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/syscalls.h>
126#include <linux/time.h>
127#include <linux/rcupdate.h>
128#include <linux/pid_namespace.h>
129
130#include <asm/uaccess.h>
131
132#define IS_POSIX(fl) (fl->fl_flags & FL_POSIX)
133#define IS_FLOCK(fl) (fl->fl_flags & FL_FLOCK)
134#define IS_LEASE(fl) (fl->fl_flags & FL_LEASE)
135
136int leases_enable = 1;
137int lease_break_time = 45;
138
139#define for_each_lock(inode, lockp) \
140    for (lockp = &inode->i_flock; *lockp != NULL; lockp = &(*lockp)->fl_next)
141
142static LIST_HEAD(file_lock_list);
143static LIST_HEAD(blocked_list);
144static DEFINE_SPINLOCK(file_lock_lock);
145
146/*
147 * Protects the two list heads above, plus the inode->i_flock list
148 */
149void lock_flocks(void)
150{
151    spin_lock(&file_lock_lock);
152}
153EXPORT_SYMBOL_GPL(lock_flocks);
154
155void unlock_flocks(void)
156{
157    spin_unlock(&file_lock_lock);
158}
159EXPORT_SYMBOL_GPL(unlock_flocks);
160
161static struct kmem_cache *filelock_cache __read_mostly;
162
163static void locks_init_lock_always(struct file_lock *fl)
164{
165    fl->fl_next = NULL;
166    fl->fl_fasync = NULL;
167    fl->fl_owner = NULL;
168    fl->fl_pid = 0;
169    fl->fl_nspid = NULL;
170    fl->fl_file = NULL;
171    fl->fl_flags = 0;
172    fl->fl_type = 0;
173    fl->fl_start = fl->fl_end = 0;
174}
175
176/* Allocate an empty lock structure. */
177struct file_lock *locks_alloc_lock(void)
178{
179    struct file_lock *fl = kmem_cache_alloc(filelock_cache, GFP_KERNEL);
180
181    if (fl)
182        locks_init_lock_always(fl);
183
184    return fl;
185}
186EXPORT_SYMBOL_GPL(locks_alloc_lock);
187
188void locks_release_private(struct file_lock *fl)
189{
190    if (fl->fl_ops) {
191        if (fl->fl_ops->fl_release_private)
192            fl->fl_ops->fl_release_private(fl);
193        fl->fl_ops = NULL;
194    }
195    if (fl->fl_lmops) {
196        if (fl->fl_lmops->fl_release_private)
197            fl->fl_lmops->fl_release_private(fl);
198        fl->fl_lmops = NULL;
199    }
200
201}
202EXPORT_SYMBOL_GPL(locks_release_private);
203
204/* Free a lock which is not in use. */
205void locks_free_lock(struct file_lock *fl)
206{
207    BUG_ON(waitqueue_active(&fl->fl_wait));
208    BUG_ON(!list_empty(&fl->fl_block));
209    BUG_ON(!list_empty(&fl->fl_link));
210
211    locks_release_private(fl);
212    kmem_cache_free(filelock_cache, fl);
213}
214EXPORT_SYMBOL(locks_free_lock);
215
216void locks_init_lock(struct file_lock *fl)
217{
218    INIT_LIST_HEAD(&fl->fl_link);
219    INIT_LIST_HEAD(&fl->fl_block);
220    init_waitqueue_head(&fl->fl_wait);
221    fl->fl_ops = NULL;
222    fl->fl_lmops = NULL;
223    locks_init_lock_always(fl);
224}
225
226EXPORT_SYMBOL(locks_init_lock);
227
228/*
229 * Initialises the fields of the file lock which are invariant for
230 * free file_locks.
231 */
232static void init_once(void *foo)
233{
234    struct file_lock *lock = (struct file_lock *) foo;
235
236    locks_init_lock(lock);
237}
238
239static void locks_copy_private(struct file_lock *new, struct file_lock *fl)
240{
241    if (fl->fl_ops) {
242        if (fl->fl_ops->fl_copy_lock)
243            fl->fl_ops->fl_copy_lock(new, fl);
244        new->fl_ops = fl->fl_ops;
245    }
246    if (fl->fl_lmops)
247        new->fl_lmops = fl->fl_lmops;
248}
249
250/*
251 * Initialize a new lock from an existing file_lock structure.
252 */
253void __locks_copy_lock(struct file_lock *new, const struct file_lock *fl)
254{
255    new->fl_owner = fl->fl_owner;
256    new->fl_pid = fl->fl_pid;
257    new->fl_file = NULL;
258    new->fl_flags = fl->fl_flags;
259    new->fl_type = fl->fl_type;
260    new->fl_start = fl->fl_start;
261    new->fl_end = fl->fl_end;
262    new->fl_ops = NULL;
263    new->fl_lmops = NULL;
264}
265EXPORT_SYMBOL(__locks_copy_lock);
266
267void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
268{
269    locks_release_private(new);
270
271    __locks_copy_lock(new, fl);
272    new->fl_file = fl->fl_file;
273    new->fl_ops = fl->fl_ops;
274    new->fl_lmops = fl->fl_lmops;
275
276    locks_copy_private(new, fl);
277}
278
279EXPORT_SYMBOL(locks_copy_lock);
280
281static inline int flock_translate_cmd(int cmd) {
282    if (cmd & LOCK_MAND)
283        return cmd & (LOCK_MAND | LOCK_RW);
284    switch (cmd) {
285    case LOCK_SH:
286        return F_RDLCK;
287    case LOCK_EX:
288        return F_WRLCK;
289    case LOCK_UN:
290        return F_UNLCK;
291    }
292    return -EINVAL;
293}
294
295/* Fill in a file_lock structure with an appropriate FLOCK lock. */
296static int flock_make_lock(struct file *filp, struct file_lock **lock,
297        unsigned int cmd)
298{
299    struct file_lock *fl;
300    int type = flock_translate_cmd(cmd);
301    if (type < 0)
302        return type;
303    
304    fl = locks_alloc_lock();
305    if (fl == NULL)
306        return -ENOMEM;
307
308    fl->fl_file = filp;
309    fl->fl_pid = current->tgid;
310    fl->fl_flags = FL_FLOCK;
311    fl->fl_type = type;
312    fl->fl_end = OFFSET_MAX;
313    
314    *lock = fl;
315    return 0;
316}
317
318static int assign_type(struct file_lock *fl, int type)
319{
320    switch (type) {
321    case F_RDLCK:
322    case F_WRLCK:
323    case F_UNLCK:
324        fl->fl_type = type;
325        break;
326    default:
327        return -EINVAL;
328    }
329    return 0;
330}
331
332/* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX
333 * style lock.
334 */
335static int flock_to_posix_lock(struct file *filp, struct file_lock *fl,
336                   struct flock *l)
337{
338    off_t start, end;
339
340    switch (l->l_whence) {
341    case SEEK_SET:
342        start = 0;
343        break;
344    case SEEK_CUR:
345        start = filp->f_pos;
346        break;
347    case SEEK_END:
348        start = i_size_read(filp->f_path.dentry->d_inode);
349        break;
350    default:
351        return -EINVAL;
352    }
353
354    /* POSIX-1996 leaves the case l->l_len < 0 undefined;
355       POSIX-2001 defines it. */
356    start += l->l_start;
357    if (start < 0)
358        return -EINVAL;
359    fl->fl_end = OFFSET_MAX;
360    if (l->l_len > 0) {
361        end = start + l->l_len - 1;
362        fl->fl_end = end;
363    } else if (l->l_len < 0) {
364        end = start - 1;
365        fl->fl_end = end;
366        start += l->l_len;
367        if (start < 0)
368            return -EINVAL;
369    }
370    fl->fl_start = start; /* we record the absolute position */
371    if (fl->fl_end < fl->fl_start)
372        return -EOVERFLOW;
373    
374    fl->fl_owner = current->files;
375    fl->fl_pid = current->tgid;
376    fl->fl_file = filp;
377    fl->fl_flags = FL_POSIX;
378    fl->fl_ops = NULL;
379    fl->fl_lmops = NULL;
380
381    return assign_type(fl, l->l_type);
382}
383
384#if BITS_PER_LONG == 32
385static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
386                 struct flock64 *l)
387{
388    loff_t start;
389
390    switch (l->l_whence) {
391    case SEEK_SET:
392        start = 0;
393        break;
394    case SEEK_CUR:
395        start = filp->f_pos;
396        break;
397    case SEEK_END:
398        start = i_size_read(filp->f_path.dentry->d_inode);
399        break;
400    default:
401        return -EINVAL;
402    }
403
404    start += l->l_start;
405    if (start < 0)
406        return -EINVAL;
407    fl->fl_end = OFFSET_MAX;
408    if (l->l_len > 0) {
409        fl->fl_end = start + l->l_len - 1;
410    } else if (l->l_len < 0) {
411        fl->fl_end = start - 1;
412        start += l->l_len;
413        if (start < 0)
414            return -EINVAL;
415    }
416    fl->fl_start = start; /* we record the absolute position */
417    if (fl->fl_end < fl->fl_start)
418        return -EOVERFLOW;
419    
420    fl->fl_owner = current->files;
421    fl->fl_pid = current->tgid;
422    fl->fl_file = filp;
423    fl->fl_flags = FL_POSIX;
424    fl->fl_ops = NULL;
425    fl->fl_lmops = NULL;
426
427    return assign_type(fl, l->l_type);
428}
429#endif
430
431/* default lease lock manager operations */
432static void lease_break_callback(struct file_lock *fl)
433{
434    kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG);
435}
436
437static void lease_release_private_callback(struct file_lock *fl)
438{
439    if (!fl->fl_file)
440        return;
441
442    f_delown(fl->fl_file);
443    fl->fl_file->f_owner.signum = 0;
444}
445
446static const struct lock_manager_operations lease_manager_ops = {
447    .fl_break = lease_break_callback,
448    .fl_release_private = lease_release_private_callback,
449    .fl_change = lease_modify,
450};
451
452/*
453 * Initialize a lease, use the default lock manager operations
454 */
455static int lease_init(struct file *filp, int type, struct file_lock *fl)
456 {
457    if (assign_type(fl, type) != 0)
458        return -EINVAL;
459
460    fl->fl_owner = current->files;
461    fl->fl_pid = current->tgid;
462
463    fl->fl_file = filp;
464    fl->fl_flags = FL_LEASE;
465    fl->fl_start = 0;
466    fl->fl_end = OFFSET_MAX;
467    fl->fl_ops = NULL;
468    fl->fl_lmops = &lease_manager_ops;
469    return 0;
470}
471
472/* Allocate a file_lock initialised to this type of lease */
473static struct file_lock *lease_alloc(struct file *filp, int type)
474{
475    struct file_lock *fl = locks_alloc_lock();
476    int error = -ENOMEM;
477
478    if (fl == NULL)
479        return ERR_PTR(error);
480
481    error = lease_init(filp, type, fl);
482    if (error) {
483        locks_free_lock(fl);
484        return ERR_PTR(error);
485    }
486    return fl;
487}
488
489/* Check if two locks overlap each other.
490 */
491static inline int locks_overlap(struct file_lock *fl1, struct file_lock *fl2)
492{
493    return ((fl1->fl_end >= fl2->fl_start) &&
494        (fl2->fl_end >= fl1->fl_start));
495}
496
497/*
498 * Check whether two locks have the same owner.
499 */
500static int posix_same_owner(struct file_lock *fl1, struct file_lock *fl2)
501{
502    if (fl1->fl_lmops && fl1->fl_lmops->fl_compare_owner)
503        return fl2->fl_lmops == fl1->fl_lmops &&
504            fl1->fl_lmops->fl_compare_owner(fl1, fl2);
505    return fl1->fl_owner == fl2->fl_owner;
506}
507
508/* Remove waiter from blocker's block list.
509 * When blocker ends up pointing to itself then the list is empty.
510 */
511static void __locks_delete_block(struct file_lock *waiter)
512{
513    list_del_init(&waiter->fl_block);
514    list_del_init(&waiter->fl_link);
515    waiter->fl_next = NULL;
516}
517
518/*
519 */
520static void locks_delete_block(struct file_lock *waiter)
521{
522    lock_flocks();
523    __locks_delete_block(waiter);
524    unlock_flocks();
525}
526
527/* Insert waiter into blocker's block list.
528 * We use a circular list so that processes can be easily woken up in
529 * the order they blocked. The documentation doesn't require this but
530 * it seems like the reasonable thing to do.
531 */
532static void locks_insert_block(struct file_lock *blocker,
533                   struct file_lock *waiter)
534{
535    BUG_ON(!list_empty(&waiter->fl_block));
536    list_add_tail(&waiter->fl_block, &blocker->fl_block);
537    waiter->fl_next = blocker;
538    if (IS_POSIX(blocker))
539        list_add(&waiter->fl_link, &blocked_list);
540}
541
542/* Wake up processes blocked waiting for blocker.
543 * If told to wait then schedule the processes until the block list
544 * is empty, otherwise empty the block list ourselves.
545 */
546static void locks_wake_up_blocks(struct file_lock *blocker)
547{
548    while (!list_empty(&blocker->fl_block)) {
549        struct file_lock *waiter;
550
551        waiter = list_first_entry(&blocker->fl_block,
552                struct file_lock, fl_block);
553        __locks_delete_block(waiter);
554        if (waiter->fl_lmops && waiter->fl_lmops->fl_notify)
555            waiter->fl_lmops->fl_notify(waiter);
556        else
557            wake_up(&waiter->fl_wait);
558    }
559}
560
561/* Insert file lock fl into an inode's lock list at the position indicated
562 * by pos. At the same time add the lock to the global file lock list.
563 */
564static void locks_insert_lock(struct file_lock **pos, struct file_lock *fl)
565{
566    list_add(&fl->fl_link, &file_lock_list);
567
568    fl->fl_nspid = get_pid(task_tgid(current));
569
570    /* insert into file's list */
571    fl->fl_next = *pos;
572    *pos = fl;
573}
574
575/*
576 * Delete a lock and then free it.
577 * Wake up processes that are blocked waiting for this lock,
578 * notify the FS that the lock has been cleared and
579 * finally free the lock.
580 */
581static void locks_delete_lock(struct file_lock **thisfl_p)
582{
583    struct file_lock *fl = *thisfl_p;
584
585    *thisfl_p = fl->fl_next;
586    fl->fl_next = NULL;
587    list_del_init(&fl->fl_link);
588
589    fasync_helper(0, fl->fl_file, 0, &fl->fl_fasync);
590    if (fl->fl_fasync != NULL) {
591        printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync);
592        fl->fl_fasync = NULL;
593    }
594
595    if (fl->fl_nspid) {
596        put_pid(fl->fl_nspid);
597        fl->fl_nspid = NULL;
598    }
599
600    locks_wake_up_blocks(fl);
601    locks_free_lock(fl);
602}
603
604/* Determine if lock sys_fl blocks lock caller_fl. Common functionality
605 * checks for shared/exclusive status of overlapping locks.
606 */
607static int locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
608{
609    if (sys_fl->fl_type == F_WRLCK)
610        return 1;
611    if (caller_fl->fl_type == F_WRLCK)
612        return 1;
613    return 0;
614}
615
616/* Determine if lock sys_fl blocks lock caller_fl. POSIX specific
617 * checking before calling the locks_conflict().
618 */
619static int posix_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
620{
621    /* POSIX locks owned by the same process do not conflict with
622     * each other.
623     */
624    if (!IS_POSIX(sys_fl) || posix_same_owner(caller_fl, sys_fl))
625        return (0);
626
627    /* Check whether they overlap */
628    if (!locks_overlap(caller_fl, sys_fl))
629        return 0;
630
631    return (locks_conflict(caller_fl, sys_fl));
632}
633
634/* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific
635 * checking before calling the locks_conflict().
636 */
637static int flock_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
638{
639    /* FLOCK locks referring to the same filp do not conflict with
640     * each other.
641     */
642    if (!IS_FLOCK(sys_fl) || (caller_fl->fl_file == sys_fl->fl_file))
643        return (0);
644    if ((caller_fl->fl_type & LOCK_MAND) || (sys_fl->fl_type & LOCK_MAND))
645        return 0;
646
647    return (locks_conflict(caller_fl, sys_fl));
648}
649
650void
651posix_test_lock(struct file *filp, struct file_lock *fl)
652{
653    struct file_lock *cfl;
654
655    lock_flocks();
656    for (cfl = filp->f_path.dentry->d_inode->i_flock; cfl; cfl = cfl->fl_next) {
657        if (!IS_POSIX(cfl))
658            continue;
659        if (posix_locks_conflict(fl, cfl))
660            break;
661    }
662    if (cfl) {
663        __locks_copy_lock(fl, cfl);
664        if (cfl->fl_nspid)
665            fl->fl_pid = pid_vnr(cfl->fl_nspid);
666    } else
667        fl->fl_type = F_UNLCK;
668    unlock_flocks();
669    return;
670}
671EXPORT_SYMBOL(posix_test_lock);
672
673/*
674 * Deadlock detection:
675 *
676 * We attempt to detect deadlocks that are due purely to posix file
677 * locks.
678 *
679 * We assume that a task can be waiting for at most one lock at a time.
680 * So for any acquired lock, the process holding that lock may be
681 * waiting on at most one other lock. That lock in turns may be held by
682 * someone waiting for at most one other lock. Given a requested lock
683 * caller_fl which is about to wait for a conflicting lock block_fl, we
684 * follow this chain of waiters to ensure we are not about to create a
685 * cycle.
686 *
687 * Since we do this before we ever put a process to sleep on a lock, we
688 * are ensured that there is never a cycle; that is what guarantees that
689 * the while() loop in posix_locks_deadlock() eventually completes.
690 *
691 * Note: the above assumption may not be true when handling lock
692 * requests from a broken NFS client. It may also fail in the presence
693 * of tasks (such as posix threads) sharing the same open file table.
694 *
695 * To handle those cases, we just bail out after a few iterations.
696 */
697
698#define MAX_DEADLK_ITERATIONS 10
699
700/* Find a lock that the owner of the given block_fl is blocking on. */
701static struct file_lock *what_owner_is_waiting_for(struct file_lock *block_fl)
702{
703    struct file_lock *fl;
704
705    list_for_each_entry(fl, &blocked_list, fl_link) {
706        if (posix_same_owner(fl, block_fl))
707            return fl->fl_next;
708    }
709    return NULL;
710}
711
712static int posix_locks_deadlock(struct file_lock *caller_fl,
713                struct file_lock *block_fl)
714{
715    int i = 0;
716
717    while ((block_fl = what_owner_is_waiting_for(block_fl))) {
718        if (i++ > MAX_DEADLK_ITERATIONS)
719            return 0;
720        if (posix_same_owner(caller_fl, block_fl))
721            return 1;
722    }
723    return 0;
724}
725
726/* Try to create a FLOCK lock on filp. We always insert new FLOCK locks
727 * after any leases, but before any posix locks.
728 *
729 * Note that if called with an FL_EXISTS argument, the caller may determine
730 * whether or not a lock was successfully freed by testing the return
731 * value for -ENOENT.
732 */
733static int flock_lock_file(struct file *filp, struct file_lock *request)
734{
735    struct file_lock *new_fl = NULL;
736    struct file_lock **before;
737    struct inode * inode = filp->f_path.dentry->d_inode;
738    int error = 0;
739    int found = 0;
740
741    if (!(request->fl_flags & FL_ACCESS) && (request->fl_type != F_UNLCK)) {
742        new_fl = locks_alloc_lock();
743        if (!new_fl)
744            return -ENOMEM;
745    }
746
747    lock_flocks();
748    if (request->fl_flags & FL_ACCESS)
749        goto find_conflict;
750
751    for_each_lock(inode, before) {
752        struct file_lock *fl = *before;
753        if (IS_POSIX(fl))
754            break;
755        if (IS_LEASE(fl))
756            continue;
757        if (filp != fl->fl_file)
758            continue;
759        if (request->fl_type == fl->fl_type)
760            goto out;
761        found = 1;
762        locks_delete_lock(before);
763        break;
764    }
765
766    if (request->fl_type == F_UNLCK) {
767        if ((request->fl_flags & FL_EXISTS) && !found)
768            error = -ENOENT;
769        goto out;
770    }
771
772    /*
773     * If a higher-priority process was blocked on the old file lock,
774     * give it the opportunity to lock the file.
775     */
776    if (found) {
777        unlock_flocks();
778        cond_resched();
779        lock_flocks();
780    }
781
782find_conflict:
783    for_each_lock(inode, before) {
784        struct file_lock *fl = *before;
785        if (IS_POSIX(fl))
786            break;
787        if (IS_LEASE(fl))
788            continue;
789        if (!flock_locks_conflict(request, fl))
790            continue;
791        error = -EAGAIN;
792        if (!(request->fl_flags & FL_SLEEP))
793            goto out;
794        error = FILE_LOCK_DEFERRED;
795        locks_insert_block(fl, request);
796        goto out;
797    }
798    if (request->fl_flags & FL_ACCESS)
799        goto out;
800    locks_copy_lock(new_fl, request);
801    locks_insert_lock(before, new_fl);
802    new_fl = NULL;
803    error = 0;
804
805out:
806    unlock_flocks();
807    if (new_fl)
808        locks_free_lock(new_fl);
809    return error;
810}
811
812static int __posix_lock_file(struct inode *inode, struct file_lock *request, struct file_lock *conflock)
813{
814    struct file_lock *fl;
815    struct file_lock *new_fl = NULL;
816    struct file_lock *new_fl2 = NULL;
817    struct file_lock *left = NULL;
818    struct file_lock *right = NULL;
819    struct file_lock **before;
820    int error, added = 0;
821
822    /*
823     * We may need two file_lock structures for this operation,
824     * so we get them in advance to avoid races.
825     *
826     * In some cases we can be sure, that no new locks will be needed
827     */
828    if (!(request->fl_flags & FL_ACCESS) &&
829        (request->fl_type != F_UNLCK ||
830         request->fl_start != 0 || request->fl_end != OFFSET_MAX)) {
831        new_fl = locks_alloc_lock();
832        new_fl2 = locks_alloc_lock();
833    }
834
835    lock_flocks();
836    if (request->fl_type != F_UNLCK) {
837        for_each_lock(inode, before) {
838            fl = *before;
839            if (!IS_POSIX(fl))
840                continue;
841            if (!posix_locks_conflict(request, fl))
842                continue;
843            if (conflock)
844                __locks_copy_lock(conflock, fl);
845            error = -EAGAIN;
846            if (!(request->fl_flags & FL_SLEEP))
847                goto out;
848            error = -EDEADLK;
849            if (posix_locks_deadlock(request, fl))
850                goto out;
851            error = FILE_LOCK_DEFERRED;
852            locks_insert_block(fl, request);
853            goto out;
854          }
855      }
856
857    /* If we're just looking for a conflict, we're done. */
858    error = 0;
859    if (request->fl_flags & FL_ACCESS)
860        goto out;
861
862    /*
863     * Find the first old lock with the same owner as the new lock.
864     */
865    
866    before = &inode->i_flock;
867
868    /* First skip locks owned by other processes. */
869    while ((fl = *before) && (!IS_POSIX(fl) ||
870                  !posix_same_owner(request, fl))) {
871        before = &fl->fl_next;
872    }
873
874    /* Process locks with this owner. */
875    while ((fl = *before) && posix_same_owner(request, fl)) {
876        /* Detect adjacent or overlapping regions (if same lock type)
877         */
878        if (request->fl_type == fl->fl_type) {
879            /* In all comparisons of start vs end, use
880             * "start - 1" rather than "end + 1". If end
881             * is OFFSET_MAX, end + 1 will become negative.
882             */
883            if (fl->fl_end < request->fl_start - 1)
884                goto next_lock;
885            /* If the next lock in the list has entirely bigger
886             * addresses than the new one, insert the lock here.
887             */
888            if (fl->fl_start - 1 > request->fl_end)
889                break;
890
891            /* If we come here, the new and old lock are of the
892             * same type and adjacent or overlapping. Make one
893             * lock yielding from the lower start address of both
894             * locks to the higher end address.
895             */
896            if (fl->fl_start > request->fl_start)
897                fl->fl_start = request->fl_start;
898            else
899                request->fl_start = fl->fl_start;
900            if (fl->fl_end < request->fl_end)
901                fl->fl_end = request->fl_end;
902            else
903                request->fl_end = fl->fl_end;
904            if (added) {
905                locks_delete_lock(before);
906                continue;
907            }
908            request = fl;
909            added = 1;
910        }
911        else {
912            /* Processing for different lock types is a bit
913             * more complex.
914             */
915            if (fl->fl_end < request->fl_start)
916                goto next_lock;
917            if (fl->fl_start > request->fl_end)
918                break;
919            if (request->fl_type == F_UNLCK)
920                added = 1;
921            if (fl->fl_start < request->fl_start)
922                left = fl;
923            /* If the next lock in the list has a higher end
924             * address than the new one, insert the new one here.
925             */
926            if (fl->fl_end > request->fl_end) {
927                right = fl;
928                break;
929            }
930            if (fl->fl_start >= request->fl_start) {
931                /* The new lock completely replaces an old
932                 * one (This may happen several times).
933                 */
934                if (added) {
935                    locks_delete_lock(before);
936                    continue;
937                }
938                /* Replace the old lock with the new one.
939                 * Wake up anybody waiting for the old one,
940                 * as the change in lock type might satisfy
941                 * their needs.
942                 */
943                locks_wake_up_blocks(fl);
944                fl->fl_start = request->fl_start;
945                fl->fl_end = request->fl_end;
946                fl->fl_type = request->fl_type;
947                locks_release_private(fl);
948                locks_copy_private(fl, request);
949                request = fl;
950                added = 1;
951            }
952        }
953        /* Go on to next lock.
954         */
955    next_lock:
956        before = &fl->fl_next;
957    }
958
959    /*
960     * The above code only modifies existing locks in case of
961     * merging or replacing. If new lock(s) need to be inserted
962     * all modifications are done bellow this, so it's safe yet to
963     * bail out.
964     */
965    error = -ENOLCK; /* "no luck" */
966    if (right && left == right && !new_fl2)
967        goto out;
968
969    error = 0;
970    if (!added) {
971        if (request->fl_type == F_UNLCK) {
972            if (request->fl_flags & FL_EXISTS)
973                error = -ENOENT;
974            goto out;
975        }
976
977        if (!new_fl) {
978            error = -ENOLCK;
979            goto out;
980        }
981        locks_copy_lock(new_fl, request);
982        locks_insert_lock(before, new_fl);
983        new_fl = NULL;
984    }
985    if (right) {
986        if (left == right) {
987            /* The new lock breaks the old one in two pieces,
988             * so we have to use the second new lock.
989             */
990            left = new_fl2;
991            new_fl2 = NULL;
992            locks_copy_lock(left, right);
993            locks_insert_lock(before, left);
994        }
995        right->fl_start = request->fl_end + 1;
996        locks_wake_up_blocks(right);
997    }
998    if (left) {
999        left->fl_end = request->fl_start - 1;
1000        locks_wake_up_blocks(left);
1001    }
1002 out:
1003    unlock_flocks();
1004    /*
1005     * Free any unused locks.
1006     */
1007    if (new_fl)
1008        locks_free_lock(new_fl);
1009    if (new_fl2)
1010        locks_free_lock(new_fl2);
1011    return error;
1012}
1013
1014/**
1015 * posix_lock_file - Apply a POSIX-style lock to a file
1016 * @filp: The file to apply the lock to
1017 * @fl: The lock to be applied
1018 * @conflock: Place to return a copy of the conflicting lock, if found.
1019 *
1020 * Add a POSIX style lock to a file.
1021 * We merge adjacent & overlapping locks whenever possible.
1022 * POSIX locks are sorted by owner task, then by starting address
1023 *
1024 * Note that if called with an FL_EXISTS argument, the caller may determine
1025 * whether or not a lock was successfully freed by testing the return
1026 * value for -ENOENT.
1027 */
1028int posix_lock_file(struct file *filp, struct file_lock *fl,
1029            struct file_lock *conflock)
1030{
1031    return __posix_lock_file(filp->f_path.dentry->d_inode, fl, conflock);
1032}
1033EXPORT_SYMBOL(posix_lock_file);
1034
1035/**
1036 * posix_lock_file_wait - Apply a POSIX-style lock to a file
1037 * @filp: The file to apply the lock to
1038 * @fl: The lock to be applied
1039 *
1040 * Add a POSIX style lock to a file.
1041 * We merge adjacent & overlapping locks whenever possible.
1042 * POSIX locks are sorted by owner task, then by starting address
1043 */
1044int posix_lock_file_wait(struct file *filp, struct file_lock *fl)
1045{
1046    int error;
1047    might_sleep ();
1048    for (;;) {
1049        error = posix_lock_file(filp, fl, NULL);
1050        if (error != FILE_LOCK_DEFERRED)
1051            break;
1052        error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
1053        if (!error)
1054            continue;
1055
1056        locks_delete_block(fl);
1057        break;
1058    }
1059    return error;
1060}
1061EXPORT_SYMBOL(posix_lock_file_wait);
1062
1063/**
1064 * locks_mandatory_locked - Check for an active lock
1065 * @inode: the file to check
1066 *
1067 * Searches the inode's list of locks to find any POSIX locks which conflict.
1068 * This function is called from locks_verify_locked() only.
1069 */
1070int locks_mandatory_locked(struct inode *inode)
1071{
1072    fl_owner_t owner = current->files;
1073    struct file_lock *fl;
1074
1075    /*
1076     * Search the lock list for this inode for any POSIX locks.
1077     */
1078    lock_flocks();
1079    for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
1080        if (!IS_POSIX(fl))
1081            continue;
1082        if (fl->fl_owner != owner)
1083            break;
1084    }
1085    unlock_flocks();
1086    return fl ? -EAGAIN : 0;
1087}
1088
1089/**
1090 * locks_mandatory_area - Check for a conflicting lock
1091 * @read_write: %FLOCK_VERIFY_WRITE for exclusive access, %FLOCK_VERIFY_READ
1092 * for shared
1093 * @inode: the file to check
1094 * @filp: how the file was opened (if it was)
1095 * @offset: start of area to check
1096 * @count: length of area to check
1097 *
1098 * Searches the inode's list of locks to find any POSIX locks which conflict.
1099 * This function is called from rw_verify_area() and
1100 * locks_verify_truncate().
1101 */
1102int locks_mandatory_area(int read_write, struct inode *inode,
1103             struct file *filp, loff_t offset,
1104             size_t count)
1105{
1106    struct file_lock fl;
1107    int error;
1108
1109    locks_init_lock(&fl);
1110    fl.fl_owner = current->files;
1111    fl.fl_pid = current->tgid;
1112    fl.fl_file = filp;
1113    fl.fl_flags = FL_POSIX | FL_ACCESS;
1114    if (filp && !(filp->f_flags & O_NONBLOCK))
1115        fl.fl_flags |= FL_SLEEP;
1116    fl.fl_type = (read_write == FLOCK_VERIFY_WRITE) ? F_WRLCK : F_RDLCK;
1117    fl.fl_start = offset;
1118    fl.fl_end = offset + count - 1;
1119
1120    for (;;) {
1121        error = __posix_lock_file(inode, &fl, NULL);
1122        if (error != FILE_LOCK_DEFERRED)
1123            break;
1124        error = wait_event_interruptible(fl.fl_wait, !fl.fl_next);
1125        if (!error) {
1126            /*
1127             * If we've been sleeping someone might have
1128             * changed the permissions behind our back.
1129             */
1130            if (__mandatory_lock(inode))
1131                continue;
1132        }
1133
1134        locks_delete_block(&fl);
1135        break;
1136    }
1137
1138    return error;
1139}
1140
1141EXPORT_SYMBOL(locks_mandatory_area);
1142
1143/* We already had a lease on this file; just change its type */
1144int lease_modify(struct file_lock **before, int arg)
1145{
1146    struct file_lock *fl = *before;
1147    int error = assign_type(fl, arg);
1148
1149    if (error)
1150        return error;
1151    locks_wake_up_blocks(fl);
1152    if (arg == F_UNLCK)
1153        locks_delete_lock(before);
1154    return 0;
1155}
1156
1157EXPORT_SYMBOL(lease_modify);
1158
1159static void time_out_leases(struct inode *inode)
1160{
1161    struct file_lock **before;
1162    struct file_lock *fl;
1163
1164    before = &inode->i_flock;
1165    while ((fl = *before) && IS_LEASE(fl) && (fl->fl_type & F_INPROGRESS)) {
1166        if ((fl->fl_break_time == 0)
1167                || time_before(jiffies, fl->fl_break_time)) {
1168            before = &fl->fl_next;
1169            continue;
1170        }
1171        lease_modify(before, fl->fl_type & ~F_INPROGRESS);
1172        if (fl == *before) /* lease_modify may have freed fl */
1173            before = &fl->fl_next;
1174    }
1175}
1176
1177/**
1178 * __break_lease - revoke all outstanding leases on file
1179 * @inode: the inode of the file to return
1180 * @mode: the open mode (read or write)
1181 *
1182 * break_lease (inlined for speed) has checked there already is at least
1183 * some kind of lock (maybe a lease) on this file. Leases are broken on
1184 * a call to open() or truncate(). This function can sleep unless you
1185 * specified %O_NONBLOCK to your open().
1186 */
1187int __break_lease(struct inode *inode, unsigned int mode)
1188{
1189    int error = 0, future;
1190    struct file_lock *new_fl, *flock;
1191    struct file_lock *fl;
1192    unsigned long break_time;
1193    int i_have_this_lease = 0;
1194    int want_write = (mode & O_ACCMODE) != O_RDONLY;
1195
1196    new_fl = lease_alloc(NULL, want_write ? F_WRLCK : F_RDLCK);
1197
1198    lock_flocks();
1199
1200    time_out_leases(inode);
1201
1202    flock = inode->i_flock;
1203    if ((flock == NULL) || !IS_LEASE(flock))
1204        goto out;
1205
1206    for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next)
1207        if (fl->fl_owner == current->files)
1208            i_have_this_lease = 1;
1209
1210    if (want_write) {
1211        /* If we want write access, we have to revoke any lease. */
1212        future = F_UNLCK | F_INPROGRESS;
1213    } else if (flock->fl_type & F_INPROGRESS) {
1214        /* If the lease is already being broken, we just leave it */
1215        future = flock->fl_type;
1216    } else if (flock->fl_type & F_WRLCK) {
1217        /* Downgrade the exclusive lease to a read-only lease. */
1218        future = F_RDLCK | F_INPROGRESS;
1219    } else {
1220        /* the existing lease was read-only, so we can read too. */
1221        goto out;
1222    }
1223
1224    if (IS_ERR(new_fl) && !i_have_this_lease
1225            && ((mode & O_NONBLOCK) == 0)) {
1226        error = PTR_ERR(new_fl);
1227        goto out;
1228    }
1229
1230    break_time = 0;
1231    if (lease_break_time > 0) {
1232        break_time = jiffies + lease_break_time * HZ;
1233        if (break_time == 0)
1234            break_time++; /* so that 0 means no break time */
1235    }
1236
1237    for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next) {
1238        if (fl->fl_type != future) {
1239            fl->fl_type = future;
1240            fl->fl_break_time = break_time;
1241            /* lease must have lmops break callback */
1242            fl->fl_lmops->fl_break(fl);
1243        }
1244    }
1245
1246    if (i_have_this_lease || (mode & O_NONBLOCK)) {
1247        error = -EWOULDBLOCK;
1248        goto out;
1249    }
1250
1251restart:
1252    break_time = flock->fl_break_time;
1253    if (break_time != 0) {
1254        break_time -= jiffies;
1255        if (break_time == 0)
1256            break_time++;
1257    }
1258    locks_insert_block(flock, new_fl);
1259    unlock_flocks();
1260    error = wait_event_interruptible_timeout(new_fl->fl_wait,
1261                        !new_fl->fl_next, break_time);
1262    lock_flocks();
1263    __locks_delete_block(new_fl);
1264    if (error >= 0) {
1265        if (error == 0)
1266            time_out_leases(inode);
1267        /* Wait for the next lease that has not been broken yet */
1268        for (flock = inode->i_flock; flock && IS_LEASE(flock);
1269                flock = flock->fl_next) {
1270            if (flock->fl_type & F_INPROGRESS)
1271                goto restart;
1272        }
1273        error = 0;
1274    }
1275
1276out:
1277    unlock_flocks();
1278    if (!IS_ERR(new_fl))
1279        locks_free_lock(new_fl);
1280    return error;
1281}
1282
1283EXPORT_SYMBOL(__break_lease);
1284
1285/**
1286 * lease_get_mtime - get the last modified time of an inode
1287 * @inode: the inode
1288 * @time: pointer to a timespec which will contain the last modified time
1289 *
1290 * This is to force NFS clients to flush their caches for files with
1291 * exclusive leases. The justification is that if someone has an
1292 * exclusive lease, then they could be modifying it.
1293 */
1294void lease_get_mtime(struct inode *inode, struct timespec *time)
1295{
1296    struct file_lock *flock = inode->i_flock;
1297    if (flock && IS_LEASE(flock) && (flock->fl_type & F_WRLCK))
1298        *time = current_fs_time(inode->i_sb);
1299    else
1300        *time = inode->i_mtime;
1301}
1302
1303EXPORT_SYMBOL(lease_get_mtime);
1304
1305/**
1306 * fcntl_getlease - Enquire what lease is currently active
1307 * @filp: the file
1308 *
1309 * The value returned by this function will be one of
1310 * (if no lease break is pending):
1311 *
1312 * %F_RDLCK to indicate a shared lease is held.
1313 *
1314 * %F_WRLCK to indicate an exclusive lease is held.
1315 *
1316 * %F_UNLCK to indicate no lease is held.
1317 *
1318 * (if a lease break is pending):
1319 *
1320 * %F_RDLCK to indicate an exclusive lease needs to be
1321 * changed to a shared lease (or removed).
1322 *
1323 * %F_UNLCK to indicate the lease needs to be removed.
1324 *
1325 * XXX: sfr & willy disagree over whether F_INPROGRESS
1326 * should be returned to userspace.
1327 */
1328int fcntl_getlease(struct file *filp)
1329{
1330    struct file_lock *fl;
1331    int type = F_UNLCK;
1332
1333    lock_flocks();
1334    time_out_leases(filp->f_path.dentry->d_inode);
1335    for (fl = filp->f_path.dentry->d_inode->i_flock; fl && IS_LEASE(fl);
1336            fl = fl->fl_next) {
1337        if (fl->fl_file == filp) {
1338            type = fl->fl_type & ~F_INPROGRESS;
1339            break;
1340        }
1341    }
1342    unlock_flocks();
1343    return type;
1344}
1345
1346/**
1347 * generic_setlease - sets a lease on an open file
1348 * @filp: file pointer
1349 * @arg: type of lease to obtain
1350 * @flp: input - file_lock to use, output - file_lock inserted
1351 *
1352 * The (input) flp->fl_lmops->fl_break function is required
1353 * by break_lease().
1354 *
1355 * Called with file_lock_lock held.
1356 */
1357int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
1358{
1359    struct file_lock *fl, **before, **my_before = NULL, *lease;
1360    struct dentry *dentry = filp->f_path.dentry;
1361    struct inode *inode = dentry->d_inode;
1362    int error, rdlease_count = 0, wrlease_count = 0;
1363
1364    lease = *flp;
1365
1366    error = -EACCES;
1367    if ((current_fsuid() != inode->i_uid) && !capable(CAP_LEASE))
1368        goto out;
1369    error = -EINVAL;
1370    if (!S_ISREG(inode->i_mode))
1371        goto out;
1372    error = security_file_lock(filp, arg);
1373    if (error)
1374        goto out;
1375
1376    time_out_leases(inode);
1377
1378    BUG_ON(!(*flp)->fl_lmops->fl_break);
1379
1380    if (arg != F_UNLCK) {
1381        error = -EAGAIN;
1382        if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0))
1383            goto out;
1384        if ((arg == F_WRLCK)
1385            && ((dentry->d_count > 1)
1386            || (atomic_read(&inode->i_count) > 1)))
1387            goto out;
1388    }
1389
1390    /*
1391     * At this point, we know that if there is an exclusive
1392     * lease on this file, then we hold it on this filp
1393     * (otherwise our open of this file would have blocked).
1394     * And if we are trying to acquire an exclusive lease,
1395     * then the file is not open by anyone (including us)
1396     * except for this filp.
1397     */
1398    for (before = &inode->i_flock;
1399            ((fl = *before) != NULL) && IS_LEASE(fl);
1400            before = &fl->fl_next) {
1401        if (fl->fl_file == filp)
1402            my_before = before;
1403        else if (fl->fl_type == (F_INPROGRESS | F_UNLCK))
1404            /*
1405             * Someone is in the process of opening this
1406             * file for writing so we may not take an
1407             * exclusive lease on it.
1408             */
1409            wrlease_count++;
1410        else
1411            rdlease_count++;
1412    }
1413
1414    error = -EAGAIN;
1415    if ((arg == F_RDLCK && (wrlease_count > 0)) ||
1416        (arg == F_WRLCK && ((rdlease_count + wrlease_count) > 0)))
1417        goto out;
1418
1419    if (my_before != NULL) {
1420        error = lease->fl_lmops->fl_change(my_before, arg);
1421        if (!error)
1422            *flp = *my_before;
1423        goto out;
1424    }
1425
1426    if (arg == F_UNLCK)
1427        goto out;
1428
1429    error = -EINVAL;
1430    if (!leases_enable)
1431        goto out;
1432
1433    locks_insert_lock(before, lease);
1434    return 0;
1435
1436out:
1437    return error;
1438}
1439EXPORT_SYMBOL(generic_setlease);
1440
1441static int __vfs_setlease(struct file *filp, long arg, struct file_lock **lease)
1442{
1443    if (filp->f_op && filp->f_op->setlease)
1444        return filp->f_op->setlease(filp, arg, lease);
1445    else
1446        return generic_setlease(filp, arg, lease);
1447}
1448
1449/**
1450 * vfs_setlease - sets a lease on an open file
1451 * @filp: file pointer
1452 * @arg: type of lease to obtain
1453 * @lease: file_lock to use
1454 *
1455 * Call this to establish a lease on the file.
1456 * The (*lease)->fl_lmops->fl_break operation must be set; if not,
1457 * break_lease will oops!
1458 *
1459 * This will call the filesystem's setlease file method, if
1460 * defined. Note that there is no getlease method; instead, the
1461 * filesystem setlease method should call back to setlease() to
1462 * add a lease to the inode's lease list, where fcntl_getlease() can
1463 * find it. Since fcntl_getlease() only reports whether the current
1464 * task holds a lease, a cluster filesystem need only do this for
1465 * leases held by processes on this node.
1466 *
1467 * There is also no break_lease method; filesystems that
1468 * handle their own leases should break leases themselves from the
1469 * filesystem's open, create, and (on truncate) setattr methods.
1470 *
1471 * Warning: the only current setlease methods exist only to disable
1472 * leases in certain cases. More vfs changes may be required to
1473 * allow a full filesystem lease implementation.
1474 */
1475
1476int vfs_setlease(struct file *filp, long arg, struct file_lock **lease)
1477{
1478    int error;
1479
1480    lock_flocks();
1481    error = __vfs_setlease(filp, arg, lease);
1482    unlock_flocks();
1483
1484    return error;
1485}
1486EXPORT_SYMBOL_GPL(vfs_setlease);
1487
1488static int do_fcntl_delete_lease(struct file *filp)
1489{
1490    struct file_lock fl, *flp = &fl;
1491
1492    lease_init(filp, F_UNLCK, flp);
1493
1494    return vfs_setlease(filp, F_UNLCK, &flp);
1495}
1496
1497static int do_fcntl_add_lease(unsigned int fd, struct file *filp, long arg)
1498{
1499    struct file_lock *fl, *ret;
1500    struct fasync_struct *new;
1501    int error;
1502
1503    fl = lease_alloc(filp, arg);
1504    if (IS_ERR(fl))
1505        return PTR_ERR(fl);
1506
1507    new = fasync_alloc();
1508    if (!new) {
1509        locks_free_lock(fl);
1510        return -ENOMEM;
1511    }
1512    ret = fl;
1513    lock_flocks();
1514    error = __vfs_setlease(filp, arg, &ret);
1515    if (error) {
1516        unlock_flocks();
1517        locks_free_lock(fl);
1518        goto out_free_fasync;
1519    }
1520    if (ret != fl)
1521        locks_free_lock(fl);
1522
1523    /*
1524     * fasync_insert_entry() returns the old entry if any.
1525     * If there was no old entry, then it used 'new' and
1526     * inserted it into the fasync list. Clear new so that
1527     * we don't release it here.
1528     */
1529    if (!fasync_insert_entry(fd, filp, &ret->fl_fasync, new))
1530        new = NULL;
1531
1532    error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
1533    unlock_flocks();
1534
1535out_free_fasync:
1536    if (new)
1537        fasync_free(new);
1538    return error;
1539}
1540
1541/**
1542 * fcntl_setlease - sets a lease on an open file
1543 * @fd: open file descriptor
1544 * @filp: file pointer
1545 * @arg: type of lease to obtain
1546 *
1547 * Call this fcntl to establish a lease on the file.
1548 * Note that you also need to call %F_SETSIG to
1549 * receive a signal when the lease is broken.
1550 */
1551int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
1552{
1553    if (arg == F_UNLCK)
1554        return do_fcntl_delete_lease(filp);
1555    return do_fcntl_add_lease(fd, filp, arg);
1556}
1557
1558/**
1559 * flock_lock_file_wait - Apply a FLOCK-style lock to a file
1560 * @filp: The file to apply the lock to
1561 * @fl: The lock to be applied
1562 *
1563 * Add a FLOCK style lock to a file.
1564 */
1565int flock_lock_file_wait(struct file *filp, struct file_lock *fl)
1566{
1567    int error;
1568    might_sleep();
1569    for (;;) {
1570        error = flock_lock_file(filp, fl);
1571        if (error != FILE_LOCK_DEFERRED)
1572            break;
1573        error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
1574        if (!error)
1575            continue;
1576
1577        locks_delete_block(fl);
1578        break;
1579    }
1580    return error;
1581}
1582
1583EXPORT_SYMBOL(flock_lock_file_wait);
1584
1585/**
1586 * sys_flock: - flock() system call.
1587 * @fd: the file descriptor to lock.
1588 * @cmd: the type of lock to apply.
1589 *
1590 * Apply a %FL_FLOCK style lock to an open file descriptor.
1591 * The @cmd can be one of
1592 *
1593 * %LOCK_SH -- a shared lock.
1594 *
1595 * %LOCK_EX -- an exclusive lock.
1596 *
1597 * %LOCK_UN -- remove an existing lock.
1598 *
1599 * %LOCK_MAND -- a `mandatory' flock. This exists to emulate Windows Share Modes.
1600 *
1601 * %LOCK_MAND can be combined with %LOCK_READ or %LOCK_WRITE to allow other
1602 * processes read and write access respectively.
1603 */
1604SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd)
1605{
1606    struct file *filp;
1607    struct file_lock *lock;
1608    int can_sleep, unlock;
1609    int error;
1610
1611    error = -EBADF;
1612    filp = fget(fd);
1613    if (!filp)
1614        goto out;
1615
1616    can_sleep = !(cmd & LOCK_NB);
1617    cmd &= ~LOCK_NB;
1618    unlock = (cmd == LOCK_UN);
1619
1620    if (!unlock && !(cmd & LOCK_MAND) &&
1621        !(filp->f_mode & (FMODE_READ|FMODE_WRITE)))
1622        goto out_putf;
1623
1624    error = flock_make_lock(filp, &lock, cmd);
1625    if (error)
1626        goto out_putf;
1627    if (can_sleep)
1628        lock->fl_flags |= FL_SLEEP;
1629
1630    error = security_file_lock(filp, lock->fl_type);
1631    if (error)
1632        goto out_free;
1633
1634    if (filp->f_op && filp->f_op->flock)
1635        error = filp->f_op->flock(filp,
1636                      (can_sleep) ? F_SETLKW : F_SETLK,
1637                      lock);
1638    else
1639        error = flock_lock_file_wait(filp, lock);
1640
1641 out_free:
1642    locks_free_lock(lock);
1643
1644 out_putf:
1645    fput(filp);
1646 out:
1647    return error;
1648}
1649
1650/**
1651 * vfs_test_lock - test file byte range lock
1652 * @filp: The file to test lock for
1653 * @fl: The lock to test; also used to hold result
1654 *
1655 * Returns -ERRNO on failure. Indicates presence of conflicting lock by
1656 * setting conf->fl_type to something other than F_UNLCK.
1657 */
1658int vfs_test_lock(struct file *filp, struct file_lock *fl)
1659{
1660    if (filp->f_op && filp->f_op->lock)
1661        return filp->f_op->lock(filp, F_GETLK, fl);
1662    posix_test_lock(filp, fl);
1663    return 0;
1664}
1665EXPORT_SYMBOL_GPL(vfs_test_lock);
1666
1667static int posix_lock_to_flock(struct flock *flock, struct file_lock *fl)
1668{
1669    flock->l_pid = fl->fl_pid;
1670#if BITS_PER_LONG == 32
1671    /*
1672     * Make sure we can represent the posix lock via
1673     * legacy 32bit flock.
1674     */
1675    if (fl->fl_start > OFFT_OFFSET_MAX)
1676        return -EOVERFLOW;
1677    if (fl->fl_end != OFFSET_MAX && fl->fl_end > OFFT_OFFSET_MAX)
1678        return -EOVERFLOW;
1679#endif
1680    flock->l_start = fl->fl_start;
1681    flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
1682        fl->fl_end - fl->fl_start + 1;
1683    flock->l_whence = 0;
1684    flock->l_type = fl->fl_type;
1685    return 0;
1686}
1687
1688#if BITS_PER_LONG == 32
1689static void posix_lock_to_flock64(struct flock64 *flock, struct file_lock *fl)
1690{
1691    flock->l_pid = fl->fl_pid;
1692    flock->l_start = fl->fl_start;
1693    flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
1694        fl->fl_end - fl->fl_start + 1;
1695    flock->l_whence = 0;
1696    flock->l_type = fl->fl_type;
1697}
1698#endif
1699
1700/* Report the first existing lock that would conflict with l.
1701 * This implements the F_GETLK command of fcntl().
1702 */
1703int fcntl_getlk(struct file *filp, struct flock __user *l)
1704{
1705    struct file_lock file_lock;
1706    struct flock flock;
1707    int error;
1708
1709    error = -EFAULT;
1710    if (copy_from_user(&flock, l, sizeof(flock)))
1711        goto out;
1712    error = -EINVAL;
1713    if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
1714        goto out;
1715
1716    error = flock_to_posix_lock(filp, &file_lock, &flock);
1717    if (error)
1718        goto out;
1719
1720    error = vfs_test_lock(filp, &file_lock);
1721    if (error)
1722        goto out;
1723 
1724    flock.l_type = file_lock.fl_type;
1725    if (file_lock.fl_type != F_UNLCK) {
1726        error = posix_lock_to_flock(&flock, &file_lock);
1727        if (error)
1728            goto out;
1729    }
1730    error = -EFAULT;
1731    if (!copy_to_user(l, &flock, sizeof(flock)))
1732        error = 0;
1733out:
1734    return error;
1735}
1736
1737/**
1738 * vfs_lock_file - file byte range lock
1739 * @filp: The file to apply the lock to
1740 * @cmd: type of locking operation (F_SETLK, F_GETLK, etc.)
1741 * @fl: The lock to be applied
1742 * @conf: Place to return a copy of the conflicting lock, if found.
1743 *
1744 * A caller that doesn't care about the conflicting lock may pass NULL
1745 * as the final argument.
1746 *
1747 * If the filesystem defines a private ->lock() method, then @conf will
1748 * be left unchanged; so a caller that cares should initialize it to
1749 * some acceptable default.
1750 *
1751 * To avoid blocking kernel daemons, such as lockd, that need to acquire POSIX
1752 * locks, the ->lock() interface may return asynchronously, before the lock has
1753 * been granted or denied by the underlying filesystem, if (and only if)
1754 * fl_grant is set. Callers expecting ->lock() to return asynchronously
1755 * will only use F_SETLK, not F_SETLKW; they will set FL_SLEEP if (and only if)
1756 * the request is for a blocking lock. When ->lock() does return asynchronously,
1757 * it must return FILE_LOCK_DEFERRED, and call ->fl_grant() when the lock
1758 * request completes.
1759 * If the request is for non-blocking lock the file system should return
1760 * FILE_LOCK_DEFERRED then try to get the lock and call the callback routine
1761 * with the result. If the request timed out the callback routine will return a
1762 * nonzero return code and the file system should release the lock. The file
1763 * system is also responsible to keep a corresponding posix lock when it
1764 * grants a lock so the VFS can find out which locks are locally held and do
1765 * the correct lock cleanup when required.
1766 * The underlying filesystem must not drop the kernel lock or call
1767 * ->fl_grant() before returning to the caller with a FILE_LOCK_DEFERRED
1768 * return code.
1769 */
1770int vfs_lock_file(struct file *filp, unsigned int cmd, struct file_lock *fl, struct file_lock *conf)
1771{
1772    if (filp->f_op && filp->f_op->lock)
1773        return filp->f_op->lock(filp, cmd, fl);
1774    else
1775        return posix_lock_file(filp, fl, conf);
1776}
1777EXPORT_SYMBOL_GPL(vfs_lock_file);
1778
1779static int do_lock_file_wait(struct file *filp, unsigned int cmd,
1780                 struct file_lock *fl)
1781{
1782    int error;
1783
1784    error = security_file_lock(filp, fl->fl_type);
1785    if (error)
1786        return error;
1787
1788    for (;;) {
1789        error = vfs_lock_file(filp, cmd, fl, NULL);
1790        if (error != FILE_LOCK_DEFERRED)
1791            break;
1792        error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
1793        if (!error)
1794            continue;
1795
1796        locks_delete_block(fl);
1797        break;
1798    }
1799
1800    return error;
1801}
1802
1803/* Apply the lock described by l to an open file descriptor.
1804 * This implements both the F_SETLK and F_SETLKW commands of fcntl().
1805 */
1806int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
1807        struct flock __user *l)
1808{
1809    struct file_lock *file_lock = locks_alloc_lock();
1810    struct flock flock;
1811    struct inode *inode;
1812    struct file *f;
1813    int error;
1814
1815    if (file_lock == NULL)
1816        return -ENOLCK;
1817
1818    /*
1819     * This might block, so we do it before checking the inode.
1820     */
1821    error = -EFAULT;
1822    if (copy_from_user(&flock, l, sizeof(flock)))
1823        goto out;
1824
1825    inode = filp->f_path.dentry->d_inode;
1826
1827    /* Don't allow mandatory locks on files that may be memory mapped
1828     * and shared.
1829     */
1830    if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) {
1831        error = -EAGAIN;
1832        goto out;
1833    }
1834
1835again:
1836    error = flock_to_posix_lock(filp, file_lock, &flock);
1837    if (error)
1838        goto out;
1839    if (cmd == F_SETLKW) {
1840        file_lock->fl_flags |= FL_SLEEP;
1841    }
1842    
1843    error = -EBADF;
1844    switch (flock.l_type) {
1845    case F_RDLCK:
1846        if (!(filp->f_mode & FMODE_READ))
1847            goto out;
1848        break;
1849    case F_WRLCK:
1850        if (!(filp->f_mode & FMODE_WRITE))
1851            goto out;
1852        break;
1853    case F_UNLCK:
1854        break;
1855    default:
1856        error = -EINVAL;
1857        goto out;
1858    }
1859
1860    error = do_lock_file_wait(filp, cmd, file_lock);
1861
1862    /*
1863     * Attempt to detect a close/fcntl race and recover by
1864     * releasing the lock that was just acquired.
1865     */
1866    /*
1867     * we need that spin_lock here - it prevents reordering between
1868     * update of inode->i_flock and check for it done in close().
1869     * rcu_read_lock() wouldn't do.
1870     */
1871    spin_lock(&current->files->file_lock);
1872    f = fcheck(fd);
1873    spin_unlock(&current->files->file_lock);
1874    if (!error && f != filp && flock.l_type != F_UNLCK) {
1875        flock.l_type = F_UNLCK;
1876        goto again;
1877    }
1878
1879out:
1880    locks_free_lock(file_lock);
1881    return error;
1882}
1883
1884#if BITS_PER_LONG == 32
1885/* Report the first existing lock that would conflict with l.
1886 * This implements the F_GETLK command of fcntl().
1887 */
1888int fcntl_getlk64(struct file *filp, struct flock64 __user *l)
1889{
1890    struct file_lock file_lock;
1891    struct flock64 flock;
1892    int error;
1893
1894    error = -EFAULT;
1895    if (copy_from_user(&flock, l, sizeof(flock)))
1896        goto out;
1897    error = -EINVAL;
1898    if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
1899        goto out;
1900
1901    error = flock64_to_posix_lock(filp, &file_lock, &flock);
1902    if (error)
1903        goto out;
1904
1905    error = vfs_test_lock(filp, &file_lock);
1906    if (error)
1907        goto out;
1908
1909    flock.l_type = file_lock.fl_type;
1910    if (file_lock.fl_type != F_UNLCK)
1911        posix_lock_to_flock64(&flock, &file_lock);
1912
1913    error = -EFAULT;
1914    if (!copy_to_user(l, &flock, sizeof(flock)))
1915        error = 0;
1916  
1917out:
1918    return error;
1919}
1920
1921/* Apply the lock described by l to an open file descriptor.
1922 * This implements both the F_SETLK and F_SETLKW commands of fcntl().
1923 */
1924int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
1925        struct flock64 __user *l)
1926{
1927    struct file_lock *file_lock = locks_alloc_lock();
1928    struct flock64 flock;
1929    struct inode *inode;
1930    struct file *f;
1931    int error;
1932
1933    if (file_lock == NULL)
1934        return -ENOLCK;
1935
1936    /*
1937     * This might block, so we do it before checking the inode.
1938     */
1939    error = -EFAULT;
1940    if (copy_from_user(&flock, l, sizeof(flock)))
1941        goto out;
1942
1943    inode = filp->f_path.dentry->d_inode;
1944
1945    /* Don't allow mandatory locks on files that may be memory mapped
1946     * and shared.
1947     */
1948    if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) {
1949        error = -EAGAIN;
1950        goto out;
1951    }
1952
1953again:
1954    error = flock64_to_posix_lock(filp, file_lock, &flock);
1955    if (error)
1956        goto out;
1957    if (cmd == F_SETLKW64) {
1958        file_lock->fl_flags |= FL_SLEEP;
1959    }
1960    
1961    error = -EBADF;
1962    switch (flock.l_type) {
1963    case F_RDLCK:
1964        if (!(filp->f_mode & FMODE_READ))
1965            goto out;
1966        break;
1967    case F_WRLCK:
1968        if (!(filp->f_mode & FMODE_WRITE))
1969            goto out;
1970        break;
1971    case F_UNLCK:
1972        break;
1973    default:
1974        error = -EINVAL;
1975        goto out;
1976    }
1977
1978    error = do_lock_file_wait(filp, cmd, file_lock);
1979
1980    /*
1981     * Attempt to detect a close/fcntl race and recover by
1982     * releasing the lock that was just acquired.
1983     */
1984    spin_lock(&current->files->file_lock);
1985    f = fcheck(fd);
1986    spin_unlock(&current->files->file_lock);
1987    if (!error && f != filp && flock.l_type != F_UNLCK) {
1988        flock.l_type = F_UNLCK;
1989        goto again;
1990    }
1991
1992out:
1993    locks_free_lock(file_lock);
1994    return error;
1995}
1996#endif /* BITS_PER_LONG == 32 */
1997
1998/*
1999 * This function is called when the file is being removed
2000 * from the task's fd array. POSIX locks belonging to this task
2001 * are deleted at this time.
2002 */
2003void locks_remove_posix(struct file *filp, fl_owner_t owner)
2004{
2005    struct file_lock lock;
2006
2007    /*
2008     * If there are no locks held on this file, we don't need to call
2009     * posix_lock_file(). Another process could be setting a lock on this
2010     * file at the same time, but we wouldn't remove that lock anyway.
2011     */
2012    if (!filp->f_path.dentry->d_inode->i_flock)
2013        return;
2014
2015    lock.fl_type = F_UNLCK;
2016    lock.fl_flags = FL_POSIX | FL_CLOSE;
2017    lock.fl_start = 0;
2018    lock.fl_end = OFFSET_MAX;
2019    lock.fl_owner = owner;
2020    lock.fl_pid = current->tgid;
2021    lock.fl_file = filp;
2022    lock.fl_ops = NULL;
2023    lock.fl_lmops = NULL;
2024
2025    vfs_lock_file(filp, F_SETLK, &lock, NULL);
2026
2027    if (lock.fl_ops && lock.fl_ops->fl_release_private)
2028        lock.fl_ops->fl_release_private(&lock);
2029}
2030
2031EXPORT_SYMBOL(locks_remove_posix);
2032
2033/*
2034 * This function is called on the last close of an open file.
2035 */
2036void locks_remove_flock(struct file *filp)
2037{
2038    struct inode * inode = filp->f_path.dentry->d_inode;
2039    struct file_lock *fl;
2040    struct file_lock **before;
2041
2042    if (!inode->i_flock)
2043        return;
2044
2045    if (filp->f_op && filp->f_op->flock) {
2046        struct file_lock fl = {
2047            .fl_pid = current->tgid,
2048            .fl_file = filp,
2049            .fl_flags = FL_FLOCK,
2050            .fl_type = F_UNLCK,
2051            .fl_end = OFFSET_MAX,
2052        };
2053        filp->f_op->flock(filp, F_SETLKW, &fl);
2054        if (fl.fl_ops && fl.fl_ops->fl_release_private)
2055            fl.fl_ops->fl_release_private(&fl);
2056    }
2057
2058    lock_flocks();
2059    before = &inode->i_flock;
2060
2061    while ((fl = *before) != NULL) {
2062        if (fl->fl_file == filp) {
2063            if (IS_FLOCK(fl)) {
2064                locks_delete_lock(before);
2065                continue;
2066            }
2067            if (IS_LEASE(fl)) {
2068                lease_modify(before, F_UNLCK);
2069                continue;
2070            }
2071            /* What? */
2072            BUG();
2073         }
2074        before = &fl->fl_next;
2075    }
2076    unlock_flocks();
2077}
2078
2079/**
2080 * posix_unblock_lock - stop waiting for a file lock
2081 * @filp: how the file was opened
2082 * @waiter: the lock which was waiting
2083 *
2084 * lockd needs to block waiting for locks.
2085 */
2086int
2087posix_unblock_lock(struct file *filp, struct file_lock *waiter)
2088{
2089    int status = 0;
2090
2091    lock_flocks();
2092    if (waiter->fl_next)
2093        __locks_delete_block(waiter);
2094    else
2095        status = -ENOENT;
2096    unlock_flocks();
2097    return status;
2098}
2099
2100EXPORT_SYMBOL(posix_unblock_lock);
2101
2102/**
2103 * vfs_cancel_lock - file byte range unblock lock
2104 * @filp: The file to apply the unblock to
2105 * @fl: The lock to be unblocked
2106 *
2107 * Used by lock managers to cancel blocked requests
2108 */
2109int vfs_cancel_lock(struct file *filp, struct file_lock *fl)
2110{
2111    if (filp->f_op && filp->f_op->lock)
2112        return filp->f_op->lock(filp, F_CANCELLK, fl);
2113    return 0;
2114}
2115
2116EXPORT_SYMBOL_GPL(vfs_cancel_lock);
2117
2118#ifdef CONFIG_PROC_FS
2119#include <linux/proc_fs.h>
2120#include <linux/seq_file.h>
2121
2122static void lock_get_status(struct seq_file *f, struct file_lock *fl,
2123                loff_t id, char *pfx)
2124{
2125    struct inode *inode = NULL;
2126    unsigned int fl_pid;
2127
2128    if (fl->fl_nspid)
2129        fl_pid = pid_vnr(fl->fl_nspid);
2130    else
2131        fl_pid = fl->fl_pid;
2132
2133    if (fl->fl_file != NULL)
2134        inode = fl->fl_file->f_path.dentry->d_inode;
2135
2136    seq_printf(f, "%lld:%s ", id, pfx);
2137    if (IS_POSIX(fl)) {
2138        seq_printf(f, "%6s %s ",
2139                 (fl->fl_flags & FL_ACCESS) ? "ACCESS" : "POSIX ",
2140                 (inode == NULL) ? "*NOINODE*" :
2141                 mandatory_lock(inode) ? "MANDATORY" : "ADVISORY ");
2142    } else if (IS_FLOCK(fl)) {
2143        if (fl->fl_type & LOCK_MAND) {
2144            seq_printf(f, "FLOCK MSNFS ");
2145        } else {
2146            seq_printf(f, "FLOCK ADVISORY ");
2147        }
2148    } else if (IS_LEASE(fl)) {
2149        seq_printf(f, "LEASE ");
2150        if (fl->fl_type & F_INPROGRESS)
2151            seq_printf(f, "BREAKING ");
2152        else if (fl->fl_file)
2153            seq_printf(f, "ACTIVE ");
2154        else
2155            seq_printf(f, "BREAKER ");
2156    } else {
2157        seq_printf(f, "UNKNOWN UNKNOWN ");
2158    }
2159    if (fl->fl_type & LOCK_MAND) {
2160        seq_printf(f, "%s ",
2161                   (fl->fl_type & LOCK_READ)
2162                   ? (fl->fl_type & LOCK_WRITE) ? "RW " : "READ "
2163                   : (fl->fl_type & LOCK_WRITE) ? "WRITE" : "NONE ");
2164    } else {
2165        seq_printf(f, "%s ",
2166                   (fl->fl_type & F_INPROGRESS)
2167                   ? (fl->fl_type & F_UNLCK) ? "UNLCK" : "READ "
2168                   : (fl->fl_type & F_WRLCK) ? "WRITE" : "READ ");
2169    }
2170    if (inode) {
2171#ifdef WE_CAN_BREAK_LSLK_NOW
2172        seq_printf(f, "%d %s:%ld ", fl_pid,
2173                inode->i_sb->s_id, inode->i_ino);
2174#else
2175        /* userspace relies on this representation of dev_t ;-( */
2176        seq_printf(f, "%d %02x:%02x:%ld ", fl_pid,
2177                MAJOR(inode->i_sb->s_dev),
2178                MINOR(inode->i_sb->s_dev), inode->i_ino);
2179#endif
2180    } else {
2181        seq_printf(f, "%d <none>:0 ", fl_pid);
2182    }
2183    if (IS_POSIX(fl)) {
2184        if (fl->fl_end == OFFSET_MAX)
2185            seq_printf(f, "%Ld EOF\n", fl->fl_start);
2186        else
2187            seq_printf(f, "%Ld %Ld\n", fl->fl_start, fl->fl_end);
2188    } else {
2189        seq_printf(f, "0 EOF\n");
2190    }
2191}
2192
2193static int locks_show(struct seq_file *f, void *v)
2194{
2195    struct file_lock *fl, *bfl;
2196
2197    fl = list_entry(v, struct file_lock, fl_link);
2198
2199    lock_get_status(f, fl, *((loff_t *)f->private), "");
2200
2201    list_for_each_entry(bfl, &fl->fl_block, fl_block)
2202        lock_get_status(f, bfl, *((loff_t *)f->private), " ->");
2203
2204    return 0;
2205}
2206
2207static void *locks_start(struct seq_file *f, loff_t *pos)
2208{
2209    loff_t *p = f->private;
2210
2211    lock_flocks();
2212    *p = (*pos + 1);
2213    return seq_list_start(&file_lock_list, *pos);
2214}
2215
2216static void *locks_next(struct seq_file *f, void *v, loff_t *pos)
2217{
2218    loff_t *p = f->private;
2219    ++*p;
2220    return seq_list_next(v, &file_lock_list, pos);
2221}
2222
2223static void locks_stop(struct seq_file *f, void *v)
2224{
2225    unlock_flocks();
2226}
2227
2228static const struct seq_operations locks_seq_operations = {
2229    .start = locks_start,
2230    .next = locks_next,
2231    .stop = locks_stop,
2232    .show = locks_show,
2233};
2234
2235static int locks_open(struct inode *inode, struct file *filp)
2236{
2237    return seq_open_private(filp, &locks_seq_operations, sizeof(loff_t));
2238}
2239
2240static const struct file_operations proc_locks_operations = {
2241    .open = locks_open,
2242    .read = seq_read,
2243    .llseek = seq_lseek,
2244    .release = seq_release_private,
2245};
2246
2247static int __init proc_locks_init(void)
2248{
2249    proc_create("locks", 0, NULL, &proc_locks_operations);
2250    return 0;
2251}
2252module_init(proc_locks_init);
2253#endif
2254
2255/**
2256 * lock_may_read - checks that the region is free of locks
2257 * @inode: the inode that is being read
2258 * @start: the first byte to read
2259 * @len: the number of bytes to read
2260 *
2261 * Emulates Windows locking requirements. Whole-file
2262 * mandatory locks (share modes) can prohibit a read and
2263 * byte-range POSIX locks can prohibit a read if they overlap.
2264 *
2265 * N.B. this function is only ever called
2266 * from knfsd and ownership of locks is never checked.
2267 */
2268int lock_may_read(struct inode *inode, loff_t start, unsigned long len)
2269{
2270    struct file_lock *fl;
2271    int result = 1;
2272    lock_flocks();
2273    for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
2274        if (IS_POSIX(fl)) {
2275            if (fl->fl_type == F_RDLCK)
2276                continue;
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_READ)
2283                continue;
2284        } else
2285            continue;
2286        result = 0;
2287        break;
2288    }
2289    unlock_flocks();
2290    return result;
2291}
2292
2293EXPORT_SYMBOL(lock_may_read);
2294
2295/**
2296 * lock_may_write - checks that the region is free of locks
2297 * @inode: the inode that is being written
2298 * @start: the first byte to write
2299 * @len: the number of bytes to write
2300 *
2301 * Emulates Windows locking requirements. Whole-file
2302 * mandatory locks (share modes) can prohibit a write and
2303 * byte-range POSIX locks can prohibit a write if they overlap.
2304 *
2305 * N.B. this function is only ever called
2306 * from knfsd and ownership of locks is never checked.
2307 */
2308int lock_may_write(struct inode *inode, loff_t start, unsigned long len)
2309{
2310    struct file_lock *fl;
2311    int result = 1;
2312    lock_flocks();
2313    for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
2314        if (IS_POSIX(fl)) {
2315            if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
2316                continue;
2317        } else if (IS_FLOCK(fl)) {
2318            if (!(fl->fl_type & LOCK_MAND))
2319                continue;
2320            if (fl->fl_type & LOCK_WRITE)
2321                continue;
2322        } else
2323            continue;
2324        result = 0;
2325        break;
2326    }
2327    unlock_flocks();
2328    return result;
2329}
2330
2331EXPORT_SYMBOL(lock_may_write);
2332
2333static int __init filelock_init(void)
2334{
2335    filelock_cache = kmem_cache_create("file_lock_cache",
2336            sizeof(struct file_lock), 0, SLAB_PANIC,
2337            init_once);
2338    return 0;
2339}
2340
2341core_initcall(filelock_init);
2342

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