Root/fs/locks.c

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/smp_lock.h>
126#include <linux/syscalls.h>
127#include <linux/time.h>
128#include <linux/rcupdate.h>
129#include <linux/pid_namespace.h>
130
131#include <asm/uaccess.h>
132
133#define IS_POSIX(fl) (fl->fl_flags & FL_POSIX)
134#define IS_FLOCK(fl) (fl->fl_flags & FL_FLOCK)
135#define IS_LEASE(fl) (fl->fl_flags & FL_LEASE)
136
137int leases_enable = 1;
138int lease_break_time = 45;
139
140#define for_each_lock(inode, lockp) \
141    for (lockp = &inode->i_flock; *lockp != NULL; lockp = &(*lockp)->fl_next)
142
143static LIST_HEAD(file_lock_list);
144static LIST_HEAD(blocked_list);
145
146static struct kmem_cache *filelock_cache __read_mostly;
147
148/* Allocate an empty lock structure. */
149static struct file_lock *locks_alloc_lock(void)
150{
151    return kmem_cache_alloc(filelock_cache, GFP_KERNEL);
152}
153
154void locks_release_private(struct file_lock *fl)
155{
156    if (fl->fl_ops) {
157        if (fl->fl_ops->fl_release_private)
158            fl->fl_ops->fl_release_private(fl);
159        fl->fl_ops = NULL;
160    }
161    if (fl->fl_lmops) {
162        if (fl->fl_lmops->fl_release_private)
163            fl->fl_lmops->fl_release_private(fl);
164        fl->fl_lmops = NULL;
165    }
166
167}
168EXPORT_SYMBOL_GPL(locks_release_private);
169
170/* Free a lock which is not in use. */
171static void locks_free_lock(struct file_lock *fl)
172{
173    BUG_ON(waitqueue_active(&fl->fl_wait));
174    BUG_ON(!list_empty(&fl->fl_block));
175    BUG_ON(!list_empty(&fl->fl_link));
176
177    locks_release_private(fl);
178    kmem_cache_free(filelock_cache, fl);
179}
180
181void locks_init_lock(struct file_lock *fl)
182{
183    INIT_LIST_HEAD(&fl->fl_link);
184    INIT_LIST_HEAD(&fl->fl_block);
185    init_waitqueue_head(&fl->fl_wait);
186    fl->fl_next = NULL;
187    fl->fl_fasync = NULL;
188    fl->fl_owner = NULL;
189    fl->fl_pid = 0;
190    fl->fl_nspid = NULL;
191    fl->fl_file = NULL;
192    fl->fl_flags = 0;
193    fl->fl_type = 0;
194    fl->fl_start = fl->fl_end = 0;
195    fl->fl_ops = NULL;
196    fl->fl_lmops = NULL;
197}
198
199EXPORT_SYMBOL(locks_init_lock);
200
201/*
202 * Initialises the fields of the file lock which are invariant for
203 * free file_locks.
204 */
205static void init_once(void *foo)
206{
207    struct file_lock *lock = (struct file_lock *) foo;
208
209    locks_init_lock(lock);
210}
211
212static void locks_copy_private(struct file_lock *new, struct file_lock *fl)
213{
214    if (fl->fl_ops) {
215        if (fl->fl_ops->fl_copy_lock)
216            fl->fl_ops->fl_copy_lock(new, fl);
217        new->fl_ops = fl->fl_ops;
218    }
219    if (fl->fl_lmops) {
220        if (fl->fl_lmops->fl_copy_lock)
221            fl->fl_lmops->fl_copy_lock(new, fl);
222        new->fl_lmops = fl->fl_lmops;
223    }
224}
225
226/*
227 * Initialize a new lock from an existing file_lock structure.
228 */
229void __locks_copy_lock(struct file_lock *new, const struct file_lock *fl)
230{
231    new->fl_owner = fl->fl_owner;
232    new->fl_pid = fl->fl_pid;
233    new->fl_file = NULL;
234    new->fl_flags = fl->fl_flags;
235    new->fl_type = fl->fl_type;
236    new->fl_start = fl->fl_start;
237    new->fl_end = fl->fl_end;
238    new->fl_ops = NULL;
239    new->fl_lmops = NULL;
240}
241EXPORT_SYMBOL(__locks_copy_lock);
242
243void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
244{
245    locks_release_private(new);
246
247    __locks_copy_lock(new, fl);
248    new->fl_file = fl->fl_file;
249    new->fl_ops = fl->fl_ops;
250    new->fl_lmops = fl->fl_lmops;
251
252    locks_copy_private(new, fl);
253}
254
255EXPORT_SYMBOL(locks_copy_lock);
256
257static inline int flock_translate_cmd(int cmd) {
258    if (cmd & LOCK_MAND)
259        return cmd & (LOCK_MAND | LOCK_RW);
260    switch (cmd) {
261    case LOCK_SH:
262        return F_RDLCK;
263    case LOCK_EX:
264        return F_WRLCK;
265    case LOCK_UN:
266        return F_UNLCK;
267    }
268    return -EINVAL;
269}
270
271/* Fill in a file_lock structure with an appropriate FLOCK lock. */
272static int flock_make_lock(struct file *filp, struct file_lock **lock,
273        unsigned int cmd)
274{
275    struct file_lock *fl;
276    int type = flock_translate_cmd(cmd);
277    if (type < 0)
278        return type;
279    
280    fl = locks_alloc_lock();
281    if (fl == NULL)
282        return -ENOMEM;
283
284    fl->fl_file = filp;
285    fl->fl_pid = current->tgid;
286    fl->fl_flags = FL_FLOCK;
287    fl->fl_type = type;
288    fl->fl_end = OFFSET_MAX;
289    
290    *lock = fl;
291    return 0;
292}
293
294static int assign_type(struct file_lock *fl, int type)
295{
296    switch (type) {
297    case F_RDLCK:
298    case F_WRLCK:
299    case F_UNLCK:
300        fl->fl_type = type;
301        break;
302    default:
303        return -EINVAL;
304    }
305    return 0;
306}
307
308/* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX
309 * style lock.
310 */
311static int flock_to_posix_lock(struct file *filp, struct file_lock *fl,
312                   struct flock *l)
313{
314    off_t start, end;
315
316    switch (l->l_whence) {
317    case SEEK_SET:
318        start = 0;
319        break;
320    case SEEK_CUR:
321        start = filp->f_pos;
322        break;
323    case SEEK_END:
324        start = i_size_read(filp->f_path.dentry->d_inode);
325        break;
326    default:
327        return -EINVAL;
328    }
329
330    /* POSIX-1996 leaves the case l->l_len < 0 undefined;
331       POSIX-2001 defines it. */
332    start += l->l_start;
333    if (start < 0)
334        return -EINVAL;
335    fl->fl_end = OFFSET_MAX;
336    if (l->l_len > 0) {
337        end = start + l->l_len - 1;
338        fl->fl_end = end;
339    } else if (l->l_len < 0) {
340        end = start - 1;
341        fl->fl_end = end;
342        start += l->l_len;
343        if (start < 0)
344            return -EINVAL;
345    }
346    fl->fl_start = start; /* we record the absolute position */
347    if (fl->fl_end < fl->fl_start)
348        return -EOVERFLOW;
349    
350    fl->fl_owner = current->files;
351    fl->fl_pid = current->tgid;
352    fl->fl_file = filp;
353    fl->fl_flags = FL_POSIX;
354    fl->fl_ops = NULL;
355    fl->fl_lmops = NULL;
356
357    return assign_type(fl, l->l_type);
358}
359
360#if BITS_PER_LONG == 32
361static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
362                 struct flock64 *l)
363{
364    loff_t start;
365
366    switch (l->l_whence) {
367    case SEEK_SET:
368        start = 0;
369        break;
370    case SEEK_CUR:
371        start = filp->f_pos;
372        break;
373    case SEEK_END:
374        start = i_size_read(filp->f_path.dentry->d_inode);
375        break;
376    default:
377        return -EINVAL;
378    }
379
380    start += l->l_start;
381    if (start < 0)
382        return -EINVAL;
383    fl->fl_end = OFFSET_MAX;
384    if (l->l_len > 0) {
385        fl->fl_end = start + l->l_len - 1;
386    } else if (l->l_len < 0) {
387        fl->fl_end = start - 1;
388        start += l->l_len;
389        if (start < 0)
390            return -EINVAL;
391    }
392    fl->fl_start = start; /* we record the absolute position */
393    if (fl->fl_end < fl->fl_start)
394        return -EOVERFLOW;
395    
396    fl->fl_owner = current->files;
397    fl->fl_pid = current->tgid;
398    fl->fl_file = filp;
399    fl->fl_flags = FL_POSIX;
400    fl->fl_ops = NULL;
401    fl->fl_lmops = NULL;
402
403    switch (l->l_type) {
404    case F_RDLCK:
405    case F_WRLCK:
406    case F_UNLCK:
407        fl->fl_type = l->l_type;
408        break;
409    default:
410        return -EINVAL;
411    }
412
413    return (0);
414}
415#endif
416
417/* default lease lock manager operations */
418static void lease_break_callback(struct file_lock *fl)
419{
420    kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG);
421}
422
423static void lease_release_private_callback(struct file_lock *fl)
424{
425    if (!fl->fl_file)
426        return;
427
428    f_delown(fl->fl_file);
429    fl->fl_file->f_owner.signum = 0;
430}
431
432static int lease_mylease_callback(struct file_lock *fl, struct file_lock *try)
433{
434    return fl->fl_file == try->fl_file;
435}
436
437static const struct lock_manager_operations lease_manager_ops = {
438    .fl_break = lease_break_callback,
439    .fl_release_private = lease_release_private_callback,
440    .fl_mylease = lease_mylease_callback,
441    .fl_change = lease_modify,
442};
443
444/*
445 * Initialize a lease, use the default lock manager operations
446 */
447static int lease_init(struct file *filp, int type, struct file_lock *fl)
448 {
449    if (assign_type(fl, type) != 0)
450        return -EINVAL;
451
452    fl->fl_owner = current->files;
453    fl->fl_pid = current->tgid;
454
455    fl->fl_file = filp;
456    fl->fl_flags = FL_LEASE;
457    fl->fl_start = 0;
458    fl->fl_end = OFFSET_MAX;
459    fl->fl_ops = NULL;
460    fl->fl_lmops = &lease_manager_ops;
461    return 0;
462}
463
464/* Allocate a file_lock initialised to this type of lease */
465static struct file_lock *lease_alloc(struct file *filp, int type)
466{
467    struct file_lock *fl = locks_alloc_lock();
468    int error = -ENOMEM;
469
470    if (fl == NULL)
471        return ERR_PTR(error);
472
473    error = lease_init(filp, type, fl);
474    if (error) {
475        locks_free_lock(fl);
476        return ERR_PTR(error);
477    }
478    return fl;
479}
480
481/* Check if two locks overlap each other.
482 */
483static inline int locks_overlap(struct file_lock *fl1, struct file_lock *fl2)
484{
485    return ((fl1->fl_end >= fl2->fl_start) &&
486        (fl2->fl_end >= fl1->fl_start));
487}
488
489/*
490 * Check whether two locks have the same owner.
491 */
492static int posix_same_owner(struct file_lock *fl1, struct file_lock *fl2)
493{
494    if (fl1->fl_lmops && fl1->fl_lmops->fl_compare_owner)
495        return fl2->fl_lmops == fl1->fl_lmops &&
496            fl1->fl_lmops->fl_compare_owner(fl1, fl2);
497    return fl1->fl_owner == fl2->fl_owner;
498}
499
500/* Remove waiter from blocker's block list.
501 * When blocker ends up pointing to itself then the list is empty.
502 */
503static void __locks_delete_block(struct file_lock *waiter)
504{
505    list_del_init(&waiter->fl_block);
506    list_del_init(&waiter->fl_link);
507    waiter->fl_next = NULL;
508}
509
510/*
511 */
512static void locks_delete_block(struct file_lock *waiter)
513{
514    lock_kernel();
515    __locks_delete_block(waiter);
516    unlock_kernel();
517}
518
519/* Insert waiter into blocker's block list.
520 * We use a circular list so that processes can be easily woken up in
521 * the order they blocked. The documentation doesn't require this but
522 * it seems like the reasonable thing to do.
523 */
524static void locks_insert_block(struct file_lock *blocker,
525                   struct file_lock *waiter)
526{
527    BUG_ON(!list_empty(&waiter->fl_block));
528    list_add_tail(&waiter->fl_block, &blocker->fl_block);
529    waiter->fl_next = blocker;
530    if (IS_POSIX(blocker))
531        list_add(&waiter->fl_link, &blocked_list);
532}
533
534/* Wake up processes blocked waiting for blocker.
535 * If told to wait then schedule the processes until the block list
536 * is empty, otherwise empty the block list ourselves.
537 */
538static void locks_wake_up_blocks(struct file_lock *blocker)
539{
540    while (!list_empty(&blocker->fl_block)) {
541        struct file_lock *waiter;
542
543        waiter = list_first_entry(&blocker->fl_block,
544                struct file_lock, fl_block);
545        __locks_delete_block(waiter);
546        if (waiter->fl_lmops && waiter->fl_lmops->fl_notify)
547            waiter->fl_lmops->fl_notify(waiter);
548        else
549            wake_up(&waiter->fl_wait);
550    }
551}
552
553/* Insert file lock fl into an inode's lock list at the position indicated
554 * by pos. At the same time add the lock to the global file lock list.
555 */
556static void locks_insert_lock(struct file_lock **pos, struct file_lock *fl)
557{
558    list_add(&fl->fl_link, &file_lock_list);
559
560    fl->fl_nspid = get_pid(task_tgid(current));
561
562    /* insert into file's list */
563    fl->fl_next = *pos;
564    *pos = fl;
565}
566
567/*
568 * Delete a lock and then free it.
569 * Wake up processes that are blocked waiting for this lock,
570 * notify the FS that the lock has been cleared and
571 * finally free the lock.
572 */
573static void locks_delete_lock(struct file_lock **thisfl_p)
574{
575    struct file_lock *fl = *thisfl_p;
576
577    *thisfl_p = fl->fl_next;
578    fl->fl_next = NULL;
579    list_del_init(&fl->fl_link);
580
581    fasync_helper(0, fl->fl_file, 0, &fl->fl_fasync);
582    if (fl->fl_fasync != NULL) {
583        printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync);
584        fl->fl_fasync = NULL;
585    }
586
587    if (fl->fl_nspid) {
588        put_pid(fl->fl_nspid);
589        fl->fl_nspid = NULL;
590    }
591
592    locks_wake_up_blocks(fl);
593    locks_free_lock(fl);
594}
595
596/* Determine if lock sys_fl blocks lock caller_fl. Common functionality
597 * checks for shared/exclusive status of overlapping locks.
598 */
599static int locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
600{
601    if (sys_fl->fl_type == F_WRLCK)
602        return 1;
603    if (caller_fl->fl_type == F_WRLCK)
604        return 1;
605    return 0;
606}
607
608/* Determine if lock sys_fl blocks lock caller_fl. POSIX specific
609 * checking before calling the locks_conflict().
610 */
611static int posix_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
612{
613    /* POSIX locks owned by the same process do not conflict with
614     * each other.
615     */
616    if (!IS_POSIX(sys_fl) || posix_same_owner(caller_fl, sys_fl))
617        return (0);
618
619    /* Check whether they overlap */
620    if (!locks_overlap(caller_fl, sys_fl))
621        return 0;
622
623    return (locks_conflict(caller_fl, sys_fl));
624}
625
626/* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific
627 * checking before calling the locks_conflict().
628 */
629static int flock_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
630{
631    /* FLOCK locks referring to the same filp do not conflict with
632     * each other.
633     */
634    if (!IS_FLOCK(sys_fl) || (caller_fl->fl_file == sys_fl->fl_file))
635        return (0);
636    if ((caller_fl->fl_type & LOCK_MAND) || (sys_fl->fl_type & LOCK_MAND))
637        return 0;
638
639    return (locks_conflict(caller_fl, sys_fl));
640}
641
642void
643posix_test_lock(struct file *filp, struct file_lock *fl)
644{
645    struct file_lock *cfl;
646
647    lock_kernel();
648    for (cfl = filp->f_path.dentry->d_inode->i_flock; cfl; cfl = cfl->fl_next) {
649        if (!IS_POSIX(cfl))
650            continue;
651        if (posix_locks_conflict(fl, cfl))
652            break;
653    }
654    if (cfl) {
655        __locks_copy_lock(fl, cfl);
656        if (cfl->fl_nspid)
657            fl->fl_pid = pid_vnr(cfl->fl_nspid);
658    } else
659        fl->fl_type = F_UNLCK;
660    unlock_kernel();
661    return;
662}
663EXPORT_SYMBOL(posix_test_lock);
664
665/*
666 * Deadlock detection:
667 *
668 * We attempt to detect deadlocks that are due purely to posix file
669 * locks.
670 *
671 * We assume that a task can be waiting for at most one lock at a time.
672 * So for any acquired lock, the process holding that lock may be
673 * waiting on at most one other lock. That lock in turns may be held by
674 * someone waiting for at most one other lock. Given a requested lock
675 * caller_fl which is about to wait for a conflicting lock block_fl, we
676 * follow this chain of waiters to ensure we are not about to create a
677 * cycle.
678 *
679 * Since we do this before we ever put a process to sleep on a lock, we
680 * are ensured that there is never a cycle; that is what guarantees that
681 * the while() loop in posix_locks_deadlock() eventually completes.
682 *
683 * Note: the above assumption may not be true when handling lock
684 * requests from a broken NFS client. It may also fail in the presence
685 * of tasks (such as posix threads) sharing the same open file table.
686 *
687 * To handle those cases, we just bail out after a few iterations.
688 */
689
690#define MAX_DEADLK_ITERATIONS 10
691
692/* Find a lock that the owner of the given block_fl is blocking on. */
693static struct file_lock *what_owner_is_waiting_for(struct file_lock *block_fl)
694{
695    struct file_lock *fl;
696
697    list_for_each_entry(fl, &blocked_list, fl_link) {
698        if (posix_same_owner(fl, block_fl))
699            return fl->fl_next;
700    }
701    return NULL;
702}
703
704static int posix_locks_deadlock(struct file_lock *caller_fl,
705                struct file_lock *block_fl)
706{
707    int i = 0;
708
709    while ((block_fl = what_owner_is_waiting_for(block_fl))) {
710        if (i++ > MAX_DEADLK_ITERATIONS)
711            return 0;
712        if (posix_same_owner(caller_fl, block_fl))
713            return 1;
714    }
715    return 0;
716}
717
718/* Try to create a FLOCK lock on filp. We always insert new FLOCK locks
719 * after any leases, but before any posix locks.
720 *
721 * Note that if called with an FL_EXISTS argument, the caller may determine
722 * whether or not a lock was successfully freed by testing the return
723 * value for -ENOENT.
724 */
725static int flock_lock_file(struct file *filp, struct file_lock *request)
726{
727    struct file_lock *new_fl = NULL;
728    struct file_lock **before;
729    struct inode * inode = filp->f_path.dentry->d_inode;
730    int error = 0;
731    int found = 0;
732
733    lock_kernel();
734    if (request->fl_flags & FL_ACCESS)
735        goto find_conflict;
736
737    if (request->fl_type != F_UNLCK) {
738        error = -ENOMEM;
739        new_fl = locks_alloc_lock();
740        if (new_fl == NULL)
741            goto out;
742        error = 0;
743    }
744
745    for_each_lock(inode, before) {
746        struct file_lock *fl = *before;
747        if (IS_POSIX(fl))
748            break;
749        if (IS_LEASE(fl))
750            continue;
751        if (filp != fl->fl_file)
752            continue;
753        if (request->fl_type == fl->fl_type)
754            goto out;
755        found = 1;
756        locks_delete_lock(before);
757        break;
758    }
759
760    if (request->fl_type == F_UNLCK) {
761        if ((request->fl_flags & FL_EXISTS) && !found)
762            error = -ENOENT;
763        goto out;
764    }
765
766    /*
767     * If a higher-priority process was blocked on the old file lock,
768     * give it the opportunity to lock the file.
769     */
770    if (found)
771        cond_resched();
772
773find_conflict:
774    for_each_lock(inode, before) {
775        struct file_lock *fl = *before;
776        if (IS_POSIX(fl))
777            break;
778        if (IS_LEASE(fl))
779            continue;
780        if (!flock_locks_conflict(request, fl))
781            continue;
782        error = -EAGAIN;
783        if (!(request->fl_flags & FL_SLEEP))
784            goto out;
785        error = FILE_LOCK_DEFERRED;
786        locks_insert_block(fl, request);
787        goto out;
788    }
789    if (request->fl_flags & FL_ACCESS)
790        goto out;
791    locks_copy_lock(new_fl, request);
792    locks_insert_lock(before, new_fl);
793    new_fl = NULL;
794    error = 0;
795
796out:
797    unlock_kernel();
798    if (new_fl)
799        locks_free_lock(new_fl);
800    return error;
801}
802
803static int __posix_lock_file(struct inode *inode, struct file_lock *request, struct file_lock *conflock)
804{
805    struct file_lock *fl;
806    struct file_lock *new_fl = NULL;
807    struct file_lock *new_fl2 = NULL;
808    struct file_lock *left = NULL;
809    struct file_lock *right = NULL;
810    struct file_lock **before;
811    int error, added = 0;
812
813    /*
814     * We may need two file_lock structures for this operation,
815     * so we get them in advance to avoid races.
816     *
817     * In some cases we can be sure, that no new locks will be needed
818     */
819    if (!(request->fl_flags & FL_ACCESS) &&
820        (request->fl_type != F_UNLCK ||
821         request->fl_start != 0 || request->fl_end != OFFSET_MAX)) {
822        new_fl = locks_alloc_lock();
823        new_fl2 = locks_alloc_lock();
824    }
825
826    lock_kernel();
827    if (request->fl_type != F_UNLCK) {
828        for_each_lock(inode, before) {
829            fl = *before;
830            if (!IS_POSIX(fl))
831                continue;
832            if (!posix_locks_conflict(request, fl))
833                continue;
834            if (conflock)
835                __locks_copy_lock(conflock, fl);
836            error = -EAGAIN;
837            if (!(request->fl_flags & FL_SLEEP))
838                goto out;
839            error = -EDEADLK;
840            if (posix_locks_deadlock(request, fl))
841                goto out;
842            error = FILE_LOCK_DEFERRED;
843            locks_insert_block(fl, request);
844            goto out;
845          }
846      }
847
848    /* If we're just looking for a conflict, we're done. */
849    error = 0;
850    if (request->fl_flags & FL_ACCESS)
851        goto out;
852
853    /*
854     * Find the first old lock with the same owner as the new lock.
855     */
856    
857    before = &inode->i_flock;
858
859    /* First skip locks owned by other processes. */
860    while ((fl = *before) && (!IS_POSIX(fl) ||
861                  !posix_same_owner(request, fl))) {
862        before = &fl->fl_next;
863    }
864
865    /* Process locks with this owner. */
866    while ((fl = *before) && posix_same_owner(request, fl)) {
867        /* Detect adjacent or overlapping regions (if same lock type)
868         */
869        if (request->fl_type == fl->fl_type) {
870            /* In all comparisons of start vs end, use
871             * "start - 1" rather than "end + 1". If end
872             * is OFFSET_MAX, end + 1 will become negative.
873             */
874            if (fl->fl_end < request->fl_start - 1)
875                goto next_lock;
876            /* If the next lock in the list has entirely bigger
877             * addresses than the new one, insert the lock here.
878             */
879            if (fl->fl_start - 1 > request->fl_end)
880                break;
881
882            /* If we come here, the new and old lock are of the
883             * same type and adjacent or overlapping. Make one
884             * lock yielding from the lower start address of both
885             * locks to the higher end address.
886             */
887            if (fl->fl_start > request->fl_start)
888                fl->fl_start = request->fl_start;
889            else
890                request->fl_start = fl->fl_start;
891            if (fl->fl_end < request->fl_end)
892                fl->fl_end = request->fl_end;
893            else
894                request->fl_end = fl->fl_end;
895            if (added) {
896                locks_delete_lock(before);
897                continue;
898            }
899            request = fl;
900            added = 1;
901        }
902        else {
903            /* Processing for different lock types is a bit
904             * more complex.
905             */
906            if (fl->fl_end < request->fl_start)
907                goto next_lock;
908            if (fl->fl_start > request->fl_end)
909                break;
910            if (request->fl_type == F_UNLCK)
911                added = 1;
912            if (fl->fl_start < request->fl_start)
913                left = fl;
914            /* If the next lock in the list has a higher end
915             * address than the new one, insert the new one here.
916             */
917            if (fl->fl_end > request->fl_end) {
918                right = fl;
919                break;
920            }
921            if (fl->fl_start >= request->fl_start) {
922                /* The new lock completely replaces an old
923                 * one (This may happen several times).
924                 */
925                if (added) {
926                    locks_delete_lock(before);
927                    continue;
928                }
929                /* Replace the old lock with the new one.
930                 * Wake up anybody waiting for the old one,
931                 * as the change in lock type might satisfy
932                 * their needs.
933                 */
934                locks_wake_up_blocks(fl);
935                fl->fl_start = request->fl_start;
936                fl->fl_end = request->fl_end;
937                fl->fl_type = request->fl_type;
938                locks_release_private(fl);
939                locks_copy_private(fl, request);
940                request = fl;
941                added = 1;
942            }
943        }
944        /* Go on to next lock.
945         */
946    next_lock:
947        before = &fl->fl_next;
948    }
949
950    /*
951     * The above code only modifies existing locks in case of
952     * merging or replacing. If new lock(s) need to be inserted
953     * all modifications are done bellow this, so it's safe yet to
954     * bail out.
955     */
956    error = -ENOLCK; /* "no luck" */
957    if (right && left == right && !new_fl2)
958        goto out;
959
960    error = 0;
961    if (!added) {
962        if (request->fl_type == F_UNLCK) {
963            if (request->fl_flags & FL_EXISTS)
964                error = -ENOENT;
965            goto out;
966        }
967
968        if (!new_fl) {
969            error = -ENOLCK;
970            goto out;
971        }
972        locks_copy_lock(new_fl, request);
973        locks_insert_lock(before, new_fl);
974        new_fl = NULL;
975    }
976    if (right) {
977        if (left == right) {
978            /* The new lock breaks the old one in two pieces,
979             * so we have to use the second new lock.
980             */
981            left = new_fl2;
982            new_fl2 = NULL;
983            locks_copy_lock(left, right);
984            locks_insert_lock(before, left);
985        }
986        right->fl_start = request->fl_end + 1;
987        locks_wake_up_blocks(right);
988    }
989    if (left) {
990        left->fl_end = request->fl_start - 1;
991        locks_wake_up_blocks(left);
992    }
993 out:
994    unlock_kernel();
995    /*
996     * Free any unused locks.
997     */
998    if (new_fl)
999        locks_free_lock(new_fl);
1000    if (new_fl2)
1001        locks_free_lock(new_fl2);
1002    return error;
1003}
1004
1005/**
1006 * posix_lock_file - Apply a POSIX-style lock to a file
1007 * @filp: The file to apply the lock to
1008 * @fl: The lock to be applied
1009 * @conflock: Place to return a copy of the conflicting lock, if found.
1010 *
1011 * Add a POSIX style lock to a file.
1012 * We merge adjacent & overlapping locks whenever possible.
1013 * POSIX locks are sorted by owner task, then by starting address
1014 *
1015 * Note that if called with an FL_EXISTS argument, the caller may determine
1016 * whether or not a lock was successfully freed by testing the return
1017 * value for -ENOENT.
1018 */
1019int posix_lock_file(struct file *filp, struct file_lock *fl,
1020            struct file_lock *conflock)
1021{
1022    return __posix_lock_file(filp->f_path.dentry->d_inode, fl, conflock);
1023}
1024EXPORT_SYMBOL(posix_lock_file);
1025
1026/**
1027 * posix_lock_file_wait - Apply a POSIX-style lock to a file
1028 * @filp: The file to apply the lock to
1029 * @fl: The lock to be applied
1030 *
1031 * Add a POSIX style lock to a file.
1032 * We merge adjacent & overlapping locks whenever possible.
1033 * POSIX locks are sorted by owner task, then by starting address
1034 */
1035int posix_lock_file_wait(struct file *filp, struct file_lock *fl)
1036{
1037    int error;
1038    might_sleep ();
1039    for (;;) {
1040        error = posix_lock_file(filp, fl, NULL);
1041        if (error != FILE_LOCK_DEFERRED)
1042            break;
1043        error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
1044        if (!error)
1045            continue;
1046
1047        locks_delete_block(fl);
1048        break;
1049    }
1050    return error;
1051}
1052EXPORT_SYMBOL(posix_lock_file_wait);
1053
1054/**
1055 * locks_mandatory_locked - Check for an active lock
1056 * @inode: the file to check
1057 *
1058 * Searches the inode's list of locks to find any POSIX locks which conflict.
1059 * This function is called from locks_verify_locked() only.
1060 */
1061int locks_mandatory_locked(struct inode *inode)
1062{
1063    fl_owner_t owner = current->files;
1064    struct file_lock *fl;
1065
1066    /*
1067     * Search the lock list for this inode for any POSIX locks.
1068     */
1069    lock_kernel();
1070    for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
1071        if (!IS_POSIX(fl))
1072            continue;
1073        if (fl->fl_owner != owner)
1074            break;
1075    }
1076    unlock_kernel();
1077    return fl ? -EAGAIN : 0;
1078}
1079
1080/**
1081 * locks_mandatory_area - Check for a conflicting lock
1082 * @read_write: %FLOCK_VERIFY_WRITE for exclusive access, %FLOCK_VERIFY_READ
1083 * for shared
1084 * @inode: the file to check
1085 * @filp: how the file was opened (if it was)
1086 * @offset: start of area to check
1087 * @count: length of area to check
1088 *
1089 * Searches the inode's list of locks to find any POSIX locks which conflict.
1090 * This function is called from rw_verify_area() and
1091 * locks_verify_truncate().
1092 */
1093int locks_mandatory_area(int read_write, struct inode *inode,
1094             struct file *filp, loff_t offset,
1095             size_t count)
1096{
1097    struct file_lock fl;
1098    int error;
1099
1100    locks_init_lock(&fl);
1101    fl.fl_owner = current->files;
1102    fl.fl_pid = current->tgid;
1103    fl.fl_file = filp;
1104    fl.fl_flags = FL_POSIX | FL_ACCESS;
1105    if (filp && !(filp->f_flags & O_NONBLOCK))
1106        fl.fl_flags |= FL_SLEEP;
1107    fl.fl_type = (read_write == FLOCK_VERIFY_WRITE) ? F_WRLCK : F_RDLCK;
1108    fl.fl_start = offset;
1109    fl.fl_end = offset + count - 1;
1110
1111    for (;;) {
1112        error = __posix_lock_file(inode, &fl, NULL);
1113        if (error != FILE_LOCK_DEFERRED)
1114            break;
1115        error = wait_event_interruptible(fl.fl_wait, !fl.fl_next);
1116        if (!error) {
1117            /*
1118             * If we've been sleeping someone might have
1119             * changed the permissions behind our back.
1120             */
1121            if (__mandatory_lock(inode))
1122                continue;
1123        }
1124
1125        locks_delete_block(&fl);
1126        break;
1127    }
1128
1129    return error;
1130}
1131
1132EXPORT_SYMBOL(locks_mandatory_area);
1133
1134/* We already had a lease on this file; just change its type */
1135int lease_modify(struct file_lock **before, int arg)
1136{
1137    struct file_lock *fl = *before;
1138    int error = assign_type(fl, arg);
1139
1140    if (error)
1141        return error;
1142    locks_wake_up_blocks(fl);
1143    if (arg == F_UNLCK)
1144        locks_delete_lock(before);
1145    return 0;
1146}
1147
1148EXPORT_SYMBOL(lease_modify);
1149
1150static void time_out_leases(struct inode *inode)
1151{
1152    struct file_lock **before;
1153    struct file_lock *fl;
1154
1155    before = &inode->i_flock;
1156    while ((fl = *before) && IS_LEASE(fl) && (fl->fl_type & F_INPROGRESS)) {
1157        if ((fl->fl_break_time == 0)
1158                || time_before(jiffies, fl->fl_break_time)) {
1159            before = &fl->fl_next;
1160            continue;
1161        }
1162        lease_modify(before, fl->fl_type & ~F_INPROGRESS);
1163        if (fl == *before) /* lease_modify may have freed fl */
1164            before = &fl->fl_next;
1165    }
1166}
1167
1168/**
1169 * __break_lease - revoke all outstanding leases on file
1170 * @inode: the inode of the file to return
1171 * @mode: the open mode (read or write)
1172 *
1173 * break_lease (inlined for speed) has checked there already is at least
1174 * some kind of lock (maybe a lease) on this file. Leases are broken on
1175 * a call to open() or truncate(). This function can sleep unless you
1176 * specified %O_NONBLOCK to your open().
1177 */
1178int __break_lease(struct inode *inode, unsigned int mode)
1179{
1180    int error = 0, future;
1181    struct file_lock *new_fl, *flock;
1182    struct file_lock *fl;
1183    unsigned long break_time;
1184    int i_have_this_lease = 0;
1185    int want_write = (mode & O_ACCMODE) != O_RDONLY;
1186
1187    new_fl = lease_alloc(NULL, want_write ? F_WRLCK : F_RDLCK);
1188
1189    lock_kernel();
1190
1191    time_out_leases(inode);
1192
1193    flock = inode->i_flock;
1194    if ((flock == NULL) || !IS_LEASE(flock))
1195        goto out;
1196
1197    for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next)
1198        if (fl->fl_owner == current->files)
1199            i_have_this_lease = 1;
1200
1201    if (want_write) {
1202        /* If we want write access, we have to revoke any lease. */
1203        future = F_UNLCK | F_INPROGRESS;
1204    } else if (flock->fl_type & F_INPROGRESS) {
1205        /* If the lease is already being broken, we just leave it */
1206        future = flock->fl_type;
1207    } else if (flock->fl_type & F_WRLCK) {
1208        /* Downgrade the exclusive lease to a read-only lease. */
1209        future = F_RDLCK | F_INPROGRESS;
1210    } else {
1211        /* the existing lease was read-only, so we can read too. */
1212        goto out;
1213    }
1214
1215    if (IS_ERR(new_fl) && !i_have_this_lease
1216            && ((mode & O_NONBLOCK) == 0)) {
1217        error = PTR_ERR(new_fl);
1218        goto out;
1219    }
1220
1221    break_time = 0;
1222    if (lease_break_time > 0) {
1223        break_time = jiffies + lease_break_time * HZ;
1224        if (break_time == 0)
1225            break_time++; /* so that 0 means no break time */
1226    }
1227
1228    for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next) {
1229        if (fl->fl_type != future) {
1230            fl->fl_type = future;
1231            fl->fl_break_time = break_time;
1232            /* lease must have lmops break callback */
1233            fl->fl_lmops->fl_break(fl);
1234        }
1235    }
1236
1237    if (i_have_this_lease || (mode & O_NONBLOCK)) {
1238        error = -EWOULDBLOCK;
1239        goto out;
1240    }
1241
1242restart:
1243    break_time = flock->fl_break_time;
1244    if (break_time != 0) {
1245        break_time -= jiffies;
1246        if (break_time == 0)
1247            break_time++;
1248    }
1249    locks_insert_block(flock, new_fl);
1250    error = wait_event_interruptible_timeout(new_fl->fl_wait,
1251                        !new_fl->fl_next, break_time);
1252    __locks_delete_block(new_fl);
1253    if (error >= 0) {
1254        if (error == 0)
1255            time_out_leases(inode);
1256        /* Wait for the next lease that has not been broken yet */
1257        for (flock = inode->i_flock; flock && IS_LEASE(flock);
1258                flock = flock->fl_next) {
1259            if (flock->fl_type & F_INPROGRESS)
1260                goto restart;
1261        }
1262        error = 0;
1263    }
1264
1265out:
1266    unlock_kernel();
1267    if (!IS_ERR(new_fl))
1268        locks_free_lock(new_fl);
1269    return error;
1270}
1271
1272EXPORT_SYMBOL(__break_lease);
1273
1274/**
1275 * lease_get_mtime - get the last modified time of an inode
1276 * @inode: the inode
1277 * @time: pointer to a timespec which will contain the last modified time
1278 *
1279 * This is to force NFS clients to flush their caches for files with
1280 * exclusive leases. The justification is that if someone has an
1281 * exclusive lease, then they could be modifying it.
1282 */
1283void lease_get_mtime(struct inode *inode, struct timespec *time)
1284{
1285    struct file_lock *flock = inode->i_flock;
1286    if (flock && IS_LEASE(flock) && (flock->fl_type & F_WRLCK))
1287        *time = current_fs_time(inode->i_sb);
1288    else
1289        *time = inode->i_mtime;
1290}
1291
1292EXPORT_SYMBOL(lease_get_mtime);
1293
1294/**
1295 * fcntl_getlease - Enquire what lease is currently active
1296 * @filp: the file
1297 *
1298 * The value returned by this function will be one of
1299 * (if no lease break is pending):
1300 *
1301 * %F_RDLCK to indicate a shared lease is held.
1302 *
1303 * %F_WRLCK to indicate an exclusive lease is held.
1304 *
1305 * %F_UNLCK to indicate no lease is held.
1306 *
1307 * (if a lease break is pending):
1308 *
1309 * %F_RDLCK to indicate an exclusive lease needs to be
1310 * changed to a shared lease (or removed).
1311 *
1312 * %F_UNLCK to indicate the lease needs to be removed.
1313 *
1314 * XXX: sfr & willy disagree over whether F_INPROGRESS
1315 * should be returned to userspace.
1316 */
1317int fcntl_getlease(struct file *filp)
1318{
1319    struct file_lock *fl;
1320    int type = F_UNLCK;
1321
1322    lock_kernel();
1323    time_out_leases(filp->f_path.dentry->d_inode);
1324    for (fl = filp->f_path.dentry->d_inode->i_flock; fl && IS_LEASE(fl);
1325            fl = fl->fl_next) {
1326        if (fl->fl_file == filp) {
1327            type = fl->fl_type & ~F_INPROGRESS;
1328            break;
1329        }
1330    }
1331    unlock_kernel();
1332    return type;
1333}
1334
1335/**
1336 * generic_setlease - sets a lease on an open file
1337 * @filp: file pointer
1338 * @arg: type of lease to obtain
1339 * @flp: input - file_lock to use, output - file_lock inserted
1340 *
1341 * The (input) flp->fl_lmops->fl_break function is required
1342 * by break_lease().
1343 *
1344 * Called with kernel lock held.
1345 */
1346int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
1347{
1348    struct file_lock *fl, **before, **my_before = NULL, *lease;
1349    struct file_lock *new_fl = NULL;
1350    struct dentry *dentry = filp->f_path.dentry;
1351    struct inode *inode = dentry->d_inode;
1352    int error, rdlease_count = 0, wrlease_count = 0;
1353
1354    if ((current_fsuid() != inode->i_uid) && !capable(CAP_LEASE))
1355        return -EACCES;
1356    if (!S_ISREG(inode->i_mode))
1357        return -EINVAL;
1358    error = security_file_lock(filp, arg);
1359    if (error)
1360        return error;
1361
1362    time_out_leases(inode);
1363
1364    BUG_ON(!(*flp)->fl_lmops->fl_break);
1365
1366    lease = *flp;
1367
1368    if (arg != F_UNLCK) {
1369        error = -ENOMEM;
1370        new_fl = locks_alloc_lock();
1371        if (new_fl == NULL)
1372            goto out;
1373
1374        error = -EAGAIN;
1375        if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0))
1376            goto out;
1377        if ((arg == F_WRLCK)
1378            && ((atomic_read(&dentry->d_count) > 1)
1379            || (atomic_read(&inode->i_count) > 1)))
1380            goto out;
1381    }
1382
1383    /*
1384     * At this point, we know that if there is an exclusive
1385     * lease on this file, then we hold it on this filp
1386     * (otherwise our open of this file would have blocked).
1387     * And if we are trying to acquire an exclusive lease,
1388     * then the file is not open by anyone (including us)
1389     * except for this filp.
1390     */
1391    for (before = &inode->i_flock;
1392            ((fl = *before) != NULL) && IS_LEASE(fl);
1393            before = &fl->fl_next) {
1394        if (lease->fl_lmops->fl_mylease(fl, lease))
1395            my_before = before;
1396        else if (fl->fl_type == (F_INPROGRESS | F_UNLCK))
1397            /*
1398             * Someone is in the process of opening this
1399             * file for writing so we may not take an
1400             * exclusive lease on it.
1401             */
1402            wrlease_count++;
1403        else
1404            rdlease_count++;
1405    }
1406
1407    error = -EAGAIN;
1408    if ((arg == F_RDLCK && (wrlease_count > 0)) ||
1409        (arg == F_WRLCK && ((rdlease_count + wrlease_count) > 0)))
1410        goto out;
1411
1412    if (my_before != NULL) {
1413        *flp = *my_before;
1414        error = lease->fl_lmops->fl_change(my_before, arg);
1415        goto out;
1416    }
1417
1418    error = 0;
1419    if (arg == F_UNLCK)
1420        goto out;
1421
1422    error = -EINVAL;
1423    if (!leases_enable)
1424        goto out;
1425
1426    locks_copy_lock(new_fl, lease);
1427    locks_insert_lock(before, new_fl);
1428
1429    *flp = new_fl;
1430    return 0;
1431
1432out:
1433    if (new_fl != NULL)
1434        locks_free_lock(new_fl);
1435    return error;
1436}
1437EXPORT_SYMBOL(generic_setlease);
1438
1439 /**
1440 * vfs_setlease - sets a lease on an open file
1441 * @filp: file pointer
1442 * @arg: type of lease to obtain
1443 * @lease: file_lock to use
1444 *
1445 * Call this to establish a lease on the file.
1446 * The (*lease)->fl_lmops->fl_break operation must be set; if not,
1447 * break_lease will oops!
1448 *
1449 * This will call the filesystem's setlease file method, if
1450 * defined. Note that there is no getlease method; instead, the
1451 * filesystem setlease method should call back to setlease() to
1452 * add a lease to the inode's lease list, where fcntl_getlease() can
1453 * find it. Since fcntl_getlease() only reports whether the current
1454 * task holds a lease, a cluster filesystem need only do this for
1455 * leases held by processes on this node.
1456 *
1457 * There is also no break_lease method; filesystems that
1458 * handle their own leases should break leases themselves from the
1459 * filesystem's open, create, and (on truncate) setattr methods.
1460 *
1461 * Warning: the only current setlease methods exist only to disable
1462 * leases in certain cases. More vfs changes may be required to
1463 * allow a full filesystem lease implementation.
1464 */
1465
1466int vfs_setlease(struct file *filp, long arg, struct file_lock **lease)
1467{
1468    int error;
1469
1470    lock_kernel();
1471    if (filp->f_op && filp->f_op->setlease)
1472        error = filp->f_op->setlease(filp, arg, lease);
1473    else
1474        error = generic_setlease(filp, arg, lease);
1475    unlock_kernel();
1476
1477    return error;
1478}
1479EXPORT_SYMBOL_GPL(vfs_setlease);
1480
1481/**
1482 * fcntl_setlease - sets a lease on an open file
1483 * @fd: open file descriptor
1484 * @filp: file pointer
1485 * @arg: type of lease to obtain
1486 *
1487 * Call this fcntl to establish a lease on the file.
1488 * Note that you also need to call %F_SETSIG to
1489 * receive a signal when the lease is broken.
1490 */
1491int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
1492{
1493    struct file_lock fl, *flp = &fl;
1494    struct inode *inode = filp->f_path.dentry->d_inode;
1495    int error;
1496
1497    locks_init_lock(&fl);
1498    error = lease_init(filp, arg, &fl);
1499    if (error)
1500        return error;
1501
1502    lock_kernel();
1503
1504    error = vfs_setlease(filp, arg, &flp);
1505    if (error || arg == F_UNLCK)
1506        goto out_unlock;
1507
1508    error = fasync_helper(fd, filp, 1, &flp->fl_fasync);
1509    if (error < 0) {
1510        /* remove lease just inserted by setlease */
1511        flp->fl_type = F_UNLCK | F_INPROGRESS;
1512        flp->fl_break_time = jiffies - 10;
1513        time_out_leases(inode);
1514        goto out_unlock;
1515    }
1516
1517    error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
1518out_unlock:
1519    unlock_kernel();
1520    return error;
1521}
1522
1523/**
1524 * flock_lock_file_wait - Apply a FLOCK-style lock to a file
1525 * @filp: The file to apply the lock to
1526 * @fl: The lock to be applied
1527 *
1528 * Add a FLOCK style lock to a file.
1529 */
1530int flock_lock_file_wait(struct file *filp, struct file_lock *fl)
1531{
1532    int error;
1533    might_sleep();
1534    for (;;) {
1535        error = flock_lock_file(filp, fl);
1536        if (error != FILE_LOCK_DEFERRED)
1537            break;
1538        error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
1539        if (!error)
1540            continue;
1541
1542        locks_delete_block(fl);
1543        break;
1544    }
1545    return error;
1546}
1547
1548EXPORT_SYMBOL(flock_lock_file_wait);
1549
1550/**
1551 * sys_flock: - flock() system call.
1552 * @fd: the file descriptor to lock.
1553 * @cmd: the type of lock to apply.
1554 *
1555 * Apply a %FL_FLOCK style lock to an open file descriptor.
1556 * The @cmd can be one of
1557 *
1558 * %LOCK_SH -- a shared lock.
1559 *
1560 * %LOCK_EX -- an exclusive lock.
1561 *
1562 * %LOCK_UN -- remove an existing lock.
1563 *
1564 * %LOCK_MAND -- a `mandatory' flock. This exists to emulate Windows Share Modes.
1565 *
1566 * %LOCK_MAND can be combined with %LOCK_READ or %LOCK_WRITE to allow other
1567 * processes read and write access respectively.
1568 */
1569SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd)
1570{
1571    struct file *filp;
1572    struct file_lock *lock;
1573    int can_sleep, unlock;
1574    int error;
1575
1576    error = -EBADF;
1577    filp = fget(fd);
1578    if (!filp)
1579        goto out;
1580
1581    can_sleep = !(cmd & LOCK_NB);
1582    cmd &= ~LOCK_NB;
1583    unlock = (cmd == LOCK_UN);
1584
1585    if (!unlock && !(cmd & LOCK_MAND) &&
1586        !(filp->f_mode & (FMODE_READ|FMODE_WRITE)))
1587        goto out_putf;
1588
1589    error = flock_make_lock(filp, &lock, cmd);
1590    if (error)
1591        goto out_putf;
1592    if (can_sleep)
1593        lock->fl_flags |= FL_SLEEP;
1594
1595    error = security_file_lock(filp, lock->fl_type);
1596    if (error)
1597        goto out_free;
1598
1599    if (filp->f_op && filp->f_op->flock)
1600        error = filp->f_op->flock(filp,
1601                      (can_sleep) ? F_SETLKW : F_SETLK,
1602                      lock);
1603    else
1604        error = flock_lock_file_wait(filp, lock);
1605
1606 out_free:
1607    locks_free_lock(lock);
1608
1609 out_putf:
1610    fput(filp);
1611 out:
1612    return error;
1613}
1614
1615/**
1616 * vfs_test_lock - test file byte range lock
1617 * @filp: The file to test lock for
1618 * @fl: The lock to test; also used to hold result
1619 *
1620 * Returns -ERRNO on failure. Indicates presence of conflicting lock by
1621 * setting conf->fl_type to something other than F_UNLCK.
1622 */
1623int vfs_test_lock(struct file *filp, struct file_lock *fl)
1624{
1625    if (filp->f_op && filp->f_op->lock)
1626        return filp->f_op->lock(filp, F_GETLK, fl);
1627    posix_test_lock(filp, fl);
1628    return 0;
1629}
1630EXPORT_SYMBOL_GPL(vfs_test_lock);
1631
1632static int posix_lock_to_flock(struct flock *flock, struct file_lock *fl)
1633{
1634    flock->l_pid = fl->fl_pid;
1635#if BITS_PER_LONG == 32
1636    /*
1637     * Make sure we can represent the posix lock via
1638     * legacy 32bit flock.
1639     */
1640    if (fl->fl_start > OFFT_OFFSET_MAX)
1641        return -EOVERFLOW;
1642    if (fl->fl_end != OFFSET_MAX && fl->fl_end > OFFT_OFFSET_MAX)
1643        return -EOVERFLOW;
1644#endif
1645    flock->l_start = fl->fl_start;
1646    flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
1647        fl->fl_end - fl->fl_start + 1;
1648    flock->l_whence = 0;
1649    flock->l_type = fl->fl_type;
1650    return 0;
1651}
1652
1653#if BITS_PER_LONG == 32
1654static void posix_lock_to_flock64(struct flock64 *flock, struct file_lock *fl)
1655{
1656    flock->l_pid = fl->fl_pid;
1657    flock->l_start = fl->fl_start;
1658    flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
1659        fl->fl_end - fl->fl_start + 1;
1660    flock->l_whence = 0;
1661    flock->l_type = fl->fl_type;
1662}
1663#endif
1664
1665/* Report the first existing lock that would conflict with l.
1666 * This implements the F_GETLK command of fcntl().
1667 */
1668int fcntl_getlk(struct file *filp, struct flock __user *l)
1669{
1670    struct file_lock file_lock;
1671    struct flock flock;
1672    int error;
1673
1674    error = -EFAULT;
1675    if (copy_from_user(&flock, l, sizeof(flock)))
1676        goto out;
1677    error = -EINVAL;
1678    if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
1679        goto out;
1680
1681    error = flock_to_posix_lock(filp, &file_lock, &flock);
1682    if (error)
1683        goto out;
1684
1685    error = vfs_test_lock(filp, &file_lock);
1686    if (error)
1687        goto out;
1688 
1689    flock.l_type = file_lock.fl_type;
1690    if (file_lock.fl_type != F_UNLCK) {
1691        error = posix_lock_to_flock(&flock, &file_lock);
1692        if (error)
1693            goto out;
1694    }
1695    error = -EFAULT;
1696    if (!copy_to_user(l, &flock, sizeof(flock)))
1697        error = 0;
1698out:
1699    return error;
1700}
1701
1702/**
1703 * vfs_lock_file - file byte range lock
1704 * @filp: The file to apply the lock to
1705 * @cmd: type of locking operation (F_SETLK, F_GETLK, etc.)
1706 * @fl: The lock to be applied
1707 * @conf: Place to return a copy of the conflicting lock, if found.
1708 *
1709 * A caller that doesn't care about the conflicting lock may pass NULL
1710 * as the final argument.
1711 *
1712 * If the filesystem defines a private ->lock() method, then @conf will
1713 * be left unchanged; so a caller that cares should initialize it to
1714 * some acceptable default.
1715 *
1716 * To avoid blocking kernel daemons, such as lockd, that need to acquire POSIX
1717 * locks, the ->lock() interface may return asynchronously, before the lock has
1718 * been granted or denied by the underlying filesystem, if (and only if)
1719 * fl_grant is set. Callers expecting ->lock() to return asynchronously
1720 * will only use F_SETLK, not F_SETLKW; they will set FL_SLEEP if (and only if)
1721 * the request is for a blocking lock. When ->lock() does return asynchronously,
1722 * it must return FILE_LOCK_DEFERRED, and call ->fl_grant() when the lock
1723 * request completes.
1724 * If the request is for non-blocking lock the file system should return
1725 * FILE_LOCK_DEFERRED then try to get the lock and call the callback routine
1726 * with the result. If the request timed out the callback routine will return a
1727 * nonzero return code and the file system should release the lock. The file
1728 * system is also responsible to keep a corresponding posix lock when it
1729 * grants a lock so the VFS can find out which locks are locally held and do
1730 * the correct lock cleanup when required.
1731 * The underlying filesystem must not drop the kernel lock or call
1732 * ->fl_grant() before returning to the caller with a FILE_LOCK_DEFERRED
1733 * return code.
1734 */
1735int vfs_lock_file(struct file *filp, unsigned int cmd, struct file_lock *fl, struct file_lock *conf)
1736{
1737    if (filp->f_op && filp->f_op->lock)
1738        return filp->f_op->lock(filp, cmd, fl);
1739    else
1740        return posix_lock_file(filp, fl, conf);
1741}
1742EXPORT_SYMBOL_GPL(vfs_lock_file);
1743
1744static int do_lock_file_wait(struct file *filp, unsigned int cmd,
1745                 struct file_lock *fl)
1746{
1747    int error;
1748
1749    error = security_file_lock(filp, fl->fl_type);
1750    if (error)
1751        return error;
1752
1753    for (;;) {
1754        error = vfs_lock_file(filp, cmd, fl, NULL);
1755        if (error != FILE_LOCK_DEFERRED)
1756            break;
1757        error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
1758        if (!error)
1759            continue;
1760
1761        locks_delete_block(fl);
1762        break;
1763    }
1764
1765    return error;
1766}
1767
1768/* Apply the lock described by l to an open file descriptor.
1769 * This implements both the F_SETLK and F_SETLKW commands of fcntl().
1770 */
1771int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
1772        struct flock __user *l)
1773{
1774    struct file_lock *file_lock = locks_alloc_lock();
1775    struct flock flock;
1776    struct inode *inode;
1777    struct file *f;
1778    int error;
1779
1780    if (file_lock == NULL)
1781        return -ENOLCK;
1782
1783    /*
1784     * This might block, so we do it before checking the inode.
1785     */
1786    error = -EFAULT;
1787    if (copy_from_user(&flock, l, sizeof(flock)))
1788        goto out;
1789
1790    inode = filp->f_path.dentry->d_inode;
1791
1792    /* Don't allow mandatory locks on files that may be memory mapped
1793     * and shared.
1794     */
1795    if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) {
1796        error = -EAGAIN;
1797        goto out;
1798    }
1799
1800again:
1801    error = flock_to_posix_lock(filp, file_lock, &flock);
1802    if (error)
1803        goto out;
1804    if (cmd == F_SETLKW) {
1805        file_lock->fl_flags |= FL_SLEEP;
1806    }
1807    
1808    error = -EBADF;
1809    switch (flock.l_type) {
1810    case F_RDLCK:
1811        if (!(filp->f_mode & FMODE_READ))
1812            goto out;
1813        break;
1814    case F_WRLCK:
1815        if (!(filp->f_mode & FMODE_WRITE))
1816            goto out;
1817        break;
1818    case F_UNLCK:
1819        break;
1820    default:
1821        error = -EINVAL;
1822        goto out;
1823    }
1824
1825    error = do_lock_file_wait(filp, cmd, file_lock);
1826
1827    /*
1828     * Attempt to detect a close/fcntl race and recover by
1829     * releasing the lock that was just acquired.
1830     */
1831    /*
1832     * we need that spin_lock here - it prevents reordering between
1833     * update of inode->i_flock and check for it done in close().
1834     * rcu_read_lock() wouldn't do.
1835     */
1836    spin_lock(&current->files->file_lock);
1837    f = fcheck(fd);
1838    spin_unlock(&current->files->file_lock);
1839    if (!error && f != filp && flock.l_type != F_UNLCK) {
1840        flock.l_type = F_UNLCK;
1841        goto again;
1842    }
1843
1844out:
1845    locks_free_lock(file_lock);
1846    return error;
1847}
1848
1849#if BITS_PER_LONG == 32
1850/* Report the first existing lock that would conflict with l.
1851 * This implements the F_GETLK command of fcntl().
1852 */
1853int fcntl_getlk64(struct file *filp, struct flock64 __user *l)
1854{
1855    struct file_lock file_lock;
1856    struct flock64 flock;
1857    int error;
1858
1859    error = -EFAULT;
1860    if (copy_from_user(&flock, l, sizeof(flock)))
1861        goto out;
1862    error = -EINVAL;
1863    if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
1864        goto out;
1865
1866    error = flock64_to_posix_lock(filp, &file_lock, &flock);
1867    if (error)
1868        goto out;
1869
1870    error = vfs_test_lock(filp, &file_lock);
1871    if (error)
1872        goto out;
1873
1874    flock.l_type = file_lock.fl_type;
1875    if (file_lock.fl_type != F_UNLCK)
1876        posix_lock_to_flock64(&flock, &file_lock);
1877
1878    error = -EFAULT;
1879    if (!copy_to_user(l, &flock, sizeof(flock)))
1880        error = 0;
1881  
1882out:
1883    return error;
1884}
1885
1886/* Apply the lock described by l to an open file descriptor.
1887 * This implements both the F_SETLK and F_SETLKW commands of fcntl().
1888 */
1889int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
1890        struct flock64 __user *l)
1891{
1892    struct file_lock *file_lock = locks_alloc_lock();
1893    struct flock64 flock;
1894    struct inode *inode;
1895    struct file *f;
1896    int error;
1897
1898    if (file_lock == NULL)
1899        return -ENOLCK;
1900
1901    /*
1902     * This might block, so we do it before checking the inode.
1903     */
1904    error = -EFAULT;
1905    if (copy_from_user(&flock, l, sizeof(flock)))
1906        goto out;
1907
1908    inode = filp->f_path.dentry->d_inode;
1909
1910    /* Don't allow mandatory locks on files that may be memory mapped
1911     * and shared.
1912     */
1913    if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) {
1914        error = -EAGAIN;
1915        goto out;
1916    }
1917
1918again:
1919    error = flock64_to_posix_lock(filp, file_lock, &flock);
1920    if (error)
1921        goto out;
1922    if (cmd == F_SETLKW64) {
1923        file_lock->fl_flags |= FL_SLEEP;
1924    }
1925    
1926    error = -EBADF;
1927    switch (flock.l_type) {
1928    case F_RDLCK:
1929        if (!(filp->f_mode & FMODE_READ))
1930            goto out;
1931        break;
1932    case F_WRLCK:
1933        if (!(filp->f_mode & FMODE_WRITE))
1934            goto out;
1935        break;
1936    case F_UNLCK:
1937        break;
1938    default:
1939        error = -EINVAL;
1940        goto out;
1941    }
1942
1943    error = do_lock_file_wait(filp, cmd, file_lock);
1944
1945    /*
1946     * Attempt to detect a close/fcntl race and recover by
1947     * releasing the lock that was just acquired.
1948     */
1949    spin_lock(&current->files->file_lock);
1950    f = fcheck(fd);
1951    spin_unlock(&current->files->file_lock);
1952    if (!error && f != filp && flock.l_type != F_UNLCK) {
1953        flock.l_type = F_UNLCK;
1954        goto again;
1955    }
1956
1957out:
1958    locks_free_lock(file_lock);
1959    return error;
1960}
1961#endif /* BITS_PER_LONG == 32 */
1962
1963/*
1964 * This function is called when the file is being removed
1965 * from the task's fd array. POSIX locks belonging to this task
1966 * are deleted at this time.
1967 */
1968void locks_remove_posix(struct file *filp, fl_owner_t owner)
1969{
1970    struct file_lock lock;
1971
1972    /*
1973     * If there are no locks held on this file, we don't need to call
1974     * posix_lock_file(). Another process could be setting a lock on this
1975     * file at the same time, but we wouldn't remove that lock anyway.
1976     */
1977    if (!filp->f_path.dentry->d_inode->i_flock)
1978        return;
1979
1980    lock.fl_type = F_UNLCK;
1981    lock.fl_flags = FL_POSIX | FL_CLOSE;
1982    lock.fl_start = 0;
1983    lock.fl_end = OFFSET_MAX;
1984    lock.fl_owner = owner;
1985    lock.fl_pid = current->tgid;
1986    lock.fl_file = filp;
1987    lock.fl_ops = NULL;
1988    lock.fl_lmops = NULL;
1989
1990    vfs_lock_file(filp, F_SETLK, &lock, NULL);
1991
1992    if (lock.fl_ops && lock.fl_ops->fl_release_private)
1993        lock.fl_ops->fl_release_private(&lock);
1994}
1995
1996EXPORT_SYMBOL(locks_remove_posix);
1997
1998/*
1999 * This function is called on the last close of an open file.
2000 */
2001void locks_remove_flock(struct file *filp)
2002{
2003    struct inode * inode = filp->f_path.dentry->d_inode;
2004    struct file_lock *fl;
2005    struct file_lock **before;
2006
2007    if (!inode->i_flock)
2008        return;
2009
2010    if (filp->f_op && filp->f_op->flock) {
2011        struct file_lock fl = {
2012            .fl_pid = current->tgid,
2013            .fl_file = filp,
2014            .fl_flags = FL_FLOCK,
2015            .fl_type = F_UNLCK,
2016            .fl_end = OFFSET_MAX,
2017        };
2018        filp->f_op->flock(filp, F_SETLKW, &fl);
2019        if (fl.fl_ops && fl.fl_ops->fl_release_private)
2020            fl.fl_ops->fl_release_private(&fl);
2021    }
2022
2023    lock_kernel();
2024    before = &inode->i_flock;
2025
2026    while ((fl = *before) != NULL) {
2027        if (fl->fl_file == filp) {
2028            if (IS_FLOCK(fl)) {
2029                locks_delete_lock(before);
2030                continue;
2031            }
2032            if (IS_LEASE(fl)) {
2033                lease_modify(before, F_UNLCK);
2034                continue;
2035            }
2036            /* What? */
2037            BUG();
2038         }
2039        before = &fl->fl_next;
2040    }
2041    unlock_kernel();
2042}
2043
2044/**
2045 * posix_unblock_lock - stop waiting for a file lock
2046 * @filp: how the file was opened
2047 * @waiter: the lock which was waiting
2048 *
2049 * lockd needs to block waiting for locks.
2050 */
2051int
2052posix_unblock_lock(struct file *filp, struct file_lock *waiter)
2053{
2054    int status = 0;
2055
2056    lock_kernel();
2057    if (waiter->fl_next)
2058        __locks_delete_block(waiter);
2059    else
2060        status = -ENOENT;
2061    unlock_kernel();
2062    return status;
2063}
2064
2065EXPORT_SYMBOL(posix_unblock_lock);
2066
2067/**
2068 * vfs_cancel_lock - file byte range unblock lock
2069 * @filp: The file to apply the unblock to
2070 * @fl: The lock to be unblocked
2071 *
2072 * Used by lock managers to cancel blocked requests
2073 */
2074int vfs_cancel_lock(struct file *filp, struct file_lock *fl)
2075{
2076    if (filp->f_op && filp->f_op->lock)
2077        return filp->f_op->lock(filp, F_CANCELLK, fl);
2078    return 0;
2079}
2080
2081EXPORT_SYMBOL_GPL(vfs_cancel_lock);
2082
2083#ifdef CONFIG_PROC_FS
2084#include <linux/proc_fs.h>
2085#include <linux/seq_file.h>
2086
2087static void lock_get_status(struct seq_file *f, struct file_lock *fl,
2088                            int id, char *pfx)
2089{
2090    struct inode *inode = NULL;
2091    unsigned int fl_pid;
2092
2093    if (fl->fl_nspid)
2094        fl_pid = pid_vnr(fl->fl_nspid);
2095    else
2096        fl_pid = fl->fl_pid;
2097
2098    if (fl->fl_file != NULL)
2099        inode = fl->fl_file->f_path.dentry->d_inode;
2100
2101    seq_printf(f, "%d:%s ", id, pfx);
2102    if (IS_POSIX(fl)) {
2103        seq_printf(f, "%6s %s ",
2104                 (fl->fl_flags & FL_ACCESS) ? "ACCESS" : "POSIX ",
2105                 (inode == NULL) ? "*NOINODE*" :
2106                 mandatory_lock(inode) ? "MANDATORY" : "ADVISORY ");
2107    } else if (IS_FLOCK(fl)) {
2108        if (fl->fl_type & LOCK_MAND) {
2109            seq_printf(f, "FLOCK MSNFS ");
2110        } else {
2111            seq_printf(f, "FLOCK ADVISORY ");
2112        }
2113    } else if (IS_LEASE(fl)) {
2114        seq_printf(f, "LEASE ");
2115        if (fl->fl_type & F_INPROGRESS)
2116            seq_printf(f, "BREAKING ");
2117        else if (fl->fl_file)
2118            seq_printf(f, "ACTIVE ");
2119        else
2120            seq_printf(f, "BREAKER ");
2121    } else {
2122        seq_printf(f, "UNKNOWN UNKNOWN ");
2123    }
2124    if (fl->fl_type & LOCK_MAND) {
2125        seq_printf(f, "%s ",
2126                   (fl->fl_type & LOCK_READ)
2127                   ? (fl->fl_type & LOCK_WRITE) ? "RW " : "READ "
2128                   : (fl->fl_type & LOCK_WRITE) ? "WRITE" : "NONE ");
2129    } else {
2130        seq_printf(f, "%s ",
2131                   (fl->fl_type & F_INPROGRESS)
2132                   ? (fl->fl_type & F_UNLCK) ? "UNLCK" : "READ "
2133                   : (fl->fl_type & F_WRLCK) ? "WRITE" : "READ ");
2134    }
2135    if (inode) {
2136#ifdef WE_CAN_BREAK_LSLK_NOW
2137        seq_printf(f, "%d %s:%ld ", fl_pid,
2138                inode->i_sb->s_id, inode->i_ino);
2139#else
2140        /* userspace relies on this representation of dev_t ;-( */
2141        seq_printf(f, "%d %02x:%02x:%ld ", fl_pid,
2142                MAJOR(inode->i_sb->s_dev),
2143                MINOR(inode->i_sb->s_dev), inode->i_ino);
2144#endif
2145    } else {
2146        seq_printf(f, "%d <none>:0 ", fl_pid);
2147    }
2148    if (IS_POSIX(fl)) {
2149        if (fl->fl_end == OFFSET_MAX)
2150            seq_printf(f, "%Ld EOF\n", fl->fl_start);
2151        else
2152            seq_printf(f, "%Ld %Ld\n", fl->fl_start, fl->fl_end);
2153    } else {
2154        seq_printf(f, "0 EOF\n");
2155    }
2156}
2157
2158static int locks_show(struct seq_file *f, void *v)
2159{
2160    struct file_lock *fl, *bfl;
2161
2162    fl = list_entry(v, struct file_lock, fl_link);
2163
2164    lock_get_status(f, fl, (long)f->private, "");
2165
2166    list_for_each_entry(bfl, &fl->fl_block, fl_block)
2167        lock_get_status(f, bfl, (long)f->private, " ->");
2168
2169    f->private++;
2170    return 0;
2171}
2172
2173static void *locks_start(struct seq_file *f, loff_t *pos)
2174{
2175    lock_kernel();
2176    f->private = (void *)1;
2177    return seq_list_start(&file_lock_list, *pos);
2178}
2179
2180static void *locks_next(struct seq_file *f, void *v, loff_t *pos)
2181{
2182    return seq_list_next(v, &file_lock_list, pos);
2183}
2184
2185static void locks_stop(struct seq_file *f, void *v)
2186{
2187    unlock_kernel();
2188}
2189
2190static const struct seq_operations locks_seq_operations = {
2191    .start = locks_start,
2192    .next = locks_next,
2193    .stop = locks_stop,
2194    .show = locks_show,
2195};
2196
2197static int locks_open(struct inode *inode, struct file *filp)
2198{
2199    return seq_open(filp, &locks_seq_operations);
2200}
2201
2202static const struct file_operations proc_locks_operations = {
2203    .open = locks_open,
2204    .read = seq_read,
2205    .llseek = seq_lseek,
2206    .release = seq_release,
2207};
2208
2209static int __init proc_locks_init(void)
2210{
2211    proc_create("locks", 0, NULL, &proc_locks_operations);
2212    return 0;
2213}
2214module_init(proc_locks_init);
2215#endif
2216
2217/**
2218 * lock_may_read - checks that the region is free of locks
2219 * @inode: the inode that is being read
2220 * @start: the first byte to read
2221 * @len: the number of bytes to read
2222 *
2223 * Emulates Windows locking requirements. Whole-file
2224 * mandatory locks (share modes) can prohibit a read and
2225 * byte-range POSIX locks can prohibit a read if they overlap.
2226 *
2227 * N.B. this function is only ever called
2228 * from knfsd and ownership of locks is never checked.
2229 */
2230int lock_may_read(struct inode *inode, loff_t start, unsigned long len)
2231{
2232    struct file_lock *fl;
2233    int result = 1;
2234    lock_kernel();
2235    for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
2236        if (IS_POSIX(fl)) {
2237            if (fl->fl_type == F_RDLCK)
2238                continue;
2239            if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
2240                continue;
2241        } else if (IS_FLOCK(fl)) {
2242            if (!(fl->fl_type & LOCK_MAND))
2243                continue;
2244            if (fl->fl_type & LOCK_READ)
2245                continue;
2246        } else
2247            continue;
2248        result = 0;
2249        break;
2250    }
2251    unlock_kernel();
2252    return result;
2253}
2254
2255EXPORT_SYMBOL(lock_may_read);
2256
2257/**
2258 * lock_may_write - checks that the region is free of locks
2259 * @inode: the inode that is being written
2260 * @start: the first byte to write
2261 * @len: the number of bytes to write
2262 *
2263 * Emulates Windows locking requirements. Whole-file
2264 * mandatory locks (share modes) can prohibit a write and
2265 * byte-range POSIX locks can prohibit a write if they overlap.
2266 *
2267 * N.B. this function is only ever called
2268 * from knfsd and ownership of locks is never checked.
2269 */
2270int lock_may_write(struct inode *inode, loff_t start, unsigned long len)
2271{
2272    struct file_lock *fl;
2273    int result = 1;
2274    lock_kernel();
2275    for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
2276        if (IS_POSIX(fl)) {
2277            if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
2278                continue;
2279        } else if (IS_FLOCK(fl)) {
2280            if (!(fl->fl_type & LOCK_MAND))
2281                continue;
2282            if (fl->fl_type & LOCK_WRITE)
2283                continue;
2284        } else
2285            continue;
2286        result = 0;
2287        break;
2288    }
2289    unlock_kernel();
2290    return result;
2291}
2292
2293EXPORT_SYMBOL(lock_may_write);
2294
2295static int __init filelock_init(void)
2296{
2297    filelock_cache = kmem_cache_create("file_lock_cache",
2298            sizeof(struct file_lock), 0, SLAB_PANIC,
2299            init_once);
2300    return 0;
2301}
2302
2303core_initcall(filelock_init);
2304

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