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Linux/fs/locks.c

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  1 #define MSNFS   /* HACK HACK */
  2 /*
  3  *  linux/fs/locks.c
  4  *
  5  *  Provide support for fcntl()'s F_GETLK, F_SETLK, and F_SETLKW calls.
  6  *  Doug Evans (dje@spiff.uucp), August 07, 1992
  7  *
  8  *  Deadlock detection added.
  9  *  FIXME: one thing isn't handled yet:
 10  *      - mandatory locks (requires lots of changes elsewhere)
 11  *  Kelly Carmichael (kelly@[142.24.8.65]), September 17, 1994.
 12  *
 13  *  Miscellaneous edits, and a total rewrite of posix_lock_file() code.
 14  *  Kai Petzke (wpp@marie.physik.tu-berlin.de), 1994
 15  *  
 16  *  Converted file_lock_table to a linked list from an array, which eliminates
 17  *  the limits on how many active file locks are open.
 18  *  Chad Page (pageone@netcom.com), November 27, 1994
 19  * 
 20  *  Removed dependency on file descriptors. dup()'ed file descriptors now
 21  *  get the same locks as the original file descriptors, and a close() on
 22  *  any file descriptor removes ALL the locks on the file for the current
 23  *  process. Since locks still depend on the process id, locks are inherited
 24  *  after an exec() but not after a fork(). This agrees with POSIX, and both
 25  *  BSD and SVR4 practice.
 26  *  Andy Walker (andy@lysaker.kvaerner.no), February 14, 1995
 27  *
 28  *  Scrapped free list which is redundant now that we allocate locks
 29  *  dynamically with kmalloc()/kfree().
 30  *  Andy Walker (andy@lysaker.kvaerner.no), February 21, 1995
 31  *
 32  *  Implemented two lock personalities - FL_FLOCK and FL_POSIX.
 33  *
 34  *  FL_POSIX locks are created with calls to fcntl() and lockf() through the
 35  *  fcntl() system call. They have the semantics described above.
 36  *
 37  *  FL_FLOCK locks are created with calls to flock(), through the flock()
 38  *  system call, which is new. Old C libraries implement flock() via fcntl()
 39  *  and will continue to use the old, broken implementation.
 40  *
 41  *  FL_FLOCK locks follow the 4.4 BSD flock() semantics. They are associated
 42  *  with a file pointer (filp). As a result they can be shared by a parent
 43  *  process and its children after a fork(). They are removed when the last
 44  *  file descriptor referring to the file pointer is closed (unless explicitly
 45  *  unlocked). 
 46  *
 47  *  FL_FLOCK locks never deadlock, an existing lock is always removed before
 48  *  upgrading from shared to exclusive (or vice versa). When this happens
 49  *  any processes blocked by the current lock are woken up and allowed to
 50  *  run before the new lock is applied.
 51  *  Andy Walker (andy@lysaker.kvaerner.no), June 09, 1995
 52  *
 53  *  Removed some race conditions in flock_lock_file(), marked other possible
 54  *  races. Just grep for FIXME to see them. 
 55  *  Dmitry Gorodchanin (pgmdsg@ibi.com), February 09, 1996.
 56  *
 57  *  Addressed Dmitry's concerns. Deadlock checking no longer recursive.
 58  *  Lock allocation changed to GFP_ATOMIC as we can't afford to sleep
 59  *  once we've checked for blocking and deadlocking.
 60  *  Andy Walker (andy@lysaker.kvaerner.no), April 03, 1996.
 61  *
 62  *  Initial implementation of mandatory locks. SunOS turned out to be
 63  *  a rotten model, so I implemented the "obvious" semantics.
 64  *  See 'linux/Documentation/mandatory.txt' for details.
 65  *  Andy Walker (andy@lysaker.kvaerner.no), April 06, 1996.
 66  *
 67  *  Don't allow mandatory locks on mmap()'ed files. Added simple functions to
 68  *  check if a file has mandatory locks, used by mmap(), open() and creat() to
 69  *  see if system call should be rejected. Ref. HP-UX/SunOS/Solaris Reference
 70  *  Manual, Section 2.
 71  *  Andy Walker (andy@lysaker.kvaerner.no), April 09, 1996.
 72  *
 73  *  Tidied up block list handling. Added '/proc/locks' interface.
 74  *  Andy Walker (andy@lysaker.kvaerner.no), April 24, 1996.
 75  *
 76  *  Fixed deadlock condition for pathological code that mixes calls to
 77  *  flock() and fcntl().
 78  *  Andy Walker (andy@lysaker.kvaerner.no), April 29, 1996.
 79  *
 80  *  Allow only one type of locking scheme (FL_POSIX or FL_FLOCK) to be in use
 81  *  for a given file at a time. Changed the CONFIG_LOCK_MANDATORY scheme to
 82  *  guarantee sensible behaviour in the case where file system modules might
 83  *  be compiled with different options than the kernel itself.
 84  *  Andy Walker (andy@lysaker.kvaerner.no), May 15, 1996.
 85  *
 86  *  Added a couple of missing wake_up() calls. Thanks to Thomas Meckel
 87  *  (Thomas.Meckel@mni.fh-giessen.de) for spotting this.
 88  *  Andy Walker (andy@lysaker.kvaerner.no), May 15, 1996.
 89  *
 90  *  Changed FL_POSIX locks to use the block list in the same way as FL_FLOCK
 91  *  locks. Changed process synchronisation to avoid dereferencing locks that
 92  *  have already been freed.
 93  *  Andy Walker (andy@lysaker.kvaerner.no), Sep 21, 1996.
 94  *
 95  *  Made the block list a circular list to minimise searching in the list.
 96  *  Andy Walker (andy@lysaker.kvaerner.no), Sep 25, 1996.
 97  *
 98  *  Made mandatory locking a mount option. Default is not to allow mandatory
 99  *  locking.
100  *  Andy Walker (andy@lysaker.kvaerner.no), Oct 04, 1996.
101  *
102  *  Some adaptations for NFS support.
103  *  Olaf Kirch (okir@monad.swb.de), Dec 1996,
104  *
105  *  Fixed /proc/locks interface so that we can't overrun the buffer we are handed.
106  *  Andy Walker (andy@lysaker.kvaerner.no), May 12, 1997.
107  *
108  *  Use slab allocator instead of kmalloc/kfree.
109  *  Use generic list implementation from <linux/list.h>.
110  *  Sped up posix_locks_deadlock by only considering blocked locks.
111  *  Matthew Wilcox <willy@thepuffingroup.com>, March, 2000.
112  *
113  *  Leases and LOCK_MAND
114  *  Matthew Wilcox <willy@linuxcare.com>, June, 2000.
115  *  Stephen Rothwell <sfr@canb.auug.org.au>, June, 2000.
116  */
117 
118 #include <linux/slab.h>
119 #include <linux/file.h>
120 #include <linux/smp_lock.h>
121 #include <linux/init.h>
122 #include <linux/capability.h>
123 #include <linux/sched.h>
124 #include <linux/timer.h>
125 
126 #include <asm/semaphore.h>
127 #include <asm/uaccess.h>
128 
129 int leases_enable = 1;
130 int lease_break_time = 45;
131 
132 LIST_HEAD(file_lock_list);
133 static LIST_HEAD(blocked_list);
134 
135 static kmem_cache_t *filelock_cache;
136 
137 /* Allocate an empty lock structure. */
138 static struct file_lock *locks_alloc_lock(void)
139 {
140         return kmem_cache_alloc(filelock_cache, SLAB_KERNEL);
141 }
142 
143 /* Free a lock which is not in use. */
144 static inline void locks_free_lock(struct file_lock *fl)
145 {
146         if (fl == NULL) {
147                 BUG();
148                 return;
149         }
150         if (waitqueue_active(&fl->fl_wait))
151                 panic("Attempting to free lock with active wait queue");
152 
153         if (!list_empty(&fl->fl_block))
154                 panic("Attempting to free lock with active block list");
155 
156         if (!list_empty(&fl->fl_link))
157                 panic("Attempting to free lock on active lock list");
158 
159         kmem_cache_free(filelock_cache, fl);
160 }
161 
162 void locks_init_lock(struct file_lock *fl)
163 {
164         INIT_LIST_HEAD(&fl->fl_link);
165         INIT_LIST_HEAD(&fl->fl_block);
166         init_waitqueue_head(&fl->fl_wait);
167         fl->fl_next = NULL;
168         fl->fl_fasync = NULL;
169         fl->fl_owner = 0;
170         fl->fl_pid = 0;
171         fl->fl_file = NULL;
172         fl->fl_flags = 0;
173         fl->fl_type = 0;
174         fl->fl_start = fl->fl_end = 0;
175         fl->fl_notify = NULL;
176         fl->fl_insert = NULL;
177         fl->fl_remove = NULL;
178 }
179 
180 /*
181  * Initialises the fields of the file lock which are invariant for
182  * free file_locks.
183  */
184 static void init_once(void *foo, kmem_cache_t *cache, unsigned long flags)
185 {
186         struct file_lock *lock = (struct file_lock *) foo;
187 
188         if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) !=
189                                         SLAB_CTOR_CONSTRUCTOR)
190                 return;
191 
192         locks_init_lock(lock);
193 }
194 
195 /*
196  * Initialize a new lock from an existing file_lock structure.
197  */
198 void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
199 {
200         new->fl_owner = fl->fl_owner;
201         new->fl_pid = fl->fl_pid;
202         new->fl_file = fl->fl_file;
203         new->fl_flags = fl->fl_flags;
204         new->fl_type = fl->fl_type;
205         new->fl_start = fl->fl_start;
206         new->fl_end = fl->fl_end;
207         new->fl_notify = fl->fl_notify;
208         new->fl_insert = fl->fl_insert;
209         new->fl_remove = fl->fl_remove;
210         new->fl_u = fl->fl_u;
211 }
212 
213 /* Fill in a file_lock structure with an appropriate FLOCK lock. */
214 static struct file_lock *flock_make_lock(struct file *filp, unsigned int type)
215 {
216         struct file_lock *fl = locks_alloc_lock();
217         if (fl == NULL)
218                 return NULL;
219 
220         fl->fl_owner = NULL;
221         fl->fl_file = filp;
222         fl->fl_pid = current->pid;
223         fl->fl_flags = FL_FLOCK;
224         fl->fl_type = type;
225         fl->fl_start = 0;
226         fl->fl_end = OFFSET_MAX;
227         fl->fl_notify = NULL;
228         fl->fl_insert = NULL;
229         fl->fl_remove = NULL;
230         
231         return fl;
232 }
233 
234 static int assign_type(struct file_lock *fl, int type)
235 {
236         switch (type) {
237         case F_RDLCK:
238         case F_WRLCK:
239         case F_UNLCK:
240                 fl->fl_type = type;
241                 break;
242         default:
243                 return -EINVAL;
244         }
245         return 0;
246 }
247 
248 /* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX
249  * style lock.
250  */
251 static int flock_to_posix_lock(struct file *filp, struct file_lock *fl,
252                                struct flock *l)
253 {
254         off_t start, end;
255 
256         switch (l->l_whence) {
257         case 0: /*SEEK_SET*/
258                 start = 0;
259                 break;
260         case 1: /*SEEK_CUR*/
261                 start = filp->f_pos;
262                 break;
263         case 2: /*SEEK_END*/
264                 start = filp->f_dentry->d_inode->i_size;
265                 break;
266         default:
267                 return -EINVAL;
268         }
269 
270         /* POSIX-1996 leaves the case l->l_len < 0 undefined;
271            POSIX-2001 defines it. */
272         start += l->l_start;
273         if (l->l_len < 0) {
274                 end = start - 1;
275                 start += l->l_len;
276         } else {
277                 end = start + l->l_len - 1;
278         }
279 
280         if (start < 0)
281                 return -EINVAL;
282         if (l->l_len > 0 && end < 0)
283                 return -EOVERFLOW;
284         fl->fl_start = start;   /* we record the absolute position */
285         fl->fl_end = end;
286         if (l->l_len == 0)
287                 fl->fl_end = OFFSET_MAX;
288         
289         fl->fl_owner = current->files;
290         fl->fl_pid = current->pid;
291         fl->fl_file = filp;
292         fl->fl_flags = FL_POSIX;
293         fl->fl_notify = NULL;
294         fl->fl_insert = NULL;
295         fl->fl_remove = NULL;
296 
297         return assign_type(fl, l->l_type);
298 }
299 
300 #if BITS_PER_LONG == 32
301 static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
302                                  struct flock64 *l)
303 {
304         loff_t start;
305 
306         switch (l->l_whence) {
307         case 0: /*SEEK_SET*/
308                 start = 0;
309                 break;
310         case 1: /*SEEK_CUR*/
311                 start = filp->f_pos;
312                 break;
313         case 2: /*SEEK_END*/
314                 start = filp->f_dentry->d_inode->i_size;
315                 break;
316         default:
317                 return -EINVAL;
318         }
319 
320         if (((start += l->l_start) < 0) || (l->l_len < 0))
321                 return -EINVAL;
322         fl->fl_end = start + l->l_len - 1;
323         if (l->l_len > 0 && fl->fl_end < 0)
324                 return -EOVERFLOW;
325         fl->fl_start = start;   /* we record the absolute position */
326         if (l->l_len == 0)
327                 fl->fl_end = OFFSET_MAX;
328         
329         fl->fl_owner = current->files;
330         fl->fl_pid = current->pid;
331         fl->fl_file = filp;
332         fl->fl_flags = FL_POSIX;
333         fl->fl_notify = NULL;
334         fl->fl_insert = NULL;
335         fl->fl_remove = NULL;
336 
337         switch (l->l_type) {
338         case F_RDLCK:
339         case F_WRLCK:
340         case F_UNLCK:
341                 fl->fl_type = l->l_type;
342                 break;
343         default:
344                 return -EINVAL;
345         }
346 
347         return (0);
348 }
349 #endif
350 
351 /* Allocate a file_lock initialised to this type of lease */
352 static int lease_alloc(struct file *filp, int type, struct file_lock **flp)
353 {
354         struct file_lock *fl = locks_alloc_lock();
355         if (fl == NULL)
356                 return -ENOMEM;
357 
358         fl->fl_owner = current->files;
359         fl->fl_pid = current->pid;
360 
361         fl->fl_file = filp;
362         fl->fl_flags = FL_LEASE;
363         if (assign_type(fl, type) != 0) {
364                 locks_free_lock(fl);
365                 return -EINVAL;
366         }
367         fl->fl_start = 0;
368         fl->fl_end = OFFSET_MAX;
369         fl->fl_notify = NULL;
370         fl->fl_insert = NULL;
371         fl->fl_remove = NULL;
372 
373         *flp = fl;
374         return 0;
375 }
376 
377 /* Check if two locks overlap each other.
378  */
379 static inline int locks_overlap(struct file_lock *fl1, struct file_lock *fl2)
380 {
381         return ((fl1->fl_end >= fl2->fl_start) &&
382                 (fl2->fl_end >= fl1->fl_start));
383 }
384 
385 /*
386  * Check whether two locks have the same owner
387  * N.B. Do we need the test on PID as well as owner?
388  * (Clone tasks should be considered as one "owner".)
389  */
390 static inline int
391 locks_same_owner(struct file_lock *fl1, struct file_lock *fl2)
392 {
393         return (fl1->fl_owner == fl2->fl_owner) &&
394                (fl1->fl_pid   == fl2->fl_pid);
395 }
396 
397 /* Remove waiter from blocker's block list.
398  * When blocker ends up pointing to itself then the list is empty.
399  */
400 static void locks_delete_block(struct file_lock *waiter)
401 {
402         list_del(&waiter->fl_block);
403         INIT_LIST_HEAD(&waiter->fl_block);
404         list_del(&waiter->fl_link);
405         INIT_LIST_HEAD(&waiter->fl_link);
406         waiter->fl_next = NULL;
407 }
408 
409 /* Insert waiter into blocker's block list.
410  * We use a circular list so that processes can be easily woken up in
411  * the order they blocked. The documentation doesn't require this but
412  * it seems like the reasonable thing to do.
413  */
414 static void locks_insert_block(struct file_lock *blocker, 
415                                struct file_lock *waiter)
416 {
417         if (!list_empty(&waiter->fl_block)) {
418                 printk(KERN_ERR "locks_insert_block: removing duplicated lock "
419                         "(pid=%d %Ld-%Ld type=%d)\n", waiter->fl_pid,
420                         waiter->fl_start, waiter->fl_end, waiter->fl_type);
421                 locks_delete_block(waiter);
422         }
423         list_add_tail(&waiter->fl_block, &blocker->fl_block);
424         waiter->fl_next = blocker;
425         list_add(&waiter->fl_link, &blocked_list);
426 }
427 
428 static inline
429 void locks_notify_blocked(struct file_lock *waiter)
430 {
431         if (waiter->fl_notify)
432                 waiter->fl_notify(waiter);
433         else
434                 wake_up(&waiter->fl_wait);
435 }
436 
437 /* Wake up processes blocked waiting for blocker.
438  * If told to wait then schedule the processes until the block list
439  * is empty, otherwise empty the block list ourselves.
440  */
441 static void locks_wake_up_blocks(struct file_lock *blocker, unsigned int wait)
442 {
443         while (!list_empty(&blocker->fl_block)) {
444                 struct file_lock *waiter = list_entry(blocker->fl_block.next, struct file_lock, fl_block);
445 
446                 if (wait) {
447                         locks_notify_blocked(waiter);
448                         /* Let the blocked process remove waiter from the
449                          * block list when it gets scheduled.
450                          */
451                         yield();
452                 } else {
453                         /* Remove waiter from the block list, because by the
454                          * time it wakes up blocker won't exist any more.
455                          */
456                         locks_delete_block(waiter);
457                         locks_notify_blocked(waiter);
458                 }
459         }
460 }
461 
462 /* Insert file lock fl into an inode's lock list at the position indicated
463  * by pos. At the same time add the lock to the global file lock list.
464  */
465 static void locks_insert_lock(struct file_lock **pos, struct file_lock *fl)
466 {
467         list_add(&fl->fl_link, &file_lock_list);
468 
469         /* insert into file's list */
470         fl->fl_next = *pos;
471         *pos = fl;
472 
473         if (fl->fl_insert)
474                 fl->fl_insert(fl);
475 }
476 
477 /*
478  * Remove lock from the lock lists
479  */
480 static inline void _unhash_lock(struct file_lock **thisfl_p)
481 {
482         struct file_lock *fl = *thisfl_p;
483 
484         *thisfl_p = fl->fl_next;
485         fl->fl_next = NULL;
486 
487         list_del_init(&fl->fl_link);
488 }
489 
490 /*
491  * Wake up processes that are blocked waiting for this lock,
492  * notify the FS that the lock has been cleared and
493  * finally free the lock.
494  */
495 static inline void _delete_lock(struct file_lock *fl, unsigned int wait)
496 {
497         fasync_helper(0, fl->fl_file, 0, &fl->fl_fasync);
498         if (fl->fl_fasync != NULL){
499                 printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync);
500                 fl->fl_fasync = NULL;
501         }
502 
503         if (fl->fl_remove)
504                 fl->fl_remove(fl);
505 
506         locks_wake_up_blocks(fl, wait);
507         locks_free_lock(fl);
508 }
509 
510 /*
511  * Delete a lock and then free it.
512  */
513 static void locks_delete_lock(struct file_lock **thisfl_p, unsigned int wait)
514 {
515         struct file_lock *fl = *thisfl_p;
516 
517         _unhash_lock(thisfl_p);
518         _delete_lock(fl, wait);
519 }
520 
521 /*
522  * Call back client filesystem in order to get it to unregister a lock,
523  * then delete lock. Essentially useful only in locks_remove_*().
524  * Note: this must be called with the semaphore already held!
525  */
526 static inline void locks_unlock_delete(struct file_lock **thisfl_p)
527 {
528         struct file_lock *fl = *thisfl_p;
529         int (*lock)(struct file *, int, struct file_lock *);
530 
531         _unhash_lock(thisfl_p);
532         if (fl->fl_file->f_op &&
533             (lock = fl->fl_file->f_op->lock) != NULL) {
534                 fl->fl_type = F_UNLCK;
535                 lock(fl->fl_file, F_SETLK, fl);
536         }
537         _delete_lock(fl, 0);
538 }
539 
540 /* Determine if lock sys_fl blocks lock caller_fl. Common functionality
541  * checks for shared/exclusive status of overlapping locks.
542  */
543 static int locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
544 {
545         switch (caller_fl->fl_type) {
546         case F_RDLCK:
547                 return (sys_fl->fl_type == F_WRLCK);
548 
549         case F_WRLCK:
550                 return (1);
551 
552         default:
553                 printk(KERN_ERR "locks_conflict(): impossible lock type - %d\n",
554                        caller_fl->fl_type);
555                 break;
556         }
557         return (0);     /* This should never happen */
558 }
559 
560 /* Determine if lock sys_fl blocks lock caller_fl. POSIX specific
561  * checking before calling the locks_conflict().
562  */
563 static int posix_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
564 {
565         /* POSIX locks owned by the same process do not conflict with
566          * each other.
567          */
568         if (!(sys_fl->fl_flags & FL_POSIX) ||
569             locks_same_owner(caller_fl, sys_fl))
570                 return (0);
571 
572         /* Check whether they overlap */
573         if (!locks_overlap(caller_fl, sys_fl))
574                 return 0;
575 
576         return (locks_conflict(caller_fl, sys_fl));
577 }
578 
579 /* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific
580  * checking before calling the locks_conflict().
581  */
582 static int flock_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
583 {
584         /* FLOCK locks referring to the same filp do not conflict with
585          * each other.
586          */
587         if (!(sys_fl->fl_flags & FL_FLOCK) ||
588             (caller_fl->fl_file == sys_fl->fl_file))
589                 return (0);
590 #ifdef MSNFS
591         if ((caller_fl->fl_type & LOCK_MAND) || (sys_fl->fl_type & LOCK_MAND))
592                 return 0;
593 #endif
594 
595         return (locks_conflict(caller_fl, sys_fl));
596 }
597 
598 static int interruptible_sleep_on_locked(wait_queue_head_t *fl_wait, int timeout)
599 {
600         int result = 0;
601         DECLARE_WAITQUEUE(wait, current);
602 
603         current->state = TASK_INTERRUPTIBLE;
604         add_wait_queue(fl_wait, &wait);
605         if (timeout == 0)
606                 schedule();
607         else
608                 result = schedule_timeout(timeout);
609         if (signal_pending(current))
610                 result = -ERESTARTSYS;
611         remove_wait_queue(fl_wait, &wait);
612         current->state = TASK_RUNNING;
613         return result;
614 }
615 
616 static int locks_block_on(struct file_lock *blocker, struct file_lock *waiter)
617 {
618         int result;
619         locks_insert_block(blocker, waiter);
620         result = interruptible_sleep_on_locked(&waiter->fl_wait, 0);
621         locks_delete_block(waiter);
622         return result;
623 }
624 
625 static int locks_block_on_timeout(struct file_lock *blocker, struct file_lock *waiter, int time)
626 {
627         int result;
628         locks_insert_block(blocker, waiter);
629         result = interruptible_sleep_on_locked(&waiter->fl_wait, time);
630         locks_delete_block(waiter);
631         return result;
632 }
633 
634 struct file_lock *
635 posix_test_lock(struct file *filp, struct file_lock *fl)
636 {
637         struct file_lock *cfl;
638 
639         lock_kernel();
640         for (cfl = filp->f_dentry->d_inode->i_flock; cfl; cfl = cfl->fl_next) {
641                 if (!(cfl->fl_flags & FL_POSIX))
642                         continue;
643                 if (posix_locks_conflict(cfl, fl))
644                         break;
645         }
646         unlock_kernel();
647 
648         return (cfl);
649 }
650 
651 /* This function tests for deadlock condition before putting a process to
652  * sleep. The detection scheme is no longer recursive. Recursive was neat,
653  * but dangerous - we risked stack corruption if the lock data was bad, or
654  * if the recursion was too deep for any other reason.
655  *
656  * We rely on the fact that a task can only be on one lock's wait queue
657  * at a time. When we find blocked_task on a wait queue we can re-search
658  * with blocked_task equal to that queue's owner, until either blocked_task
659  * isn't found, or blocked_task is found on a queue owned by my_task.
660  *
661  * Note: the above assumption may not be true when handling lock requests
662  * from a broken NFS client. But broken NFS clients have a lot more to
663  * worry about than proper deadlock detection anyway... --okir
664  */
665 int posix_locks_deadlock(struct file_lock *caller_fl,
666                                 struct file_lock *block_fl)
667 {
668         struct list_head *tmp;
669         fl_owner_t caller_owner, blocked_owner;
670         unsigned int     caller_pid, blocked_pid;
671 
672         caller_owner = caller_fl->fl_owner;
673         caller_pid = caller_fl->fl_pid;
674         blocked_owner = block_fl->fl_owner;
675         blocked_pid = block_fl->fl_pid;
676 
677 next_task:
678         if (caller_owner == blocked_owner && caller_pid == blocked_pid)
679                 return 1;
680         list_for_each(tmp, &blocked_list) {
681                 struct file_lock *fl = list_entry(tmp, struct file_lock, fl_link);
682                 if ((fl->fl_owner == blocked_owner)
683                     && (fl->fl_pid == blocked_pid)) {
684                         fl = fl->fl_next;
685                         blocked_owner = fl->fl_owner;
686                         blocked_pid = fl->fl_pid;
687                         goto next_task;
688                 }
689         }
690         return 0;
691 }
692 
693 int locks_mandatory_locked(struct inode *inode)
694 {
695         fl_owner_t owner = current->files;
696         struct file_lock *fl;
697 
698         /*
699          * Search the lock list for this inode for any POSIX locks.
700          */
701         lock_kernel();
702         for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
703                 if (!(fl->fl_flags & FL_POSIX))
704                         continue;
705                 if (fl->fl_owner != owner)
706                         break;
707         }
708         unlock_kernel();
709         return fl ? -EAGAIN : 0;
710 }
711 
712 int locks_mandatory_area(int read_write, struct inode *inode,
713                          struct file *filp, loff_t offset,
714                          size_t count)
715 {
716         struct file_lock *fl;
717         struct file_lock *new_fl = locks_alloc_lock();
718         int error;
719 
720         if (new_fl == NULL)
721                 return -ENOMEM;
722 
723         new_fl->fl_owner = current->files;
724         new_fl->fl_pid = current->pid;
725         new_fl->fl_file = filp;
726         new_fl->fl_flags = FL_POSIX | FL_ACCESS;
727         new_fl->fl_type = (read_write == FLOCK_VERIFY_WRITE) ? F_WRLCK : F_RDLCK;
728         new_fl->fl_start = offset;
729         new_fl->fl_end = offset + count - 1;
730 
731         error = 0;
732         lock_kernel();
733 
734 repeat:
735         /* Search the lock list for this inode for locks that conflict with
736          * the proposed read/write.
737          */
738         for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
739                 if (!(fl->fl_flags & FL_POSIX))
740                         continue;
741                 if (fl->fl_start > new_fl->fl_end)
742                         break;
743                 if (posix_locks_conflict(new_fl, fl)) {
744                         error = -EAGAIN;
745                         if (filp && (filp->f_flags & O_NONBLOCK))
746                                 break;
747                         error = -EDEADLK;
748                         if (posix_locks_deadlock(new_fl, fl))
749                                 break;
750         
751                         error = locks_block_on(fl, new_fl);
752                         if (error != 0)
753                                 break;
754         
755                         /*
756                          * If we've been sleeping someone might have
757                          * changed the permissions behind our back.
758                          */
759                         if ((inode->i_mode & (S_ISGID | S_IXGRP)) != S_ISGID)
760                                 break;
761                         goto repeat;
762                 }
763         }
764         locks_free_lock(new_fl);
765         unlock_kernel();
766         return error;
767 }
768 
769 /* Try to create a FLOCK lock on filp. We always insert new FLOCK locks
770  * at the head of the list, but that's secret knowledge known only to
771  * flock_lock_file and posix_lock_file.
772  */
773 static int flock_lock_file(struct file *filp, unsigned int lock_type,
774                            unsigned int wait)
775 {
776         struct file_lock *fl;
777         struct file_lock *new_fl = NULL;
778         struct file_lock **before;
779         struct inode * inode = filp->f_dentry->d_inode;
780         int error, change;
781         int unlock = (lock_type == F_UNLCK);
782 
783         /*
784          * If we need a new lock, get it in advance to avoid races.
785          */
786         if (!unlock) {
787                 error = -ENOLCK;
788                 new_fl = flock_make_lock(filp, lock_type);
789                 if (!new_fl)
790                         return error;
791         }
792 
793         error = 0;
794 search:
795         change = 0;
796         before = &inode->i_flock;
797         while (((fl = *before) != NULL) && (fl->fl_flags & FL_FLOCK)) {
798                 if (filp == fl->fl_file) {
799                         if (lock_type == fl->fl_type)
800                                 goto out;
801                         change = 1;
802                         break;
803                 }
804                 before = &fl->fl_next;
805         }
806         /* change means that we are changing the type of an existing lock,
807          * or else unlocking it.
808          */
809         if (change) {
810                 /* N.B. What if the wait argument is false? */
811                 locks_delete_lock(before, !unlock);
812                 /*
813                  * If we waited, another lock may have been added ...
814                  */
815                 if (!unlock)
816                         goto search;
817         }
818         if (unlock)
819                 goto out;
820 
821 repeat:
822         for (fl = inode->i_flock; (fl != NULL) && (fl->fl_flags & FL_FLOCK);
823              fl = fl->fl_next) {
824                 if (!flock_locks_conflict(new_fl, fl))
825                         continue;
826                 error = -EAGAIN;
827                 if (!wait)
828                         goto out;
829                 error = locks_block_on(fl, new_fl);
830                 if (error != 0)
831                         goto out;
832                 goto repeat;
833         }
834         locks_insert_lock(&inode->i_flock, new_fl);
835         new_fl = NULL;
836         error = 0;
837 
838 out:
839         if (new_fl)
840                 locks_free_lock(new_fl);
841         return error;
842 }
843 
844 /**
845  *      posix_lock_file:
846  *      @filp: The file to apply the lock to
847  *      @caller: The lock to be applied
848  *      @wait: 1 to retry automatically, 0 to return -EAGAIN
849  *
850  * Add a POSIX style lock to a file.
851  * We merge adjacent locks whenever possible. POSIX locks are sorted by owner
852  * task, then by starting address
853  *
854  * Kai Petzke writes:
855  * To make freeing a lock much faster, we keep a pointer to the lock before the
856  * actual one. But the real gain of the new coding was, that lock_it() and
857  * unlock_it() became one function.
858  *
859  * To all purists: Yes, I use a few goto's. Just pass on to the next function.
860  */
861 
862 int posix_lock_file(struct file *filp, struct file_lock *caller,
863                            unsigned int wait)
864 {
865         struct file_lock *fl;
866         struct file_lock *new_fl, *new_fl2;
867         struct file_lock *left = NULL;
868         struct file_lock *right = NULL;
869         struct file_lock **before;
870         struct inode * inode = filp->f_dentry->d_inode;
871         int error, added = 0;
872 
873         /*
874          * We may need two file_lock structures for this operation,
875          * so we get them in advance to avoid races.
876          */
877         new_fl = locks_alloc_lock();
878         new_fl2 = locks_alloc_lock();
879         error = -ENOLCK; /* "no luck" */
880         if (!(new_fl && new_fl2))
881                 goto out_nolock;
882 
883         lock_kernel();
884         if (caller->fl_type != F_UNLCK) {
885   repeat:
886                 for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
887                         if (!(fl->fl_flags & FL_POSIX))
888                                 continue;
889                         if (!posix_locks_conflict(caller, fl))
890                                 continue;
891                         error = -EAGAIN;
892                         if (!wait)
893                                 goto out;
894                         error = -EDEADLK;
895                         if (posix_locks_deadlock(caller, fl))
896                                 goto out;
897 
898                         error = locks_block_on(fl, caller);
899                         if (error != 0)
900                                 goto out;
901                         goto repeat;
902                 }
903         }
904 
905         /*
906          * We've allocated the new locks in advance, so there are no
907          * errors possible (and no blocking operations) from here on.
908          * 
909          * Find the first old lock with the same owner as the new lock.
910          */
911         
912         before = &inode->i_flock;
913 
914         /* First skip locks owned by other processes.
915          */
916         while ((fl = *before) && (!(fl->fl_flags & FL_POSIX) ||
917                                   !locks_same_owner(caller, fl))) {
918                 before = &fl->fl_next;
919         }
920 
921         /* Process locks with this owner.
922          */
923         while ((fl = *before) && locks_same_owner(caller, fl)) {
924                 /* Detect adjacent or overlapping regions (if same lock type)
925                  */
926                 if (caller->fl_type == fl->fl_type) {
927                         if (fl->fl_end < caller->fl_start - 1)
928                                 goto next_lock;
929                         /* If the next lock in the list has entirely bigger
930                          * addresses than the new one, insert the lock here.
931                          */
932                         if (fl->fl_start > caller->fl_end + 1)
933                                 break;
934 
935                         /* If we come here, the new and old lock are of the
936                          * same type and adjacent or overlapping. Make one
937                          * lock yielding from the lower start address of both
938                          * locks to the higher end address.
939                          */
940                         if (fl->fl_start > caller->fl_start)
941                                 fl->fl_start = caller->fl_start;
942                         else
943                                 caller->fl_start = fl->fl_start;
944                         if (fl->fl_end < caller->fl_end)
945                                 fl->fl_end = caller->fl_end;
946                         else
947                                 caller->fl_end = fl->fl_end;
948                         if (added) {
949                                 locks_delete_lock(before, 0);
950                                 continue;
951                         }
952                         caller = fl;
953                         added = 1;
954                 }
955                 else {
956                         /* Processing for different lock types is a bit
957                          * more complex.
958                          */
959                         if (fl->fl_end < caller->fl_start)
960                                 goto next_lock;
961                         if (fl->fl_start > caller->fl_end)
962                                 break;
963                         if (caller->fl_type == F_UNLCK)
964                                 added = 1;
965                         if (fl->fl_start < caller->fl_start)
966                                 left = fl;
967                         /* If the next lock in the list has a higher end
968                          * address than the new one, insert the new one here.
969                          */
970                         if (fl->fl_end > caller->fl_end) {
971                                 right = fl;
972                                 break;
973                         }
974                         if (fl->fl_start >= caller->fl_start) {
975                                 /* The new lock completely replaces an old
976                                  * one (This may happen several times).
977                                  */
978                                 if (added) {
979                                         locks_delete_lock(before, 0);
980                                         continue;
981                                 }
982                                 /* Replace the old lock with the new one.
983                                  * Wake up anybody waiting for the old one,
984                                  * as the change in lock type might satisfy
985                                  * their needs.
986                                  */
987                                 locks_wake_up_blocks(fl, 0);    /* This cannot schedule()! */
988                                 fl->fl_start = caller->fl_start;
989                                 fl->fl_end = caller->fl_end;
990                                 fl->fl_type = caller->fl_type;
991                                 fl->fl_u = caller->fl_u;
992                                 caller = fl;
993                                 added = 1;
994                         }
995                 }
996                 /* Go on to next lock.
997                  */
998         next_lock:
999                 before = &fl->fl_next;
1000         }
1001 
1002         error = 0;
1003         if (!added) {
1004                 if (caller->fl_type == F_UNLCK)
1005                         goto out;
1006                 locks_copy_lock(new_fl, caller);
1007                 locks_insert_lock(before, new_fl);
1008                 new_fl = NULL;
1009         }
1010         if (right) {
1011                 if (left == right) {
1012                         /* The new lock breaks the old one in two pieces,
1013                          * so we have to use the second new lock.
1014                          */
1015                         left = new_fl2;
1016                         new_fl2 = NULL;
1017                         locks_copy_lock(left, right);
1018                         locks_insert_lock(before, left);
1019                 }
1020                 right->fl_start = caller->fl_end + 1;
1021                 locks_wake_up_blocks(right, 0);
1022         }
1023         if (left) {
1024                 left->fl_end = caller->fl_start - 1;
1025                 locks_wake_up_blocks(left, 0);
1026         }
1027 out:
1028         unlock_kernel();
1029 out_nolock:
1030         /*
1031          * Free any unused locks.
1032          */
1033         if (new_fl)
1034                 locks_free_lock(new_fl);
1035         if (new_fl2)
1036                 locks_free_lock(new_fl2);
1037         return error;
1038 }
1039 
1040 static inline int flock_translate_cmd(int cmd) {
1041 #ifdef MSNFS
1042         if (cmd & LOCK_MAND)
1043                 return cmd & (LOCK_MAND | LOCK_RW);
1044 #endif
1045         switch (cmd &~ LOCK_NB) {
1046         case LOCK_SH:
1047                 return F_RDLCK;
1048         case LOCK_EX:
1049                 return F_WRLCK;
1050         case LOCK_UN:
1051                 return F_UNLCK;
1052         }
1053         return -EINVAL;
1054 }
1055 
1056 /* We already had a lease on this file; just change its type */
1057 static int lease_modify(struct file_lock **before, int arg)
1058 {
1059         struct file_lock *fl = *before;
1060         int error = assign_type(fl, arg);
1061 
1062         if (error)
1063                 return error;
1064         locks_wake_up_blocks(fl, 0);
1065         if (arg == F_UNLCK) {
1066                 struct file *filp = fl->fl_file;
1067 
1068                 filp->f_owner.pid = 0;
1069                 filp->f_owner.uid = 0;
1070                 filp->f_owner.euid = 0;
1071                 filp->f_owner.signum = 0;
1072                 locks_delete_lock(before, 0);
1073         }
1074         return 0;
1075 }
1076 
1077 static void time_out_leases(struct inode *inode)
1078 {
1079         struct file_lock **before;
1080         struct file_lock *fl;
1081 
1082         before = &inode->i_flock;
1083         while ((fl = *before) && (fl->fl_flags & FL_LEASE)
1084                         && (fl->fl_type & F_INPROGRESS)) {
1085                 if ((fl->fl_break_time == 0)
1086                                 || time_before(jiffies, fl->fl_break_time)) {
1087                         before = &fl->fl_next;
1088                         continue;
1089                 }
1090                 lease_modify(before, fl->fl_type & ~F_INPROGRESS);
1091                 if (fl == *before)      /* lease_modify may have freed fl */
1092                         before = &fl->fl_next;
1093         }
1094 }
1095 
1096 /**
1097  *      __get_lease     -       revoke all outstanding leases on file
1098  *      @inode: the inode of the file to return
1099  *      @mode: the open mode (read or write)
1100  *
1101  *      get_lease (inlined for speed) has checked there already
1102  *      is a lease on this file.  Leases are broken on a call to open()
1103  *      or truncate().  This function can sleep unless you
1104  *      specified %O_NONBLOCK to your open().
1105  */
1106 int __get_lease(struct inode *inode, unsigned int mode)
1107 {
1108         int error = 0, future;
1109         struct file_lock *new_fl, *flock;
1110         struct file_lock *fl;
1111         int alloc_err;
1112         unsigned long break_time;
1113         int i_have_this_lease = 0;
1114 
1115         alloc_err = lease_alloc(NULL, mode & FMODE_WRITE ? F_WRLCK : F_RDLCK,
1116                         &new_fl);
1117 
1118         lock_kernel();
1119 
1120         time_out_leases(inode);
1121 
1122         flock = inode->i_flock;
1123         if ((flock == NULL) || (flock->fl_flags & FL_LEASE) == 0)
1124                 goto out;
1125 
1126         for (fl = flock; fl && (fl->fl_flags & FL_LEASE); fl = fl->fl_next)
1127                 if (fl->fl_owner == current->files)
1128                         i_have_this_lease = 1;
1129 
1130         if (mode & FMODE_WRITE) {
1131                 /* If we want write access, we have to revoke any lease. */
1132                 future = F_UNLCK | F_INPROGRESS;
1133         } else if (flock->fl_type & F_INPROGRESS) {
1134                 /* If the lease is already being broken, we just leave it */
1135                 future = flock->fl_type;
1136         } else if (flock->fl_type & F_WRLCK) {
1137                 /* Downgrade the exclusive lease to a read-only lease. */
1138                 future = F_RDLCK | F_INPROGRESS;
1139         } else {
1140                 /* the existing lease was read-only, so we can read too. */
1141                 goto out;
1142         }
1143 
1144         if (alloc_err && !i_have_this_lease && ((mode & O_NONBLOCK) == 0)) {
1145                 error = alloc_err;
1146                 goto out;
1147         }
1148 
1149         break_time = 0;
1150         if (lease_break_time > 0) {
1151                 break_time = jiffies + lease_break_time * HZ;
1152                 if (break_time == 0)
1153                         break_time++;   /* so that 0 means no break time */
1154         }
1155 
1156         for (fl = flock; fl && (fl->fl_flags & FL_LEASE); fl = fl->fl_next) {
1157                 if (fl->fl_type != future) {
1158                         fl->fl_type = future;
1159                         fl->fl_break_time = break_time;
1160                         kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG);
1161                 }
1162         }
1163 
1164         if (i_have_this_lease || (mode & O_NONBLOCK)) {
1165                 error = -EWOULDBLOCK;
1166                 goto out;
1167         }
1168 
1169 restart:
1170         break_time = flock->fl_break_time;
1171         if (break_time != 0) {
1172                 break_time -= jiffies;
1173                 if (break_time == 0)
1174                         break_time++;
1175         }
1176         error = locks_block_on_timeout(flock, new_fl, break_time);
1177         if (error >= 0) {
1178                 if (error == 0)
1179                         time_out_leases(inode);
1180                 /* Wait for the next lease that has not been broken yet */
1181                 for (flock = inode->i_flock;
1182                                 flock && (flock->fl_flags & FL_LEASE);
1183                                 flock = flock->fl_next) {
1184                         if (flock->fl_type & F_INPROGRESS)
1185                                 goto restart;
1186                 }
1187                 error = 0;
1188         }
1189 
1190 out:
1191         unlock_kernel();
1192         if (!alloc_err)
1193                 locks_free_lock(new_fl);
1194         return error;
1195 }
1196 
1197 /**
1198  *      lease_get_mtime
1199  *      @inode: the inode
1200  *
1201  * This is to force NFS clients to flush their caches for files with
1202  * exclusive leases.  The justification is that if someone has an
1203  * exclusive lease, then they could be modifiying it.
1204  */
1205 time_t lease_get_mtime(struct inode *inode)
1206 {
1207         struct file_lock *flock = inode->i_flock;
1208         if (flock && (flock->fl_flags & FL_LEASE) && (flock->fl_type & F_WRLCK))
1209                 return CURRENT_TIME;
1210         return inode->i_mtime;
1211 }
1212 
1213 /**
1214  *      fcntl_getlease - Enquire what lease is currently active
1215  *      @filp: the file
1216  *
1217  *      The value returned by this function will be one of
1218  *      (if no lease break is pending):
1219  *
1220  *      %F_RDLCK to indicate a shared lease is held.
1221  *
1222  *      %F_WRLCK to indicate an exclusive lease is held.
1223  *
1224  *      %F_UNLCK to indicate no lease is held.
1225  *
1226  *      (if a lease break is pending):
1227  *
1228  *      %F_RDLCK to indicate an exclusive lease needs to be
1229  *              changed to a shared lease (or removed).
1230  *
1231  *      %F_UNLCK to indicate the lease needs to be removed.
1232  *
1233  *      XXX: sfr & willy disagree over whether F_INPROGRESS
1234  *      should be returned to userspace.
1235  */
1236 int fcntl_getlease(struct file *filp)
1237 {
1238         struct file_lock *fl;
1239         int type = F_UNLCK;
1240 
1241         lock_kernel();
1242         time_out_leases(filp->f_dentry->d_inode);
1243         for (fl = filp->f_dentry->d_inode->i_flock;
1244                         fl && (fl->fl_flags & FL_LEASE);
1245                         fl = fl->fl_next) {
1246                 if (fl->fl_file == filp) {
1247                         type = fl->fl_type & ~F_INPROGRESS;
1248                         break;
1249                 }
1250         }
1251         unlock_kernel();
1252         return type;
1253 }
1254 
1255 /**
1256  *      fcntl_setlease  -       sets a lease on an open file
1257  *      @fd: open file descriptor
1258  *      @filp: file pointer
1259  *      @arg: type of lease to obtain
1260  *
1261  *      Call this fcntl to establish a lease on the file.
1262  *      Note that you also need to call %F_SETSIG to
1263  *      receive a signal when the lease is broken.
1264  */
1265 int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
1266 {
1267         struct file_lock *fl, **before, **my_before = NULL;
1268         struct dentry *dentry;
1269         struct inode *inode;
1270         int error, rdlease_count = 0, wrlease_count = 0;
1271 
1272         dentry = filp->f_dentry;
1273         inode = dentry->d_inode;
1274 
1275         if ((current->fsuid != inode->i_uid) && !capable(CAP_LEASE))
1276                 return -EACCES;
1277         if (!S_ISREG(inode->i_mode))
1278                 return -EINVAL;
1279 
1280         lock_kernel();
1281 
1282         time_out_leases(inode);
1283 
1284         /*
1285          * FIXME: What about F_RDLCK and files open for writing?
1286          */
1287         error = -EAGAIN;
1288         if ((arg == F_WRLCK)
1289             && ((atomic_read(&dentry->d_count) > 1)
1290                 || (atomic_read(&inode->i_count) > 1)))
1291                 goto out_unlock;
1292 
1293         /*
1294          * At this point, we know that if there is an exclusive
1295          * lease on this file, then we hold it on this filp
1296          * (otherwise our open of this file would have blocked).
1297          * And if we are trying to acquire an exclusive lease,
1298          * then the file is not open by anyone (including us)
1299          * except for this filp.
1300          */
1301         for (before = &inode->i_flock;
1302                         ((fl = *before) != NULL) && (fl->fl_flags & FL_LEASE);
1303                         before = &fl->fl_next) {
1304                 if (fl->fl_file == filp)
1305                         my_before = before;
1306                 else if (fl->fl_type == (F_INPROGRESS | F_UNLCK))
1307                         /*
1308                          * Someone is in the process of opening this
1309                          * file for writing so we may not take an
1310                          * exclusive lease on it.
1311                          */
1312                         wrlease_count++;
1313                 else
1314                         rdlease_count++;
1315         }
1316 
1317         if ((arg == F_RDLCK && (wrlease_count > 0)) ||
1318             (arg == F_WRLCK && ((rdlease_count + wrlease_count) > 0)))
1319                 goto out_unlock;
1320 
1321         if (my_before != NULL) {
1322                 error = lease_modify(my_before, arg);
1323                 goto out_unlock;
1324         }
1325 
1326         error = 0;
1327         if (arg == F_UNLCK)
1328                 goto out_unlock;
1329 
1330         error = -EINVAL;
1331         if (!leases_enable)
1332                 goto out_unlock;
1333 
1334         error = lease_alloc(filp, arg, &fl);
1335         if (error)
1336                 goto out_unlock;
1337 
1338         error = fasync_helper(fd, filp, 1, &fl->fl_fasync);
1339         if (error < 0) {
1340                 locks_free_lock(fl);
1341                 goto out_unlock;
1342         }
1343         fl->fl_next = *before;
1344         *before = fl;
1345         list_add(&fl->fl_link, &file_lock_list);
1346         filp->f_owner.pid = current->pid;
1347         filp->f_owner.uid = current->uid;
1348         filp->f_owner.euid = current->euid;
1349 out_unlock:
1350         unlock_kernel();
1351         return error;
1352 }
1353 
1354 /**
1355  *      sys_flock: - flock() system call.
1356  *      @fd: the file descriptor to lock.
1357  *      @cmd: the type of lock to apply.
1358  *
1359  *      Apply a %FL_FLOCK style lock to an open file descriptor.
1360  *      The @cmd can be one of
1361  *
1362  *      %LOCK_SH -- a shared lock.
1363  *
1364  *      %LOCK_EX -- an exclusive lock.
1365  *
1366  *      %LOCK_UN -- remove an existing lock.
1367  *
1368  *      %LOCK_MAND -- a `mandatory' flock.  This exists to emulate Windows Share Modes.
1369  *
1370  *      %LOCK_MAND can be combined with %LOCK_READ or %LOCK_WRITE to allow other
1371  *      processes read and write access respectively.
1372  */
1373 asmlinkage long sys_flock(unsigned int fd, unsigned int cmd)
1374 {
1375         struct file *filp;
1376         int error, type;
1377 
1378         error = -EBADF;
1379         filp = fget(fd);
1380         if (!filp)
1381                 goto out;
1382 
1383         error = flock_translate_cmd(cmd);
1384         if (error < 0)
1385                 goto out_putf;
1386         type = error;
1387 
1388         error = -EBADF;
1389         if ((type != F_UNLCK)
1390 #ifdef MSNFS
1391                 && !(type & LOCK_MAND)
1392 #endif
1393                 && !(filp->f_mode & 3))
1394                 goto out_putf;
1395 
1396         lock_kernel();
1397         error = flock_lock_file(filp, type,
1398                                 (cmd & (LOCK_UN | LOCK_NB)) ? 0 : 1);
1399         unlock_kernel();
1400 
1401 out_putf:
1402         fput(filp);
1403 out:
1404         return error;
1405 }
1406 
1407 /* Report the first existing lock that would conflict with l.
1408  * This implements the F_GETLK command of fcntl().
1409  */
1410 int fcntl_getlk(unsigned int fd, struct flock *l)
1411 {
1412         struct file *filp;
1413         struct file_lock *fl, file_lock;
1414         struct flock flock;
1415         int error;
1416 
1417         error = -EFAULT;
1418         if (copy_from_user(&flock, l, sizeof(flock)))
1419                 goto out;
1420         error = -EINVAL;
1421         if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
1422                 goto out;
1423 
1424         error = -EBADF;
1425         filp = fget(fd);
1426         if (!filp)
1427                 goto out;
1428 
1429         error = flock_to_posix_lock(filp, &file_lock, &flock);
1430         if (error)
1431                 goto out_putf;
1432 
1433         if (filp->f_op && filp->f_op->lock) {
1434                 error = filp->f_op->lock(filp, F_GETLK, &file_lock);
1435                 if (error < 0)
1436                         goto out_putf;
1437                 else if (error == LOCK_USE_CLNT)
1438                   /* Bypass for NFS with no locking - 2.0.36 compat */
1439                   fl = posix_test_lock(filp, &file_lock);
1440                 else
1441                   fl = (file_lock.fl_type == F_UNLCK ? NULL : &file_lock);
1442         } else {
1443                 fl = posix_test_lock(filp, &file_lock);
1444         }
1445  
1446         flock.l_type = F_UNLCK;
1447         if (fl != NULL) {
1448                 flock.l_pid = fl->fl_pid;
1449 #if BITS_PER_LONG == 32
1450                 /*
1451                  * Make sure we can represent the posix lock via
1452                  * legacy 32bit flock.
1453                  */
1454                 error = -EOVERFLOW;
1455                 if (fl->fl_start > OFFT_OFFSET_MAX)
1456                         goto out_putf;
1457                 if ((fl->fl_end != OFFSET_MAX)
1458                     && (fl->fl_end > OFFT_OFFSET_MAX))
1459                         goto out_putf;
1460 #endif
1461                 flock.l_start = fl->fl_start;
1462                 flock.l_len = fl->fl_end == OFFSET_MAX ? 0 :
1463                         fl->fl_end - fl->fl_start + 1;
1464                 flock.l_whence = 0;
1465                 flock.l_type = fl->fl_type;
1466         }
1467         error = -EFAULT;
1468         if (!copy_to_user(l, &flock, sizeof(flock)))
1469                 error = 0;
1470   
1471 out_putf:
1472         fput(filp);
1473 out:
1474         return error;
1475 }
1476 
1477 /* Apply the lock described by l to an open file descriptor.
1478  * This implements both the F_SETLK and F_SETLKW commands of fcntl().
1479  */
1480 int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
1481                 struct flock *l)
1482 {
1483         struct file *f;
1484         struct file_lock *file_lock = locks_alloc_lock();
1485         struct flock flock;
1486         struct inode *inode;
1487         int error;
1488 
1489         if (file_lock == NULL)
1490                 return -ENOLCK;
1491 
1492         /*
1493          * This might block, so we do it before checking the inode.
1494          */
1495         error = -EFAULT;
1496         if (copy_from_user(&flock, l, sizeof(flock)))
1497                 goto out;
1498 
1499         /* Get arguments and validate them ...
1500          */
1501 
1502         error = -EINVAL;
1503         inode = filp->f_dentry->d_inode;
1504 
1505         /* Don't allow mandatory locks on files that may be memory mapped
1506          * and shared.
1507          */
1508         if (IS_MANDLOCK(inode) &&
1509             (inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID) {
1510                 struct address_space *mapping = inode->i_mapping;
1511 
1512                 if (mapping->i_mmap_shared != NULL) {
1513                         error = -EAGAIN;
1514                         goto out;
1515                 }
1516         }
1517 
1518         error = flock_to_posix_lock(filp, file_lock, &flock);
1519         if (error)
1520                 goto out;
1521         
1522         error = -EBADF;
1523         switch (flock.l_type) {
1524         case F_RDLCK:
1525                 if (!(filp->f_mode & FMODE_READ))
1526                         goto out;
1527                 break;
1528         case F_WRLCK:
1529                 if (!(filp->f_mode & FMODE_WRITE))
1530                         goto out;
1531                 break;
1532         case F_UNLCK:
1533                 break;
1534         case F_SHLCK:
1535         case F_EXLCK:
1536 #ifdef __sparc__
1537 /* warn a bit for now, but don't overdo it */
1538 {
1539         static int count = 0;
1540         if (!count) {
1541                 count=1;
1542                 printk(KERN_WARNING
1543                        "fcntl_setlk() called by process %d (%s) with broken flock() emulation\n",
1544                        current->pid, current->comm);
1545         }
1546 }
1547                 if (!(filp->f_mode & 3))
1548                         goto out;
1549                 break;
1550 #endif
1551         default:
1552                 error = -EINVAL;
1553                 goto out;
1554         }
1555 
1556 do_it:
1557         if (filp->f_op && filp->f_op->lock != NULL) {
1558                 error = filp->f_op->lock(filp, cmd, file_lock);
1559                 if (error < 0)
1560                         goto out;
1561         }
1562         error = posix_lock_file(filp, file_lock, cmd == F_SETLKW);
1563         read_lock(&current->files->file_lock);
1564         f = fcheck(fd);
1565         read_unlock(&current->files->file_lock);
1566         /* lost race with close, kill stuck lock if close didn't get it */
1567         if (!error && flock.l_type != F_UNLCK && filp != f) {
1568                 file_lock->fl_type = F_UNLCK;
1569                 goto do_it;
1570         }
1571 out:
1572         locks_free_lock(file_lock);
1573         return error;
1574 }
1575 
1576 #if BITS_PER_LONG == 32
1577 /* Report the first existing lock that would conflict with l.
1578  * This implements the F_GETLK command of fcntl().
1579  */
1580 int fcntl_getlk64(unsigned int fd, struct flock64 *l)
1581 {
1582         struct file *filp;
1583         struct file_lock *fl, file_lock;
1584         struct flock64 flock;
1585         int error;
1586 
1587         error = -EFAULT;
1588         if (copy_from_user(&flock, l, sizeof(flock)))
1589                 goto out;
1590         error = -EINVAL;
1591         if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
1592                 goto out;
1593 
1594         error = -EBADF;
1595         filp = fget(fd);
1596         if (!filp)
1597                 goto out;
1598 
1599         error = flock64_to_posix_lock(filp, &file_lock, &flock);
1600         if (error)
1601                 goto out_putf;
1602 
1603         if (filp->f_op && filp->f_op->lock) {
1604                 error = filp->f_op->lock(filp, F_GETLK, &file_lock);
1605                 if (error < 0)
1606                         goto out_putf;
1607                 else if (error == LOCK_USE_CLNT)
1608                   /* Bypass for NFS with no locking - 2.0.36 compat */
1609                   fl = posix_test_lock(filp, &file_lock);
1610                 else
1611                   fl = (file_lock.fl_type == F_UNLCK ? NULL : &file_lock);
1612         } else {
1613                 fl = posix_test_lock(filp, &file_lock);
1614         }
1615  
1616         flock.l_type = F_UNLCK;
1617         if (fl != NULL) {
1618                 flock.l_pid = fl->fl_pid;
1619                 flock.l_start = fl->fl_start;
1620                 flock.l_len = fl->fl_end == OFFSET_MAX ? 0 :
1621                         fl->fl_end - fl->fl_start + 1;
1622                 flock.l_whence = 0;
1623                 flock.l_type = fl->fl_type;
1624         }
1625         error = -EFAULT;
1626         if (!copy_to_user(l, &flock, sizeof(flock)))
1627                 error = 0;
1628   
1629 out_putf:
1630         fput(filp);
1631 out:
1632         return error;
1633 }
1634 
1635 /* Apply the lock described by l to an open file descriptor.
1636  * This implements both the F_SETLK and F_SETLKW commands of fcntl().
1637  */
1638 int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
1639                 struct flock64 *l)
1640 {
1641         struct file *f;
1642         struct file_lock *file_lock = locks_alloc_lock();
1643         struct flock64 flock;
1644         struct inode *inode;
1645         int error;
1646 
1647         if (file_lock == NULL)
1648                 return -ENOLCK;
1649 
1650         /*
1651          * This might block, so we do it before checking the inode.
1652          */
1653         error = -EFAULT;
1654         if (copy_from_user(&flock, l, sizeof(flock)))
1655                 goto out;
1656 
1657         /* Get arguments and validate them ...
1658          */
1659 
1660         error = -EINVAL;
1661         inode = filp->f_dentry->d_inode;
1662 
1663         /* Don't allow mandatory locks on files that may be memory mapped
1664          * and shared.
1665          */
1666         if (IS_MANDLOCK(inode) &&
1667             (inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID) {
1668                 struct address_space *mapping = inode->i_mapping;
1669 
1670                 if (mapping->i_mmap_shared != NULL) {
1671                         error = -EAGAIN;
1672                         goto out;
1673                 }
1674         }
1675 
1676         error = flock64_to_posix_lock(filp, file_lock, &flock);
1677         if (error)
1678                 goto out;
1679         
1680         error = -EBADF;
1681         switch (flock.l_type) {
1682         case F_RDLCK:
1683                 if (!(filp->f_mode & FMODE_READ))
1684                         goto out;
1685                 break;
1686         case F_WRLCK:
1687                 if (!(filp->f_mode & FMODE_WRITE))
1688                         goto out;
1689                 break;
1690         case F_UNLCK:
1691                 break;
1692         case F_SHLCK:
1693         case F_EXLCK:
1694         default:
1695                 error = -EINVAL;
1696                 goto out;
1697         }
1698 
1699 do_it:
1700         if (filp->f_op && filp->f_op->lock != NULL) {
1701                 error = filp->f_op->lock(filp, cmd, file_lock);
1702                 if (error < 0)
1703                         goto out;
1704         }
1705         error = posix_lock_file(filp, file_lock, cmd == F_SETLKW64);
1706         read_lock(&current->files->file_lock);
1707         f = fcheck(fd);
1708         read_unlock(&current->files->file_lock);
1709         /* lost race with close, kill stuck lock if close didn't get it */
1710         if (!error && flock.l_type != F_UNLCK && filp != f) {
1711                 file_lock->fl_type = F_UNLCK;
1712                 goto do_it;
1713         }
1714 out:
1715         locks_free_lock(file_lock);
1716         return error;
1717 }
1718 #endif /* BITS_PER_LONG == 32 */
1719 
1720 /*
1721  * This function is called when the file is being removed
1722  * from the task's fd array.
1723  */
1724 void locks_remove_posix(struct file *filp, fl_owner_t owner)
1725 {
1726         struct inode * inode = filp->f_dentry->d_inode;
1727         struct file_lock *fl;
1728         struct file_lock **before;
1729 
1730         /*
1731          * For POSIX locks we free all locks on this file for the given task.
1732          */
1733         if (!inode->i_flock) {
1734                 /*
1735                  * Notice that something might be grabbing a lock right now.
1736                  * Consider it as a race won by us - event is async, so even if
1737                  * we miss the lock added we can trivially consider it as added
1738                  * after we went through this call.
1739                  */
1740                 return;
1741         }
1742         lock_kernel();
1743         before = &inode->i_flock;
1744         while ((fl = *before) != NULL) {
1745                 if ((fl->fl_flags & FL_POSIX) && fl->fl_owner == owner) {
1746                         struct file *filp = fl->fl_file;
1747                         /* Note: locks_unlock_delete() can sleep, and
1748                          * so we may race with the call to sys_close()
1749                          * by the thread that actually owns this filp.
1750                          */
1751                         get_file(filp);
1752                         locks_unlock_delete(before);
1753                         fput(filp);
1754                         before = &inode->i_flock;
1755                         continue;
1756                 }
1757                 before = &fl->fl_next;
1758         }
1759         unlock_kernel();
1760 }
1761 
1762 /*
1763  * This function is called on the last close of an open file.
1764  */
1765 void locks_remove_flock(struct file *filp)
1766 {
1767         struct inode * inode = filp->f_dentry->d_inode; 
1768         struct file_lock *fl;
1769         struct file_lock **before;
1770 
1771         if (!inode->i_flock)
1772                 return;
1773 
1774         lock_kernel();
1775         before = &inode->i_flock;
1776 
1777         while ((fl = *before) != NULL) {
1778                 if (fl->fl_file == filp) {
1779                         if (fl->fl_flags & FL_FLOCK) {
1780                                 locks_delete_lock(before, 0);
1781                                 continue;
1782                         }
1783                         if (fl->fl_flags & FL_LEASE) {
1784                                 lease_modify(before, F_UNLCK);
1785                                 continue;
1786                         }
1787                 }
1788                 before = &fl->fl_next;
1789         }
1790         unlock_kernel();
1791 }
1792 
1793 /**
1794  *      posix_block_lock - blocks waiting for a file lock
1795  *      @blocker: the lock which is blocking
1796  *      @waiter: the lock which conflicts and has to wait
1797  *
1798  * lockd needs to block waiting for locks.
1799  */
1800 void
1801 posix_block_lock(struct file_lock *blocker, struct file_lock *waiter)
1802 {
1803         locks_insert_block(blocker, waiter);
1804 }
1805 
1806 /**
1807  *      posix_unblock_lock - stop waiting for a file lock
1808  *      @waiter: the lock which was waiting
1809  *
1810  *      lockd needs to block waiting for locks.
1811  */
1812 void
1813 posix_unblock_lock(struct file_lock *waiter)
1814 {
1815         if (!list_empty(&waiter->fl_block))
1816                 locks_delete_block(waiter);
1817 }
1818 
1819 static void lock_get_status(char* out, struct file_lock *fl, int id, char *pfx)
1820 {
1821         struct inode *inode = NULL;
1822 
1823         if (fl->fl_file != NULL)
1824                 inode = fl->fl_file->f_dentry->d_inode;
1825 
1826         out += sprintf(out, "%d:%s ", id, pfx);
1827         if (fl->fl_flags & FL_POSIX) {
1828                 out += sprintf(out, "%6s %s ",
1829                              (fl->fl_flags & FL_ACCESS) ? "ACCESS" : "POSIX ",
1830                              (inode == NULL) ? "*NOINODE*" :
1831                              (IS_MANDLOCK(inode) &&
1832                               (inode->i_mode & (S_IXGRP | S_ISGID)) == S_ISGID) ?
1833                              "MANDATORY" : "ADVISORY ");
1834         } else if (fl->fl_flags & FL_FLOCK) {
1835 #ifdef MSNFS
1836                 if (fl->fl_type & LOCK_MAND) {
1837                         out += sprintf(out, "FLOCK  MSNFS     ");
1838                 } else
1839 #endif
1840                         out += sprintf(out, "FLOCK  ADVISORY  ");
1841         } else if (fl->fl_flags & FL_LEASE) {
1842                 out += sprintf(out, "LEASE  ");
1843                 if (fl->fl_type & F_INPROGRESS)
1844                         out += sprintf(out, "BREAKING  ");
1845                 else if (fl->fl_file)
1846                         out += sprintf(out, "ACTIVE    ");
1847                 else
1848                         out += sprintf(out, "BREAKER   ");
1849         } else {
1850                 out += sprintf(out, "UNKNOWN UNKNOWN  ");
1851         }
1852 #ifdef MSNFS
1853         if (fl->fl_type & LOCK_MAND) {
1854                 out += sprintf(out, "%s ",
1855                                (fl->fl_type & LOCK_READ)
1856                                ? (fl->fl_type & LOCK_WRITE) ? "RW   " : "READ "
1857                                : (fl->fl_type & LOCK_WRITE) ? "WRITE" : "NONE ");
1858         } else
1859 #endif
1860                 out += sprintf(out, "%s ",
1861                                (fl->fl_type & F_INPROGRESS)
1862                                ? (fl->fl_type & F_UNLCK) ? "UNLCK" : "READ "
1863                                : (fl->fl_type & F_WRLCK) ? "WRITE" : "READ ");
1864         out += sprintf(out, "%d %s:%ld ",
1865                      fl->fl_pid,
1866                      inode ? kdevname(inode->i_dev) : "<none>",
1867                      inode ? inode->i_ino : 0);
1868         out += sprintf(out, "%Ld ", fl->fl_start);
1869         if (fl->fl_end == OFFSET_MAX)
1870                 out += sprintf(out, "EOF ");
1871         else
1872                 out += sprintf(out, "%Ld ", fl->fl_end);
1873         sprintf(out, "%08lx %08lx %08lx %08lx %08lx\n",
1874                 (long)fl, (long)fl->fl_link.prev, (long)fl->fl_link.next,
1875                 (long)fl->fl_next, (long)fl->fl_block.next);
1876 }
1877 
1878 static void move_lock_status(char **p, off_t* pos, off_t offset)
1879 {
1880         int len;
1881         len = strlen(*p);
1882         if(*pos >= offset) {
1883                 /* the complete line is valid */
1884                 *p += len;
1885                 *pos += len;
1886                 return;
1887         }
1888         if(*pos+len > offset) {
1889                 /* use the second part of the line */
1890                 int i = offset-*pos;
1891                 memmove(*p,*p+i,len-i);
1892                 *p += len-i;
1893                 *pos += len;
1894                 return;
1895         }
1896         /* discard the complete line */
1897         *pos += len;
1898 }
1899 
1900 /**
1901  *      get_locks_status        -       reports lock usage in /proc/locks
1902  *      @buffer: address in userspace to write into
1903  *      @start: ?
1904  *      @offset: how far we are through the buffer
1905  *      @length: how much to read
1906  */
1907 
1908 int get_locks_status(char *buffer, char **start, off_t offset, int length)
1909 {
1910         struct list_head *tmp;
1911         char *q = buffer;
1912         off_t pos = 0;
1913         int i = 0;
1914 
1915         lock_kernel();
1916         list_for_each(tmp, &file_lock_list) {
1917                 struct list_head *btmp;
1918                 struct file_lock *fl = list_entry(tmp, struct file_lock, fl_link);
1919                 lock_get_status(q, fl, ++i, "");
1920                 move_lock_status(&q, &pos, offset);
1921 
1922                 if(pos >= offset+length)
1923                         goto done;
1924 
1925                 list_for_each(btmp, &fl->fl_block) {
1926                         struct file_lock *bfl = list_entry(btmp,
1927                                         struct file_lock, fl_block);
1928                         lock_get_status(q, bfl, i, " ->");
1929                         move_lock_status(&q, &pos, offset);
1930 
1931                         if(pos >= offset+length)
1932                                 goto done;
1933                 }
1934         }
1935 done:
1936         unlock_kernel();
1937         *start = buffer;
1938         if(q-buffer < length)
1939                 return (q-buffer);
1940         return length;
1941 }
1942 
1943 void steal_locks(fl_owner_t from)
1944 {
1945         struct list_head *tmp;
1946 
1947         if (from == current->files)
1948                 return;
1949 
1950         lock_kernel();
1951         list_for_each(tmp, &file_lock_list) {
1952                 struct file_lock *fl = list_entry(tmp, struct file_lock,
1953                                                   fl_link);
1954                 if (fl->fl_owner == from)
1955                         fl->fl_owner = current->files;
1956         }
1957         unlock_kernel();
1958 }
1959 
1960 #ifdef MSNFS
1961 /**
1962  *      lock_may_read - checks that the region is free of locks
1963  *      @inode: the inode that is being read
1964  *      @start: the first byte to read
1965  *      @len: the number of bytes to read
1966  *
1967  *      Emulates Windows locking requirements.  Whole-file
1968  *      mandatory locks (share modes) can prohibit a read and
1969  *      byte-range POSIX locks can prohibit a read if they overlap.
1970  *
1971  *      N.B. this function is only ever called
1972  *      from knfsd and ownership of locks is never checked.
1973  */
1974 int lock_may_read(struct inode *inode, loff_t start, unsigned long len)
1975 {
1976         struct file_lock *fl;
1977         int result = 1;
1978         lock_kernel();
1979         for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
1980                 if (fl->fl_flags == FL_POSIX) {
1981                         if (fl->fl_type == F_RDLCK)
1982                                 continue;
1983                         if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
1984                                 continue;
1985                 } else if (fl->fl_flags == FL_FLOCK) {
1986                         if (!(fl->fl_type & LOCK_MAND))
1987                                 continue;
1988                         if (fl->fl_type & LOCK_READ)
1989                                 continue;
1990                 } else
1991                         continue;
1992                 result = 0;
1993                 break;
1994         }
1995         unlock_kernel();
1996         return result;
1997 }
1998 
1999 /**
2000  *      lock_may_write - checks that the region is free of locks
2001  *      @inode: the inode that is being written
2002  *      @start: the first byte to write
2003  *      @len: the number of bytes to write
2004  *
2005  *      Emulates Windows locking requirements.  Whole-file
2006  *      mandatory locks (share modes) can prohibit a write and
2007  *      byte-range POSIX locks can prohibit a write if they overlap.
2008  *
2009  *      N.B. this function is only ever called
2010  *      from knfsd and ownership of locks is never checked.
2011  */
2012 int lock_may_write(struct inode *inode, loff_t start, unsigned long len)
2013 {
2014         struct file_lock *fl;
2015         int result = 1;
2016         lock_kernel();
2017         for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
2018                 if (fl->fl_flags == FL_POSIX) {
2019                         if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
2020                                 continue;
2021                 } else if (fl->fl_flags == FL_FLOCK) {
2022                         if (!(fl->fl_type & LOCK_MAND))
2023                                 continue;
2024                         if (fl->fl_type & LOCK_WRITE)
2025                                 continue;
2026                 } else
2027                         continue;
2028                 result = 0;
2029                 break;
2030         }
2031         unlock_kernel();
2032         return result;
2033 }
2034 #endif
2035 
2036 static int __init filelock_init(void)
2037 {
2038         filelock_cache = kmem_cache_create("file_lock_cache",
2039                         sizeof(struct file_lock), 0, 0, init_once, NULL);
2040         if (!filelock_cache)
2041                 panic("cannot create file lock slab cache");
2042         return 0;
2043 }
2044 
2045 module_init(filelock_init)
2046 

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