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Linux/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/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/security.h>
123 #include <linux/slab.h>
124 #include <linux/syscalls.h>
125 #include <linux/time.h>
126 #include <linux/rcupdate.h>
127 #include <linux/pid_namespace.h>
128 #include <linux/hashtable.h>
129 #include <linux/percpu.h>
130 
131 #define CREATE_TRACE_POINTS
132 #include <trace/events/filelock.h>
133 
134 #include <linux/uaccess.h>
135 
136 #define IS_POSIX(fl)    (fl->fl_flags & FL_POSIX)
137 #define IS_FLOCK(fl)    (fl->fl_flags & FL_FLOCK)
138 #define IS_LEASE(fl)    (fl->fl_flags & (FL_LEASE|FL_DELEG|FL_LAYOUT))
139 #define IS_OFDLCK(fl)   (fl->fl_flags & FL_OFDLCK)
140 
141 static inline bool is_remote_lock(struct file *filp)
142 {
143         return likely(!(filp->f_path.dentry->d_sb->s_flags & MS_NOREMOTELOCK));
144 }
145 
146 static bool lease_breaking(struct file_lock *fl)
147 {
148         return fl->fl_flags & (FL_UNLOCK_PENDING | FL_DOWNGRADE_PENDING);
149 }
150 
151 static int target_leasetype(struct file_lock *fl)
152 {
153         if (fl->fl_flags & FL_UNLOCK_PENDING)
154                 return F_UNLCK;
155         if (fl->fl_flags & FL_DOWNGRADE_PENDING)
156                 return F_RDLCK;
157         return fl->fl_type;
158 }
159 
160 int leases_enable = 1;
161 int lease_break_time = 45;
162 
163 /*
164  * The global file_lock_list is only used for displaying /proc/locks, so we
165  * keep a list on each CPU, with each list protected by its own spinlock.
166  * Global serialization is done using file_rwsem.
167  *
168  * Note that alterations to the list also require that the relevant flc_lock is
169  * held.
170  */
171 struct file_lock_list_struct {
172         spinlock_t              lock;
173         struct hlist_head       hlist;
174 };
175 static DEFINE_PER_CPU(struct file_lock_list_struct, file_lock_list);
176 DEFINE_STATIC_PERCPU_RWSEM(file_rwsem);
177 
178 /*
179  * The blocked_hash is used to find POSIX lock loops for deadlock detection.
180  * It is protected by blocked_lock_lock.
181  *
182  * We hash locks by lockowner in order to optimize searching for the lock a
183  * particular lockowner is waiting on.
184  *
185  * FIXME: make this value scale via some heuristic? We generally will want more
186  * buckets when we have more lockowners holding locks, but that's a little
187  * difficult to determine without knowing what the workload will look like.
188  */
189 #define BLOCKED_HASH_BITS       7
190 static DEFINE_HASHTABLE(blocked_hash, BLOCKED_HASH_BITS);
191 
192 /*
193  * This lock protects the blocked_hash. Generally, if you're accessing it, you
194  * want to be holding this lock.
195  *
196  * In addition, it also protects the fl->fl_block list, and the fl->fl_next
197  * pointer for file_lock structures that are acting as lock requests (in
198  * contrast to those that are acting as records of acquired locks).
199  *
200  * Note that when we acquire this lock in order to change the above fields,
201  * we often hold the flc_lock as well. In certain cases, when reading the fields
202  * protected by this lock, we can skip acquiring it iff we already hold the
203  * flc_lock.
204  *
205  * In particular, adding an entry to the fl_block list requires that you hold
206  * both the flc_lock and the blocked_lock_lock (acquired in that order).
207  * Deleting an entry from the list however only requires the file_lock_lock.
208  */
209 static DEFINE_SPINLOCK(blocked_lock_lock);
210 
211 static struct kmem_cache *flctx_cache __read_mostly;
212 static struct kmem_cache *filelock_cache __read_mostly;
213 
214 static struct file_lock_context *
215 locks_get_lock_context(struct inode *inode, int type)
216 {
217         struct file_lock_context *ctx;
218 
219         /* paired with cmpxchg() below */
220         ctx = smp_load_acquire(&inode->i_flctx);
221         if (likely(ctx) || type == F_UNLCK)
222                 goto out;
223 
224         ctx = kmem_cache_alloc(flctx_cache, GFP_KERNEL);
225         if (!ctx)
226                 goto out;
227 
228         spin_lock_init(&ctx->flc_lock);
229         INIT_LIST_HEAD(&ctx->flc_flock);
230         INIT_LIST_HEAD(&ctx->flc_posix);
231         INIT_LIST_HEAD(&ctx->flc_lease);
232 
233         /*
234          * Assign the pointer if it's not already assigned. If it is, then
235          * free the context we just allocated.
236          */
237         if (cmpxchg(&inode->i_flctx, NULL, ctx)) {
238                 kmem_cache_free(flctx_cache, ctx);
239                 ctx = smp_load_acquire(&inode->i_flctx);
240         }
241 out:
242         trace_locks_get_lock_context(inode, type, ctx);
243         return ctx;
244 }
245 
246 static void
247 locks_dump_ctx_list(struct list_head *list, char *list_type)
248 {
249         struct file_lock *fl;
250 
251         list_for_each_entry(fl, list, fl_list) {
252                 pr_warn("%s: fl_owner=%p fl_flags=0x%x fl_type=0x%x fl_pid=%u\n", list_type, fl->fl_owner, fl->fl_flags, fl->fl_type, fl->fl_pid);
253         }
254 }
255 
256 static void
257 locks_check_ctx_lists(struct inode *inode)
258 {
259         struct file_lock_context *ctx = inode->i_flctx;
260 
261         if (unlikely(!list_empty(&ctx->flc_flock) ||
262                      !list_empty(&ctx->flc_posix) ||
263                      !list_empty(&ctx->flc_lease))) {
264                 pr_warn("Leaked locks on dev=0x%x:0x%x ino=0x%lx:\n",
265                         MAJOR(inode->i_sb->s_dev), MINOR(inode->i_sb->s_dev),
266                         inode->i_ino);
267                 locks_dump_ctx_list(&ctx->flc_flock, "FLOCK");
268                 locks_dump_ctx_list(&ctx->flc_posix, "POSIX");
269                 locks_dump_ctx_list(&ctx->flc_lease, "LEASE");
270         }
271 }
272 
273 void
274 locks_free_lock_context(struct inode *inode)
275 {
276         struct file_lock_context *ctx = inode->i_flctx;
277 
278         if (unlikely(ctx)) {
279                 locks_check_ctx_lists(inode);
280                 kmem_cache_free(flctx_cache, ctx);
281         }
282 }
283 
284 static void locks_init_lock_heads(struct file_lock *fl)
285 {
286         INIT_HLIST_NODE(&fl->fl_link);
287         INIT_LIST_HEAD(&fl->fl_list);
288         INIT_LIST_HEAD(&fl->fl_block);
289         init_waitqueue_head(&fl->fl_wait);
290 }
291 
292 /* Allocate an empty lock structure. */
293 struct file_lock *locks_alloc_lock(void)
294 {
295         struct file_lock *fl = kmem_cache_zalloc(filelock_cache, GFP_KERNEL);
296 
297         if (fl)
298                 locks_init_lock_heads(fl);
299 
300         return fl;
301 }
302 EXPORT_SYMBOL_GPL(locks_alloc_lock);
303 
304 void locks_release_private(struct file_lock *fl)
305 {
306         if (fl->fl_ops) {
307                 if (fl->fl_ops->fl_release_private)
308                         fl->fl_ops->fl_release_private(fl);
309                 fl->fl_ops = NULL;
310         }
311 
312         if (fl->fl_lmops) {
313                 if (fl->fl_lmops->lm_put_owner) {
314                         fl->fl_lmops->lm_put_owner(fl->fl_owner);
315                         fl->fl_owner = NULL;
316                 }
317                 fl->fl_lmops = NULL;
318         }
319 }
320 EXPORT_SYMBOL_GPL(locks_release_private);
321 
322 /* Free a lock which is not in use. */
323 void locks_free_lock(struct file_lock *fl)
324 {
325         BUG_ON(waitqueue_active(&fl->fl_wait));
326         BUG_ON(!list_empty(&fl->fl_list));
327         BUG_ON(!list_empty(&fl->fl_block));
328         BUG_ON(!hlist_unhashed(&fl->fl_link));
329 
330         locks_release_private(fl);
331         kmem_cache_free(filelock_cache, fl);
332 }
333 EXPORT_SYMBOL(locks_free_lock);
334 
335 static void
336 locks_dispose_list(struct list_head *dispose)
337 {
338         struct file_lock *fl;
339 
340         while (!list_empty(dispose)) {
341                 fl = list_first_entry(dispose, struct file_lock, fl_list);
342                 list_del_init(&fl->fl_list);
343                 locks_free_lock(fl);
344         }
345 }
346 
347 void locks_init_lock(struct file_lock *fl)
348 {
349         memset(fl, 0, sizeof(struct file_lock));
350         locks_init_lock_heads(fl);
351 }
352 
353 EXPORT_SYMBOL(locks_init_lock);
354 
355 /*
356  * Initialize a new lock from an existing file_lock structure.
357  */
358 void locks_copy_conflock(struct file_lock *new, struct file_lock *fl)
359 {
360         new->fl_owner = fl->fl_owner;
361         new->fl_pid = fl->fl_pid;
362         new->fl_file = NULL;
363         new->fl_flags = fl->fl_flags;
364         new->fl_type = fl->fl_type;
365         new->fl_start = fl->fl_start;
366         new->fl_end = fl->fl_end;
367         new->fl_lmops = fl->fl_lmops;
368         new->fl_ops = NULL;
369 
370         if (fl->fl_lmops) {
371                 if (fl->fl_lmops->lm_get_owner)
372                         fl->fl_lmops->lm_get_owner(fl->fl_owner);
373         }
374 }
375 EXPORT_SYMBOL(locks_copy_conflock);
376 
377 void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
378 {
379         /* "new" must be a freshly-initialized lock */
380         WARN_ON_ONCE(new->fl_ops);
381 
382         locks_copy_conflock(new, fl);
383 
384         new->fl_file = fl->fl_file;
385         new->fl_ops = fl->fl_ops;
386 
387         if (fl->fl_ops) {
388                 if (fl->fl_ops->fl_copy_lock)
389                         fl->fl_ops->fl_copy_lock(new, fl);
390         }
391 }
392 
393 EXPORT_SYMBOL(locks_copy_lock);
394 
395 static inline int flock_translate_cmd(int cmd) {
396         if (cmd & LOCK_MAND)
397                 return cmd & (LOCK_MAND | LOCK_RW);
398         switch (cmd) {
399         case LOCK_SH:
400                 return F_RDLCK;
401         case LOCK_EX:
402                 return F_WRLCK;
403         case LOCK_UN:
404                 return F_UNLCK;
405         }
406         return -EINVAL;
407 }
408 
409 /* Fill in a file_lock structure with an appropriate FLOCK lock. */
410 static struct file_lock *
411 flock_make_lock(struct file *filp, unsigned int cmd)
412 {
413         struct file_lock *fl;
414         int type = flock_translate_cmd(cmd);
415 
416         if (type < 0)
417                 return ERR_PTR(type);
418         
419         fl = locks_alloc_lock();
420         if (fl == NULL)
421                 return ERR_PTR(-ENOMEM);
422 
423         fl->fl_file = filp;
424         fl->fl_owner = filp;
425         fl->fl_pid = current->tgid;
426         fl->fl_flags = FL_FLOCK;
427         fl->fl_type = type;
428         fl->fl_end = OFFSET_MAX;
429         
430         return fl;
431 }
432 
433 static int assign_type(struct file_lock *fl, long type)
434 {
435         switch (type) {
436         case F_RDLCK:
437         case F_WRLCK:
438         case F_UNLCK:
439                 fl->fl_type = type;
440                 break;
441         default:
442                 return -EINVAL;
443         }
444         return 0;
445 }
446 
447 static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
448                                  struct flock64 *l)
449 {
450         switch (l->l_whence) {
451         case SEEK_SET:
452                 fl->fl_start = 0;
453                 break;
454         case SEEK_CUR:
455                 fl->fl_start = filp->f_pos;
456                 break;
457         case SEEK_END:
458                 fl->fl_start = i_size_read(file_inode(filp));
459                 break;
460         default:
461                 return -EINVAL;
462         }
463         if (l->l_start > OFFSET_MAX - fl->fl_start)
464                 return -EOVERFLOW;
465         fl->fl_start += l->l_start;
466         if (fl->fl_start < 0)
467                 return -EINVAL;
468 
469         /* POSIX-1996 leaves the case l->l_len < 0 undefined;
470            POSIX-2001 defines it. */
471         if (l->l_len > 0) {
472                 if (l->l_len - 1 > OFFSET_MAX - fl->fl_start)
473                         return -EOVERFLOW;
474                 fl->fl_end = fl->fl_start + l->l_len - 1;
475 
476         } else if (l->l_len < 0) {
477                 if (fl->fl_start + l->l_len < 0)
478                         return -EINVAL;
479                 fl->fl_end = fl->fl_start - 1;
480                 fl->fl_start += l->l_len;
481         } else
482                 fl->fl_end = OFFSET_MAX;
483 
484         fl->fl_owner = current->files;
485         fl->fl_pid = current->tgid;
486         fl->fl_file = filp;
487         fl->fl_flags = FL_POSIX;
488         fl->fl_ops = NULL;
489         fl->fl_lmops = NULL;
490 
491         return assign_type(fl, l->l_type);
492 }
493 
494 /* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX
495  * style lock.
496  */
497 static int flock_to_posix_lock(struct file *filp, struct file_lock *fl,
498                                struct flock *l)
499 {
500         struct flock64 ll = {
501                 .l_type = l->l_type,
502                 .l_whence = l->l_whence,
503                 .l_start = l->l_start,
504                 .l_len = l->l_len,
505         };
506 
507         return flock64_to_posix_lock(filp, fl, &ll);
508 }
509 
510 /* default lease lock manager operations */
511 static bool
512 lease_break_callback(struct file_lock *fl)
513 {
514         kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG);
515         return false;
516 }
517 
518 static void
519 lease_setup(struct file_lock *fl, void **priv)
520 {
521         struct file *filp = fl->fl_file;
522         struct fasync_struct *fa = *priv;
523 
524         /*
525          * fasync_insert_entry() returns the old entry if any. If there was no
526          * old entry, then it used "priv" and inserted it into the fasync list.
527          * Clear the pointer to indicate that it shouldn't be freed.
528          */
529         if (!fasync_insert_entry(fa->fa_fd, filp, &fl->fl_fasync, fa))
530                 *priv = NULL;
531 
532         __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
533 }
534 
535 static const struct lock_manager_operations lease_manager_ops = {
536         .lm_break = lease_break_callback,
537         .lm_change = lease_modify,
538         .lm_setup = lease_setup,
539 };
540 
541 /*
542  * Initialize a lease, use the default lock manager operations
543  */
544 static int lease_init(struct file *filp, long type, struct file_lock *fl)
545  {
546         if (assign_type(fl, type) != 0)
547                 return -EINVAL;
548 
549         fl->fl_owner = filp;
550         fl->fl_pid = current->tgid;
551 
552         fl->fl_file = filp;
553         fl->fl_flags = FL_LEASE;
554         fl->fl_start = 0;
555         fl->fl_end = OFFSET_MAX;
556         fl->fl_ops = NULL;
557         fl->fl_lmops = &lease_manager_ops;
558         return 0;
559 }
560 
561 /* Allocate a file_lock initialised to this type of lease */
562 static struct file_lock *lease_alloc(struct file *filp, long type)
563 {
564         struct file_lock *fl = locks_alloc_lock();
565         int error = -ENOMEM;
566 
567         if (fl == NULL)
568                 return ERR_PTR(error);
569 
570         error = lease_init(filp, type, fl);
571         if (error) {
572                 locks_free_lock(fl);
573                 return ERR_PTR(error);
574         }
575         return fl;
576 }
577 
578 /* Check if two locks overlap each other.
579  */
580 static inline int locks_overlap(struct file_lock *fl1, struct file_lock *fl2)
581 {
582         return ((fl1->fl_end >= fl2->fl_start) &&
583                 (fl2->fl_end >= fl1->fl_start));
584 }
585 
586 /*
587  * Check whether two locks have the same owner.
588  */
589 static int posix_same_owner(struct file_lock *fl1, struct file_lock *fl2)
590 {
591         if (fl1->fl_lmops && fl1->fl_lmops->lm_compare_owner)
592                 return fl2->fl_lmops == fl1->fl_lmops &&
593                         fl1->fl_lmops->lm_compare_owner(fl1, fl2);
594         return fl1->fl_owner == fl2->fl_owner;
595 }
596 
597 /* Must be called with the flc_lock held! */
598 static void locks_insert_global_locks(struct file_lock *fl)
599 {
600         struct file_lock_list_struct *fll = this_cpu_ptr(&file_lock_list);
601 
602         percpu_rwsem_assert_held(&file_rwsem);
603 
604         spin_lock(&fll->lock);
605         fl->fl_link_cpu = smp_processor_id();
606         hlist_add_head(&fl->fl_link, &fll->hlist);
607         spin_unlock(&fll->lock);
608 }
609 
610 /* Must be called with the flc_lock held! */
611 static void locks_delete_global_locks(struct file_lock *fl)
612 {
613         struct file_lock_list_struct *fll;
614 
615         percpu_rwsem_assert_held(&file_rwsem);
616 
617         /*
618          * Avoid taking lock if already unhashed. This is safe since this check
619          * is done while holding the flc_lock, and new insertions into the list
620          * also require that it be held.
621          */
622         if (hlist_unhashed(&fl->fl_link))
623                 return;
624 
625         fll = per_cpu_ptr(&file_lock_list, fl->fl_link_cpu);
626         spin_lock(&fll->lock);
627         hlist_del_init(&fl->fl_link);
628         spin_unlock(&fll->lock);
629 }
630 
631 static unsigned long
632 posix_owner_key(struct file_lock *fl)
633 {
634         if (fl->fl_lmops && fl->fl_lmops->lm_owner_key)
635                 return fl->fl_lmops->lm_owner_key(fl);
636         return (unsigned long)fl->fl_owner;
637 }
638 
639 static void locks_insert_global_blocked(struct file_lock *waiter)
640 {
641         lockdep_assert_held(&blocked_lock_lock);
642 
643         hash_add(blocked_hash, &waiter->fl_link, posix_owner_key(waiter));
644 }
645 
646 static void locks_delete_global_blocked(struct file_lock *waiter)
647 {
648         lockdep_assert_held(&blocked_lock_lock);
649 
650         hash_del(&waiter->fl_link);
651 }
652 
653 /* Remove waiter from blocker's block list.
654  * When blocker ends up pointing to itself then the list is empty.
655  *
656  * Must be called with blocked_lock_lock held.
657  */
658 static void __locks_delete_block(struct file_lock *waiter)
659 {
660         locks_delete_global_blocked(waiter);
661         list_del_init(&waiter->fl_block);
662         waiter->fl_next = NULL;
663 }
664 
665 static void locks_delete_block(struct file_lock *waiter)
666 {
667         spin_lock(&blocked_lock_lock);
668         __locks_delete_block(waiter);
669         spin_unlock(&blocked_lock_lock);
670 }
671 
672 /* Insert waiter into blocker's block list.
673  * We use a circular list so that processes can be easily woken up in
674  * the order they blocked. The documentation doesn't require this but
675  * it seems like the reasonable thing to do.
676  *
677  * Must be called with both the flc_lock and blocked_lock_lock held. The
678  * fl_block list itself is protected by the blocked_lock_lock, but by ensuring
679  * that the flc_lock is also held on insertions we can avoid taking the
680  * blocked_lock_lock in some cases when we see that the fl_block list is empty.
681  */
682 static void __locks_insert_block(struct file_lock *blocker,
683                                         struct file_lock *waiter)
684 {
685         BUG_ON(!list_empty(&waiter->fl_block));
686         waiter->fl_next = blocker;
687         list_add_tail(&waiter->fl_block, &blocker->fl_block);
688         if (IS_POSIX(blocker) && !IS_OFDLCK(blocker))
689                 locks_insert_global_blocked(waiter);
690 }
691 
692 /* Must be called with flc_lock held. */
693 static void locks_insert_block(struct file_lock *blocker,
694                                         struct file_lock *waiter)
695 {
696         spin_lock(&blocked_lock_lock);
697         __locks_insert_block(blocker, waiter);
698         spin_unlock(&blocked_lock_lock);
699 }
700 
701 /*
702  * Wake up processes blocked waiting for blocker.
703  *
704  * Must be called with the inode->flc_lock held!
705  */
706 static void locks_wake_up_blocks(struct file_lock *blocker)
707 {
708         /*
709          * Avoid taking global lock if list is empty. This is safe since new
710          * blocked requests are only added to the list under the flc_lock, and
711          * the flc_lock is always held here. Note that removal from the fl_block
712          * list does not require the flc_lock, so we must recheck list_empty()
713          * after acquiring the blocked_lock_lock.
714          */
715         if (list_empty(&blocker->fl_block))
716                 return;
717 
718         spin_lock(&blocked_lock_lock);
719         while (!list_empty(&blocker->fl_block)) {
720                 struct file_lock *waiter;
721 
722                 waiter = list_first_entry(&blocker->fl_block,
723                                 struct file_lock, fl_block);
724                 __locks_delete_block(waiter);
725                 if (waiter->fl_lmops && waiter->fl_lmops->lm_notify)
726                         waiter->fl_lmops->lm_notify(waiter);
727                 else
728                         wake_up(&waiter->fl_wait);
729         }
730         spin_unlock(&blocked_lock_lock);
731 }
732 
733 static void
734 locks_insert_lock_ctx(struct file_lock *fl, struct list_head *before)
735 {
736         fl->fl_nspid = get_pid(task_tgid(current));
737         list_add_tail(&fl->fl_list, before);
738         locks_insert_global_locks(fl);
739 }
740 
741 static void
742 locks_unlink_lock_ctx(struct file_lock *fl)
743 {
744         locks_delete_global_locks(fl);
745         list_del_init(&fl->fl_list);
746         if (fl->fl_nspid) {
747                 put_pid(fl->fl_nspid);
748                 fl->fl_nspid = NULL;
749         }
750         locks_wake_up_blocks(fl);
751 }
752 
753 static void
754 locks_delete_lock_ctx(struct file_lock *fl, struct list_head *dispose)
755 {
756         locks_unlink_lock_ctx(fl);
757         if (dispose)
758                 list_add(&fl->fl_list, dispose);
759         else
760                 locks_free_lock(fl);
761 }
762 
763 /* Determine if lock sys_fl blocks lock caller_fl. Common functionality
764  * checks for shared/exclusive status of overlapping locks.
765  */
766 static int locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
767 {
768         if (sys_fl->fl_type == F_WRLCK)
769                 return 1;
770         if (caller_fl->fl_type == F_WRLCK)
771                 return 1;
772         return 0;
773 }
774 
775 /* Determine if lock sys_fl blocks lock caller_fl. POSIX specific
776  * checking before calling the locks_conflict().
777  */
778 static int posix_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
779 {
780         /* POSIX locks owned by the same process do not conflict with
781          * each other.
782          */
783         if (posix_same_owner(caller_fl, sys_fl))
784                 return (0);
785 
786         /* Check whether they overlap */
787         if (!locks_overlap(caller_fl, sys_fl))
788                 return 0;
789 
790         return (locks_conflict(caller_fl, sys_fl));
791 }
792 
793 /* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific
794  * checking before calling the locks_conflict().
795  */
796 static int flock_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
797 {
798         /* FLOCK locks referring to the same filp do not conflict with
799          * each other.
800          */
801         if (caller_fl->fl_file == sys_fl->fl_file)
802                 return (0);
803         if ((caller_fl->fl_type & LOCK_MAND) || (sys_fl->fl_type & LOCK_MAND))
804                 return 0;
805 
806         return (locks_conflict(caller_fl, sys_fl));
807 }
808 
809 void
810 posix_test_lock(struct file *filp, struct file_lock *fl)
811 {
812         struct file_lock *cfl;
813         struct file_lock_context *ctx;
814         struct inode *inode = locks_inode(filp);
815 
816         ctx = smp_load_acquire(&inode->i_flctx);
817         if (!ctx || list_empty_careful(&ctx->flc_posix)) {
818                 fl->fl_type = F_UNLCK;
819                 return;
820         }
821 
822         spin_lock(&ctx->flc_lock);
823         list_for_each_entry(cfl, &ctx->flc_posix, fl_list) {
824                 if (posix_locks_conflict(fl, cfl)) {
825                         locks_copy_conflock(fl, cfl);
826                         if (cfl->fl_nspid)
827                                 fl->fl_pid = pid_vnr(cfl->fl_nspid);
828                         goto out;
829                 }
830         }
831         fl->fl_type = F_UNLCK;
832 out:
833         spin_unlock(&ctx->flc_lock);
834         return;
835 }
836 EXPORT_SYMBOL(posix_test_lock);
837 
838 /*
839  * Deadlock detection:
840  *
841  * We attempt to detect deadlocks that are due purely to posix file
842  * locks.
843  *
844  * We assume that a task can be waiting for at most one lock at a time.
845  * So for any acquired lock, the process holding that lock may be
846  * waiting on at most one other lock.  That lock in turns may be held by
847  * someone waiting for at most one other lock.  Given a requested lock
848  * caller_fl which is about to wait for a conflicting lock block_fl, we
849  * follow this chain of waiters to ensure we are not about to create a
850  * cycle.
851  *
852  * Since we do this before we ever put a process to sleep on a lock, we
853  * are ensured that there is never a cycle; that is what guarantees that
854  * the while() loop in posix_locks_deadlock() eventually completes.
855  *
856  * Note: the above assumption may not be true when handling lock
857  * requests from a broken NFS client. It may also fail in the presence
858  * of tasks (such as posix threads) sharing the same open file table.
859  * To handle those cases, we just bail out after a few iterations.
860  *
861  * For FL_OFDLCK locks, the owner is the filp, not the files_struct.
862  * Because the owner is not even nominally tied to a thread of
863  * execution, the deadlock detection below can't reasonably work well. Just
864  * skip it for those.
865  *
866  * In principle, we could do a more limited deadlock detection on FL_OFDLCK
867  * locks that just checks for the case where two tasks are attempting to
868  * upgrade from read to write locks on the same inode.
869  */
870 
871 #define MAX_DEADLK_ITERATIONS 10
872 
873 /* Find a lock that the owner of the given block_fl is blocking on. */
874 static struct file_lock *what_owner_is_waiting_for(struct file_lock *block_fl)
875 {
876         struct file_lock *fl;
877 
878         hash_for_each_possible(blocked_hash, fl, fl_link, posix_owner_key(block_fl)) {
879                 if (posix_same_owner(fl, block_fl))
880                         return fl->fl_next;
881         }
882         return NULL;
883 }
884 
885 /* Must be called with the blocked_lock_lock held! */
886 static int posix_locks_deadlock(struct file_lock *caller_fl,
887                                 struct file_lock *block_fl)
888 {
889         int i = 0;
890 
891         lockdep_assert_held(&blocked_lock_lock);
892 
893         /*
894          * This deadlock detector can't reasonably detect deadlocks with
895          * FL_OFDLCK locks, since they aren't owned by a process, per-se.
896          */
897         if (IS_OFDLCK(caller_fl))
898                 return 0;
899 
900         while ((block_fl = what_owner_is_waiting_for(block_fl))) {
901                 if (i++ > MAX_DEADLK_ITERATIONS)
902                         return 0;
903                 if (posix_same_owner(caller_fl, block_fl))
904                         return 1;
905         }
906         return 0;
907 }
908 
909 /* Try to create a FLOCK lock on filp. We always insert new FLOCK locks
910  * after any leases, but before any posix locks.
911  *
912  * Note that if called with an FL_EXISTS argument, the caller may determine
913  * whether or not a lock was successfully freed by testing the return
914  * value for -ENOENT.
915  */
916 static int flock_lock_inode(struct inode *inode, struct file_lock *request)
917 {
918         struct file_lock *new_fl = NULL;
919         struct file_lock *fl;
920         struct file_lock_context *ctx;
921         int error = 0;
922         bool found = false;
923         LIST_HEAD(dispose);
924 
925         ctx = locks_get_lock_context(inode, request->fl_type);
926         if (!ctx) {
927                 if (request->fl_type != F_UNLCK)
928                         return -ENOMEM;
929                 return (request->fl_flags & FL_EXISTS) ? -ENOENT : 0;
930         }
931 
932         if (!(request->fl_flags & FL_ACCESS) && (request->fl_type != F_UNLCK)) {
933                 new_fl = locks_alloc_lock();
934                 if (!new_fl)
935                         return -ENOMEM;
936         }
937 
938         percpu_down_read_preempt_disable(&file_rwsem);
939         spin_lock(&ctx->flc_lock);
940         if (request->fl_flags & FL_ACCESS)
941                 goto find_conflict;
942 
943         list_for_each_entry(fl, &ctx->flc_flock, fl_list) {
944                 if (request->fl_file != fl->fl_file)
945                         continue;
946                 if (request->fl_type == fl->fl_type)
947                         goto out;
948                 found = true;
949                 locks_delete_lock_ctx(fl, &dispose);
950                 break;
951         }
952 
953         if (request->fl_type == F_UNLCK) {
954                 if ((request->fl_flags & FL_EXISTS) && !found)
955                         error = -ENOENT;
956                 goto out;
957         }
958 
959 find_conflict:
960         list_for_each_entry(fl, &ctx->flc_flock, fl_list) {
961                 if (!flock_locks_conflict(request, fl))
962                         continue;
963                 error = -EAGAIN;
964                 if (!(request->fl_flags & FL_SLEEP))
965                         goto out;
966                 error = FILE_LOCK_DEFERRED;
967                 locks_insert_block(fl, request);
968                 goto out;
969         }
970         if (request->fl_flags & FL_ACCESS)
971                 goto out;
972         locks_copy_lock(new_fl, request);
973         locks_insert_lock_ctx(new_fl, &ctx->flc_flock);
974         new_fl = NULL;
975         error = 0;
976 
977 out:
978         spin_unlock(&ctx->flc_lock);
979         percpu_up_read_preempt_enable(&file_rwsem);
980         if (new_fl)
981                 locks_free_lock(new_fl);
982         locks_dispose_list(&dispose);
983         return error;
984 }
985 
986 static int posix_lock_inode(struct inode *inode, struct file_lock *request,
987                             struct file_lock *conflock)
988 {
989         struct file_lock *fl, *tmp;
990         struct file_lock *new_fl = NULL;
991         struct file_lock *new_fl2 = NULL;
992         struct file_lock *left = NULL;
993         struct file_lock *right = NULL;
994         struct file_lock_context *ctx;
995         int error;
996         bool added = false;
997         LIST_HEAD(dispose);
998 
999         ctx = locks_get_lock_context(inode, request->fl_type);
1000         if (!ctx)
1001                 return (request->fl_type == F_UNLCK) ? 0 : -ENOMEM;
1002 
1003         /*
1004          * We may need two file_lock structures for this operation,
1005          * so we get them in advance to avoid races.
1006          *
1007          * In some cases we can be sure, that no new locks will be needed
1008          */
1009         if (!(request->fl_flags & FL_ACCESS) &&
1010             (request->fl_type != F_UNLCK ||
1011              request->fl_start != 0 || request->fl_end != OFFSET_MAX)) {
1012                 new_fl = locks_alloc_lock();
1013                 new_fl2 = locks_alloc_lock();
1014         }
1015 
1016         percpu_down_read_preempt_disable(&file_rwsem);
1017         spin_lock(&ctx->flc_lock);
1018         /*
1019          * New lock request. Walk all POSIX locks and look for conflicts. If
1020          * there are any, either return error or put the request on the
1021          * blocker's list of waiters and the global blocked_hash.
1022          */
1023         if (request->fl_type != F_UNLCK) {
1024                 list_for_each_entry(fl, &ctx->flc_posix, fl_list) {
1025                         if (!posix_locks_conflict(request, fl))
1026                                 continue;
1027                         if (conflock)
1028                                 locks_copy_conflock(conflock, fl);
1029                         error = -EAGAIN;
1030                         if (!(request->fl_flags & FL_SLEEP))
1031                                 goto out;
1032                         /*
1033                          * Deadlock detection and insertion into the blocked
1034                          * locks list must be done while holding the same lock!
1035                          */
1036                         error = -EDEADLK;
1037                         spin_lock(&blocked_lock_lock);
1038                         if (likely(!posix_locks_deadlock(request, fl))) {
1039                                 error = FILE_LOCK_DEFERRED;
1040                                 __locks_insert_block(fl, request);
1041                         }
1042                         spin_unlock(&blocked_lock_lock);
1043                         goto out;
1044                 }
1045         }
1046 
1047         /* If we're just looking for a conflict, we're done. */
1048         error = 0;
1049         if (request->fl_flags & FL_ACCESS)
1050                 goto out;
1051 
1052         /* Find the first old lock with the same owner as the new lock */
1053         list_for_each_entry(fl, &ctx->flc_posix, fl_list) {
1054                 if (posix_same_owner(request, fl))
1055                         break;
1056         }
1057 
1058         /* Process locks with this owner. */
1059         list_for_each_entry_safe_from(fl, tmp, &ctx->flc_posix, fl_list) {
1060                 if (!posix_same_owner(request, fl))
1061                         break;
1062 
1063                 /* Detect adjacent or overlapping regions (if same lock type) */
1064                 if (request->fl_type == fl->fl_type) {
1065                         /* In all comparisons of start vs end, use
1066                          * "start - 1" rather than "end + 1". If end
1067                          * is OFFSET_MAX, end + 1 will become negative.
1068                          */
1069                         if (fl->fl_end < request->fl_start - 1)
1070                                 continue;
1071                         /* If the next lock in the list has entirely bigger
1072                          * addresses than the new one, insert the lock here.
1073                          */
1074                         if (fl->fl_start - 1 > request->fl_end)
1075                                 break;
1076 
1077                         /* If we come here, the new and old lock are of the
1078                          * same type and adjacent or overlapping. Make one
1079                          * lock yielding from the lower start address of both
1080                          * locks to the higher end address.
1081                          */
1082                         if (fl->fl_start > request->fl_start)
1083                                 fl->fl_start = request->fl_start;
1084                         else
1085                                 request->fl_start = fl->fl_start;
1086                         if (fl->fl_end < request->fl_end)
1087                                 fl->fl_end = request->fl_end;
1088                         else
1089                                 request->fl_end = fl->fl_end;
1090                         if (added) {
1091                                 locks_delete_lock_ctx(fl, &dispose);
1092                                 continue;
1093                         }
1094                         request = fl;
1095                         added = true;
1096                 } else {
1097                         /* Processing for different lock types is a bit
1098                          * more complex.
1099                          */
1100                         if (fl->fl_end < request->fl_start)
1101                                 continue;
1102                         if (fl->fl_start > request->fl_end)
1103                                 break;
1104                         if (request->fl_type == F_UNLCK)
1105                                 added = true;
1106                         if (fl->fl_start < request->fl_start)
1107                                 left = fl;
1108                         /* If the next lock in the list has a higher end
1109                          * address than the new one, insert the new one here.
1110                          */
1111                         if (fl->fl_end > request->fl_end) {
1112                                 right = fl;
1113                                 break;
1114                         }
1115                         if (fl->fl_start >= request->fl_start) {
1116                                 /* The new lock completely replaces an old
1117                                  * one (This may happen several times).
1118                                  */
1119                                 if (added) {
1120                                         locks_delete_lock_ctx(fl, &dispose);
1121                                         continue;
1122                                 }
1123                                 /*
1124                                  * Replace the old lock with new_fl, and
1125                                  * remove the old one. It's safe to do the
1126                                  * insert here since we know that we won't be
1127                                  * using new_fl later, and that the lock is
1128                                  * just replacing an existing lock.
1129                                  */
1130                                 error = -ENOLCK;
1131                                 if (!new_fl)
1132                                         goto out;
1133                                 locks_copy_lock(new_fl, request);
1134                                 request = new_fl;
1135                                 new_fl = NULL;
1136                                 locks_insert_lock_ctx(request, &fl->fl_list);
1137                                 locks_delete_lock_ctx(fl, &dispose);
1138                                 added = true;
1139                         }
1140                 }
1141         }
1142 
1143         /*
1144          * The above code only modifies existing locks in case of merging or
1145          * replacing. If new lock(s) need to be inserted all modifications are
1146          * done below this, so it's safe yet to bail out.
1147          */
1148         error = -ENOLCK; /* "no luck" */
1149         if (right && left == right && !new_fl2)
1150                 goto out;
1151 
1152         error = 0;
1153         if (!added) {
1154                 if (request->fl_type == F_UNLCK) {
1155                         if (request->fl_flags & FL_EXISTS)
1156                                 error = -ENOENT;
1157                         goto out;
1158                 }
1159 
1160                 if (!new_fl) {
1161                         error = -ENOLCK;
1162                         goto out;
1163                 }
1164                 locks_copy_lock(new_fl, request);
1165                 locks_insert_lock_ctx(new_fl, &fl->fl_list);
1166                 fl = new_fl;
1167                 new_fl = NULL;
1168         }
1169         if (right) {
1170                 if (left == right) {
1171                         /* The new lock breaks the old one in two pieces,
1172                          * so we have to use the second new lock.
1173                          */
1174                         left = new_fl2;
1175                         new_fl2 = NULL;
1176                         locks_copy_lock(left, right);
1177                         locks_insert_lock_ctx(left, &fl->fl_list);
1178                 }
1179                 right->fl_start = request->fl_end + 1;
1180                 locks_wake_up_blocks(right);
1181         }
1182         if (left) {
1183                 left->fl_end = request->fl_start - 1;
1184                 locks_wake_up_blocks(left);
1185         }
1186  out:
1187         spin_unlock(&ctx->flc_lock);
1188         percpu_up_read_preempt_enable(&file_rwsem);
1189         /*
1190          * Free any unused locks.
1191          */
1192         if (new_fl)
1193                 locks_free_lock(new_fl);
1194         if (new_fl2)
1195                 locks_free_lock(new_fl2);
1196         locks_dispose_list(&dispose);
1197         trace_posix_lock_inode(inode, request, error);
1198 
1199         return error;
1200 }
1201 
1202 /**
1203  * posix_lock_file - Apply a POSIX-style lock to a file
1204  * @filp: The file to apply the lock to
1205  * @fl: The lock to be applied
1206  * @conflock: Place to return a copy of the conflicting lock, if found.
1207  *
1208  * Add a POSIX style lock to a file.
1209  * We merge adjacent & overlapping locks whenever possible.
1210  * POSIX locks are sorted by owner task, then by starting address
1211  *
1212  * Note that if called with an FL_EXISTS argument, the caller may determine
1213  * whether or not a lock was successfully freed by testing the return
1214  * value for -ENOENT.
1215  */
1216 int posix_lock_file(struct file *filp, struct file_lock *fl,
1217                         struct file_lock *conflock)
1218 {
1219         return posix_lock_inode(locks_inode(filp), fl, conflock);
1220 }
1221 EXPORT_SYMBOL(posix_lock_file);
1222 
1223 /**
1224  * posix_lock_inode_wait - Apply a POSIX-style lock to a file
1225  * @inode: inode of file to which lock request should be applied
1226  * @fl: The lock to be applied
1227  *
1228  * Apply a POSIX style lock request to an inode.
1229  */
1230 static int posix_lock_inode_wait(struct inode *inode, struct file_lock *fl)
1231 {
1232         int error;
1233         might_sleep ();
1234         for (;;) {
1235                 error = posix_lock_inode(inode, fl, NULL);
1236                 if (error != FILE_LOCK_DEFERRED)
1237                         break;
1238                 error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
1239                 if (!error)
1240                         continue;
1241 
1242                 locks_delete_block(fl);
1243                 break;
1244         }
1245         return error;
1246 }
1247 
1248 #ifdef CONFIG_MANDATORY_FILE_LOCKING
1249 /**
1250  * locks_mandatory_locked - Check for an active lock
1251  * @file: the file to check
1252  *
1253  * Searches the inode's list of locks to find any POSIX locks which conflict.
1254  * This function is called from locks_verify_locked() only.
1255  */
1256 int locks_mandatory_locked(struct file *file)
1257 {
1258         int ret;
1259         struct inode *inode = locks_inode(file);
1260         struct file_lock_context *ctx;
1261         struct file_lock *fl;
1262 
1263         ctx = smp_load_acquire(&inode->i_flctx);
1264         if (!ctx || list_empty_careful(&ctx->flc_posix))
1265                 return 0;
1266 
1267         /*
1268          * Search the lock list for this inode for any POSIX locks.
1269          */
1270         spin_lock(&ctx->flc_lock);
1271         ret = 0;
1272         list_for_each_entry(fl, &ctx->flc_posix, fl_list) {
1273                 if (fl->fl_owner != current->files &&
1274                     fl->fl_owner != file) {
1275                         ret = -EAGAIN;
1276                         break;
1277                 }
1278         }
1279         spin_unlock(&ctx->flc_lock);
1280         return ret;
1281 }
1282 
1283 /**
1284  * locks_mandatory_area - Check for a conflicting lock
1285  * @inode:      the file to check
1286  * @filp:       how the file was opened (if it was)
1287  * @start:      first byte in the file to check
1288  * @end:        lastbyte in the file to check
1289  * @type:       %F_WRLCK for a write lock, else %F_RDLCK
1290  *
1291  * Searches the inode's list of locks to find any POSIX locks which conflict.
1292  */
1293 int locks_mandatory_area(struct inode *inode, struct file *filp, loff_t start,
1294                          loff_t end, unsigned char type)
1295 {
1296         struct file_lock fl;
1297         int error;
1298         bool sleep = false;
1299 
1300         locks_init_lock(&fl);
1301         fl.fl_pid = current->tgid;
1302         fl.fl_file = filp;
1303         fl.fl_flags = FL_POSIX | FL_ACCESS;
1304         if (filp && !(filp->f_flags & O_NONBLOCK))
1305                 sleep = true;
1306         fl.fl_type = type;
1307         fl.fl_start = start;
1308         fl.fl_end = end;
1309 
1310         for (;;) {
1311                 if (filp) {
1312                         fl.fl_owner = filp;
1313                         fl.fl_flags &= ~FL_SLEEP;
1314                         error = posix_lock_inode(inode, &fl, NULL);
1315                         if (!error)
1316                                 break;
1317                 }
1318 
1319                 if (sleep)
1320                         fl.fl_flags |= FL_SLEEP;
1321                 fl.fl_owner = current->files;
1322                 error = posix_lock_inode(inode, &fl, NULL);
1323                 if (error != FILE_LOCK_DEFERRED)
1324                         break;
1325                 error = wait_event_interruptible(fl.fl_wait, !fl.fl_next);
1326                 if (!error) {
1327                         /*
1328                          * If we've been sleeping someone might have
1329                          * changed the permissions behind our back.
1330                          */
1331                         if (__mandatory_lock(inode))
1332                                 continue;
1333                 }
1334 
1335                 locks_delete_block(&fl);
1336                 break;
1337         }
1338 
1339         return error;
1340 }
1341 
1342 EXPORT_SYMBOL(locks_mandatory_area);
1343 #endif /* CONFIG_MANDATORY_FILE_LOCKING */
1344 
1345 static void lease_clear_pending(struct file_lock *fl, int arg)
1346 {
1347         switch (arg) {
1348         case F_UNLCK:
1349                 fl->fl_flags &= ~FL_UNLOCK_PENDING;
1350                 /* fall through: */
1351         case F_RDLCK:
1352                 fl->fl_flags &= ~FL_DOWNGRADE_PENDING;
1353         }
1354 }
1355 
1356 /* We already had a lease on this file; just change its type */
1357 int lease_modify(struct file_lock *fl, int arg, struct list_head *dispose)
1358 {
1359         int error = assign_type(fl, arg);
1360 
1361         if (error)
1362                 return error;
1363         lease_clear_pending(fl, arg);
1364         locks_wake_up_blocks(fl);
1365         if (arg == F_UNLCK) {
1366                 struct file *filp = fl->fl_file;
1367 
1368                 f_delown(filp);
1369                 filp->f_owner.signum = 0;
1370                 fasync_helper(0, fl->fl_file, 0, &fl->fl_fasync);
1371                 if (fl->fl_fasync != NULL) {
1372                         printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync);
1373                         fl->fl_fasync = NULL;
1374                 }
1375                 locks_delete_lock_ctx(fl, dispose);
1376         }
1377         return 0;
1378 }
1379 EXPORT_SYMBOL(lease_modify);
1380 
1381 static bool past_time(unsigned long then)
1382 {
1383         if (!then)
1384                 /* 0 is a special value meaning "this never expires": */
1385                 return false;
1386         return time_after(jiffies, then);
1387 }
1388 
1389 static void time_out_leases(struct inode *inode, struct list_head *dispose)
1390 {
1391         struct file_lock_context *ctx = inode->i_flctx;
1392         struct file_lock *fl, *tmp;
1393 
1394         lockdep_assert_held(&ctx->flc_lock);
1395 
1396         list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, fl_list) {
1397                 trace_time_out_leases(inode, fl);
1398                 if (past_time(fl->fl_downgrade_time))
1399                         lease_modify(fl, F_RDLCK, dispose);
1400                 if (past_time(fl->fl_break_time))
1401                         lease_modify(fl, F_UNLCK, dispose);
1402         }
1403 }
1404 
1405 static bool leases_conflict(struct file_lock *lease, struct file_lock *breaker)
1406 {
1407         if ((breaker->fl_flags & FL_LAYOUT) != (lease->fl_flags & FL_LAYOUT))
1408                 return false;
1409         if ((breaker->fl_flags & FL_DELEG) && (lease->fl_flags & FL_LEASE))
1410                 return false;
1411         return locks_conflict(breaker, lease);
1412 }
1413 
1414 static bool
1415 any_leases_conflict(struct inode *inode, struct file_lock *breaker)
1416 {
1417         struct file_lock_context *ctx = inode->i_flctx;
1418         struct file_lock *fl;
1419 
1420         lockdep_assert_held(&ctx->flc_lock);
1421 
1422         list_for_each_entry(fl, &ctx->flc_lease, fl_list) {
1423                 if (leases_conflict(fl, breaker))
1424                         return true;
1425         }
1426         return false;
1427 }
1428 
1429 /**
1430  *      __break_lease   -       revoke all outstanding leases on file
1431  *      @inode: the inode of the file to return
1432  *      @mode: O_RDONLY: break only write leases; O_WRONLY or O_RDWR:
1433  *          break all leases
1434  *      @type: FL_LEASE: break leases and delegations; FL_DELEG: break
1435  *          only delegations
1436  *
1437  *      break_lease (inlined for speed) has checked there already is at least
1438  *      some kind of lock (maybe a lease) on this file.  Leases are broken on
1439  *      a call to open() or truncate().  This function can sleep unless you
1440  *      specified %O_NONBLOCK to your open().
1441  */
1442 int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
1443 {
1444         int error = 0;
1445         struct file_lock_context *ctx;
1446         struct file_lock *new_fl, *fl, *tmp;
1447         unsigned long break_time;
1448         int want_write = (mode & O_ACCMODE) != O_RDONLY;
1449         LIST_HEAD(dispose);
1450 
1451         new_fl = lease_alloc(NULL, want_write ? F_WRLCK : F_RDLCK);
1452         if (IS_ERR(new_fl))
1453                 return PTR_ERR(new_fl);
1454         new_fl->fl_flags = type;
1455 
1456         /* typically we will check that ctx is non-NULL before calling */
1457         ctx = smp_load_acquire(&inode->i_flctx);
1458         if (!ctx) {
1459                 WARN_ON_ONCE(1);
1460                 return error;
1461         }
1462 
1463         percpu_down_read_preempt_disable(&file_rwsem);
1464         spin_lock(&ctx->flc_lock);
1465 
1466         time_out_leases(inode, &dispose);
1467 
1468         if (!any_leases_conflict(inode, new_fl))
1469                 goto out;
1470 
1471         break_time = 0;
1472         if (lease_break_time > 0) {
1473                 break_time = jiffies + lease_break_time * HZ;
1474                 if (break_time == 0)
1475                         break_time++;   /* so that 0 means no break time */
1476         }
1477 
1478         list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, fl_list) {
1479                 if (!leases_conflict(fl, new_fl))
1480                         continue;
1481                 if (want_write) {
1482                         if (fl->fl_flags & FL_UNLOCK_PENDING)
1483                                 continue;
1484                         fl->fl_flags |= FL_UNLOCK_PENDING;
1485                         fl->fl_break_time = break_time;
1486                 } else {
1487                         if (lease_breaking(fl))
1488                                 continue;
1489                         fl->fl_flags |= FL_DOWNGRADE_PENDING;
1490                         fl->fl_downgrade_time = break_time;
1491                 }
1492                 if (fl->fl_lmops->lm_break(fl))
1493                         locks_delete_lock_ctx(fl, &dispose);
1494         }
1495 
1496         if (list_empty(&ctx->flc_lease))
1497                 goto out;
1498 
1499         if (mode & O_NONBLOCK) {
1500                 trace_break_lease_noblock(inode, new_fl);
1501                 error = -EWOULDBLOCK;
1502                 goto out;
1503         }
1504 
1505 restart:
1506         fl = list_first_entry(&ctx->flc_lease, struct file_lock, fl_list);
1507         break_time = fl->fl_break_time;
1508         if (break_time != 0)
1509                 break_time -= jiffies;
1510         if (break_time == 0)
1511                 break_time++;
1512         locks_insert_block(fl, new_fl);
1513         trace_break_lease_block(inode, new_fl);
1514         spin_unlock(&ctx->flc_lock);
1515         percpu_up_read_preempt_enable(&file_rwsem);
1516 
1517         locks_dispose_list(&dispose);
1518         error = wait_event_interruptible_timeout(new_fl->fl_wait,
1519                                                 !new_fl->fl_next, break_time);
1520 
1521         percpu_down_read_preempt_disable(&file_rwsem);
1522         spin_lock(&ctx->flc_lock);
1523         trace_break_lease_unblock(inode, new_fl);
1524         locks_delete_block(new_fl);
1525         if (error >= 0) {
1526                 /*
1527                  * Wait for the next conflicting lease that has not been
1528                  * broken yet
1529                  */
1530                 if (error == 0)
1531                         time_out_leases(inode, &dispose);
1532                 if (any_leases_conflict(inode, new_fl))
1533                         goto restart;
1534                 error = 0;
1535         }
1536 out:
1537         spin_unlock(&ctx->flc_lock);
1538         percpu_up_read_preempt_enable(&file_rwsem);
1539         locks_dispose_list(&dispose);
1540         locks_free_lock(new_fl);
1541         return error;
1542 }
1543 
1544 EXPORT_SYMBOL(__break_lease);
1545 
1546 /**
1547  *      lease_get_mtime - get the last modified time of an inode
1548  *      @inode: the inode
1549  *      @time:  pointer to a timespec which will contain the last modified time
1550  *
1551  * This is to force NFS clients to flush their caches for files with
1552  * exclusive leases.  The justification is that if someone has an
1553  * exclusive lease, then they could be modifying it.
1554  */
1555 void lease_get_mtime(struct inode *inode, struct timespec *time)
1556 {
1557         bool has_lease = false;
1558         struct file_lock_context *ctx;
1559         struct file_lock *fl;
1560 
1561         ctx = smp_load_acquire(&inode->i_flctx);
1562         if (ctx && !list_empty_careful(&ctx->flc_lease)) {
1563                 spin_lock(&ctx->flc_lock);
1564                 fl = list_first_entry_or_null(&ctx->flc_lease,
1565                                               struct file_lock, fl_list);
1566                 if (fl && (fl->fl_type == F_WRLCK))
1567                         has_lease = true;
1568                 spin_unlock(&ctx->flc_lock);
1569         }
1570 
1571         if (has_lease)
1572                 *time = current_time(inode);
1573         else
1574                 *time = inode->i_mtime;
1575 }
1576 
1577 EXPORT_SYMBOL(lease_get_mtime);
1578 
1579 /**
1580  *      fcntl_getlease - Enquire what lease is currently active
1581  *      @filp: the file
1582  *
1583  *      The value returned by this function will be one of
1584  *      (if no lease break is pending):
1585  *
1586  *      %F_RDLCK to indicate a shared lease is held.
1587  *
1588  *      %F_WRLCK to indicate an exclusive lease is held.
1589  *
1590  *      %F_UNLCK to indicate no lease is held.
1591  *
1592  *      (if a lease break is pending):
1593  *
1594  *      %F_RDLCK to indicate an exclusive lease needs to be
1595  *              changed to a shared lease (or removed).
1596  *
1597  *      %F_UNLCK to indicate the lease needs to be removed.
1598  *
1599  *      XXX: sfr & willy disagree over whether F_INPROGRESS
1600  *      should be returned to userspace.
1601  */
1602 int fcntl_getlease(struct file *filp)
1603 {
1604         struct file_lock *fl;
1605         struct inode *inode = locks_inode(filp);
1606         struct file_lock_context *ctx;
1607         int type = F_UNLCK;
1608         LIST_HEAD(dispose);
1609 
1610         ctx = smp_load_acquire(&inode->i_flctx);
1611         if (ctx && !list_empty_careful(&ctx->flc_lease)) {
1612                 percpu_down_read_preempt_disable(&file_rwsem);
1613                 spin_lock(&ctx->flc_lock);
1614                 time_out_leases(inode, &dispose);
1615                 list_for_each_entry(fl, &ctx->flc_lease, fl_list) {
1616                         if (fl->fl_file != filp)
1617                                 continue;
1618                         type = target_leasetype(fl);
1619                         break;
1620                 }
1621                 spin_unlock(&ctx->flc_lock);
1622                 percpu_up_read_preempt_enable(&file_rwsem);
1623 
1624                 locks_dispose_list(&dispose);
1625         }
1626         return type;
1627 }
1628 
1629 /**
1630  * check_conflicting_open - see if the given dentry points to a file that has
1631  *                          an existing open that would conflict with the
1632  *                          desired lease.
1633  * @dentry:     dentry to check
1634  * @arg:        type of lease that we're trying to acquire
1635  * @flags:      current lock flags
1636  *
1637  * Check to see if there's an existing open fd on this file that would
1638  * conflict with the lease we're trying to set.
1639  */
1640 static int
1641 check_conflicting_open(const struct dentry *dentry, const long arg, int flags)
1642 {
1643         int ret = 0;
1644         struct inode *inode = dentry->d_inode;
1645 
1646         if (flags & FL_LAYOUT)
1647                 return 0;
1648 
1649         if ((arg == F_RDLCK) &&
1650             (atomic_read(&d_real_inode(dentry)->i_writecount) > 0))
1651                 return -EAGAIN;
1652 
1653         if ((arg == F_WRLCK) && ((d_count(dentry) > 1) ||
1654             (atomic_read(&inode->i_count) > 1)))
1655                 ret = -EAGAIN;
1656 
1657         return ret;
1658 }
1659 
1660 static int
1661 generic_add_lease(struct file *filp, long arg, struct file_lock **flp, void **priv)
1662 {
1663         struct file_lock *fl, *my_fl = NULL, *lease;
1664         struct dentry *dentry = filp->f_path.dentry;
1665         struct inode *inode = dentry->d_inode;
1666         struct file_lock_context *ctx;
1667         bool is_deleg = (*flp)->fl_flags & FL_DELEG;
1668         int error;
1669         LIST_HEAD(dispose);
1670 
1671         lease = *flp;
1672         trace_generic_add_lease(inode, lease);
1673 
1674         /* Note that arg is never F_UNLCK here */
1675         ctx = locks_get_lock_context(inode, arg);
1676         if (!ctx)
1677                 return -ENOMEM;
1678 
1679         /*
1680          * In the delegation case we need mutual exclusion with
1681          * a number of operations that take the i_mutex.  We trylock
1682          * because delegations are an optional optimization, and if
1683          * there's some chance of a conflict--we'd rather not
1684          * bother, maybe that's a sign this just isn't a good file to
1685          * hand out a delegation on.
1686          */
1687         if (is_deleg && !inode_trylock(inode))
1688                 return -EAGAIN;
1689 
1690         if (is_deleg && arg == F_WRLCK) {
1691                 /* Write delegations are not currently supported: */
1692                 inode_unlock(inode);
1693                 WARN_ON_ONCE(1);
1694                 return -EINVAL;
1695         }
1696 
1697         percpu_down_read_preempt_disable(&file_rwsem);
1698         spin_lock(&ctx->flc_lock);
1699         time_out_leases(inode, &dispose);
1700         error = check_conflicting_open(dentry, arg, lease->fl_flags);
1701         if (error)
1702                 goto out;
1703 
1704         /*
1705          * At this point, we know that if there is an exclusive
1706          * lease on this file, then we hold it on this filp
1707          * (otherwise our open of this file would have blocked).
1708          * And if we are trying to acquire an exclusive lease,
1709          * then the file is not open by anyone (including us)
1710          * except for this filp.
1711          */
1712         error = -EAGAIN;
1713         list_for_each_entry(fl, &ctx->flc_lease, fl_list) {
1714                 if (fl->fl_file == filp &&
1715                     fl->fl_owner == lease->fl_owner) {
1716                         my_fl = fl;
1717                         continue;
1718                 }
1719 
1720                 /*
1721                  * No exclusive leases if someone else has a lease on
1722                  * this file:
1723                  */
1724                 if (arg == F_WRLCK)
1725                         goto out;
1726                 /*
1727                  * Modifying our existing lease is OK, but no getting a
1728                  * new lease if someone else is opening for write:
1729                  */
1730                 if (fl->fl_flags & FL_UNLOCK_PENDING)
1731                         goto out;
1732         }
1733 
1734         if (my_fl != NULL) {
1735                 lease = my_fl;
1736                 error = lease->fl_lmops->lm_change(lease, arg, &dispose);
1737                 if (error)
1738                         goto out;
1739                 goto out_setup;
1740         }
1741 
1742         error = -EINVAL;
1743         if (!leases_enable)
1744                 goto out;
1745 
1746         locks_insert_lock_ctx(lease, &ctx->flc_lease);
1747         /*
1748          * The check in break_lease() is lockless. It's possible for another
1749          * open to race in after we did the earlier check for a conflicting
1750          * open but before the lease was inserted. Check again for a
1751          * conflicting open and cancel the lease if there is one.
1752          *
1753          * We also add a barrier here to ensure that the insertion of the lock
1754          * precedes these checks.
1755          */
1756         smp_mb();
1757         error = check_conflicting_open(dentry, arg, lease->fl_flags);
1758         if (error) {
1759                 locks_unlink_lock_ctx(lease);
1760                 goto out;
1761         }
1762 
1763 out_setup:
1764         if (lease->fl_lmops->lm_setup)
1765                 lease->fl_lmops->lm_setup(lease, priv);
1766 out:
1767         spin_unlock(&ctx->flc_lock);
1768         percpu_up_read_preempt_enable(&file_rwsem);
1769         locks_dispose_list(&dispose);
1770         if (is_deleg)
1771                 inode_unlock(inode);
1772         if (!error && !my_fl)
1773                 *flp = NULL;
1774         return error;
1775 }
1776 
1777 static int generic_delete_lease(struct file *filp, void *owner)
1778 {
1779         int error = -EAGAIN;
1780         struct file_lock *fl, *victim = NULL;
1781         struct inode *inode = locks_inode(filp);
1782         struct file_lock_context *ctx;
1783         LIST_HEAD(dispose);
1784 
1785         ctx = smp_load_acquire(&inode->i_flctx);
1786         if (!ctx) {
1787                 trace_generic_delete_lease(inode, NULL);
1788                 return error;
1789         }
1790 
1791         percpu_down_read_preempt_disable(&file_rwsem);
1792         spin_lock(&ctx->flc_lock);
1793         list_for_each_entry(fl, &ctx->flc_lease, fl_list) {
1794                 if (fl->fl_file == filp &&
1795                     fl->fl_owner == owner) {
1796                         victim = fl;
1797                         break;
1798                 }
1799         }
1800         trace_generic_delete_lease(inode, victim);
1801         if (victim)
1802                 error = fl->fl_lmops->lm_change(victim, F_UNLCK, &dispose);
1803         spin_unlock(&ctx->flc_lock);
1804         percpu_up_read_preempt_enable(&file_rwsem);
1805         locks_dispose_list(&dispose);
1806         return error;
1807 }
1808 
1809 /**
1810  *      generic_setlease        -       sets a lease on an open file
1811  *      @filp:  file pointer
1812  *      @arg:   type of lease to obtain
1813  *      @flp:   input - file_lock to use, output - file_lock inserted
1814  *      @priv:  private data for lm_setup (may be NULL if lm_setup
1815  *              doesn't require it)
1816  *
1817  *      The (input) flp->fl_lmops->lm_break function is required
1818  *      by break_lease().
1819  */
1820 int generic_setlease(struct file *filp, long arg, struct file_lock **flp,
1821                         void **priv)
1822 {
1823         struct inode *inode = locks_inode(filp);
1824         int error;
1825 
1826         if ((!uid_eq(current_fsuid(), inode->i_uid)) && !capable(CAP_LEASE))
1827                 return -EACCES;
1828         if (!S_ISREG(inode->i_mode))
1829                 return -EINVAL;
1830         error = security_file_lock(filp, arg);
1831         if (error)
1832                 return error;
1833 
1834         switch (arg) {
1835         case F_UNLCK:
1836                 return generic_delete_lease(filp, *priv);
1837         case F_RDLCK:
1838         case F_WRLCK:
1839                 if (!(*flp)->fl_lmops->lm_break) {
1840                         WARN_ON_ONCE(1);
1841                         return -ENOLCK;
1842                 }
1843 
1844                 return generic_add_lease(filp, arg, flp, priv);
1845         default:
1846                 return -EINVAL;
1847         }
1848 }
1849 EXPORT_SYMBOL(generic_setlease);
1850 
1851 /**
1852  * vfs_setlease        -       sets a lease on an open file
1853  * @filp:       file pointer
1854  * @arg:        type of lease to obtain
1855  * @lease:      file_lock to use when adding a lease
1856  * @priv:       private info for lm_setup when adding a lease (may be
1857  *              NULL if lm_setup doesn't require it)
1858  *
1859  * Call this to establish a lease on the file. The "lease" argument is not
1860  * used for F_UNLCK requests and may be NULL. For commands that set or alter
1861  * an existing lease, the (*lease)->fl_lmops->lm_break operation must be set;
1862  * if not, this function will return -ENOLCK (and generate a scary-looking
1863  * stack trace).
1864  *
1865  * The "priv" pointer is passed directly to the lm_setup function as-is. It
1866  * may be NULL if the lm_setup operation doesn't require it.
1867  */
1868 int
1869 vfs_setlease(struct file *filp, long arg, struct file_lock **lease, void **priv)
1870 {
1871         if (filp->f_op->setlease && is_remote_lock(filp))
1872                 return filp->f_op->setlease(filp, arg, lease, priv);
1873         else
1874                 return generic_setlease(filp, arg, lease, priv);
1875 }
1876 EXPORT_SYMBOL_GPL(vfs_setlease);
1877 
1878 static int do_fcntl_add_lease(unsigned int fd, struct file *filp, long arg)
1879 {
1880         struct file_lock *fl;
1881         struct fasync_struct *new;
1882         int error;
1883 
1884         fl = lease_alloc(filp, arg);
1885         if (IS_ERR(fl))
1886                 return PTR_ERR(fl);
1887 
1888         new = fasync_alloc();
1889         if (!new) {
1890                 locks_free_lock(fl);
1891                 return -ENOMEM;
1892         }
1893         new->fa_fd = fd;
1894 
1895         error = vfs_setlease(filp, arg, &fl, (void **)&new);
1896         if (fl)
1897                 locks_free_lock(fl);
1898         if (new)
1899                 fasync_free(new);
1900         return error;
1901 }
1902 
1903 /**
1904  *      fcntl_setlease  -       sets a lease on an open file
1905  *      @fd: open file descriptor
1906  *      @filp: file pointer
1907  *      @arg: type of lease to obtain
1908  *
1909  *      Call this fcntl to establish a lease on the file.
1910  *      Note that you also need to call %F_SETSIG to
1911  *      receive a signal when the lease is broken.
1912  */
1913 int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
1914 {
1915         if (arg == F_UNLCK)
1916                 return vfs_setlease(filp, F_UNLCK, NULL, (void **)&filp);
1917         return do_fcntl_add_lease(fd, filp, arg);
1918 }
1919 
1920 /**
1921  * flock_lock_inode_wait - Apply a FLOCK-style lock to a file
1922  * @inode: inode of the file to apply to
1923  * @fl: The lock to be applied
1924  *
1925  * Apply a FLOCK style lock request to an inode.
1926  */
1927 static int flock_lock_inode_wait(struct inode *inode, struct file_lock *fl)
1928 {
1929         int error;
1930         might_sleep();
1931         for (;;) {
1932                 error = flock_lock_inode(inode, fl);
1933                 if (error != FILE_LOCK_DEFERRED)
1934                         break;
1935                 error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
1936                 if (!error)
1937                         continue;
1938 
1939                 locks_delete_block(fl);
1940                 break;
1941         }
1942         return error;
1943 }
1944 
1945 /**
1946  * locks_lock_inode_wait - Apply a lock to an inode
1947  * @inode: inode of the file to apply to
1948  * @fl: The lock to be applied
1949  *
1950  * Apply a POSIX or FLOCK style lock request to an inode.
1951  */
1952 int locks_lock_inode_wait(struct inode *inode, struct file_lock *fl)
1953 {
1954         int res = 0;
1955         switch (fl->fl_flags & (FL_POSIX|FL_FLOCK)) {
1956                 case FL_POSIX:
1957                         res = posix_lock_inode_wait(inode, fl);
1958                         break;
1959                 case FL_FLOCK:
1960                         res = flock_lock_inode_wait(inode, fl);
1961                         break;
1962                 default:
1963                         BUG();
1964         }
1965         return res;
1966 }
1967 EXPORT_SYMBOL(locks_lock_inode_wait);
1968 
1969 /**
1970  *      sys_flock: - flock() system call.
1971  *      @fd: the file descriptor to lock.
1972  *      @cmd: the type of lock to apply.
1973  *
1974  *      Apply a %FL_FLOCK style lock to an open file descriptor.
1975  *      The @cmd can be one of
1976  *
1977  *      %LOCK_SH -- a shared lock.
1978  *
1979  *      %LOCK_EX -- an exclusive lock.
1980  *
1981  *      %LOCK_UN -- remove an existing lock.
1982  *
1983  *      %LOCK_MAND -- a `mandatory' flock.  This exists to emulate Windows Share Modes.
1984  *
1985  *      %LOCK_MAND can be combined with %LOCK_READ or %LOCK_WRITE to allow other
1986  *      processes read and write access respectively.
1987  */
1988 SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd)
1989 {
1990         struct fd f = fdget(fd);
1991         struct file_lock *lock;
1992         int can_sleep, unlock;
1993         int error;
1994 
1995         error = -EBADF;
1996         if (!f.file)
1997                 goto out;
1998 
1999         can_sleep = !(cmd & LOCK_NB);
2000         cmd &= ~LOCK_NB;
2001         unlock = (cmd == LOCK_UN);
2002 
2003         if (!unlock && !(cmd & LOCK_MAND) &&
2004             !(f.file->f_mode & (FMODE_READ|FMODE_WRITE)))
2005                 goto out_putf;
2006 
2007         lock = flock_make_lock(f.file, cmd);
2008         if (IS_ERR(lock)) {
2009                 error = PTR_ERR(lock);
2010                 goto out_putf;
2011         }
2012 
2013         if (can_sleep)
2014                 lock->fl_flags |= FL_SLEEP;
2015 
2016         error = security_file_lock(f.file, lock->fl_type);
2017         if (error)
2018                 goto out_free;
2019 
2020         if (f.file->f_op->flock && is_remote_lock(f.file))
2021                 error = f.file->f_op->flock(f.file,
2022                                           (can_sleep) ? F_SETLKW : F_SETLK,
2023                                           lock);
2024         else
2025                 error = locks_lock_file_wait(f.file, lock);
2026 
2027  out_free:
2028         locks_free_lock(lock);
2029 
2030  out_putf:
2031         fdput(f);
2032  out:
2033         return error;
2034 }
2035 
2036 /**
2037  * vfs_test_lock - test file byte range lock
2038  * @filp: The file to test lock for
2039  * @fl: The lock to test; also used to hold result
2040  *
2041  * Returns -ERRNO on failure.  Indicates presence of conflicting lock by
2042  * setting conf->fl_type to something other than F_UNLCK.
2043  */
2044 int vfs_test_lock(struct file *filp, struct file_lock *fl)
2045 {
2046         if (filp->f_op->lock && is_remote_lock(filp))
2047                 return filp->f_op->lock(filp, F_GETLK, fl);
2048         posix_test_lock(filp, fl);
2049         return 0;
2050 }
2051 EXPORT_SYMBOL_GPL(vfs_test_lock);
2052 
2053 static int posix_lock_to_flock(struct flock *flock, struct file_lock *fl)
2054 {
2055         flock->l_pid = IS_OFDLCK(fl) ? -1 : fl->fl_pid;
2056 #if BITS_PER_LONG == 32
2057         /*
2058          * Make sure we can represent the posix lock via
2059          * legacy 32bit flock.
2060          */
2061         if (fl->fl_start > OFFT_OFFSET_MAX)
2062                 return -EOVERFLOW;
2063         if (fl->fl_end != OFFSET_MAX && fl->fl_end > OFFT_OFFSET_MAX)
2064                 return -EOVERFLOW;
2065 #endif
2066         flock->l_start = fl->fl_start;
2067         flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
2068                 fl->fl_end - fl->fl_start + 1;
2069         flock->l_whence = 0;
2070         flock->l_type = fl->fl_type;
2071         return 0;
2072 }
2073 
2074 #if BITS_PER_LONG == 32
2075 static void posix_lock_to_flock64(struct flock64 *flock, struct file_lock *fl)
2076 {
2077         flock->l_pid = IS_OFDLCK(fl) ? -1 : fl->fl_pid;
2078         flock->l_start = fl->fl_start;
2079         flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
2080                 fl->fl_end - fl->fl_start + 1;
2081         flock->l_whence = 0;
2082         flock->l_type = fl->fl_type;
2083 }
2084 #endif
2085 
2086 /* Report the first existing lock that would conflict with l.
2087  * This implements the F_GETLK command of fcntl().
2088  */
2089 int fcntl_getlk(struct file *filp, unsigned int cmd, struct flock __user *l)
2090 {
2091         struct file_lock file_lock;
2092         struct flock flock;
2093         int error;
2094 
2095         error = -EFAULT;
2096         if (copy_from_user(&flock, l, sizeof(flock)))
2097                 goto out;
2098         error = -EINVAL;
2099         if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
2100                 goto out;
2101 
2102         error = flock_to_posix_lock(filp, &file_lock, &flock);
2103         if (error)
2104                 goto out;
2105 
2106         if (cmd == F_OFD_GETLK) {
2107                 error = -EINVAL;
2108                 if (flock.l_pid != 0)
2109                         goto out;
2110 
2111                 cmd = F_GETLK;
2112                 file_lock.fl_flags |= FL_OFDLCK;
2113                 file_lock.fl_owner = filp;
2114         }
2115 
2116         error = vfs_test_lock(filp, &file_lock);
2117         if (error)
2118                 goto out;
2119  
2120         flock.l_type = file_lock.fl_type;
2121         if (file_lock.fl_type != F_UNLCK) {
2122                 error = posix_lock_to_flock(&flock, &file_lock);
2123                 if (error)
2124                         goto rel_priv;
2125         }
2126         error = -EFAULT;
2127         if (!copy_to_user(l, &flock, sizeof(flock)))
2128                 error = 0;
2129 rel_priv:
2130         locks_release_private(&file_lock);
2131 out:
2132         return error;
2133 }
2134 
2135 /**
2136  * vfs_lock_file - file byte range lock
2137  * @filp: The file to apply the lock to
2138  * @cmd: type of locking operation (F_SETLK, F_GETLK, etc.)
2139  * @fl: The lock to be applied
2140  * @conf: Place to return a copy of the conflicting lock, if found.
2141  *
2142  * A caller that doesn't care about the conflicting lock may pass NULL
2143  * as the final argument.
2144  *
2145  * If the filesystem defines a private ->lock() method, then @conf will
2146  * be left unchanged; so a caller that cares should initialize it to
2147  * some acceptable default.
2148  *
2149  * To avoid blocking kernel daemons, such as lockd, that need to acquire POSIX
2150  * locks, the ->lock() interface may return asynchronously, before the lock has
2151  * been granted or denied by the underlying filesystem, if (and only if)
2152  * lm_grant is set. Callers expecting ->lock() to return asynchronously
2153  * will only use F_SETLK, not F_SETLKW; they will set FL_SLEEP if (and only if)
2154  * the request is for a blocking lock. When ->lock() does return asynchronously,
2155  * it must return FILE_LOCK_DEFERRED, and call ->lm_grant() when the lock
2156  * request completes.
2157  * If the request is for non-blocking lock the file system should return
2158  * FILE_LOCK_DEFERRED then try to get the lock and call the callback routine
2159  * with the result. If the request timed out the callback routine will return a
2160  * nonzero return code and the file system should release the lock. The file
2161  * system is also responsible to keep a corresponding posix lock when it
2162  * grants a lock so the VFS can find out which locks are locally held and do
2163  * the correct lock cleanup when required.
2164  * The underlying filesystem must not drop the kernel lock or call
2165  * ->lm_grant() before returning to the caller with a FILE_LOCK_DEFERRED
2166  * return code.
2167  */
2168 int vfs_lock_file(struct file *filp, unsigned int cmd, struct file_lock *fl, struct file_lock *conf)
2169 {
2170         if (filp->f_op->lock && is_remote_lock(filp))
2171                 return filp->f_op->lock(filp, cmd, fl);
2172         else
2173                 return posix_lock_file(filp, fl, conf);
2174 }
2175 EXPORT_SYMBOL_GPL(vfs_lock_file);
2176 
2177 static int do_lock_file_wait(struct file *filp, unsigned int cmd,
2178                              struct file_lock *fl)
2179 {
2180         int error;
2181 
2182         error = security_file_lock(filp, fl->fl_type);
2183         if (error)
2184                 return error;
2185 
2186         for (;;) {
2187                 error = vfs_lock_file(filp, cmd, fl, NULL);
2188                 if (error != FILE_LOCK_DEFERRED)
2189                         break;
2190                 error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
2191                 if (!error)
2192                         continue;
2193 
2194                 locks_delete_block(fl);
2195                 break;
2196         }
2197 
2198         return error;
2199 }
2200 
2201 /* Ensure that fl->fl_file has compatible f_mode for F_SETLK calls */
2202 static int
2203 check_fmode_for_setlk(struct file_lock *fl)
2204 {
2205         switch (fl->fl_type) {
2206         case F_RDLCK:
2207                 if (!(fl->fl_file->f_mode & FMODE_READ))
2208                         return -EBADF;
2209                 break;
2210         case F_WRLCK:
2211                 if (!(fl->fl_file->f_mode & FMODE_WRITE))
2212                         return -EBADF;
2213         }
2214         return 0;
2215 }
2216 
2217 /* Apply the lock described by l to an open file descriptor.
2218  * This implements both the F_SETLK and F_SETLKW commands of fcntl().
2219  */
2220 int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
2221                 struct flock __user *l)
2222 {
2223         struct file_lock *file_lock = locks_alloc_lock();
2224         struct flock flock;
2225         struct inode *inode;
2226         struct file *f;
2227         int error;
2228 
2229         if (file_lock == NULL)
2230                 return -ENOLCK;
2231 
2232         inode = locks_inode(filp);
2233 
2234         /*
2235          * This might block, so we do it before checking the inode.
2236          */
2237         error = -EFAULT;
2238         if (copy_from_user(&flock, l, sizeof(flock)))
2239                 goto out;
2240 
2241         /* Don't allow mandatory locks on files that may be memory mapped
2242          * and shared.
2243          */
2244         if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) {
2245                 error = -EAGAIN;
2246                 goto out;
2247         }
2248 
2249         error = flock_to_posix_lock(filp, file_lock, &flock);
2250         if (error)
2251                 goto out;
2252 
2253         error = check_fmode_for_setlk(file_lock);
2254         if (error)
2255                 goto out;
2256 
2257         /*
2258          * If the cmd is requesting file-private locks, then set the
2259          * FL_OFDLCK flag and override the owner.
2260          */
2261         switch (cmd) {
2262         case F_OFD_SETLK:
2263                 error = -EINVAL;
2264                 if (flock.l_pid != 0)
2265                         goto out;
2266 
2267                 cmd = F_SETLK;
2268                 file_lock->fl_flags |= FL_OFDLCK;
2269                 file_lock->fl_owner = filp;
2270                 break;
2271         case F_OFD_SETLKW:
2272                 error = -EINVAL;
2273                 if (flock.l_pid != 0)
2274                         goto out;
2275 
2276                 cmd = F_SETLKW;
2277                 file_lock->fl_flags |= FL_OFDLCK;
2278                 file_lock->fl_owner = filp;
2279                 /* Fallthrough */
2280         case F_SETLKW:
2281                 file_lock->fl_flags |= FL_SLEEP;
2282         }
2283 
2284         error = do_lock_file_wait(filp, cmd, file_lock);
2285 
2286         /*
2287          * Attempt to detect a close/fcntl race and recover by releasing the
2288          * lock that was just acquired. There is no need to do that when we're
2289          * unlocking though, or for OFD locks.
2290          */
2291         if (!error && file_lock->fl_type != F_UNLCK &&
2292             !(file_lock->fl_flags & FL_OFDLCK)) {
2293                 /*
2294                  * We need that spin_lock here - it prevents reordering between
2295                  * update of i_flctx->flc_posix and check for it done in
2296                  * close(). rcu_read_lock() wouldn't do.
2297                  */
2298                 spin_lock(&current->files->file_lock);
2299                 f = fcheck(fd);
2300                 spin_unlock(&current->files->file_lock);
2301                 if (f != filp) {
2302                         file_lock->fl_type = F_UNLCK;
2303                         error = do_lock_file_wait(filp, cmd, file_lock);
2304                         WARN_ON_ONCE(error);
2305                         error = -EBADF;
2306                 }
2307         }
2308 out:
2309         trace_fcntl_setlk(inode, file_lock, error);
2310         locks_free_lock(file_lock);
2311         return error;
2312 }
2313 
2314 #if BITS_PER_LONG == 32
2315 /* Report the first existing lock that would conflict with l.
2316  * This implements the F_GETLK command of fcntl().
2317  */
2318 int fcntl_getlk64(struct file *filp, unsigned int cmd, struct flock64 __user *l)
2319 {
2320         struct file_lock file_lock;
2321         struct flock64 flock;
2322         int error;
2323 
2324         error = -EFAULT;
2325         if (copy_from_user(&flock, l, sizeof(flock)))
2326                 goto out;
2327         error = -EINVAL;
2328         if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
2329                 goto out;
2330 
2331         error = flock64_to_posix_lock(filp, &file_lock, &flock);
2332         if (error)
2333                 goto out;
2334 
2335         if (cmd == F_OFD_GETLK) {
2336                 error = -EINVAL;
2337                 if (flock.l_pid != 0)
2338                         goto out;
2339 
2340                 cmd = F_GETLK64;
2341                 file_lock.fl_flags |= FL_OFDLCK;
2342                 file_lock.fl_owner = filp;
2343         }
2344 
2345         error = vfs_test_lock(filp, &file_lock);
2346         if (error)
2347                 goto out;
2348 
2349         flock.l_type = file_lock.fl_type;
2350         if (file_lock.fl_type != F_UNLCK)
2351                 posix_lock_to_flock64(&flock, &file_lock);
2352 
2353         error = -EFAULT;
2354         if (!copy_to_user(l, &flock, sizeof(flock)))
2355                 error = 0;
2356 
2357         locks_release_private(&file_lock);
2358 out:
2359         return error;
2360 }
2361 
2362 /* Apply the lock described by l to an open file descriptor.
2363  * This implements both the F_SETLK and F_SETLKW commands of fcntl().
2364  */
2365 int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
2366                 struct flock64 __user *l)
2367 {
2368         struct file_lock *file_lock = locks_alloc_lock();
2369         struct flock64 flock;
2370         struct inode *inode;
2371         struct file *f;
2372         int error;
2373 
2374         if (file_lock == NULL)
2375                 return -ENOLCK;
2376 
2377         /*
2378          * This might block, so we do it before checking the inode.
2379          */
2380         error = -EFAULT;
2381         if (copy_from_user(&flock, l, sizeof(flock)))
2382                 goto out;
2383 
2384         inode = locks_inode(filp);
2385 
2386         /* Don't allow mandatory locks on files that may be memory mapped
2387          * and shared.
2388          */
2389         if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) {
2390                 error = -EAGAIN;
2391                 goto out;
2392         }
2393 
2394         error = flock64_to_posix_lock(filp, file_lock, &flock);
2395         if (error)
2396                 goto out;
2397 
2398         error = check_fmode_for_setlk(file_lock);
2399         if (error)
2400                 goto out;
2401 
2402         /*
2403          * If the cmd is requesting file-private locks, then set the
2404          * FL_OFDLCK flag and override the owner.
2405          */
2406         switch (cmd) {
2407         case F_OFD_SETLK:
2408                 error = -EINVAL;
2409                 if (flock.l_pid != 0)
2410                         goto out;
2411 
2412                 cmd = F_SETLK64;
2413                 file_lock->fl_flags |= FL_OFDLCK;
2414                 file_lock->fl_owner = filp;
2415                 break;
2416         case F_OFD_SETLKW:
2417                 error = -EINVAL;
2418                 if (flock.l_pid != 0)
2419                         goto out;
2420 
2421                 cmd = F_SETLKW64;
2422                 file_lock->fl_flags |= FL_OFDLCK;
2423                 file_lock->fl_owner = filp;
2424                 /* Fallthrough */
2425         case F_SETLKW64:
2426                 file_lock->fl_flags |= FL_SLEEP;
2427         }
2428 
2429         error = do_lock_file_wait(filp, cmd, file_lock);
2430 
2431         /*
2432          * Attempt to detect a close/fcntl race and recover by releasing the
2433          * lock that was just acquired. There is no need to do that when we're
2434          * unlocking though, or for OFD locks.
2435          */
2436         if (!error && file_lock->fl_type != F_UNLCK &&
2437             !(file_lock->fl_flags & FL_OFDLCK)) {
2438                 /*
2439                  * We need that spin_lock here - it prevents reordering between
2440                  * update of i_flctx->flc_posix and check for it done in
2441                  * close(). rcu_read_lock() wouldn't do.
2442                  */
2443                 spin_lock(&current->files->file_lock);
2444                 f = fcheck(fd);
2445                 spin_unlock(&current->files->file_lock);
2446                 if (f != filp) {
2447                         file_lock->fl_type = F_UNLCK;
2448                         error = do_lock_file_wait(filp, cmd, file_lock);
2449                         WARN_ON_ONCE(error);
2450                         error = -EBADF;
2451                 }
2452         }
2453 out:
2454         locks_free_lock(file_lock);
2455         return error;
2456 }
2457 #endif /* BITS_PER_LONG == 32 */
2458 
2459 /*
2460  * This function is called when the file is being removed
2461  * from the task's fd array.  POSIX locks belonging to this task
2462  * are deleted at this time.
2463  */
2464 void locks_remove_posix(struct file *filp, fl_owner_t owner)
2465 {
2466         int error;
2467         struct inode *inode = locks_inode(filp);
2468         struct file_lock lock;
2469         struct file_lock_context *ctx;
2470 
2471         /*
2472          * If there are no locks held on this file, we don't need to call
2473          * posix_lock_file().  Another process could be setting a lock on this
2474          * file at the same time, but we wouldn't remove that lock anyway.
2475          */
2476         ctx =  smp_load_acquire(&inode->i_flctx);
2477         if (!ctx || list_empty(&ctx->flc_posix))
2478                 return;
2479 
2480         lock.fl_type = F_UNLCK;
2481         lock.fl_flags = FL_POSIX | FL_CLOSE;
2482         lock.fl_start = 0;
2483         lock.fl_end = OFFSET_MAX;
2484         lock.fl_owner = owner;
2485         lock.fl_pid = current->tgid;
2486         lock.fl_file = filp;
2487         lock.fl_ops = NULL;
2488         lock.fl_lmops = NULL;
2489 
2490         error = vfs_lock_file(filp, F_SETLK, &lock, NULL);
2491 
2492         if (lock.fl_ops && lock.fl_ops->fl_release_private)
2493                 lock.fl_ops->fl_release_private(&lock);
2494         trace_locks_remove_posix(inode, &lock, error);
2495 }
2496 
2497 EXPORT_SYMBOL(locks_remove_posix);
2498 
2499 /* The i_flctx must be valid when calling into here */
2500 static void
2501 locks_remove_flock(struct file *filp, struct file_lock_context *flctx)
2502 {
2503         struct file_lock fl = {
2504                 .fl_owner = filp,
2505                 .fl_pid = current->tgid,
2506                 .fl_file = filp,
2507                 .fl_flags = FL_FLOCK,
2508                 .fl_type = F_UNLCK,
2509                 .fl_end = OFFSET_MAX,
2510         };
2511         struct inode *inode = locks_inode(filp);
2512 
2513         if (list_empty(&flctx->flc_flock))
2514                 return;
2515 
2516         if (filp->f_op->flock && is_remote_lock(filp))
2517                 filp->f_op->flock(filp, F_SETLKW, &fl);
2518         else
2519                 flock_lock_inode(inode, &fl);
2520 
2521         if (fl.fl_ops && fl.fl_ops->fl_release_private)
2522                 fl.fl_ops->fl_release_private(&fl);
2523 }
2524 
2525 /* The i_flctx must be valid when calling into here */
2526 static void
2527 locks_remove_lease(struct file *filp, struct file_lock_context *ctx)
2528 {
2529         struct file_lock *fl, *tmp;
2530         LIST_HEAD(dispose);
2531 
2532         if (list_empty(&ctx->flc_lease))
2533                 return;
2534 
2535         percpu_down_read_preempt_disable(&file_rwsem);
2536         spin_lock(&ctx->flc_lock);
2537         list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, fl_list)
2538                 if (filp == fl->fl_file)
2539                         lease_modify(fl, F_UNLCK, &dispose);
2540         spin_unlock(&ctx->flc_lock);
2541         percpu_up_read_preempt_enable(&file_rwsem);
2542 
2543         locks_dispose_list(&dispose);
2544 }
2545 
2546 /*
2547  * This function is called on the last close of an open file.
2548  */
2549 void locks_remove_file(struct file *filp)
2550 {
2551         struct file_lock_context *ctx;
2552 
2553         ctx = smp_load_acquire(&locks_inode(filp)->i_flctx);
2554         if (!ctx)
2555                 return;
2556 
2557         /* remove any OFD locks */
2558         locks_remove_posix(filp, filp);
2559 
2560         /* remove flock locks */
2561         locks_remove_flock(filp, ctx);
2562 
2563         /* remove any leases */
2564         locks_remove_lease(filp, ctx);
2565 }
2566 
2567 /**
2568  *      posix_unblock_lock - stop waiting for a file lock
2569  *      @waiter: the lock which was waiting
2570  *
2571  *      lockd needs to block waiting for locks.
2572  */
2573 int
2574 posix_unblock_lock(struct file_lock *waiter)
2575 {
2576         int status = 0;
2577 
2578         spin_lock(&blocked_lock_lock);
2579         if (waiter->fl_next)
2580                 __locks_delete_block(waiter);
2581         else
2582                 status = -ENOENT;
2583         spin_unlock(&blocked_lock_lock);
2584         return status;
2585 }
2586 EXPORT_SYMBOL(posix_unblock_lock);
2587 
2588 /**
2589  * vfs_cancel_lock - file byte range unblock lock
2590  * @filp: The file to apply the unblock to
2591  * @fl: The lock to be unblocked
2592  *
2593  * Used by lock managers to cancel blocked requests
2594  */
2595 int vfs_cancel_lock(struct file *filp, struct file_lock *fl)
2596 {
2597         if (filp->f_op->lock && is_remote_lock(filp))
2598                 return filp->f_op->lock(filp, F_CANCELLK, fl);
2599         return 0;
2600 }
2601 
2602 EXPORT_SYMBOL_GPL(vfs_cancel_lock);
2603 
2604 #ifdef CONFIG_PROC_FS
2605 #include <linux/proc_fs.h>
2606 #include <linux/seq_file.h>
2607 
2608 struct locks_iterator {
2609         int     li_cpu;
2610         loff_t  li_pos;
2611 };
2612 
2613 static void lock_get_status(struct seq_file *f, struct file_lock *fl,
2614                             loff_t id, char *pfx)
2615 {
2616         struct inode *inode = NULL;
2617         unsigned int fl_pid;
2618 
2619         if (fl->fl_nspid) {
2620                 struct pid_namespace *proc_pidns = file_inode(f->file)->i_sb->s_fs_info;
2621 
2622                 /* Don't let fl_pid change based on who is reading the file */
2623                 fl_pid = pid_nr_ns(fl->fl_nspid, proc_pidns);
2624 
2625                 /*
2626                  * If there isn't a fl_pid don't display who is waiting on
2627                  * the lock if we are called from locks_show, or if we are
2628                  * called from __show_fd_info - skip lock entirely
2629                  */
2630                 if (fl_pid == 0)
2631                         return;
2632         } else
2633                 fl_pid = fl->fl_pid;
2634 
2635         if (fl->fl_file != NULL)
2636                 inode = locks_inode(fl->fl_file);
2637 
2638         seq_printf(f, "%lld:%s ", id, pfx);
2639         if (IS_POSIX(fl)) {
2640                 if (fl->fl_flags & FL_ACCESS)
2641                         seq_puts(f, "ACCESS");
2642                 else if (IS_OFDLCK(fl))
2643                         seq_puts(f, "OFDLCK");
2644                 else
2645                         seq_puts(f, "POSIX ");
2646 
2647                 seq_printf(f, " %s ",
2648                              (inode == NULL) ? "*NOINODE*" :
2649                              mandatory_lock(inode) ? "MANDATORY" : "ADVISORY ");
2650         } else if (IS_FLOCK(fl)) {
2651                 if (fl->fl_type & LOCK_MAND) {
2652                         seq_puts(f, "FLOCK  MSNFS     ");
2653                 } else {
2654                         seq_puts(f, "FLOCK  ADVISORY  ");
2655                 }
2656         } else if (IS_LEASE(fl)) {
2657                 if (fl->fl_flags & FL_DELEG)
2658                         seq_puts(f, "DELEG  ");
2659                 else
2660                         seq_puts(f, "LEASE  ");
2661 
2662                 if (lease_breaking(fl))
2663                         seq_puts(f, "BREAKING  ");
2664                 else if (fl->fl_file)
2665                         seq_puts(f, "ACTIVE    ");
2666                 else
2667                         seq_puts(f, "BREAKER   ");
2668         } else {
2669                 seq_puts(f, "UNKNOWN UNKNOWN  ");
2670         }
2671         if (fl->fl_type & LOCK_MAND) {
2672                 seq_printf(f, "%s ",
2673                                (fl->fl_type & LOCK_READ)
2674                                ? (fl->fl_type & LOCK_WRITE) ? "RW   " : "READ "
2675                                : (fl->fl_type & LOCK_WRITE) ? "WRITE" : "NONE ");
2676         } else {
2677                 seq_printf(f, "%s ",
2678                                (lease_breaking(fl))
2679                                ? (fl->fl_type == F_UNLCK) ? "UNLCK" : "READ "
2680                                : (fl->fl_type == F_WRLCK) ? "WRITE" : "READ ");
2681         }
2682         if (inode) {
2683                 /* userspace relies on this representation of dev_t */
2684                 seq_printf(f, "%d %02x:%02x:%ld ", fl_pid,
2685                                 MAJOR(inode->i_sb->s_dev),
2686                                 MINOR(inode->i_sb->s_dev), inode->i_ino);
2687         } else {
2688                 seq_printf(f, "%d <none>:0 ", fl_pid);
2689         }
2690         if (IS_POSIX(fl)) {
2691                 if (fl->fl_end == OFFSET_MAX)
2692                         seq_printf(f, "%Ld EOF\n", fl->fl_start);
2693                 else
2694                         seq_printf(f, "%Ld %Ld\n", fl->fl_start, fl->fl_end);
2695         } else {
2696                 seq_puts(f, "0 EOF\n");
2697         }
2698 }
2699 
2700 static int locks_show(struct seq_file *f, void *v)
2701 {
2702         struct locks_iterator *iter = f->private;
2703         struct file_lock *fl, *bfl;
2704         struct pid_namespace *proc_pidns = file_inode(f->file)->i_sb->s_fs_info;
2705 
2706         fl = hlist_entry(v, struct file_lock, fl_link);
2707 
2708         if (fl->fl_nspid && !pid_nr_ns(fl->fl_nspid, proc_pidns))
2709                 return 0;
2710 
2711         lock_get_status(f, fl, iter->li_pos, "");
2712 
2713         list_for_each_entry(bfl, &fl->fl_block, fl_block)
2714                 lock_get_status(f, bfl, iter->li_pos, " ->");
2715 
2716         return 0;
2717 }
2718 
2719 static void __show_fd_locks(struct seq_file *f,
2720                         struct list_head *head, int *id,
2721                         struct file *filp, struct files_struct *files)
2722 {
2723         struct file_lock *fl;
2724 
2725         list_for_each_entry(fl, head, fl_list) {
2726 
2727                 if (filp != fl->fl_file)
2728                         continue;
2729                 if (fl->fl_owner != files &&
2730                     fl->fl_owner != filp)
2731                         continue;
2732 
2733                 (*id)++;
2734                 seq_puts(f, "lock:\t");
2735                 lock_get_status(f, fl, *id, "");
2736         }
2737 }
2738 
2739 void show_fd_locks(struct seq_file *f,
2740                   struct file *filp, struct files_struct *files)
2741 {
2742         struct inode *inode = locks_inode(filp);
2743         struct file_lock_context *ctx;
2744         int id = 0;
2745 
2746         ctx = smp_load_acquire(&inode->i_flctx);
2747         if (!ctx)
2748                 return;
2749 
2750         spin_lock(&ctx->flc_lock);
2751         __show_fd_locks(f, &ctx->flc_flock, &id, filp, files);
2752         __show_fd_locks(f, &ctx->flc_posix, &id, filp, files);
2753         __show_fd_locks(f, &ctx->flc_lease, &id, filp, files);
2754         spin_unlock(&ctx->flc_lock);
2755 }
2756 
2757 static void *locks_start(struct seq_file *f, loff_t *pos)
2758         __acquires(&blocked_lock_lock)
2759 {
2760         struct locks_iterator *iter = f->private;
2761 
2762         iter->li_pos = *pos + 1;
2763         percpu_down_write(&file_rwsem);
2764         spin_lock(&blocked_lock_lock);
2765         return seq_hlist_start_percpu(&file_lock_list.hlist, &iter->li_cpu, *pos);
2766 }
2767 
2768 static void *locks_next(struct seq_file *f, void *v, loff_t *pos)
2769 {
2770         struct locks_iterator *iter = f->private;
2771 
2772         ++iter->li_pos;
2773         return seq_hlist_next_percpu(v, &file_lock_list.hlist, &iter->li_cpu, pos);
2774 }
2775 
2776 static void locks_stop(struct seq_file *f, void *v)
2777         __releases(&blocked_lock_lock)
2778 {
2779         spin_unlock(&blocked_lock_lock);
2780         percpu_up_write(&file_rwsem);
2781 }
2782 
2783 static const struct seq_operations locks_seq_operations = {
2784         .start  = locks_start,
2785         .next   = locks_next,
2786         .stop   = locks_stop,
2787         .show   = locks_show,
2788 };
2789 
2790 static int locks_open(struct inode *inode, struct file *filp)
2791 {
2792         return seq_open_private(filp, &locks_seq_operations,
2793                                         sizeof(struct locks_iterator));
2794 }
2795 
2796 static const struct file_operations proc_locks_operations = {
2797         .open           = locks_open,
2798         .read           = seq_read,
2799         .llseek         = seq_lseek,
2800         .release        = seq_release_private,
2801 };
2802 
2803 static int __init proc_locks_init(void)
2804 {
2805         proc_create("locks", 0, NULL, &proc_locks_operations);
2806         return 0;
2807 }
2808 fs_initcall(proc_locks_init);
2809 #endif
2810 
2811 static int __init filelock_init(void)
2812 {
2813         int i;
2814 
2815         flctx_cache = kmem_cache_create("file_lock_ctx",
2816                         sizeof(struct file_lock_context), 0, SLAB_PANIC, NULL);
2817 
2818         filelock_cache = kmem_cache_create("file_lock_cache",
2819                         sizeof(struct file_lock), 0, SLAB_PANIC, NULL);
2820 
2821 
2822         for_each_possible_cpu(i) {
2823                 struct file_lock_list_struct *fll = per_cpu_ptr(&file_lock_list, i);
2824 
2825                 spin_lock_init(&fll->lock);
2826                 INIT_HLIST_HEAD(&fll->hlist);
2827         }
2828 
2829         return 0;
2830 }
2831 
2832 core_initcall(filelock_init);
2833 

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