Root/fs/locks.c

Source at commit 9845c1745d3d531a5b9544f5322c62bfb4d4e9bc created 1 year 2 months ago.
By Xiangfu, rtc: jz4740 fix hwclock give time out
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/filesystems/mandatory-locking.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
136static bool lease_breaking(struct file_lock *fl)
137{
138    return fl->fl_flags & (FL_UNLOCK_PENDING | FL_DOWNGRADE_PENDING);
139}
140
141static int target_leasetype(struct file_lock *fl)
142{
143    if (fl->fl_flags & FL_UNLOCK_PENDING)
144        return F_UNLCK;
145    if (fl->fl_flags & FL_DOWNGRADE_PENDING)
146        return F_RDLCK;
147    return fl->fl_type;
148}
149
150int leases_enable = 1;
151int lease_break_time = 45;
152
153#define for_each_lock(inode, lockp) \
154    for (lockp = &inode->i_flock; *lockp != NULL; lockp = &(*lockp)->fl_next)
155
156static LIST_HEAD(file_lock_list);
157static LIST_HEAD(blocked_list);
158static DEFINE_SPINLOCK(file_lock_lock);
159
160/*
161 * Protects the two list heads above, plus the inode->i_flock list
162 */
163void lock_flocks(void)
164{
165    spin_lock(&file_lock_lock);
166}
167EXPORT_SYMBOL_GPL(lock_flocks);
168
169void unlock_flocks(void)
170{
171    spin_unlock(&file_lock_lock);
172}
173EXPORT_SYMBOL_GPL(unlock_flocks);
174
175static struct kmem_cache *filelock_cache __read_mostly;
176
177static void locks_init_lock_heads(struct file_lock *fl)
178{
179    INIT_LIST_HEAD(&fl->fl_link);
180    INIT_LIST_HEAD(&fl->fl_block);
181    init_waitqueue_head(&fl->fl_wait);
182}
183
184/* Allocate an empty lock structure. */
185struct file_lock *locks_alloc_lock(void)
186{
187    struct file_lock *fl = kmem_cache_zalloc(filelock_cache, GFP_KERNEL);
188
189    if (fl)
190        locks_init_lock_heads(fl);
191
192    return fl;
193}
194EXPORT_SYMBOL_GPL(locks_alloc_lock);
195
196void locks_release_private(struct file_lock *fl)
197{
198    if (fl->fl_ops) {
199        if (fl->fl_ops->fl_release_private)
200            fl->fl_ops->fl_release_private(fl);
201        fl->fl_ops = NULL;
202    }
203    if (fl->fl_lmops) {
204        if (fl->fl_lmops->lm_release_private)
205            fl->fl_lmops->lm_release_private(fl);
206        fl->fl_lmops = NULL;
207    }
208
209}
210EXPORT_SYMBOL_GPL(locks_release_private);
211
212/* Free a lock which is not in use. */
213void locks_free_lock(struct file_lock *fl)
214{
215    BUG_ON(waitqueue_active(&fl->fl_wait));
216    BUG_ON(!list_empty(&fl->fl_block));
217    BUG_ON(!list_empty(&fl->fl_link));
218
219    locks_release_private(fl);
220    kmem_cache_free(filelock_cache, fl);
221}
222EXPORT_SYMBOL(locks_free_lock);
223
224void locks_init_lock(struct file_lock *fl)
225{
226    memset(fl, 0, sizeof(struct file_lock));
227    locks_init_lock_heads(fl);
228}
229
230EXPORT_SYMBOL(locks_init_lock);
231
232static void locks_copy_private(struct file_lock *new, struct file_lock *fl)
233{
234    if (fl->fl_ops) {
235        if (fl->fl_ops->fl_copy_lock)
236            fl->fl_ops->fl_copy_lock(new, fl);
237        new->fl_ops = fl->fl_ops;
238    }
239    if (fl->fl_lmops)
240        new->fl_lmops = fl->fl_lmops;
241}
242
243/*
244 * Initialize a new lock from an existing file_lock structure.
245 */
246void __locks_copy_lock(struct file_lock *new, const struct file_lock *fl)
247{
248    new->fl_owner = fl->fl_owner;
249    new->fl_pid = fl->fl_pid;
250    new->fl_file = NULL;
251    new->fl_flags = fl->fl_flags;
252    new->fl_type = fl->fl_type;
253    new->fl_start = fl->fl_start;
254    new->fl_end = fl->fl_end;
255    new->fl_ops = NULL;
256    new->fl_lmops = NULL;
257}
258EXPORT_SYMBOL(__locks_copy_lock);
259
260void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
261{
262    locks_release_private(new);
263
264    __locks_copy_lock(new, fl);
265    new->fl_file = fl->fl_file;
266    new->fl_ops = fl->fl_ops;
267    new->fl_lmops = fl->fl_lmops;
268
269    locks_copy_private(new, fl);
270}
271
272EXPORT_SYMBOL(locks_copy_lock);
273
274static inline int flock_translate_cmd(int cmd) {
275    if (cmd & LOCK_MAND)
276        return cmd & (LOCK_MAND | LOCK_RW);
277    switch (cmd) {
278    case LOCK_SH:
279        return F_RDLCK;
280    case LOCK_EX:
281        return F_WRLCK;
282    case LOCK_UN:
283        return F_UNLCK;
284    }
285    return -EINVAL;
286}
287
288/* Fill in a file_lock structure with an appropriate FLOCK lock. */
289static int flock_make_lock(struct file *filp, struct file_lock **lock,
290        unsigned int cmd)
291{
292    struct file_lock *fl;
293    int type = flock_translate_cmd(cmd);
294    if (type < 0)
295        return type;
296    
297    fl = locks_alloc_lock();
298    if (fl == NULL)
299        return -ENOMEM;
300
301    fl->fl_file = filp;
302    fl->fl_pid = current->tgid;
303    fl->fl_flags = FL_FLOCK;
304    fl->fl_type = type;
305    fl->fl_end = OFFSET_MAX;
306    
307    *lock = fl;
308    return 0;
309}
310
311static int assign_type(struct file_lock *fl, int type)
312{
313    switch (type) {
314    case F_RDLCK:
315    case F_WRLCK:
316    case F_UNLCK:
317        fl->fl_type = type;
318        break;
319    default:
320        return -EINVAL;
321    }
322    return 0;
323}
324
325/* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX
326 * style lock.
327 */
328static int flock_to_posix_lock(struct file *filp, struct file_lock *fl,
329                   struct flock *l)
330{
331    off_t start, end;
332
333    switch (l->l_whence) {
334    case SEEK_SET:
335        start = 0;
336        break;
337    case SEEK_CUR:
338        start = filp->f_pos;
339        break;
340    case SEEK_END:
341        start = i_size_read(filp->f_path.dentry->d_inode);
342        break;
343    default:
344        return -EINVAL;
345    }
346
347    /* POSIX-1996 leaves the case l->l_len < 0 undefined;
348       POSIX-2001 defines it. */
349    start += l->l_start;
350    if (start < 0)
351        return -EINVAL;
352    fl->fl_end = OFFSET_MAX;
353    if (l->l_len > 0) {
354        end = start + l->l_len - 1;
355        fl->fl_end = end;
356    } else if (l->l_len < 0) {
357        end = start - 1;
358        fl->fl_end = end;
359        start += l->l_len;
360        if (start < 0)
361            return -EINVAL;
362    }
363    fl->fl_start = start; /* we record the absolute position */
364    if (fl->fl_end < fl->fl_start)
365        return -EOVERFLOW;
366    
367    fl->fl_owner = current->files;
368    fl->fl_pid = current->tgid;
369    fl->fl_file = filp;
370    fl->fl_flags = FL_POSIX;
371    fl->fl_ops = NULL;
372    fl->fl_lmops = NULL;
373
374    return assign_type(fl, l->l_type);
375}
376
377#if BITS_PER_LONG == 32
378static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
379                 struct flock64 *l)
380{
381    loff_t start;
382
383    switch (l->l_whence) {
384    case SEEK_SET:
385        start = 0;
386        break;
387    case SEEK_CUR:
388        start = filp->f_pos;
389        break;
390    case SEEK_END:
391        start = i_size_read(filp->f_path.dentry->d_inode);
392        break;
393    default:
394        return -EINVAL;
395    }
396
397    start += l->l_start;
398    if (start < 0)
399        return -EINVAL;
400    fl->fl_end = OFFSET_MAX;
401    if (l->l_len > 0) {
402        fl->fl_end = start + l->l_len - 1;
403    } else if (l->l_len < 0) {
404        fl->fl_end = start - 1;
405        start += l->l_len;
406        if (start < 0)
407            return -EINVAL;
408    }
409    fl->fl_start = start; /* we record the absolute position */
410    if (fl->fl_end < fl->fl_start)
411        return -EOVERFLOW;
412    
413    fl->fl_owner = current->files;
414    fl->fl_pid = current->tgid;
415    fl->fl_file = filp;
416    fl->fl_flags = FL_POSIX;
417    fl->fl_ops = NULL;
418    fl->fl_lmops = NULL;
419
420    return assign_type(fl, l->l_type);
421}
422#endif
423
424/* default lease lock manager operations */
425static void lease_break_callback(struct file_lock *fl)
426{
427    kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG);
428}
429
430static void lease_release_private_callback(struct file_lock *fl)
431{
432    if (!fl->fl_file)
433        return;
434
435    f_delown(fl->fl_file);
436    fl->fl_file->f_owner.signum = 0;
437}
438
439static const struct lock_manager_operations lease_manager_ops = {
440    .lm_break = lease_break_callback,
441    .lm_release_private = lease_release_private_callback,
442    .lm_change = lease_modify,
443};
444
445/*
446 * Initialize a lease, use the default lock manager operations
447 */
448static int lease_init(struct file *filp, int type, struct file_lock *fl)
449 {
450    if (assign_type(fl, type) != 0)
451        return -EINVAL;
452
453    fl->fl_owner = current->files;
454    fl->fl_pid = current->tgid;
455
456    fl->fl_file = filp;
457    fl->fl_flags = FL_LEASE;
458    fl->fl_start = 0;
459    fl->fl_end = OFFSET_MAX;
460    fl->fl_ops = NULL;
461    fl->fl_lmops = &lease_manager_ops;
462    return 0;
463}
464
465/* Allocate a file_lock initialised to this type of lease */
466static struct file_lock *lease_alloc(struct file *filp, int type)
467{
468    struct file_lock *fl = locks_alloc_lock();
469    int error = -ENOMEM;
470
471    if (fl == NULL)
472        return ERR_PTR(error);
473
474    error = lease_init(filp, type, fl);
475    if (error) {
476        locks_free_lock(fl);
477        return ERR_PTR(error);
478    }
479    return fl;
480}
481
482/* Check if two locks overlap each other.
483 */
484static inline int locks_overlap(struct file_lock *fl1, struct file_lock *fl2)
485{
486    return ((fl1->fl_end >= fl2->fl_start) &&
487        (fl2->fl_end >= fl1->fl_start));
488}
489
490/*
491 * Check whether two locks have the same owner.
492 */
493static int posix_same_owner(struct file_lock *fl1, struct file_lock *fl2)
494{
495    if (fl1->fl_lmops && fl1->fl_lmops->lm_compare_owner)
496        return fl2->fl_lmops == fl1->fl_lmops &&
497            fl1->fl_lmops->lm_compare_owner(fl1, fl2);
498    return fl1->fl_owner == fl2->fl_owner;
499}
500
501/* Remove waiter from blocker's block list.
502 * When blocker ends up pointing to itself then the list is empty.
503 */
504static void __locks_delete_block(struct file_lock *waiter)
505{
506    list_del_init(&waiter->fl_block);
507    list_del_init(&waiter->fl_link);
508    waiter->fl_next = NULL;
509}
510
511/*
512 */
513static void locks_delete_block(struct file_lock *waiter)
514{
515    lock_flocks();
516    __locks_delete_block(waiter);
517    unlock_flocks();
518}
519
520/* Insert waiter into blocker's block list.
521 * We use a circular list so that processes can be easily woken up in
522 * the order they blocked. The documentation doesn't require this but
523 * it seems like the reasonable thing to do.
524 */
525static void locks_insert_block(struct file_lock *blocker,
526                   struct file_lock *waiter)
527{
528    BUG_ON(!list_empty(&waiter->fl_block));
529    list_add_tail(&waiter->fl_block, &blocker->fl_block);
530    waiter->fl_next = blocker;
531    if (IS_POSIX(blocker))
532        list_add(&waiter->fl_link, &blocked_list);
533}
534
535/* Wake up processes blocked waiting for blocker.
536 * If told to wait then schedule the processes until the block list
537 * is empty, otherwise empty the block list ourselves.
538 */
539static void locks_wake_up_blocks(struct file_lock *blocker)
540{
541    while (!list_empty(&blocker->fl_block)) {
542        struct file_lock *waiter;
543
544        waiter = list_first_entry(&blocker->fl_block,
545                struct file_lock, fl_block);
546        __locks_delete_block(waiter);
547        if (waiter->fl_lmops && waiter->fl_lmops->lm_notify)
548            waiter->fl_lmops->lm_notify(waiter);
549        else
550            wake_up(&waiter->fl_wait);
551    }
552}
553
554/* Insert file lock fl into an inode's lock list at the position indicated
555 * by pos. At the same time add the lock to the global file lock list.
556 */
557static void locks_insert_lock(struct file_lock **pos, struct file_lock *fl)
558{
559    list_add(&fl->fl_link, &file_lock_list);
560
561    fl->fl_nspid = get_pid(task_tgid(current));
562
563    /* insert into file's list */
564    fl->fl_next = *pos;
565    *pos = fl;
566}
567
568/*
569 * Delete a lock and then free it.
570 * Wake up processes that are blocked waiting for this lock,
571 * notify the FS that the lock has been cleared and
572 * finally free the lock.
573 */
574static void locks_delete_lock(struct file_lock **thisfl_p)
575{
576    struct file_lock *fl = *thisfl_p;
577
578    *thisfl_p = fl->fl_next;
579    fl->fl_next = NULL;
580    list_del_init(&fl->fl_link);
581
582    fasync_helper(0, fl->fl_file, 0, &fl->fl_fasync);
583    if (fl->fl_fasync != NULL) {
584        printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync);
585        fl->fl_fasync = NULL;
586    }
587
588    if (fl->fl_nspid) {
589        put_pid(fl->fl_nspid);
590        fl->fl_nspid = NULL;
591    }
592
593    locks_wake_up_blocks(fl);
594    locks_free_lock(fl);
595}
596
597/* Determine if lock sys_fl blocks lock caller_fl. Common functionality
598 * checks for shared/exclusive status of overlapping locks.
599 */
600static int locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
601{
602    if (sys_fl->fl_type == F_WRLCK)
603        return 1;
604    if (caller_fl->fl_type == F_WRLCK)
605        return 1;
606    return 0;
607}
608
609/* Determine if lock sys_fl blocks lock caller_fl. POSIX specific
610 * checking before calling the locks_conflict().
611 */
612static int posix_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
613{
614    /* POSIX locks owned by the same process do not conflict with
615     * each other.
616     */
617    if (!IS_POSIX(sys_fl) || posix_same_owner(caller_fl, sys_fl))
618        return (0);
619
620    /* Check whether they overlap */
621    if (!locks_overlap(caller_fl, sys_fl))
622        return 0;
623
624    return (locks_conflict(caller_fl, sys_fl));
625}
626
627/* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific
628 * checking before calling the locks_conflict().
629 */
630static int flock_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
631{
632    /* FLOCK locks referring to the same filp do not conflict with
633     * each other.
634     */
635    if (!IS_FLOCK(sys_fl) || (caller_fl->fl_file == sys_fl->fl_file))
636        return (0);
637    if ((caller_fl->fl_type & LOCK_MAND) || (sys_fl->fl_type & LOCK_MAND))
638        return 0;
639
640    return (locks_conflict(caller_fl, sys_fl));
641}
642
643void
644posix_test_lock(struct file *filp, struct file_lock *fl)
645{
646    struct file_lock *cfl;
647
648    lock_flocks();
649    for (cfl = filp->f_path.dentry->d_inode->i_flock; cfl; cfl = cfl->fl_next) {
650        if (!IS_POSIX(cfl))
651            continue;
652        if (posix_locks_conflict(fl, cfl))
653            break;
654    }
655    if (cfl) {
656        __locks_copy_lock(fl, cfl);
657        if (cfl->fl_nspid)
658            fl->fl_pid = pid_vnr(cfl->fl_nspid);
659    } else
660        fl->fl_type = F_UNLCK;
661    unlock_flocks();
662    return;
663}
664EXPORT_SYMBOL(posix_test_lock);
665
666/*
667 * Deadlock detection:
668 *
669 * We attempt to detect deadlocks that are due purely to posix file
670 * locks.
671 *
672 * We assume that a task can be waiting for at most one lock at a time.
673 * So for any acquired lock, the process holding that lock may be
674 * waiting on at most one other lock. That lock in turns may be held by
675 * someone waiting for at most one other lock. Given a requested lock
676 * caller_fl which is about to wait for a conflicting lock block_fl, we
677 * follow this chain of waiters to ensure we are not about to create a
678 * cycle.
679 *
680 * Since we do this before we ever put a process to sleep on a lock, we
681 * are ensured that there is never a cycle; that is what guarantees that
682 * the while() loop in posix_locks_deadlock() eventually completes.
683 *
684 * Note: the above assumption may not be true when handling lock
685 * requests from a broken NFS client. It may also fail in the presence
686 * of tasks (such as posix threads) sharing the same open file table.
687 *
688 * To handle those cases, we just bail out after a few iterations.
689 */
690
691#define MAX_DEADLK_ITERATIONS 10
692
693/* Find a lock that the owner of the given block_fl is blocking on. */
694static struct file_lock *what_owner_is_waiting_for(struct file_lock *block_fl)
695{
696    struct file_lock *fl;
697
698    list_for_each_entry(fl, &blocked_list, fl_link) {
699        if (posix_same_owner(fl, block_fl))
700            return fl->fl_next;
701    }
702    return NULL;
703}
704
705static int posix_locks_deadlock(struct file_lock *caller_fl,
706                struct file_lock *block_fl)
707{
708    int i = 0;
709
710    while ((block_fl = what_owner_is_waiting_for(block_fl))) {
711        if (i++ > MAX_DEADLK_ITERATIONS)
712            return 0;
713        if (posix_same_owner(caller_fl, block_fl))
714            return 1;
715    }
716    return 0;
717}
718
719/* Try to create a FLOCK lock on filp. We always insert new FLOCK locks
720 * after any leases, but before any posix locks.
721 *
722 * Note that if called with an FL_EXISTS argument, the caller may determine
723 * whether or not a lock was successfully freed by testing the return
724 * value for -ENOENT.
725 */
726static int flock_lock_file(struct file *filp, struct file_lock *request)
727{
728    struct file_lock *new_fl = NULL;
729    struct file_lock **before;
730    struct inode * inode = filp->f_path.dentry->d_inode;
731    int error = 0;
732    int found = 0;
733
734    if (!(request->fl_flags & FL_ACCESS) && (request->fl_type != F_UNLCK)) {
735        new_fl = locks_alloc_lock();
736        if (!new_fl)
737            return -ENOMEM;
738    }
739
740    lock_flocks();
741    if (request->fl_flags & FL_ACCESS)
742        goto find_conflict;
743
744    for_each_lock(inode, before) {
745        struct file_lock *fl = *before;
746        if (IS_POSIX(fl))
747            break;
748        if (IS_LEASE(fl))
749            continue;
750        if (filp != fl->fl_file)
751            continue;
752        if (request->fl_type == fl->fl_type)
753            goto out;
754        found = 1;
755        locks_delete_lock(before);
756        break;
757    }
758
759    if (request->fl_type == F_UNLCK) {
760        if ((request->fl_flags & FL_EXISTS) && !found)
761            error = -ENOENT;
762        goto out;
763    }
764
765    /*
766     * If a higher-priority process was blocked on the old file lock,
767     * give it the opportunity to lock the file.
768     */
769    if (found) {
770        unlock_flocks();
771        cond_resched();
772        lock_flocks();
773    }
774
775find_conflict:
776    for_each_lock(inode, before) {
777        struct file_lock *fl = *before;
778        if (IS_POSIX(fl))
779            break;
780        if (IS_LEASE(fl))
781            continue;
782        if (!flock_locks_conflict(request, fl))
783            continue;
784        error = -EAGAIN;
785        if (!(request->fl_flags & FL_SLEEP))
786            goto out;
787        error = FILE_LOCK_DEFERRED;
788        locks_insert_block(fl, request);
789        goto out;
790    }
791    if (request->fl_flags & FL_ACCESS)
792        goto out;
793    locks_copy_lock(new_fl, request);
794    locks_insert_lock(before, new_fl);
795    new_fl = NULL;
796    error = 0;
797
798out:
799    unlock_flocks();
800    if (new_fl)
801        locks_free_lock(new_fl);
802    return error;
803}
804
805static int __posix_lock_file(struct inode *inode, struct file_lock *request, struct file_lock *conflock)
806{
807    struct file_lock *fl;
808    struct file_lock *new_fl = NULL;
809    struct file_lock *new_fl2 = NULL;
810    struct file_lock *left = NULL;
811    struct file_lock *right = NULL;
812    struct file_lock **before;
813    int error, added = 0;
814
815    /*
816     * We may need two file_lock structures for this operation,
817     * so we get them in advance to avoid races.
818     *
819     * In some cases we can be sure, that no new locks will be needed
820     */
821    if (!(request->fl_flags & FL_ACCESS) &&
822        (request->fl_type != F_UNLCK ||
823         request->fl_start != 0 || request->fl_end != OFFSET_MAX)) {
824        new_fl = locks_alloc_lock();
825        new_fl2 = locks_alloc_lock();
826    }
827
828    lock_flocks();
829    if (request->fl_type != F_UNLCK) {
830        for_each_lock(inode, before) {
831            fl = *before;
832            if (!IS_POSIX(fl))
833                continue;
834            if (!posix_locks_conflict(request, fl))
835                continue;
836            if (conflock)
837                __locks_copy_lock(conflock, fl);
838            error = -EAGAIN;
839            if (!(request->fl_flags & FL_SLEEP))
840                goto out;
841            error = -EDEADLK;
842            if (posix_locks_deadlock(request, fl))
843                goto out;
844            error = FILE_LOCK_DEFERRED;
845            locks_insert_block(fl, request);
846            goto out;
847          }
848      }
849
850    /* If we're just looking for a conflict, we're done. */
851    error = 0;
852    if (request->fl_flags & FL_ACCESS)
853        goto out;
854
855    /*
856     * Find the first old lock with the same owner as the new lock.
857     */
858    
859    before = &inode->i_flock;
860
861    /* First skip locks owned by other processes. */
862    while ((fl = *before) && (!IS_POSIX(fl) ||
863                  !posix_same_owner(request, fl))) {
864        before = &fl->fl_next;
865    }
866
867    /* Process locks with this owner. */
868    while ((fl = *before) && posix_same_owner(request, fl)) {
869        /* Detect adjacent or overlapping regions (if same lock type)
870         */
871        if (request->fl_type == fl->fl_type) {
872            /* In all comparisons of start vs end, use
873             * "start - 1" rather than "end + 1". If end
874             * is OFFSET_MAX, end + 1 will become negative.
875             */
876            if (fl->fl_end < request->fl_start - 1)
877                goto next_lock;
878            /* If the next lock in the list has entirely bigger
879             * addresses than the new one, insert the lock here.
880             */
881            if (fl->fl_start - 1 > request->fl_end)
882                break;
883
884            /* If we come here, the new and old lock are of the
885             * same type and adjacent or overlapping. Make one
886             * lock yielding from the lower start address of both
887             * locks to the higher end address.
888             */
889            if (fl->fl_start > request->fl_start)
890                fl->fl_start = request->fl_start;
891            else
892                request->fl_start = fl->fl_start;
893            if (fl->fl_end < request->fl_end)
894                fl->fl_end = request->fl_end;
895            else
896                request->fl_end = fl->fl_end;
897            if (added) {
898                locks_delete_lock(before);
899                continue;
900            }
901            request = fl;
902            added = 1;
903        }
904        else {
905            /* Processing for different lock types is a bit
906             * more complex.
907             */
908            if (fl->fl_end < request->fl_start)
909                goto next_lock;
910            if (fl->fl_start > request->fl_end)
911                break;
912            if (request->fl_type == F_UNLCK)
913                added = 1;
914            if (fl->fl_start < request->fl_start)
915                left = fl;
916            /* If the next lock in the list has a higher end
917             * address than the new one, insert the new one here.
918             */
919            if (fl->fl_end > request->fl_end) {
920                right = fl;
921                break;
922            }
923            if (fl->fl_start >= request->fl_start) {
924                /* The new lock completely replaces an old
925                 * one (This may happen several times).
926                 */
927                if (added) {
928                    locks_delete_lock(before);
929                    continue;
930                }
931                /* Replace the old lock with the new one.
932                 * Wake up anybody waiting for the old one,
933                 * as the change in lock type might satisfy
934                 * their needs.
935                 */
936                locks_wake_up_blocks(fl);
937                fl->fl_start = request->fl_start;
938                fl->fl_end = request->fl_end;
939                fl->fl_type = request->fl_type;
940                locks_release_private(fl);
941                locks_copy_private(fl, request);
942                request = fl;
943                added = 1;
944            }
945        }
946        /* Go on to next lock.
947         */
948    next_lock:
949        before = &fl->fl_next;
950    }
951
952    /*
953     * The above code only modifies existing locks in case of
954     * merging or replacing. If new lock(s) need to be inserted
955     * all modifications are done bellow this, so it's safe yet to
956     * bail out.
957     */
958    error = -ENOLCK; /* "no luck" */
959    if (right && left == right && !new_fl2)
960        goto out;
961
962    error = 0;
963    if (!added) {
964        if (request->fl_type == F_UNLCK) {
965            if (request->fl_flags & FL_EXISTS)
966                error = -ENOENT;
967            goto out;
968        }
969
970        if (!new_fl) {
971            error = -ENOLCK;
972            goto out;
973        }
974        locks_copy_lock(new_fl, request);
975        locks_insert_lock(before, new_fl);
976        new_fl = NULL;
977    }
978    if (right) {
979        if (left == right) {
980            /* The new lock breaks the old one in two pieces,
981             * so we have to use the second new lock.
982             */
983            left = new_fl2;
984            new_fl2 = NULL;
985            locks_copy_lock(left, right);
986            locks_insert_lock(before, left);
987        }
988        right->fl_start = request->fl_end + 1;
989        locks_wake_up_blocks(right);
990    }
991    if (left) {
992        left->fl_end = request->fl_start - 1;
993        locks_wake_up_blocks(left);
994    }
995 out:
996    unlock_flocks();
997    /*
998     * Free any unused locks.
999     */
1000    if (new_fl)
1001        locks_free_lock(new_fl);
1002    if (new_fl2)
1003        locks_free_lock(new_fl2);
1004    return error;
1005}
1006
1007/**
1008 * posix_lock_file - Apply a POSIX-style lock to a file
1009 * @filp: The file to apply the lock to
1010 * @fl: The lock to be applied
1011 * @conflock: Place to return a copy of the conflicting lock, if found.
1012 *
1013 * Add a POSIX style lock to a file.
1014 * We merge adjacent & overlapping locks whenever possible.
1015 * POSIX locks are sorted by owner task, then by starting address
1016 *
1017 * Note that if called with an FL_EXISTS argument, the caller may determine
1018 * whether or not a lock was successfully freed by testing the return
1019 * value for -ENOENT.
1020 */
1021int posix_lock_file(struct file *filp, struct file_lock *fl,
1022            struct file_lock *conflock)
1023{
1024    return __posix_lock_file(filp->f_path.dentry->d_inode, fl, conflock);
1025}
1026EXPORT_SYMBOL(posix_lock_file);
1027
1028/**
1029 * posix_lock_file_wait - Apply a POSIX-style lock to a file
1030 * @filp: The file to apply the lock to
1031 * @fl: The lock to be applied
1032 *
1033 * Add a POSIX style lock to a file.
1034 * We merge adjacent & overlapping locks whenever possible.
1035 * POSIX locks are sorted by owner task, then by starting address
1036 */
1037int posix_lock_file_wait(struct file *filp, struct file_lock *fl)
1038{
1039    int error;
1040    might_sleep ();
1041    for (;;) {
1042        error = posix_lock_file(filp, fl, NULL);
1043        if (error != FILE_LOCK_DEFERRED)
1044            break;
1045        error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
1046        if (!error)
1047            continue;
1048
1049        locks_delete_block(fl);
1050        break;
1051    }
1052    return error;
1053}
1054EXPORT_SYMBOL(posix_lock_file_wait);
1055
1056/**
1057 * locks_mandatory_locked - Check for an active lock
1058 * @inode: the file to check
1059 *
1060 * Searches the inode's list of locks to find any POSIX locks which conflict.
1061 * This function is called from locks_verify_locked() only.
1062 */
1063int locks_mandatory_locked(struct inode *inode)
1064{
1065    fl_owner_t owner = current->files;
1066    struct file_lock *fl;
1067
1068    /*
1069     * Search the lock list for this inode for any POSIX locks.
1070     */
1071    lock_flocks();
1072    for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
1073        if (!IS_POSIX(fl))
1074            continue;
1075        if (fl->fl_owner != owner)
1076            break;
1077    }
1078    unlock_flocks();
1079    return fl ? -EAGAIN : 0;
1080}
1081
1082/**
1083 * locks_mandatory_area - Check for a conflicting lock
1084 * @read_write: %FLOCK_VERIFY_WRITE for exclusive access, %FLOCK_VERIFY_READ
1085 * for shared
1086 * @inode: the file to check
1087 * @filp: how the file was opened (if it was)
1088 * @offset: start of area to check
1089 * @count: length of area to check
1090 *
1091 * Searches the inode's list of locks to find any POSIX locks which conflict.
1092 * This function is called from rw_verify_area() and
1093 * locks_verify_truncate().
1094 */
1095int locks_mandatory_area(int read_write, struct inode *inode,
1096             struct file *filp, loff_t offset,
1097             size_t count)
1098{
1099    struct file_lock fl;
1100    int error;
1101
1102    locks_init_lock(&fl);
1103    fl.fl_owner = current->files;
1104    fl.fl_pid = current->tgid;
1105    fl.fl_file = filp;
1106    fl.fl_flags = FL_POSIX | FL_ACCESS;
1107    if (filp && !(filp->f_flags & O_NONBLOCK))
1108        fl.fl_flags |= FL_SLEEP;
1109    fl.fl_type = (read_write == FLOCK_VERIFY_WRITE) ? F_WRLCK : F_RDLCK;
1110    fl.fl_start = offset;
1111    fl.fl_end = offset + count - 1;
1112
1113    for (;;) {
1114        error = __posix_lock_file(inode, &fl, NULL);
1115        if (error != FILE_LOCK_DEFERRED)
1116            break;
1117        error = wait_event_interruptible(fl.fl_wait, !fl.fl_next);
1118        if (!error) {
1119            /*
1120             * If we've been sleeping someone might have
1121             * changed the permissions behind our back.
1122             */
1123            if (__mandatory_lock(inode))
1124                continue;
1125        }
1126
1127        locks_delete_block(&fl);
1128        break;
1129    }
1130
1131    return error;
1132}
1133
1134EXPORT_SYMBOL(locks_mandatory_area);
1135
1136static void lease_clear_pending(struct file_lock *fl, int arg)
1137{
1138    switch (arg) {
1139    case F_UNLCK:
1140        fl->fl_flags &= ~FL_UNLOCK_PENDING;
1141        /* fall through: */
1142    case F_RDLCK:
1143        fl->fl_flags &= ~FL_DOWNGRADE_PENDING;
1144    }
1145}
1146
1147/* We already had a lease on this file; just change its type */
1148int lease_modify(struct file_lock **before, int arg)
1149{
1150    struct file_lock *fl = *before;
1151    int error = assign_type(fl, arg);
1152
1153    if (error)
1154        return error;
1155    lease_clear_pending(fl, arg);
1156    locks_wake_up_blocks(fl);
1157    if (arg == F_UNLCK)
1158        locks_delete_lock(before);
1159    return 0;
1160}
1161
1162EXPORT_SYMBOL(lease_modify);
1163
1164static bool past_time(unsigned long then)
1165{
1166    if (!then)
1167        /* 0 is a special value meaning "this never expires": */
1168        return false;
1169    return time_after(jiffies, then);
1170}
1171
1172static void time_out_leases(struct inode *inode)
1173{
1174    struct file_lock **before;
1175    struct file_lock *fl;
1176
1177    before = &inode->i_flock;
1178    while ((fl = *before) && IS_LEASE(fl) && lease_breaking(fl)) {
1179        if (past_time(fl->fl_downgrade_time))
1180            lease_modify(before, F_RDLCK);
1181        if (past_time(fl->fl_break_time))
1182            lease_modify(before, F_UNLCK);
1183        if (fl == *before) /* lease_modify may have freed fl */
1184            before = &fl->fl_next;
1185    }
1186}
1187
1188/**
1189 * __break_lease - revoke all outstanding leases on file
1190 * @inode: the inode of the file to return
1191 * @mode: the open mode (read or write)
1192 *
1193 * break_lease (inlined for speed) has checked there already is at least
1194 * some kind of lock (maybe a lease) on this file. Leases are broken on
1195 * a call to open() or truncate(). This function can sleep unless you
1196 * specified %O_NONBLOCK to your open().
1197 */
1198int __break_lease(struct inode *inode, unsigned int mode)
1199{
1200    int error = 0;
1201    struct file_lock *new_fl, *flock;
1202    struct file_lock *fl;
1203    unsigned long break_time;
1204    int i_have_this_lease = 0;
1205    int want_write = (mode & O_ACCMODE) != O_RDONLY;
1206
1207    new_fl = lease_alloc(NULL, want_write ? F_WRLCK : F_RDLCK);
1208    if (IS_ERR(new_fl))
1209        return PTR_ERR(new_fl);
1210
1211    lock_flocks();
1212
1213    time_out_leases(inode);
1214
1215    flock = inode->i_flock;
1216    if ((flock == NULL) || !IS_LEASE(flock))
1217        goto out;
1218
1219    if (!locks_conflict(flock, new_fl))
1220        goto out;
1221
1222    for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next)
1223        if (fl->fl_owner == current->files)
1224            i_have_this_lease = 1;
1225
1226    break_time = 0;
1227    if (lease_break_time > 0) {
1228        break_time = jiffies + lease_break_time * HZ;
1229        if (break_time == 0)
1230            break_time++; /* so that 0 means no break time */
1231    }
1232
1233    for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next) {
1234        if (want_write) {
1235            if (fl->fl_flags & FL_UNLOCK_PENDING)
1236                continue;
1237            fl->fl_flags |= FL_UNLOCK_PENDING;
1238            fl->fl_break_time = break_time;
1239        } else {
1240            if (lease_breaking(flock))
1241                continue;
1242            fl->fl_flags |= FL_DOWNGRADE_PENDING;
1243            fl->fl_downgrade_time = break_time;
1244        }
1245        fl->fl_lmops->lm_break(fl);
1246    }
1247
1248    if (i_have_this_lease || (mode & O_NONBLOCK)) {
1249        error = -EWOULDBLOCK;
1250        goto out;
1251    }
1252
1253restart:
1254    break_time = flock->fl_break_time;
1255    if (break_time != 0) {
1256        break_time -= jiffies;
1257        if (break_time == 0)
1258            break_time++;
1259    }
1260    locks_insert_block(flock, new_fl);
1261    unlock_flocks();
1262    error = wait_event_interruptible_timeout(new_fl->fl_wait,
1263                        !new_fl->fl_next, break_time);
1264    lock_flocks();
1265    __locks_delete_block(new_fl);
1266    if (error >= 0) {
1267        if (error == 0)
1268            time_out_leases(inode);
1269        /*
1270         * Wait for the next conflicting lease that has not been
1271         * broken yet
1272         */
1273        for (flock = inode->i_flock; flock && IS_LEASE(flock);
1274                flock = flock->fl_next) {
1275            if (locks_conflict(new_fl, flock))
1276                goto restart;
1277        }
1278        error = 0;
1279    }
1280
1281out:
1282    unlock_flocks();
1283    locks_free_lock(new_fl);
1284    return error;
1285}
1286
1287EXPORT_SYMBOL(__break_lease);
1288
1289/**
1290 * lease_get_mtime - get the last modified time of an inode
1291 * @inode: the inode
1292 * @time: pointer to a timespec which will contain the last modified time
1293 *
1294 * This is to force NFS clients to flush their caches for files with
1295 * exclusive leases. The justification is that if someone has an
1296 * exclusive lease, then they could be modifying it.
1297 */
1298void lease_get_mtime(struct inode *inode, struct timespec *time)
1299{
1300    struct file_lock *flock = inode->i_flock;
1301    if (flock && IS_LEASE(flock) && (flock->fl_type & F_WRLCK))
1302        *time = current_fs_time(inode->i_sb);
1303    else
1304        *time = inode->i_mtime;
1305}
1306
1307EXPORT_SYMBOL(lease_get_mtime);
1308
1309/**
1310 * fcntl_getlease - Enquire what lease is currently active
1311 * @filp: the file
1312 *
1313 * The value returned by this function will be one of
1314 * (if no lease break is pending):
1315 *
1316 * %F_RDLCK to indicate a shared lease is held.
1317 *
1318 * %F_WRLCK to indicate an exclusive lease is held.
1319 *
1320 * %F_UNLCK to indicate no lease is held.
1321 *
1322 * (if a lease break is pending):
1323 *
1324 * %F_RDLCK to indicate an exclusive lease needs to be
1325 * changed to a shared lease (or removed).
1326 *
1327 * %F_UNLCK to indicate the lease needs to be removed.
1328 *
1329 * XXX: sfr & willy disagree over whether F_INPROGRESS
1330 * should be returned to userspace.
1331 */
1332int fcntl_getlease(struct file *filp)
1333{
1334    struct file_lock *fl;
1335    int type = F_UNLCK;
1336
1337    lock_flocks();
1338    time_out_leases(filp->f_path.dentry->d_inode);
1339    for (fl = filp->f_path.dentry->d_inode->i_flock; fl && IS_LEASE(fl);
1340            fl = fl->fl_next) {
1341        if (fl->fl_file == filp) {
1342            type = target_leasetype(fl);
1343            break;
1344        }
1345    }
1346    unlock_flocks();
1347    return type;
1348}
1349
1350int generic_add_lease(struct file *filp, long arg, struct file_lock **flp)
1351{
1352    struct file_lock *fl, **before, **my_before = NULL, *lease;
1353    struct dentry *dentry = filp->f_path.dentry;
1354    struct inode *inode = dentry->d_inode;
1355    int error;
1356
1357    lease = *flp;
1358
1359    error = -EAGAIN;
1360    if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0))
1361        goto out;
1362    if ((arg == F_WRLCK)
1363        && ((dentry->d_count > 1)
1364        || (atomic_read(&inode->i_count) > 1)))
1365        goto out;
1366
1367    /*
1368     * At this point, we know that if there is an exclusive
1369     * lease on this file, then we hold it on this filp
1370     * (otherwise our open of this file would have blocked).
1371     * And if we are trying to acquire an exclusive lease,
1372     * then the file is not open by anyone (including us)
1373     * except for this filp.
1374     */
1375    error = -EAGAIN;
1376    for (before = &inode->i_flock;
1377            ((fl = *before) != NULL) && IS_LEASE(fl);
1378            before = &fl->fl_next) {
1379        if (fl->fl_file == filp) {
1380            my_before = before;
1381            continue;
1382        }
1383        /*
1384         * No exclusive leases if someone else has a lease on
1385         * this file:
1386         */
1387        if (arg == F_WRLCK)
1388            goto out;
1389        /*
1390         * Modifying our existing lease is OK, but no getting a
1391         * new lease if someone else is opening for write:
1392         */
1393        if (fl->fl_flags & FL_UNLOCK_PENDING)
1394            goto out;
1395    }
1396
1397    if (my_before != NULL) {
1398        error = lease->fl_lmops->lm_change(my_before, arg);
1399        if (!error)
1400            *flp = *my_before;
1401        goto out;
1402    }
1403
1404    error = -EINVAL;
1405    if (!leases_enable)
1406        goto out;
1407
1408    locks_insert_lock(before, lease);
1409    return 0;
1410
1411out:
1412    return error;
1413}
1414
1415int generic_delete_lease(struct file *filp, struct file_lock **flp)
1416{
1417    struct file_lock *fl, **before;
1418    struct dentry *dentry = filp->f_path.dentry;
1419    struct inode *inode = dentry->d_inode;
1420
1421    for (before = &inode->i_flock;
1422            ((fl = *before) != NULL) && IS_LEASE(fl);
1423            before = &fl->fl_next) {
1424        if (fl->fl_file != filp)
1425            continue;
1426        return (*flp)->fl_lmops->lm_change(before, F_UNLCK);
1427    }
1428    return -EAGAIN;
1429}
1430
1431/**
1432 * generic_setlease - sets a lease on an open file
1433 * @filp: file pointer
1434 * @arg: type of lease to obtain
1435 * @flp: input - file_lock to use, output - file_lock inserted
1436 *
1437 * The (input) flp->fl_lmops->lm_break function is required
1438 * by break_lease().
1439 *
1440 * Called with file_lock_lock held.
1441 */
1442int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
1443{
1444    struct dentry *dentry = filp->f_path.dentry;
1445    struct inode *inode = dentry->d_inode;
1446    int error;
1447
1448    if ((current_fsuid() != inode->i_uid) && !capable(CAP_LEASE))
1449        return -EACCES;
1450    if (!S_ISREG(inode->i_mode))
1451        return -EINVAL;
1452    error = security_file_lock(filp, arg);
1453    if (error)
1454        return error;
1455
1456    time_out_leases(inode);
1457
1458    BUG_ON(!(*flp)->fl_lmops->lm_break);
1459
1460    switch (arg) {
1461    case F_UNLCK:
1462        return generic_delete_lease(filp, flp);
1463    case F_RDLCK:
1464    case F_WRLCK:
1465        return generic_add_lease(filp, arg, flp);
1466    default:
1467        BUG();
1468    }
1469}
1470EXPORT_SYMBOL(generic_setlease);
1471
1472static int __vfs_setlease(struct file *filp, long arg, struct file_lock **lease)
1473{
1474    if (filp->f_op && filp->f_op->setlease)
1475        return filp->f_op->setlease(filp, arg, lease);
1476    else
1477        return generic_setlease(filp, arg, lease);
1478}
1479
1480/**
1481 * vfs_setlease - sets a lease on an open file
1482 * @filp: file pointer
1483 * @arg: type of lease to obtain
1484 * @lease: file_lock to use
1485 *
1486 * Call this to establish a lease on the file.
1487 * The (*lease)->fl_lmops->lm_break operation must be set; if not,
1488 * break_lease will oops!
1489 *
1490 * This will call the filesystem's setlease file method, if
1491 * defined. Note that there is no getlease method; instead, the
1492 * filesystem setlease method should call back to setlease() to
1493 * add a lease to the inode's lease list, where fcntl_getlease() can
1494 * find it. Since fcntl_getlease() only reports whether the current
1495 * task holds a lease, a cluster filesystem need only do this for
1496 * leases held by processes on this node.
1497 *
1498 * There is also no break_lease method; filesystems that
1499 * handle their own leases should break leases themselves from the
1500 * filesystem's open, create, and (on truncate) setattr methods.
1501 *
1502 * Warning: the only current setlease methods exist only to disable
1503 * leases in certain cases. More vfs changes may be required to
1504 * allow a full filesystem lease implementation.
1505 */
1506
1507int vfs_setlease(struct file *filp, long arg, struct file_lock **lease)
1508{
1509    int error;
1510
1511    lock_flocks();
1512    error = __vfs_setlease(filp, arg, lease);
1513    unlock_flocks();
1514
1515    return error;
1516}
1517EXPORT_SYMBOL_GPL(vfs_setlease);
1518
1519static int do_fcntl_delete_lease(struct file *filp)
1520{
1521    struct file_lock fl, *flp = &fl;
1522
1523    lease_init(filp, F_UNLCK, flp);
1524
1525    return vfs_setlease(filp, F_UNLCK, &flp);
1526}
1527
1528static int do_fcntl_add_lease(unsigned int fd, struct file *filp, long arg)
1529{
1530    struct file_lock *fl, *ret;
1531    struct fasync_struct *new;
1532    int error;
1533
1534    fl = lease_alloc(filp, arg);
1535    if (IS_ERR(fl))
1536        return PTR_ERR(fl);
1537
1538    new = fasync_alloc();
1539    if (!new) {
1540        locks_free_lock(fl);
1541        return -ENOMEM;
1542    }
1543    ret = fl;
1544    lock_flocks();
1545    error = __vfs_setlease(filp, arg, &ret);
1546    if (error) {
1547        unlock_flocks();
1548        locks_free_lock(fl);
1549        goto out_free_fasync;
1550    }
1551    if (ret != fl)
1552        locks_free_lock(fl);
1553
1554    /*
1555     * fasync_insert_entry() returns the old entry if any.
1556     * If there was no old entry, then it used 'new' and
1557     * inserted it into the fasync list. Clear new so that
1558     * we don't release it here.
1559     */
1560    if (!fasync_insert_entry(fd, filp, &ret->fl_fasync, new))
1561        new = NULL;
1562
1563    error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
1564    unlock_flocks();
1565
1566out_free_fasync:
1567    if (new)
1568        fasync_free(new);
1569    return error;
1570}
1571
1572/**
1573 * fcntl_setlease - sets a lease on an open file
1574 * @fd: open file descriptor
1575 * @filp: file pointer
1576 * @arg: type of lease to obtain
1577 *
1578 * Call this fcntl to establish a lease on the file.
1579 * Note that you also need to call %F_SETSIG to
1580 * receive a signal when the lease is broken.
1581 */
1582int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
1583{
1584    if (arg == F_UNLCK)
1585        return do_fcntl_delete_lease(filp);
1586    return do_fcntl_add_lease(fd, filp, arg);
1587}
1588
1589/**
1590 * flock_lock_file_wait - Apply a FLOCK-style lock to a file
1591 * @filp: The file to apply the lock to
1592 * @fl: The lock to be applied
1593 *
1594 * Add a FLOCK style lock to a file.
1595 */
1596int flock_lock_file_wait(struct file *filp, struct file_lock *fl)
1597{
1598    int error;
1599    might_sleep();
1600    for (;;) {
1601        error = flock_lock_file(filp, fl);
1602        if (error != FILE_LOCK_DEFERRED)
1603            break;
1604        error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
1605        if (!error)
1606            continue;
1607
1608        locks_delete_block(fl);
1609        break;
1610    }
1611    return error;
1612}
1613
1614EXPORT_SYMBOL(flock_lock_file_wait);
1615
1616/**
1617 * sys_flock: - flock() system call.
1618 * @fd: the file descriptor to lock.
1619 * @cmd: the type of lock to apply.
1620 *
1621 * Apply a %FL_FLOCK style lock to an open file descriptor.
1622 * The @cmd can be one of
1623 *
1624 * %LOCK_SH -- a shared lock.
1625 *
1626 * %LOCK_EX -- an exclusive lock.
1627 *
1628 * %LOCK_UN -- remove an existing lock.
1629 *
1630 * %LOCK_MAND -- a `mandatory' flock. This exists to emulate Windows Share Modes.
1631 *
1632 * %LOCK_MAND can be combined with %LOCK_READ or %LOCK_WRITE to allow other
1633 * processes read and write access respectively.
1634 */
1635SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd)
1636{
1637    struct file *filp;
1638    struct file_lock *lock;
1639    int can_sleep, unlock;
1640    int error;
1641
1642    error = -EBADF;
1643    filp = fget(fd);
1644    if (!filp)
1645        goto out;
1646
1647    can_sleep = !(cmd & LOCK_NB);
1648    cmd &= ~LOCK_NB;
1649    unlock = (cmd == LOCK_UN);
1650
1651    if (!unlock && !(cmd & LOCK_MAND) &&
1652        !(filp->f_mode & (FMODE_READ|FMODE_WRITE)))
1653        goto out_putf;
1654
1655    error = flock_make_lock(filp, &lock, cmd);
1656    if (error)
1657        goto out_putf;
1658    if (can_sleep)
1659        lock->fl_flags |= FL_SLEEP;
1660
1661    error = security_file_lock(filp, lock->fl_type);
1662    if (error)
1663        goto out_free;
1664
1665    if (filp->f_op && filp->f_op->flock)
1666        error = filp->f_op->flock(filp,
1667                      (can_sleep) ? F_SETLKW : F_SETLK,
1668                      lock);
1669    else
1670        error = flock_lock_file_wait(filp, lock);
1671
1672 out_free:
1673    locks_free_lock(lock);
1674
1675 out_putf:
1676    fput(filp);
1677 out:
1678    return error;
1679}
1680
1681/**
1682 * vfs_test_lock - test file byte range lock
1683 * @filp: The file to test lock for
1684 * @fl: The lock to test; also used to hold result
1685 *
1686 * Returns -ERRNO on failure. Indicates presence of conflicting lock by
1687 * setting conf->fl_type to something other than F_UNLCK.
1688 */
1689int vfs_test_lock(struct file *filp, struct file_lock *fl)
1690{
1691    if (filp->f_op && filp->f_op->lock)
1692        return filp->f_op->lock(filp, F_GETLK, fl);
1693    posix_test_lock(filp, fl);
1694    return 0;
1695}
1696EXPORT_SYMBOL_GPL(vfs_test_lock);
1697
1698static int posix_lock_to_flock(struct flock *flock, struct file_lock *fl)
1699{
1700    flock->l_pid = fl->fl_pid;
1701#if BITS_PER_LONG == 32
1702    /*
1703     * Make sure we can represent the posix lock via
1704     * legacy 32bit flock.
1705     */
1706    if (fl->fl_start > OFFT_OFFSET_MAX)
1707        return -EOVERFLOW;
1708    if (fl->fl_end != OFFSET_MAX && fl->fl_end > OFFT_OFFSET_MAX)
1709        return -EOVERFLOW;
1710#endif
1711    flock->l_start = fl->fl_start;
1712    flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
1713        fl->fl_end - fl->fl_start + 1;
1714    flock->l_whence = 0;
1715    flock->l_type = fl->fl_type;
1716    return 0;
1717}
1718
1719#if BITS_PER_LONG == 32
1720static void posix_lock_to_flock64(struct flock64 *flock, struct file_lock *fl)
1721{
1722    flock->l_pid = fl->fl_pid;
1723    flock->l_start = fl->fl_start;
1724    flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
1725        fl->fl_end - fl->fl_start + 1;
1726    flock->l_whence = 0;
1727    flock->l_type = fl->fl_type;
1728}
1729#endif
1730
1731/* Report the first existing lock that would conflict with l.
1732 * This implements the F_GETLK command of fcntl().
1733 */
1734int fcntl_getlk(struct file *filp, struct flock __user *l)
1735{
1736    struct file_lock file_lock;
1737    struct flock flock;
1738    int error;
1739
1740    error = -EFAULT;
1741    if (copy_from_user(&flock, l, sizeof(flock)))
1742        goto out;
1743    error = -EINVAL;
1744    if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
1745        goto out;
1746
1747    error = flock_to_posix_lock(filp, &file_lock, &flock);
1748    if (error)
1749        goto out;
1750
1751    error = vfs_test_lock(filp, &file_lock);
1752    if (error)
1753        goto out;
1754 
1755    flock.l_type = file_lock.fl_type;
1756    if (file_lock.fl_type != F_UNLCK) {
1757        error = posix_lock_to_flock(&flock, &file_lock);
1758        if (error)
1759            goto out;
1760    }
1761    error = -EFAULT;
1762    if (!copy_to_user(l, &flock, sizeof(flock)))
1763        error = 0;
1764out:
1765    return error;
1766}
1767
1768/**
1769 * vfs_lock_file - file byte range lock
1770 * @filp: The file to apply the lock to
1771 * @cmd: type of locking operation (F_SETLK, F_GETLK, etc.)
1772 * @fl: The lock to be applied
1773 * @conf: Place to return a copy of the conflicting lock, if found.
1774 *
1775 * A caller that doesn't care about the conflicting lock may pass NULL
1776 * as the final argument.
1777 *
1778 * If the filesystem defines a private ->lock() method, then @conf will
1779 * be left unchanged; so a caller that cares should initialize it to
1780 * some acceptable default.
1781 *
1782 * To avoid blocking kernel daemons, such as lockd, that need to acquire POSIX
1783 * locks, the ->lock() interface may return asynchronously, before the lock has
1784 * been granted or denied by the underlying filesystem, if (and only if)
1785 * lm_grant is set. Callers expecting ->lock() to return asynchronously
1786 * will only use F_SETLK, not F_SETLKW; they will set FL_SLEEP if (and only if)
1787 * the request is for a blocking lock. When ->lock() does return asynchronously,
1788 * it must return FILE_LOCK_DEFERRED, and call ->lm_grant() when the lock
1789 * request completes.
1790 * If the request is for non-blocking lock the file system should return
1791 * FILE_LOCK_DEFERRED then try to get the lock and call the callback routine
1792 * with the result. If the request timed out the callback routine will return a
1793 * nonzero return code and the file system should release the lock. The file
1794 * system is also responsible to keep a corresponding posix lock when it
1795 * grants a lock so the VFS can find out which locks are locally held and do
1796 * the correct lock cleanup when required.
1797 * The underlying filesystem must not drop the kernel lock or call
1798 * ->lm_grant() before returning to the caller with a FILE_LOCK_DEFERRED
1799 * return code.
1800 */
1801int vfs_lock_file(struct file *filp, unsigned int cmd, struct file_lock *fl, struct file_lock *conf)
1802{
1803    if (filp->f_op && filp->f_op->lock)
1804        return filp->f_op->lock(filp, cmd, fl);
1805    else
1806        return posix_lock_file(filp, fl, conf);
1807}
1808EXPORT_SYMBOL_GPL(vfs_lock_file);
1809
1810static int do_lock_file_wait(struct file *filp, unsigned int cmd,
1811                 struct file_lock *fl)
1812{
1813    int error;
1814
1815    error = security_file_lock(filp, fl->fl_type);
1816    if (error)
1817        return error;
1818
1819    for (;;) {
1820        error = vfs_lock_file(filp, cmd, fl, NULL);
1821        if (error != FILE_LOCK_DEFERRED)
1822            break;
1823        error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
1824        if (!error)
1825            continue;
1826
1827        locks_delete_block(fl);
1828        break;
1829    }
1830
1831    return error;
1832}
1833
1834/* Apply the lock described by l to an open file descriptor.
1835 * This implements both the F_SETLK and F_SETLKW commands of fcntl().
1836 */
1837int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
1838        struct flock __user *l)
1839{
1840    struct file_lock *file_lock = locks_alloc_lock();
1841    struct flock flock;
1842    struct inode *inode;
1843    struct file *f;
1844    int error;
1845
1846    if (file_lock == NULL)
1847        return -ENOLCK;
1848
1849    /*
1850     * This might block, so we do it before checking the inode.
1851     */
1852    error = -EFAULT;
1853    if (copy_from_user(&flock, l, sizeof(flock)))
1854        goto out;
1855
1856    inode = filp->f_path.dentry->d_inode;
1857
1858    /* Don't allow mandatory locks on files that may be memory mapped
1859     * and shared.
1860     */
1861    if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) {
1862        error = -EAGAIN;
1863        goto out;
1864    }
1865
1866again:
1867    error = flock_to_posix_lock(filp, file_lock, &flock);
1868    if (error)
1869        goto out;
1870    if (cmd == F_SETLKW) {
1871        file_lock->fl_flags |= FL_SLEEP;
1872    }
1873    
1874    error = -EBADF;
1875    switch (flock.l_type) {
1876    case F_RDLCK:
1877        if (!(filp->f_mode & FMODE_READ))
1878            goto out;
1879        break;
1880    case F_WRLCK:
1881        if (!(filp->f_mode & FMODE_WRITE))
1882            goto out;
1883        break;
1884    case F_UNLCK:
1885        break;
1886    default:
1887        error = -EINVAL;
1888        goto out;
1889    }
1890
1891    error = do_lock_file_wait(filp, cmd, file_lock);
1892
1893    /*
1894     * Attempt to detect a close/fcntl race and recover by
1895     * releasing the lock that was just acquired.
1896     */
1897    /*
1898     * we need that spin_lock here - it prevents reordering between
1899     * update of inode->i_flock and check for it done in close().
1900     * rcu_read_lock() wouldn't do.
1901     */
1902    spin_lock(&current->files->file_lock);
1903    f = fcheck(fd);
1904    spin_unlock(&current->files->file_lock);
1905    if (!error && f != filp && flock.l_type != F_UNLCK) {
1906        flock.l_type = F_UNLCK;
1907        goto again;
1908    }
1909
1910out:
1911    locks_free_lock(file_lock);
1912    return error;
1913}
1914
1915#if BITS_PER_LONG == 32
1916/* Report the first existing lock that would conflict with l.
1917 * This implements the F_GETLK command of fcntl().
1918 */
1919int fcntl_getlk64(struct file *filp, struct flock64 __user *l)
1920{
1921    struct file_lock file_lock;
1922    struct flock64 flock;
1923    int error;
1924
1925    error = -EFAULT;
1926    if (copy_from_user(&flock, l, sizeof(flock)))
1927        goto out;
1928    error = -EINVAL;
1929    if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
1930        goto out;
1931
1932    error = flock64_to_posix_lock(filp, &file_lock, &flock);
1933    if (error)
1934        goto out;
1935
1936    error = vfs_test_lock(filp, &file_lock);
1937    if (error)
1938        goto out;
1939
1940    flock.l_type = file_lock.fl_type;
1941    if (file_lock.fl_type != F_UNLCK)
1942        posix_lock_to_flock64(&flock, &file_lock);
1943
1944    error = -EFAULT;
1945    if (!copy_to_user(l, &flock, sizeof(flock)))
1946        error = 0;
1947  
1948out:
1949    return error;
1950}
1951
1952/* Apply the lock described by l to an open file descriptor.
1953 * This implements both the F_SETLK and F_SETLKW commands of fcntl().
1954 */
1955int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
1956        struct flock64 __user *l)
1957{
1958    struct file_lock *file_lock = locks_alloc_lock();
1959    struct flock64 flock;
1960    struct inode *inode;
1961    struct file *f;
1962    int error;
1963
1964    if (file_lock == NULL)
1965        return -ENOLCK;
1966
1967    /*
1968     * This might block, so we do it before checking the inode.
1969     */
1970    error = -EFAULT;
1971    if (copy_from_user(&flock, l, sizeof(flock)))
1972        goto out;
1973
1974    inode = filp->f_path.dentry->d_inode;
1975
1976    /* Don't allow mandatory locks on files that may be memory mapped
1977     * and shared.
1978     */
1979    if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) {
1980        error = -EAGAIN;
1981        goto out;
1982    }
1983
1984again:
1985    error = flock64_to_posix_lock(filp, file_lock, &flock);
1986    if (error)
1987        goto out;
1988    if (cmd == F_SETLKW64) {
1989        file_lock->fl_flags |= FL_SLEEP;
1990    }
1991    
1992    error = -EBADF;
1993    switch (flock.l_type) {
1994    case F_RDLCK:
1995        if (!(filp->f_mode & FMODE_READ))
1996            goto out;
1997        break;
1998    case F_WRLCK:
1999        if (!(filp->f_mode & FMODE_WRITE))
2000            goto out;
2001        break;
2002    case F_UNLCK:
2003        break;
2004    default:
2005        error = -EINVAL;
2006        goto out;
2007    }
2008
2009    error = do_lock_file_wait(filp, cmd, file_lock);
2010
2011    /*
2012     * Attempt to detect a close/fcntl race and recover by
2013     * releasing the lock that was just acquired.
2014     */
2015    spin_lock(&current->files->file_lock);
2016    f = fcheck(fd);
2017    spin_unlock(&current->files->file_lock);
2018    if (!error && f != filp && flock.l_type != F_UNLCK) {
2019        flock.l_type = F_UNLCK;
2020        goto again;
2021    }
2022
2023out:
2024    locks_free_lock(file_lock);
2025    return error;
2026}
2027#endif /* BITS_PER_LONG == 32 */
2028
2029/*
2030 * This function is called when the file is being removed
2031 * from the task's fd array. POSIX locks belonging to this task
2032 * are deleted at this time.
2033 */
2034void locks_remove_posix(struct file *filp, fl_owner_t owner)
2035{
2036    struct file_lock lock;
2037
2038    /*
2039     * If there are no locks held on this file, we don't need to call
2040     * posix_lock_file(). Another process could be setting a lock on this
2041     * file at the same time, but we wouldn't remove that lock anyway.
2042     */
2043    if (!filp->f_path.dentry->d_inode->i_flock)
2044        return;
2045
2046    lock.fl_type = F_UNLCK;
2047    lock.fl_flags = FL_POSIX | FL_CLOSE;
2048    lock.fl_start = 0;
2049    lock.fl_end = OFFSET_MAX;
2050    lock.fl_owner = owner;
2051    lock.fl_pid = current->tgid;
2052    lock.fl_file = filp;
2053    lock.fl_ops = NULL;
2054    lock.fl_lmops = NULL;
2055
2056    vfs_lock_file(filp, F_SETLK, &lock, NULL);
2057
2058    if (lock.fl_ops && lock.fl_ops->fl_release_private)
2059        lock.fl_ops->fl_release_private(&lock);
2060}
2061
2062EXPORT_SYMBOL(locks_remove_posix);
2063
2064/*
2065 * This function is called on the last close of an open file.
2066 */
2067void locks_remove_flock(struct file *filp)
2068{
2069    struct inode * inode = filp->f_path.dentry->d_inode;
2070    struct file_lock *fl;
2071    struct file_lock **before;
2072
2073    if (!inode->i_flock)
2074        return;
2075
2076    if (filp->f_op && filp->f_op->flock) {
2077        struct file_lock fl = {
2078            .fl_pid = current->tgid,
2079            .fl_file = filp,
2080            .fl_flags = FL_FLOCK,
2081            .fl_type = F_UNLCK,
2082            .fl_end = OFFSET_MAX,
2083        };
2084        filp->f_op->flock(filp, F_SETLKW, &fl);
2085        if (fl.fl_ops && fl.fl_ops->fl_release_private)
2086            fl.fl_ops->fl_release_private(&fl);
2087    }
2088
2089    lock_flocks();
2090    before = &inode->i_flock;
2091
2092    while ((fl = *before) != NULL) {
2093        if (fl->fl_file == filp) {
2094            if (IS_FLOCK(fl)) {
2095                locks_delete_lock(before);
2096                continue;
2097            }
2098            if (IS_LEASE(fl)) {
2099                lease_modify(before, F_UNLCK);
2100                continue;
2101            }
2102            /* What? */
2103            BUG();
2104         }
2105        before = &fl->fl_next;
2106    }
2107    unlock_flocks();
2108}
2109
2110/**
2111 * posix_unblock_lock - stop waiting for a file lock
2112 * @filp: how the file was opened
2113 * @waiter: the lock which was waiting
2114 *
2115 * lockd needs to block waiting for locks.
2116 */
2117int
2118posix_unblock_lock(struct file *filp, struct file_lock *waiter)
2119{
2120    int status = 0;
2121
2122    lock_flocks();
2123    if (waiter->fl_next)
2124        __locks_delete_block(waiter);
2125    else
2126        status = -ENOENT;
2127    unlock_flocks();
2128    return status;
2129}
2130
2131EXPORT_SYMBOL(posix_unblock_lock);
2132
2133/**
2134 * vfs_cancel_lock - file byte range unblock lock
2135 * @filp: The file to apply the unblock to
2136 * @fl: The lock to be unblocked
2137 *
2138 * Used by lock managers to cancel blocked requests
2139 */
2140int vfs_cancel_lock(struct file *filp, struct file_lock *fl)
2141{
2142    if (filp->f_op && filp->f_op->lock)
2143        return filp->f_op->lock(filp, F_CANCELLK, fl);
2144    return 0;
2145}
2146
2147EXPORT_SYMBOL_GPL(vfs_cancel_lock);
2148
2149#ifdef CONFIG_PROC_FS
2150#include <linux/proc_fs.h>
2151#include <linux/seq_file.h>
2152
2153static void lock_get_status(struct seq_file *f, struct file_lock *fl,
2154                loff_t id, char *pfx)
2155{
2156    struct inode *inode = NULL;
2157    unsigned int fl_pid;
2158
2159    if (fl->fl_nspid)
2160        fl_pid = pid_vnr(fl->fl_nspid);
2161    else
2162        fl_pid = fl->fl_pid;
2163
2164    if (fl->fl_file != NULL)
2165        inode = fl->fl_file->f_path.dentry->d_inode;
2166
2167    seq_printf(f, "%lld:%s ", id, pfx);
2168    if (IS_POSIX(fl)) {
2169        seq_printf(f, "%6s %s ",
2170                 (fl->fl_flags & FL_ACCESS) ? "ACCESS" : "POSIX ",
2171                 (inode == NULL) ? "*NOINODE*" :
2172                 mandatory_lock(inode) ? "MANDATORY" : "ADVISORY ");
2173    } else if (IS_FLOCK(fl)) {
2174        if (fl->fl_type & LOCK_MAND) {
2175            seq_printf(f, "FLOCK MSNFS ");
2176        } else {
2177            seq_printf(f, "FLOCK ADVISORY ");
2178        }
2179    } else if (IS_LEASE(fl)) {
2180        seq_printf(f, "LEASE ");
2181        if (lease_breaking(fl))
2182            seq_printf(f, "BREAKING ");
2183        else if (fl->fl_file)
2184            seq_printf(f, "ACTIVE ");
2185        else
2186            seq_printf(f, "BREAKER ");
2187    } else {
2188        seq_printf(f, "UNKNOWN UNKNOWN ");
2189    }
2190    if (fl->fl_type & LOCK_MAND) {
2191        seq_printf(f, "%s ",
2192                   (fl->fl_type & LOCK_READ)
2193                   ? (fl->fl_type & LOCK_WRITE) ? "RW " : "READ "
2194                   : (fl->fl_type & LOCK_WRITE) ? "WRITE" : "NONE ");
2195    } else {
2196        seq_printf(f, "%s ",
2197                   (lease_breaking(fl))
2198                   ? (fl->fl_type & F_UNLCK) ? "UNLCK" : "READ "
2199                   : (fl->fl_type & F_WRLCK) ? "WRITE" : "READ ");
2200    }
2201    if (inode) {
2202#ifdef WE_CAN_BREAK_LSLK_NOW
2203        seq_printf(f, "%d %s:%ld ", fl_pid,
2204                inode->i_sb->s_id, inode->i_ino);
2205#else
2206        /* userspace relies on this representation of dev_t ;-( */
2207        seq_printf(f, "%d %02x:%02x:%ld ", fl_pid,
2208                MAJOR(inode->i_sb->s_dev),
2209                MINOR(inode->i_sb->s_dev), inode->i_ino);
2210#endif
2211    } else {
2212        seq_printf(f, "%d <none>:0 ", fl_pid);
2213    }
2214    if (IS_POSIX(fl)) {
2215        if (fl->fl_end == OFFSET_MAX)
2216            seq_printf(f, "%Ld EOF\n", fl->fl_start);
2217        else
2218            seq_printf(f, "%Ld %Ld\n", fl->fl_start, fl->fl_end);
2219    } else {
2220        seq_printf(f, "0 EOF\n");
2221    }
2222}
2223
2224static int locks_show(struct seq_file *f, void *v)
2225{
2226    struct file_lock *fl, *bfl;
2227
2228    fl = list_entry(v, struct file_lock, fl_link);
2229
2230    lock_get_status(f, fl, *((loff_t *)f->private), "");
2231
2232    list_for_each_entry(bfl, &fl->fl_block, fl_block)
2233        lock_get_status(f, bfl, *((loff_t *)f->private), " ->");
2234
2235    return 0;
2236}
2237
2238static void *locks_start(struct seq_file *f, loff_t *pos)
2239{
2240    loff_t *p = f->private;
2241
2242    lock_flocks();
2243    *p = (*pos + 1);
2244    return seq_list_start(&file_lock_list, *pos);
2245}
2246
2247static void *locks_next(struct seq_file *f, void *v, loff_t *pos)
2248{
2249    loff_t *p = f->private;
2250    ++*p;
2251    return seq_list_next(v, &file_lock_list, pos);
2252}
2253
2254static void locks_stop(struct seq_file *f, void *v)
2255{
2256    unlock_flocks();
2257}
2258
2259static const struct seq_operations locks_seq_operations = {
2260    .start = locks_start,
2261    .next = locks_next,
2262    .stop = locks_stop,
2263    .show = locks_show,
2264};
2265
2266static int locks_open(struct inode *inode, struct file *filp)
2267{
2268    return seq_open_private(filp, &locks_seq_operations, sizeof(loff_t));
2269}
2270
2271static const struct file_operations proc_locks_operations = {
2272    .open = locks_open,
2273    .read = seq_read,
2274    .llseek = seq_lseek,
2275    .release = seq_release_private,
2276};
2277
2278static int __init proc_locks_init(void)
2279{
2280    proc_create("locks", 0, NULL, &proc_locks_operations);
2281    return 0;
2282}
2283module_init(proc_locks_init);
2284#endif
2285
2286/**
2287 * lock_may_read - checks that the region is free of locks
2288 * @inode: the inode that is being read
2289 * @start: the first byte to read
2290 * @len: the number of bytes to read
2291 *
2292 * Emulates Windows locking requirements. Whole-file
2293 * mandatory locks (share modes) can prohibit a read and
2294 * byte-range POSIX locks can prohibit a read if they overlap.
2295 *
2296 * N.B. this function is only ever called
2297 * from knfsd and ownership of locks is never checked.
2298 */
2299int lock_may_read(struct inode *inode, loff_t start, unsigned long len)
2300{
2301    struct file_lock *fl;
2302    int result = 1;
2303    lock_flocks();
2304    for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
2305        if (IS_POSIX(fl)) {
2306            if (fl->fl_type == F_RDLCK)
2307                continue;
2308            if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
2309                continue;
2310        } else if (IS_FLOCK(fl)) {
2311            if (!(fl->fl_type & LOCK_MAND))
2312                continue;
2313            if (fl->fl_type & LOCK_READ)
2314                continue;
2315        } else
2316            continue;
2317        result = 0;
2318        break;
2319    }
2320    unlock_flocks();
2321    return result;
2322}
2323
2324EXPORT_SYMBOL(lock_may_read);
2325
2326/**
2327 * lock_may_write - checks that the region is free of locks
2328 * @inode: the inode that is being written
2329 * @start: the first byte to write
2330 * @len: the number of bytes to write
2331 *
2332 * Emulates Windows locking requirements. Whole-file
2333 * mandatory locks (share modes) can prohibit a write and
2334 * byte-range POSIX locks can prohibit a write if they overlap.
2335 *
2336 * N.B. this function is only ever called
2337 * from knfsd and ownership of locks is never checked.
2338 */
2339int lock_may_write(struct inode *inode, loff_t start, unsigned long len)
2340{
2341    struct file_lock *fl;
2342    int result = 1;
2343    lock_flocks();
2344    for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
2345        if (IS_POSIX(fl)) {
2346            if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
2347                continue;
2348        } else if (IS_FLOCK(fl)) {
2349            if (!(fl->fl_type & LOCK_MAND))
2350                continue;
2351            if (fl->fl_type & LOCK_WRITE)
2352                continue;
2353        } else
2354            continue;
2355        result = 0;
2356        break;
2357    }
2358    unlock_flocks();
2359    return result;
2360}
2361
2362EXPORT_SYMBOL(lock_may_write);
2363
2364static int __init filelock_init(void)
2365{
2366    filelock_cache = kmem_cache_create("file_lock_cache",
2367            sizeof(struct file_lock), 0, SLAB_PANIC, NULL);
2368
2369    return 0;
2370}
2371
2372core_initcall(filelock_init);
2373

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