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 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_bkl();
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
1186    new_fl = lease_alloc(NULL, mode & FMODE_WRITE ? F_WRLCK : F_RDLCK);
1187
1188    lock_kernel();
1189
1190    time_out_leases(inode);
1191
1192    flock = inode->i_flock;
1193    if ((flock == NULL) || !IS_LEASE(flock))
1194        goto out;
1195
1196    for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next)
1197        if (fl->fl_owner == current->files)
1198            i_have_this_lease = 1;
1199
1200    if (mode & FMODE_WRITE) {
1201        /* If we want write access, we have to revoke any lease. */
1202        future = F_UNLCK | F_INPROGRESS;
1203    } else if (flock->fl_type & F_INPROGRESS) {
1204        /* If the lease is already being broken, we just leave it */
1205        future = flock->fl_type;
1206    } else if (flock->fl_type & F_WRLCK) {
1207        /* Downgrade the exclusive lease to a read-only lease. */
1208        future = F_RDLCK | F_INPROGRESS;
1209    } else {
1210        /* the existing lease was read-only, so we can read too. */
1211        goto out;
1212    }
1213
1214    if (IS_ERR(new_fl) && !i_have_this_lease
1215            && ((mode & O_NONBLOCK) == 0)) {
1216        error = PTR_ERR(new_fl);
1217        goto out;
1218    }
1219
1220    break_time = 0;
1221    if (lease_break_time > 0) {
1222        break_time = jiffies + lease_break_time * HZ;
1223        if (break_time == 0)
1224            break_time++; /* so that 0 means no break time */
1225    }
1226
1227    for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next) {
1228        if (fl->fl_type != future) {
1229            fl->fl_type = future;
1230            fl->fl_break_time = break_time;
1231            /* lease must have lmops break callback */
1232            fl->fl_lmops->fl_break(fl);
1233        }
1234    }
1235
1236    if (i_have_this_lease || (mode & O_NONBLOCK)) {
1237        error = -EWOULDBLOCK;
1238        goto out;
1239    }
1240
1241restart:
1242    break_time = flock->fl_break_time;
1243    if (break_time != 0) {
1244        break_time -= jiffies;
1245        if (break_time == 0)
1246            break_time++;
1247    }
1248    locks_insert_block(flock, new_fl);
1249    error = wait_event_interruptible_timeout(new_fl->fl_wait,
1250                        !new_fl->fl_next, break_time);
1251    __locks_delete_block(new_fl);
1252    if (error >= 0) {
1253        if (error == 0)
1254            time_out_leases(inode);
1255        /* Wait for the next lease that has not been broken yet */
1256        for (flock = inode->i_flock; flock && IS_LEASE(flock);
1257                flock = flock->fl_next) {
1258            if (flock->fl_type & F_INPROGRESS)
1259                goto restart;
1260        }
1261        error = 0;
1262    }
1263
1264out:
1265    unlock_kernel();
1266    if (!IS_ERR(new_fl))
1267        locks_free_lock(new_fl);
1268    return error;
1269}
1270
1271EXPORT_SYMBOL(__break_lease);
1272
1273/**
1274 * lease_get_mtime - get the last modified time of an inode
1275 * @inode: the inode
1276 * @time: pointer to a timespec which will contain the last modified time
1277 *
1278 * This is to force NFS clients to flush their caches for files with
1279 * exclusive leases. The justification is that if someone has an
1280 * exclusive lease, then they could be modifying it.
1281 */
1282void lease_get_mtime(struct inode *inode, struct timespec *time)
1283{
1284    struct file_lock *flock = inode->i_flock;
1285    if (flock && IS_LEASE(flock) && (flock->fl_type & F_WRLCK))
1286        *time = current_fs_time(inode->i_sb);
1287    else
1288        *time = inode->i_mtime;
1289}
1290
1291EXPORT_SYMBOL(lease_get_mtime);
1292
1293/**
1294 * fcntl_getlease - Enquire what lease is currently active
1295 * @filp: the file
1296 *
1297 * The value returned by this function will be one of
1298 * (if no lease break is pending):
1299 *
1300 * %F_RDLCK to indicate a shared lease is held.
1301 *
1302 * %F_WRLCK to indicate an exclusive lease is held.
1303 *
1304 * %F_UNLCK to indicate no lease is held.
1305 *
1306 * (if a lease break is pending):
1307 *
1308 * %F_RDLCK to indicate an exclusive lease needs to be
1309 * changed to a shared lease (or removed).
1310 *
1311 * %F_UNLCK to indicate the lease needs to be removed.
1312 *
1313 * XXX: sfr & willy disagree over whether F_INPROGRESS
1314 * should be returned to userspace.
1315 */
1316int fcntl_getlease(struct file *filp)
1317{
1318    struct file_lock *fl;
1319    int type = F_UNLCK;
1320
1321    lock_kernel();
1322    time_out_leases(filp->f_path.dentry->d_inode);
1323    for (fl = filp->f_path.dentry->d_inode->i_flock; fl && IS_LEASE(fl);
1324            fl = fl->fl_next) {
1325        if (fl->fl_file == filp) {
1326            type = fl->fl_type & ~F_INPROGRESS;
1327            break;
1328        }
1329    }
1330    unlock_kernel();
1331    return type;
1332}
1333
1334/**
1335 * generic_setlease - sets a lease on an open file
1336 * @filp: file pointer
1337 * @arg: type of lease to obtain
1338 * @flp: input - file_lock to use, output - file_lock inserted
1339 *
1340 * The (input) flp->fl_lmops->fl_break function is required
1341 * by break_lease().
1342 *
1343 * Called with kernel lock held.
1344 */
1345int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
1346{
1347    struct file_lock *fl, **before, **my_before = NULL, *lease;
1348    struct file_lock *new_fl = NULL;
1349    struct dentry *dentry = filp->f_path.dentry;
1350    struct inode *inode = dentry->d_inode;
1351    int error, rdlease_count = 0, wrlease_count = 0;
1352
1353    if ((current_fsuid() != inode->i_uid) && !capable(CAP_LEASE))
1354        return -EACCES;
1355    if (!S_ISREG(inode->i_mode))
1356        return -EINVAL;
1357    error = security_file_lock(filp, arg);
1358    if (error)
1359        return error;
1360
1361    time_out_leases(inode);
1362
1363    BUG_ON(!(*flp)->fl_lmops->fl_break);
1364
1365    lease = *flp;
1366
1367    if (arg != F_UNLCK) {
1368        error = -ENOMEM;
1369        new_fl = locks_alloc_lock();
1370        if (new_fl == NULL)
1371            goto out;
1372
1373        error = -EAGAIN;
1374        if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0))
1375            goto out;
1376        if ((arg == F_WRLCK)
1377            && ((atomic_read(&dentry->d_count) > 1)
1378            || (atomic_read(&inode->i_count) > 1)))
1379            goto out;
1380    }
1381
1382    /*
1383     * At this point, we know that if there is an exclusive
1384     * lease on this file, then we hold it on this filp
1385     * (otherwise our open of this file would have blocked).
1386     * And if we are trying to acquire an exclusive lease,
1387     * then the file is not open by anyone (including us)
1388     * except for this filp.
1389     */
1390    for (before = &inode->i_flock;
1391            ((fl = *before) != NULL) && IS_LEASE(fl);
1392            before = &fl->fl_next) {
1393        if (lease->fl_lmops->fl_mylease(fl, lease))
1394            my_before = before;
1395        else if (fl->fl_type == (F_INPROGRESS | F_UNLCK))
1396            /*
1397             * Someone is in the process of opening this
1398             * file for writing so we may not take an
1399             * exclusive lease on it.
1400             */
1401            wrlease_count++;
1402        else
1403            rdlease_count++;
1404    }
1405
1406    error = -EAGAIN;
1407    if ((arg == F_RDLCK && (wrlease_count > 0)) ||
1408        (arg == F_WRLCK && ((rdlease_count + wrlease_count) > 0)))
1409        goto out;
1410
1411    if (my_before != NULL) {
1412        *flp = *my_before;
1413        error = lease->fl_lmops->fl_change(my_before, arg);
1414        goto out;
1415    }
1416
1417    error = 0;
1418    if (arg == F_UNLCK)
1419        goto out;
1420
1421    error = -EINVAL;
1422    if (!leases_enable)
1423        goto out;
1424
1425    locks_copy_lock(new_fl, lease);
1426    locks_insert_lock(before, new_fl);
1427
1428    *flp = new_fl;
1429    return 0;
1430
1431out:
1432    if (new_fl != NULL)
1433        locks_free_lock(new_fl);
1434    return error;
1435}
1436EXPORT_SYMBOL(generic_setlease);
1437
1438 /**
1439 * vfs_setlease - sets a lease on an open file
1440 * @filp: file pointer
1441 * @arg: type of lease to obtain
1442 * @lease: file_lock to use
1443 *
1444 * Call this to establish a lease on the file.
1445 * The (*lease)->fl_lmops->fl_break operation must be set; if not,
1446 * break_lease will oops!
1447 *
1448 * This will call the filesystem's setlease file method, if
1449 * defined. Note that there is no getlease method; instead, the
1450 * filesystem setlease method should call back to setlease() to
1451 * add a lease to the inode's lease list, where fcntl_getlease() can
1452 * find it. Since fcntl_getlease() only reports whether the current
1453 * task holds a lease, a cluster filesystem need only do this for
1454 * leases held by processes on this node.
1455 *
1456 * There is also no break_lease method; filesystems that
1457 * handle their own leases shoud break leases themselves from the
1458 * filesystem's open, create, and (on truncate) setattr methods.
1459 *
1460 * Warning: the only current setlease methods exist only to disable
1461 * leases in certain cases. More vfs changes may be required to
1462 * allow a full filesystem lease implementation.
1463 */
1464
1465int vfs_setlease(struct file *filp, long arg, struct file_lock **lease)
1466{
1467    int error;
1468
1469    lock_kernel();
1470    if (filp->f_op && filp->f_op->setlease)
1471        error = filp->f_op->setlease(filp, arg, lease);
1472    else
1473        error = generic_setlease(filp, arg, lease);
1474    unlock_kernel();
1475
1476    return error;
1477}
1478EXPORT_SYMBOL_GPL(vfs_setlease);
1479
1480/**
1481 * fcntl_setlease - sets a lease on an open file
1482 * @fd: open file descriptor
1483 * @filp: file pointer
1484 * @arg: type of lease to obtain
1485 *
1486 * Call this fcntl to establish a lease on the file.
1487 * Note that you also need to call %F_SETSIG to
1488 * receive a signal when the lease is broken.
1489 */
1490int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
1491{
1492    struct file_lock fl, *flp = &fl;
1493    struct inode *inode = filp->f_path.dentry->d_inode;
1494    int error;
1495
1496    locks_init_lock(&fl);
1497    error = lease_init(filp, arg, &fl);
1498    if (error)
1499        return error;
1500
1501    lock_kernel();
1502
1503    error = vfs_setlease(filp, arg, &flp);
1504    if (error || arg == F_UNLCK)
1505        goto out_unlock;
1506
1507    error = fasync_helper(fd, filp, 1, &flp->fl_fasync);
1508    if (error < 0) {
1509        /* remove lease just inserted by setlease */
1510        flp->fl_type = F_UNLCK | F_INPROGRESS;
1511        flp->fl_break_time = jiffies - 10;
1512        time_out_leases(inode);
1513        goto out_unlock;
1514    }
1515
1516    error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
1517out_unlock:
1518    unlock_kernel();
1519    return error;
1520}
1521
1522/**
1523 * flock_lock_file_wait - Apply a FLOCK-style lock to a file
1524 * @filp: The file to apply the lock to
1525 * @fl: The lock to be applied
1526 *
1527 * Add a FLOCK style lock to a file.
1528 */
1529int flock_lock_file_wait(struct file *filp, struct file_lock *fl)
1530{
1531    int error;
1532    might_sleep();
1533    for (;;) {
1534        error = flock_lock_file(filp, fl);
1535        if (error != FILE_LOCK_DEFERRED)
1536            break;
1537        error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
1538        if (!error)
1539            continue;
1540
1541        locks_delete_block(fl);
1542        break;
1543    }
1544    return error;
1545}
1546
1547EXPORT_SYMBOL(flock_lock_file_wait);
1548
1549/**
1550 * sys_flock: - flock() system call.
1551 * @fd: the file descriptor to lock.
1552 * @cmd: the type of lock to apply.
1553 *
1554 * Apply a %FL_FLOCK style lock to an open file descriptor.
1555 * The @cmd can be one of
1556 *
1557 * %LOCK_SH -- a shared lock.
1558 *
1559 * %LOCK_EX -- an exclusive lock.
1560 *
1561 * %LOCK_UN -- remove an existing lock.
1562 *
1563 * %LOCK_MAND -- a `mandatory' flock. This exists to emulate Windows Share Modes.
1564 *
1565 * %LOCK_MAND can be combined with %LOCK_READ or %LOCK_WRITE to allow other
1566 * processes read and write access respectively.
1567 */
1568SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd)
1569{
1570    struct file *filp;
1571    struct file_lock *lock;
1572    int can_sleep, unlock;
1573    int error;
1574
1575    error = -EBADF;
1576    filp = fget(fd);
1577    if (!filp)
1578        goto out;
1579
1580    can_sleep = !(cmd & LOCK_NB);
1581    cmd &= ~LOCK_NB;
1582    unlock = (cmd == LOCK_UN);
1583
1584    if (!unlock && !(cmd & LOCK_MAND) &&
1585        !(filp->f_mode & (FMODE_READ|FMODE_WRITE)))
1586        goto out_putf;
1587
1588    error = flock_make_lock(filp, &lock, cmd);
1589    if (error)
1590        goto out_putf;
1591    if (can_sleep)
1592        lock->fl_flags |= FL_SLEEP;
1593
1594    error = security_file_lock(filp, cmd);
1595    if (error)
1596        goto out_free;
1597
1598    if (filp->f_op && filp->f_op->flock)
1599        error = filp->f_op->flock(filp,
1600                      (can_sleep) ? F_SETLKW : F_SETLK,
1601                      lock);
1602    else
1603        error = flock_lock_file_wait(filp, lock);
1604
1605 out_free:
1606    locks_free_lock(lock);
1607
1608 out_putf:
1609    fput(filp);
1610 out:
1611    return error;
1612}
1613
1614/**
1615 * vfs_test_lock - test file byte range lock
1616 * @filp: The file to test lock for
1617 * @fl: The lock to test; also used to hold result
1618 *
1619 * Returns -ERRNO on failure. Indicates presence of conflicting lock by
1620 * setting conf->fl_type to something other than F_UNLCK.
1621 */
1622int vfs_test_lock(struct file *filp, struct file_lock *fl)
1623{
1624    if (filp->f_op && filp->f_op->lock)
1625        return filp->f_op->lock(filp, F_GETLK, fl);
1626    posix_test_lock(filp, fl);
1627    return 0;
1628}
1629EXPORT_SYMBOL_GPL(vfs_test_lock);
1630
1631static int posix_lock_to_flock(struct flock *flock, struct file_lock *fl)
1632{
1633    flock->l_pid = fl->fl_pid;
1634#if BITS_PER_LONG == 32
1635    /*
1636     * Make sure we can represent the posix lock via
1637     * legacy 32bit flock.
1638     */
1639    if (fl->fl_start > OFFT_OFFSET_MAX)
1640        return -EOVERFLOW;
1641    if (fl->fl_end != OFFSET_MAX && fl->fl_end > OFFT_OFFSET_MAX)
1642        return -EOVERFLOW;
1643#endif
1644    flock->l_start = fl->fl_start;
1645    flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
1646        fl->fl_end - fl->fl_start + 1;
1647    flock->l_whence = 0;
1648    flock->l_type = fl->fl_type;
1649    return 0;
1650}
1651
1652#if BITS_PER_LONG == 32
1653static void posix_lock_to_flock64(struct flock64 *flock, struct file_lock *fl)
1654{
1655    flock->l_pid = fl->fl_pid;
1656    flock->l_start = fl->fl_start;
1657    flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
1658        fl->fl_end - fl->fl_start + 1;
1659    flock->l_whence = 0;
1660    flock->l_type = fl->fl_type;
1661}
1662#endif
1663
1664/* Report the first existing lock that would conflict with l.
1665 * This implements the F_GETLK command of fcntl().
1666 */
1667int fcntl_getlk(struct file *filp, struct flock __user *l)
1668{
1669    struct file_lock file_lock;
1670    struct flock flock;
1671    int error;
1672
1673    error = -EFAULT;
1674    if (copy_from_user(&flock, l, sizeof(flock)))
1675        goto out;
1676    error = -EINVAL;
1677    if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
1678        goto out;
1679
1680    error = flock_to_posix_lock(filp, &file_lock, &flock);
1681    if (error)
1682        goto out;
1683
1684    error = vfs_test_lock(filp, &file_lock);
1685    if (error)
1686        goto out;
1687 
1688    flock.l_type = file_lock.fl_type;
1689    if (file_lock.fl_type != F_UNLCK) {
1690        error = posix_lock_to_flock(&flock, &file_lock);
1691        if (error)
1692            goto out;
1693    }
1694    error = -EFAULT;
1695    if (!copy_to_user(l, &flock, sizeof(flock)))
1696        error = 0;
1697out:
1698    return error;
1699}
1700
1701/**
1702 * vfs_lock_file - file byte range lock
1703 * @filp: The file to apply the lock to
1704 * @cmd: type of locking operation (F_SETLK, F_GETLK, etc.)
1705 * @fl: The lock to be applied
1706 * @conf: Place to return a copy of the conflicting lock, if found.
1707 *
1708 * A caller that doesn't care about the conflicting lock may pass NULL
1709 * as the final argument.
1710 *
1711 * If the filesystem defines a private ->lock() method, then @conf will
1712 * be left unchanged; so a caller that cares should initialize it to
1713 * some acceptable default.
1714 *
1715 * To avoid blocking kernel daemons, such as lockd, that need to acquire POSIX
1716 * locks, the ->lock() interface may return asynchronously, before the lock has
1717 * been granted or denied by the underlying filesystem, if (and only if)
1718 * fl_grant is set. Callers expecting ->lock() to return asynchronously
1719 * will only use F_SETLK, not F_SETLKW; they will set FL_SLEEP if (and only if)
1720 * the request is for a blocking lock. When ->lock() does return asynchronously,
1721 * it must return FILE_LOCK_DEFERRED, and call ->fl_grant() when the lock
1722 * request completes.
1723 * If the request is for non-blocking lock the file system should return
1724 * FILE_LOCK_DEFERRED then try to get the lock and call the callback routine
1725 * with the result. If the request timed out the callback routine will return a
1726 * nonzero return code and the file system should release the lock. The file
1727 * system is also responsible to keep a corresponding posix lock when it
1728 * grants a lock so the VFS can find out which locks are locally held and do
1729 * the correct lock cleanup when required.
1730 * The underlying filesystem must not drop the kernel lock or call
1731 * ->fl_grant() before returning to the caller with a FILE_LOCK_DEFERRED
1732 * return code.
1733 */
1734int vfs_lock_file(struct file *filp, unsigned int cmd, struct file_lock *fl, struct file_lock *conf)
1735{
1736    if (filp->f_op && filp->f_op->lock)
1737        return filp->f_op->lock(filp, cmd, fl);
1738    else
1739        return posix_lock_file(filp, fl, conf);
1740}
1741EXPORT_SYMBOL_GPL(vfs_lock_file);
1742
1743static int do_lock_file_wait(struct file *filp, unsigned int cmd,
1744                 struct file_lock *fl)
1745{
1746    int error;
1747
1748    error = security_file_lock(filp, fl->fl_type);
1749    if (error)
1750        return error;
1751
1752    for (;;) {
1753        error = vfs_lock_file(filp, cmd, fl, NULL);
1754        if (error != FILE_LOCK_DEFERRED)
1755            break;
1756        error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
1757        if (!error)
1758            continue;
1759
1760        locks_delete_block(fl);
1761        break;
1762    }
1763
1764    return error;
1765}
1766
1767/* Apply the lock described by l to an open file descriptor.
1768 * This implements both the F_SETLK and F_SETLKW commands of fcntl().
1769 */
1770int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
1771        struct flock __user *l)
1772{
1773    struct file_lock *file_lock = locks_alloc_lock();
1774    struct flock flock;
1775    struct inode *inode;
1776    struct file *f;
1777    int error;
1778
1779    if (file_lock == NULL)
1780        return -ENOLCK;
1781
1782    /*
1783     * This might block, so we do it before checking the inode.
1784     */
1785    error = -EFAULT;
1786    if (copy_from_user(&flock, l, sizeof(flock)))
1787        goto out;
1788
1789    inode = filp->f_path.dentry->d_inode;
1790
1791    /* Don't allow mandatory locks on files that may be memory mapped
1792     * and shared.
1793     */
1794    if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) {
1795        error = -EAGAIN;
1796        goto out;
1797    }
1798
1799again:
1800    error = flock_to_posix_lock(filp, file_lock, &flock);
1801    if (error)
1802        goto out;
1803    if (cmd == F_SETLKW) {
1804        file_lock->fl_flags |= FL_SLEEP;
1805    }
1806    
1807    error = -EBADF;
1808    switch (flock.l_type) {
1809    case F_RDLCK:
1810        if (!(filp->f_mode & FMODE_READ))
1811            goto out;
1812        break;
1813    case F_WRLCK:
1814        if (!(filp->f_mode & FMODE_WRITE))
1815            goto out;
1816        break;
1817    case F_UNLCK:
1818        break;
1819    default:
1820        error = -EINVAL;
1821        goto out;
1822    }
1823
1824    error = do_lock_file_wait(filp, cmd, file_lock);
1825
1826    /*
1827     * Attempt to detect a close/fcntl race and recover by
1828     * releasing the lock that was just acquired.
1829     */
1830    /*
1831     * we need that spin_lock here - it prevents reordering between
1832     * update of inode->i_flock and check for it done in close().
1833     * rcu_read_lock() wouldn't do.
1834     */
1835    spin_lock(&current->files->file_lock);
1836    f = fcheck(fd);
1837    spin_unlock(&current->files->file_lock);
1838    if (!error && f != filp && flock.l_type != F_UNLCK) {
1839        flock.l_type = F_UNLCK;
1840        goto again;
1841    }
1842
1843out:
1844    locks_free_lock(file_lock);
1845    return error;
1846}
1847
1848#if BITS_PER_LONG == 32
1849/* Report the first existing lock that would conflict with l.
1850 * This implements the F_GETLK command of fcntl().
1851 */
1852int fcntl_getlk64(struct file *filp, struct flock64 __user *l)
1853{
1854    struct file_lock file_lock;
1855    struct flock64 flock;
1856    int error;
1857
1858    error = -EFAULT;
1859    if (copy_from_user(&flock, l, sizeof(flock)))
1860        goto out;
1861    error = -EINVAL;
1862    if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
1863        goto out;
1864
1865    error = flock64_to_posix_lock(filp, &file_lock, &flock);
1866    if (error)
1867        goto out;
1868
1869    error = vfs_test_lock(filp, &file_lock);
1870    if (error)
1871        goto out;
1872
1873    flock.l_type = file_lock.fl_type;
1874    if (file_lock.fl_type != F_UNLCK)
1875        posix_lock_to_flock64(&flock, &file_lock);
1876
1877    error = -EFAULT;
1878    if (!copy_to_user(l, &flock, sizeof(flock)))
1879        error = 0;
1880  
1881out:
1882    return error;
1883}
1884
1885/* Apply the lock described by l to an open file descriptor.
1886 * This implements both the F_SETLK and F_SETLKW commands of fcntl().
1887 */
1888int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
1889        struct flock64 __user *l)
1890{
1891    struct file_lock *file_lock = locks_alloc_lock();
1892    struct flock64 flock;
1893    struct inode *inode;
1894    struct file *f;
1895    int error;
1896
1897    if (file_lock == NULL)
1898        return -ENOLCK;
1899
1900    /*
1901     * This might block, so we do it before checking the inode.
1902     */
1903    error = -EFAULT;
1904    if (copy_from_user(&flock, l, sizeof(flock)))
1905        goto out;
1906
1907    inode = filp->f_path.dentry->d_inode;
1908
1909    /* Don't allow mandatory locks on files that may be memory mapped
1910     * and shared.
1911     */
1912    if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) {
1913        error = -EAGAIN;
1914        goto out;
1915    }
1916
1917again:
1918    error = flock64_to_posix_lock(filp, file_lock, &flock);
1919    if (error)
1920        goto out;
1921    if (cmd == F_SETLKW64) {
1922        file_lock->fl_flags |= FL_SLEEP;
1923    }
1924    
1925    error = -EBADF;
1926    switch (flock.l_type) {
1927    case F_RDLCK:
1928        if (!(filp->f_mode & FMODE_READ))
1929            goto out;
1930        break;
1931    case F_WRLCK:
1932        if (!(filp->f_mode & FMODE_WRITE))
1933            goto out;
1934        break;
1935    case F_UNLCK:
1936        break;
1937    default:
1938        error = -EINVAL;
1939        goto out;
1940    }
1941
1942    error = do_lock_file_wait(filp, cmd, file_lock);
1943
1944    /*
1945     * Attempt to detect a close/fcntl race and recover by
1946     * releasing the lock that was just acquired.
1947     */
1948    spin_lock(&current->files->file_lock);
1949    f = fcheck(fd);
1950    spin_unlock(&current->files->file_lock);
1951    if (!error && f != filp && flock.l_type != F_UNLCK) {
1952        flock.l_type = F_UNLCK;
1953        goto again;
1954    }
1955
1956out:
1957    locks_free_lock(file_lock);
1958    return error;
1959}
1960#endif /* BITS_PER_LONG == 32 */
1961
1962/*
1963 * This function is called when the file is being removed
1964 * from the task's fd array. POSIX locks belonging to this task
1965 * are deleted at this time.
1966 */
1967void locks_remove_posix(struct file *filp, fl_owner_t owner)
1968{
1969    struct file_lock lock;
1970
1971    /*
1972     * If there are no locks held on this file, we don't need to call
1973     * posix_lock_file(). Another process could be setting a lock on this
1974     * file at the same time, but we wouldn't remove that lock anyway.
1975     */
1976    if (!filp->f_path.dentry->d_inode->i_flock)
1977        return;
1978
1979    lock.fl_type = F_UNLCK;
1980    lock.fl_flags = FL_POSIX | FL_CLOSE;
1981    lock.fl_start = 0;
1982    lock.fl_end = OFFSET_MAX;
1983    lock.fl_owner = owner;
1984    lock.fl_pid = current->tgid;
1985    lock.fl_file = filp;
1986    lock.fl_ops = NULL;
1987    lock.fl_lmops = NULL;
1988
1989    vfs_lock_file(filp, F_SETLK, &lock, NULL);
1990
1991    if (lock.fl_ops && lock.fl_ops->fl_release_private)
1992        lock.fl_ops->fl_release_private(&lock);
1993}
1994
1995EXPORT_SYMBOL(locks_remove_posix);
1996
1997/*
1998 * This function is called on the last close of an open file.
1999 */
2000void locks_remove_flock(struct file *filp)
2001{
2002    struct inode * inode = filp->f_path.dentry->d_inode;
2003    struct file_lock *fl;
2004    struct file_lock **before;
2005
2006    if (!inode->i_flock)
2007        return;
2008
2009    if (filp->f_op && filp->f_op->flock) {
2010        struct file_lock fl = {
2011            .fl_pid = current->tgid,
2012            .fl_file = filp,
2013            .fl_flags = FL_FLOCK,
2014            .fl_type = F_UNLCK,
2015            .fl_end = OFFSET_MAX,
2016        };
2017        filp->f_op->flock(filp, F_SETLKW, &fl);
2018        if (fl.fl_ops && fl.fl_ops->fl_release_private)
2019            fl.fl_ops->fl_release_private(&fl);
2020    }
2021
2022    lock_kernel();
2023    before = &inode->i_flock;
2024
2025    while ((fl = *before) != NULL) {
2026        if (fl->fl_file == filp) {
2027            if (IS_FLOCK(fl)) {
2028                locks_delete_lock(before);
2029                continue;
2030            }
2031            if (IS_LEASE(fl)) {
2032                lease_modify(before, F_UNLCK);
2033                continue;
2034            }
2035            /* What? */
2036            BUG();
2037         }
2038        before = &fl->fl_next;
2039    }
2040    unlock_kernel();
2041}
2042
2043/**
2044 * posix_unblock_lock - stop waiting for a file lock
2045 * @filp: how the file was opened
2046 * @waiter: the lock which was waiting
2047 *
2048 * lockd needs to block waiting for locks.
2049 */
2050int
2051posix_unblock_lock(struct file *filp, struct file_lock *waiter)
2052{
2053    int status = 0;
2054
2055    lock_kernel();
2056    if (waiter->fl_next)
2057        __locks_delete_block(waiter);
2058    else
2059        status = -ENOENT;
2060    unlock_kernel();
2061    return status;
2062}
2063
2064EXPORT_SYMBOL(posix_unblock_lock);
2065
2066/**
2067 * vfs_cancel_lock - file byte range unblock lock
2068 * @filp: The file to apply the unblock to
2069 * @fl: The lock to be unblocked
2070 *
2071 * Used by lock managers to cancel blocked requests
2072 */
2073int vfs_cancel_lock(struct file *filp, struct file_lock *fl)
2074{
2075    if (filp->f_op && filp->f_op->lock)
2076        return filp->f_op->lock(filp, F_CANCELLK, fl);
2077    return 0;
2078}
2079
2080EXPORT_SYMBOL_GPL(vfs_cancel_lock);
2081
2082#ifdef CONFIG_PROC_FS
2083#include <linux/proc_fs.h>
2084#include <linux/seq_file.h>
2085
2086static void lock_get_status(struct seq_file *f, struct file_lock *fl,
2087                            int id, char *pfx)
2088{
2089    struct inode *inode = NULL;
2090    unsigned int fl_pid;
2091
2092    if (fl->fl_nspid)
2093        fl_pid = pid_vnr(fl->fl_nspid);
2094    else
2095        fl_pid = fl->fl_pid;
2096
2097    if (fl->fl_file != NULL)
2098        inode = fl->fl_file->f_path.dentry->d_inode;
2099
2100    seq_printf(f, "%d:%s ", id, pfx);
2101    if (IS_POSIX(fl)) {
2102        seq_printf(f, "%6s %s ",
2103                 (fl->fl_flags & FL_ACCESS) ? "ACCESS" : "POSIX ",
2104                 (inode == NULL) ? "*NOINODE*" :
2105                 mandatory_lock(inode) ? "MANDATORY" : "ADVISORY ");
2106    } else if (IS_FLOCK(fl)) {
2107        if (fl->fl_type & LOCK_MAND) {
2108            seq_printf(f, "FLOCK MSNFS ");
2109        } else {
2110            seq_printf(f, "FLOCK ADVISORY ");
2111        }
2112    } else if (IS_LEASE(fl)) {
2113        seq_printf(f, "LEASE ");
2114        if (fl->fl_type & F_INPROGRESS)
2115            seq_printf(f, "BREAKING ");
2116        else if (fl->fl_file)
2117            seq_printf(f, "ACTIVE ");
2118        else
2119            seq_printf(f, "BREAKER ");
2120    } else {
2121        seq_printf(f, "UNKNOWN UNKNOWN ");
2122    }
2123    if (fl->fl_type & LOCK_MAND) {
2124        seq_printf(f, "%s ",
2125                   (fl->fl_type & LOCK_READ)
2126                   ? (fl->fl_type & LOCK_WRITE) ? "RW " : "READ "
2127                   : (fl->fl_type & LOCK_WRITE) ? "WRITE" : "NONE ");
2128    } else {
2129        seq_printf(f, "%s ",
2130                   (fl->fl_type & F_INPROGRESS)
2131                   ? (fl->fl_type & F_UNLCK) ? "UNLCK" : "READ "
2132                   : (fl->fl_type & F_WRLCK) ? "WRITE" : "READ ");
2133    }
2134    if (inode) {
2135#ifdef WE_CAN_BREAK_LSLK_NOW
2136        seq_printf(f, "%d %s:%ld ", fl_pid,
2137                inode->i_sb->s_id, inode->i_ino);
2138#else
2139        /* userspace relies on this representation of dev_t ;-( */
2140        seq_printf(f, "%d %02x:%02x:%ld ", fl_pid,
2141                MAJOR(inode->i_sb->s_dev),
2142                MINOR(inode->i_sb->s_dev), inode->i_ino);
2143#endif
2144    } else {
2145        seq_printf(f, "%d <none>:0 ", fl_pid);
2146    }
2147    if (IS_POSIX(fl)) {
2148        if (fl->fl_end == OFFSET_MAX)
2149            seq_printf(f, "%Ld EOF\n", fl->fl_start);
2150        else
2151            seq_printf(f, "%Ld %Ld\n", fl->fl_start, fl->fl_end);
2152    } else {
2153        seq_printf(f, "0 EOF\n");
2154    }
2155}
2156
2157static int locks_show(struct seq_file *f, void *v)
2158{
2159    struct file_lock *fl, *bfl;
2160
2161    fl = list_entry(v, struct file_lock, fl_link);
2162
2163    lock_get_status(f, fl, (long)f->private, "");
2164
2165    list_for_each_entry(bfl, &fl->fl_block, fl_block)
2166        lock_get_status(f, bfl, (long)f->private, " ->");
2167
2168    f->private++;
2169    return 0;
2170}
2171
2172static void *locks_start(struct seq_file *f, loff_t *pos)
2173{
2174    lock_kernel();
2175    f->private = (void *)1;
2176    return seq_list_start(&file_lock_list, *pos);
2177}
2178
2179static void *locks_next(struct seq_file *f, void *v, loff_t *pos)
2180{
2181    return seq_list_next(v, &file_lock_list, pos);
2182}
2183
2184static void locks_stop(struct seq_file *f, void *v)
2185{
2186    unlock_kernel();
2187}
2188
2189static const struct seq_operations locks_seq_operations = {
2190    .start = locks_start,
2191    .next = locks_next,
2192    .stop = locks_stop,
2193    .show = locks_show,
2194};
2195
2196static int locks_open(struct inode *inode, struct file *filp)
2197{
2198    return seq_open(filp, &locks_seq_operations);
2199}
2200
2201static const struct file_operations proc_locks_operations = {
2202    .open = locks_open,
2203    .read = seq_read,
2204    .llseek = seq_lseek,
2205    .release = seq_release,
2206};
2207
2208static int __init proc_locks_init(void)
2209{
2210    proc_create("locks", 0, NULL, &proc_locks_operations);
2211    return 0;
2212}
2213module_init(proc_locks_init);
2214#endif
2215
2216/**
2217 * lock_may_read - checks that the region is free of locks
2218 * @inode: the inode that is being read
2219 * @start: the first byte to read
2220 * @len: the number of bytes to read
2221 *
2222 * Emulates Windows locking requirements. Whole-file
2223 * mandatory locks (share modes) can prohibit a read and
2224 * byte-range POSIX locks can prohibit a read if they overlap.
2225 *
2226 * N.B. this function is only ever called
2227 * from knfsd and ownership of locks is never checked.
2228 */
2229int lock_may_read(struct inode *inode, loff_t start, unsigned long len)
2230{
2231    struct file_lock *fl;
2232    int result = 1;
2233    lock_kernel();
2234    for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
2235        if (IS_POSIX(fl)) {
2236            if (fl->fl_type == F_RDLCK)
2237                continue;
2238            if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
2239                continue;
2240        } else if (IS_FLOCK(fl)) {
2241            if (!(fl->fl_type & LOCK_MAND))
2242                continue;
2243            if (fl->fl_type & LOCK_READ)
2244                continue;
2245        } else
2246            continue;
2247        result = 0;
2248        break;
2249    }
2250    unlock_kernel();
2251    return result;
2252}
2253
2254EXPORT_SYMBOL(lock_may_read);
2255
2256/**
2257 * lock_may_write - checks that the region is free of locks
2258 * @inode: the inode that is being written
2259 * @start: the first byte to write
2260 * @len: the number of bytes to write
2261 *
2262 * Emulates Windows locking requirements. Whole-file
2263 * mandatory locks (share modes) can prohibit a write and
2264 * byte-range POSIX locks can prohibit a write if they overlap.
2265 *
2266 * N.B. this function is only ever called
2267 * from knfsd and ownership of locks is never checked.
2268 */
2269int lock_may_write(struct inode *inode, loff_t start, unsigned long len)
2270{
2271    struct file_lock *fl;
2272    int result = 1;
2273    lock_kernel();
2274    for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
2275        if (IS_POSIX(fl)) {
2276            if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
2277                continue;
2278        } else if (IS_FLOCK(fl)) {
2279            if (!(fl->fl_type & LOCK_MAND))
2280                continue;
2281            if (fl->fl_type & LOCK_WRITE)
2282                continue;
2283        } else
2284            continue;
2285        result = 0;
2286        break;
2287    }
2288    unlock_kernel();
2289    return result;
2290}
2291
2292EXPORT_SYMBOL(lock_may_write);
2293
2294static int __init filelock_init(void)
2295{
2296    filelock_cache = kmem_cache_create("file_lock_cache",
2297            sizeof(struct file_lock), 0, SLAB_PANIC,
2298            init_once);
2299    return 0;
2300}
2301
2302core_initcall(filelock_init);
2303

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