific
489 * checking before calling the locks_conflict().
490 */
491 static int flock_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
/* */
492 {
493 /* FLOCK locks referring to the same filp do not conflict with
494 * each other.
495 */
496 if ((sys_fl->fl_flags == F_FLOCK) &&
497 (caller_fl->fl_file == sys_fl->fl_file))
498 return (0);
499
500 return (locks_conflict(caller_fl, sys_fl));
501 }
502
503 /* Determine if lock sys_fl blocks lock caller_fl. Common functionality
504 * checks for overlapping locks and shared/exclusive status.
505 */
506 static int locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
/* */
507 {
508 if (!locks_overlap(caller_fl, sys_fl))
509 return (0);
510
511 switch (caller_fl->fl_type) {
512 case F_RDLCK :
513 return (sys_fl->fl_type == F_WRLCK);
514
515 case F_WRLCK :
516 return (1);
517
518 default:
519 printk("locks_conflict(): impossible lock type - %d\n",
520 caller_fl->fl_type);
521 break;
522 }
523 return (0); /* This should never happen */
524 }
525
526 /* Check if two locks overlap each other.
527 */
528 static int locks_overlap(struct file_lock *fl1, struct file_lock *fl2)
/* */
529 {
530 return ((fl1->fl_end >= fl2->fl_start) &&
531 (fl2->fl_end >= fl1->fl_start));
532 }
533
534 /* This function tests for deadlock condition before putting a process to
535 * sleep. The detection scheme is no longer recursive. Recursive was neat,
536 * but dangerous - we risked stack corruption if the lock data was bad, or
537 * if the recursion was too deep for any other reason.
538 *
539 * We rely on the fact that a task can only be on one lock's wait queue
540 * at a time. When we find blocked_task on a wait queue we can re-search
541 * with blocked_task equal to that queue's owner, until either blocked_task
542 * isn't found, or blocked_task is found on a queue owned by my_task.
543 */
544 static int posix_locks_deadlock(struct task_struct *my_task,
/* */
545 struct task_struct *blocked_task)
546 {
547 struct wait_queue *dlock_wait;
548 struct file_lock *fl;
549
550 next_task:
551 for (fl = file_lock_table; fl != NULL; fl = fl->fl_nextlink) {
552 if (fl->fl_owner == NULL || fl->fl_wait == NULL)
553 continue;
554 dlock_wait = fl->fl_wait;
555 do {
556 if (dlock_wait->task == blocked_task) {
557 if (fl->fl_owner == my_task) {
558 return(-EDEADLOCK);
559 }
560 blocked_task = fl->fl_owner;
561 goto next_task;
562 }
563 dlock_wait = dlock_wait->next;
564 } while (dlock_wait != fl->fl_wait);
565 }
566 return (0);
567 }
568
569 /* Try to create a FLOCK lock on filp. We rely on FLOCK locks being sorted
570 * first in an inode's lock list, and always insert new locks at the head
571 * of the list.
572 */
573 static int flock_lock_file(struct file *filp, struct file_lock *caller,
/* */
574 unsigned int wait)
575 {
576 struct file_lock *fl;
577 struct file_lock *new_fl;
578 struct file_lock **before;
579 int change = 0;
580
581 /* This a compact little algorithm based on us always placing FLOCK
582 * locks at the front of the list.
583 */
584 before = &filp->f_inode->i_flock;
585 while ((fl = *before) && (fl->fl_flags == F_FLOCK)) {
586 if (caller->fl_file == fl->fl_file) {
587 if (caller->fl_type == fl->fl_type)
588 return (0);
589 change = 1;
590 break;
591 }
592 before = &fl->fl_next;
593 }
594 /* change means that we are changing the type of an existing lock, or
595 * or else unlocking it.
596 */
597 if (change)
598 locks_delete_lock(before, caller->fl_type != F_UNLCK);
599 if (caller->fl_type == F_UNLCK)
600 return (0);
601 if ((new_fl = locks_alloc_lock(caller)) == NULL)
602 return (-ENOLCK);
603 repeat:
604 for (fl = filp->f_inode->i_flock; fl != NULL; fl = fl->fl_next) {
605 if (!flock_locks_conflict(new_fl, fl))
606 continue;
607
608 if (wait) {
609 if (current->signal & ~current->blocked) {
610 /* Note: new_fl is not in any queue at this
611 * point. So we must use locks_free_lock()
612 * instead of locks_delete_lock()
613 * Dmitry Gorodchanin 09/02/96.
614 */
615 locks_free_lock(&new_fl);
616 return (-ERESTARTSYS);
617 }
618 locks_insert_block(&fl->fl_block, new_fl);
619 interruptible_sleep_on(&new_fl->fl_wait);
620 wake_up(&new_fl->fl_wait);
621 if (current->signal & ~current->blocked) {
622 /* If we are here, than we were awaken
623 * by signal, so new_fl is still in
624 * block queue of fl. We need remove
625 * new_fl and then free it.
626 * Dmitry Gorodchanin 09/02/96.
627 */
628
629 locks_delete_block(&fl->fl_block, new_fl);
630 locks_free_lock(&new_fl);
631 return (-ERESTARTSYS);
632 }
633 goto repeat;
634 }
635
636 locks_free_lock(&new_fl);
637 return (-EAGAIN);
638 }
639 locks_insert_lock(&filp->f_inode->i_flock, new_fl);
640 return (0);
641 }
642
643 /* Add a POSIX style lock to a file.
644 * We merge adjacent locks whenever possible. POSIX locks come after FLOCK
645 * locks in the list and are sorted by owner task, then by starting address
646 *
647 * Kai Petzke writes:
648 * To make freeing a lock much faster, we keep a pointer to the lock before the
649 * actual one. But the real gain of the new coding was, that lock_it() and
650 * unlock_it() became one function.
651 *
652 * To all purists: Yes, I use a few goto's. Just pass on to the next function.
653 */
654
655 static int posix_lock_file(struct file *filp, struct file_lock *caller,
/* */
656 unsigned int wait)
657 {
658 struct file_lock *fl;
659 struct file_lock *new_fl;
660 struct file_lock *left = NULL;
661 struct file_lock *right = NULL;
662 struct file_lock **before;
663 int added = 0;
664
665 if (caller->fl_type != F_UNLCK) {
666 repeat:
667 for (fl = filp->f_inode->i_flock; fl != NULL; fl = fl->fl_next) {
668 if (!posix_locks_conflict(caller, fl))
669 continue;
670 if (wait) {
671 if (current->signal & ~current->blocked)
672 return (-ERESTARTSYS);
673 if (fl->fl_flags == F_POSIX)
674 if (posix_locks_deadlock(caller->fl_owner, fl->fl_owner))
675 return (-EDEADLOCK);
676 interruptible_sleep_on(&fl->fl_wait);
677 if (current->signal & ~current->blocked)
678 return (-ERESTARTSYS);
679 goto repeat;
680 }
681 return (-EAGAIN);
682 }
683 }
684 /*
685 * Find the first old lock with the same owner as the new lock.
686 */
687
688 before = &filp->f_inode->i_flock;
689
690 /* First skip FLOCK locks and locks owned by other processes.
691 */
692 while ((fl = *before) && ((fl->fl_flags == F_FLOCK) ||
693 (caller->fl_owner != fl->fl_owner))) {
694 before = &fl->fl_next;
695 }
696
697
698 /* Process locks with this owner.
699 */
700 while ((fl = *before) && (caller->fl_owner == fl->fl_owner)) {
701 /* Detect adjacent or overlapping regions (if same lock type)
702 */
703 if (caller->fl_type == fl->fl_type) {
704 if (fl->fl_end < caller->fl_start - 1)
705 goto next_lock;
706 /* If the next lock in the list has entirely bigger
707 * addresses than the new one, insert the lock here.
708 */
709 if (fl->fl_start > caller->fl_end + 1)
710 break;
711
712 /* If we come here, the new and old lock are of the
713 * same type and adjacent or overlapping. Make one
714 * lock yielding from the lower start address of both
715 * locks to the higher end address.
716 */
717 if (fl->fl_start > caller->fl_start)
718 fl->fl_start = caller->fl_start;
719 else
720 caller->fl_start = fl->fl_start;
721 if (fl->fl_end < caller->fl_end)
722 fl->fl_end = caller->fl_end;
723 else
724 caller->fl_end = fl->fl_end;
725 if (added) {
726 locks_delete_lock(before, 0);
727 continue;
728 }
729 caller = fl;
730 added = 1;
731 }
732 else {
733 /* Processing for different lock types is a bit
734 * more complex.
735 */
736 if (fl->fl_end < caller->fl_start)
737 goto next_lock;
738 if (fl->fl_start > caller->fl_end)
739 break;
740 if (caller->fl_type == F_UNLCK)
741 added = 1;
742 if (fl->fl_start < caller->fl_start)
743 left = fl;
744 /* If the next lock in the list has a higher end
745 * address than the new one, insert the new one here.
746 */
747 if (fl->fl_end > caller->fl_end) {
748 right = fl;
749 break;
750 }
751 if (fl->fl_start >= caller->fl_start) {
752 /* The new lock completely replaces an old
753 * one (This may happen several times).
754 */
755 if (added) {
756 locks_delete_lock(before, 0);
757 continue;
758 }
759 /* Replace the old lock with the new one.
760 * Wake up anybody waiting for the old one,
761 * as the change in lock type might satisfy
762 * their needs.
763 */
764 wake_up(&fl->fl_wait);
765 fl->fl_start = caller->fl_start;
766 fl->fl_end = caller->fl_end;
767 fl->fl_type = caller->fl_type;
768 caller = fl;
769 added = 1;
770 }
771 }
772 /* Go on to next lock.
773 */
774 next_lock:
775 before = &(*before)->fl_next;
776 }
777
778 if (!added) {
779 if (caller->fl_type == F_UNLCK)
780 return (0);
781 if ((new_fl = locks_alloc_lock(caller)) == NULL)
782 return (-ENOLCK);
783 locks_insert_lock(before, new_fl);
784
785 }
786 if (right) {
787 if (left == right) {
788 /* The new lock breaks the old one in two pieces, so we
789 * have to allocate one more lock (in this case, even
790 * F_UNLCK may fail!).
791 */
792 if ((left = locks_alloc_lock(right)) == NULL) {
793 if (!added)
794 locks_delete_lock(before, 0);
795 return (-ENOLCK);
796 }
797 locks_insert_lock(before, left);
798 }
799 right->fl_start = caller->fl_end + 1;
800 }
801 if (left)
802 left->fl_end = caller->fl_start - 1;
803 return (0);
804 }
805
806 /* Allocate memory for a new lock and initialize its fields from
807 * fl. The lock is not inserted into any lists until locks_insert_lock()
808 * or locks_insert_block() are called.
809 */
810
811 static struct file_lock *locks_alloc_lock(struct file_lock *fl)
/* */
812 {
813 struct file_lock *tmp;
814
815 /* Okay, let's make a new file_lock structure... */
816 if ((tmp = (struct file_lock *)kmalloc(sizeof(struct file_lock),
817 GFP_ATOMIC)) == NULL)
818 return (tmp);
819
820 tmp->fl_nextlink = NULL;
821 tmp->fl_prevlink = NULL;
822 tmp->fl_next = NULL;
823 tmp->fl_block = NULL;
824 tmp->fl_flags = fl->fl_flags;
825 tmp->fl_owner = fl->fl_owner;
826 tmp->fl_file = fl->fl_file;
827 tmp->fl_wait = NULL;
828 tmp->fl_type = fl->fl_type;
829 tmp->fl_start = fl->fl_start;
830 tmp->fl_end = fl->fl_end;
831
832 return (tmp);
833 }
834
835 /* Insert file lock fl into an inode's lock list at the position indicated
836 * by pos. At the same time add the lock to the global file lock list.
837 */
838
839 static void locks_insert_lock(struct file_lock **pos, struct file_lock *fl)
/* */
840 {
841 fl->fl_nextlink = file_lock_table;
842 fl->fl_prevlink = NULL;
843 if (file_lock_table != NULL)
844 file_lock_table->fl_prevlink = fl;
845 file_lock_table = fl;
846 fl->fl_next = *pos; /* insert into file's list */
847 *pos = fl;
848
849 return;
850 }
851
852 /* Delete a lock and free it.
853 * First remove our lock from the lock lists. Then remove all the blocked
854 * locks from our blocked list, waking up the processes that own them. If
855 * told to wait, then sleep on each of these lock's wait queues. Each
856 * blocked process will wake up and immediately wake up its own wait queue
857 * allowing us to be scheduled again. Lastly, wake up our own wait queue
858 * before freeing the file_lock structure.
859 */
860
861 static void locks_delete_lock(struct file_lock **fl_p, unsigned int wait)
/* ![[last]](../icons/n_last.png)
*/
862 {
863 struct file_lock *fl;
864 struct file_lock *bfl;
865
866 fl = *fl_p;
867 *fl_p = (*fl_p)->fl_next;
868
869 if (fl->fl_nextlink != NULL)
870 fl->fl_nextlink->fl_prevlink = fl->fl_prevlink;
871
872 if (fl->fl_prevlink != NULL)
873 fl->fl_prevlink->fl_nextlink = fl->fl_nextlink;
874 else {
875 file_lock_table = fl->fl_nextlink;
876 }
877
878 while ((bfl = fl->fl_block) != NULL) {
879 fl->fl_block = bfl->fl_block;
880 bfl->fl_block = NULL;
881 wake_up(&bfl->fl_wait);
882 if (wait)
883 sleep_on(&bfl->fl_wait);
884 }
885
886 wake_up(&fl->fl_wait);
887 kfree(fl);
888
889 return;
890 }
![[bottom]](../icons/n_bottom.png){kind=icon}
*/