linux/fs/locks.c
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   1/*
   2 *  linux/fs/locks.c
   3 *
   4 *  Provide support for fcntl()'s F_GETLK, F_SETLK, and F_SETLKW calls.
   5 *  Doug Evans (dje@spiff.uucp), August 07, 1992
   6 *
   7 *  Deadlock detection added.
   8 *  FIXME: one thing isn't handled yet:
   9 *      - mandatory locks (requires lots of changes elsewhere)
  10 *  Kelly Carmichael (kelly@[142.24.8.65]), September 17, 1994.
  11 *
  12 *  Miscellaneous edits, and a total rewrite of posix_lock_file() code.
  13 *  Kai Petzke (wpp@marie.physik.tu-berlin.de), 1994
  14 *  
  15 *  Converted file_lock_table to a linked list from an array, which eliminates
  16 *  the limits on how many active file locks are open.
  17 *  Chad Page (pageone@netcom.com), November 27, 1994
  18 * 
  19 *  Removed dependency on file descriptors. dup()'ed file descriptors now
  20 *  get the same locks as the original file descriptors, and a close() on
  21 *  any file descriptor removes ALL the locks on the file for the current
  22 *  process. Since locks still depend on the process id, locks are inherited
  23 *  after an exec() but not after a fork(). This agrees with POSIX, and both
  24 *  BSD and SVR4 practice.
  25 *  Andy Walker (andy@lysaker.kvaerner.no), February 14, 1995
  26 *
  27 *  Scrapped free list which is redundant now that we allocate locks
  28 *  dynamically with kmalloc()/kfree().
  29 *  Andy Walker (andy@lysaker.kvaerner.no), February 21, 1995
  30 *
  31 *  Implemented two lock personalities - FL_FLOCK and FL_POSIX.
  32 *
  33 *  FL_POSIX locks are created with calls to fcntl() and lockf() through the
  34 *  fcntl() system call. They have the semantics described above.
  35 *
  36 *  FL_FLOCK locks are created with calls to flock(), through the flock()
  37 *  system call, which is new. Old C libraries implement flock() via fcntl()
  38 *  and will continue to use the old, broken implementation.
  39 *
  40 *  FL_FLOCK locks follow the 4.4 BSD flock() semantics. They are associated
  41 *  with a file pointer (filp). As a result they can be shared by a parent
  42 *  process and its children after a fork(). They are removed when the last
  43 *  file descriptor referring to the file pointer is closed (unless explicitly
  44 *  unlocked). 
  45 *
  46 *  FL_FLOCK locks never deadlock, an existing lock is always removed before
  47 *  upgrading from shared to exclusive (or vice versa). When this happens
  48 *  any processes blocked by the current lock are woken up and allowed to
  49 *  run before the new lock is applied.
  50 *  Andy Walker (andy@lysaker.kvaerner.no), June 09, 1995
  51 *
  52 *  Removed some race conditions in flock_lock_file(), marked other possible
  53 *  races. Just grep for FIXME to see them. 
  54 *  Dmitry Gorodchanin (pgmdsg@ibi.com), February 09, 1996.
  55 *
  56 *  Addressed Dmitry's concerns. Deadlock checking no longer recursive.
  57 *  Lock allocation changed to GFP_ATOMIC as we can't afford to sleep
  58 *  once we've checked for blocking and deadlocking.
  59 *  Andy Walker (andy@lysaker.kvaerner.no), April 03, 1996.
  60 *
  61 *  Initial implementation of mandatory locks. SunOS turned out to be
  62 *  a rotten model, so I implemented the "obvious" semantics.
  63 *  See 'Documentation/filesystems/mandatory-locking.txt' for details.
  64 *  Andy Walker (andy@lysaker.kvaerner.no), April 06, 1996.
  65 *
  66 *  Don't allow mandatory locks on mmap()'ed files. Added simple functions to
  67 *  check if a file has mandatory locks, used by mmap(), open() and creat() to
  68 *  see if system call should be rejected. Ref. HP-UX/SunOS/Solaris Reference
  69 *  Manual, Section 2.
  70 *  Andy Walker (andy@lysaker.kvaerner.no), April 09, 1996.
  71 *
  72 *  Tidied up block list handling. Added '/proc/locks' interface.
  73 *  Andy Walker (andy@lysaker.kvaerner.no), April 24, 1996.
  74 *
  75 *  Fixed deadlock condition for pathological code that mixes calls to
  76 *  flock() and fcntl().
  77 *  Andy Walker (andy@lysaker.kvaerner.no), April 29, 1996.
  78 *
  79 *  Allow only one type of locking scheme (FL_POSIX or FL_FLOCK) to be in use
  80 *  for a given file at a time. Changed the CONFIG_LOCK_MANDATORY scheme to
  81 *  guarantee sensible behaviour in the case where file system modules might
  82 *  be compiled with different options than the kernel itself.
  83 *  Andy Walker (andy@lysaker.kvaerner.no), May 15, 1996.
  84 *
  85 *  Added a couple of missing wake_up() calls. Thanks to Thomas Meckel
  86 *  (Thomas.Meckel@mni.fh-giessen.de) for spotting this.
  87 *  Andy Walker (andy@lysaker.kvaerner.no), May 15, 1996.
  88 *
  89 *  Changed FL_POSIX locks to use the block list in the same way as FL_FLOCK
  90 *  locks. Changed process synchronisation to avoid dereferencing locks that
  91 *  have already been freed.
  92 *  Andy Walker (andy@lysaker.kvaerner.no), Sep 21, 1996.
  93 *
  94 *  Made the block list a circular list to minimise searching in the list.
  95 *  Andy Walker (andy@lysaker.kvaerner.no), Sep 25, 1996.
  96 *
  97 *  Made mandatory locking a mount option. Default is not to allow mandatory
  98 *  locking.
  99 *  Andy Walker (andy@lysaker.kvaerner.no), Oct 04, 1996.
 100 *
 101 *  Some adaptations for NFS support.
 102 *  Olaf Kirch (okir@monad.swb.de), Dec 1996,
 103 *
 104 *  Fixed /proc/locks interface so that we can't overrun the buffer we are handed.
 105 *  Andy Walker (andy@lysaker.kvaerner.no), May 12, 1997.
 106 *
 107 *  Use slab allocator instead of kmalloc/kfree.
 108 *  Use generic list implementation from <linux/list.h>.
 109 *  Sped up posix_locks_deadlock by only considering blocked locks.
 110 *  Matthew Wilcox <willy@debian.org>, March, 2000.
 111 *
 112 *  Leases and LOCK_MAND
 113 *  Matthew Wilcox <willy@debian.org>, June, 2000.
 114 *  Stephen Rothwell <sfr@canb.auug.org.au>, June, 2000.
 115 */
 116
 117#include <linux/capability.h>
 118#include <linux/file.h>
 119#include <linux/fdtable.h>
 120#include <linux/fs.h>
 121#include <linux/init.h>
 122#include <linux/module.h>
 123#include <linux/security.h>
 124#include <linux/slab.h>
 125#include <linux/syscalls.h>
 126#include <linux/time.h>
 127#include <linux/rcupdate.h>
 128#include <linux/pid_namespace.h>
 129
 130#include <asm/uaccess.h>
 131
 132#define IS_POSIX(fl)    (fl->fl_flags & FL_POSIX)
 133#define IS_FLOCK(fl)    (fl->fl_flags & FL_FLOCK)
 134#define IS_LEASE(fl)    (fl->fl_flags & FL_LEASE)
 135
 136static bool lease_breaking(struct file_lock *fl)
 137{
 138        return fl->fl_flags & (FL_UNLOCK_PENDING | FL_DOWNGRADE_PENDING);
 139}
 140
 141static int target_leasetype(struct file_lock *fl)
 142{
 143        if (fl->fl_flags & FL_UNLOCK_PENDING)
 144                return F_UNLCK;
 145        if (fl->fl_flags & FL_DOWNGRADE_PENDING)
 146                return F_RDLCK;
 147        return fl->fl_type;
 148}
 149
 150int leases_enable = 1;
 151int lease_break_time = 45;
 152
 153#define for_each_lock(inode, lockp) \
 154        for (lockp = &inode->i_flock; *lockp != NULL; lockp = &(*lockp)->fl_next)
 155
 156static LIST_HEAD(file_lock_list);
 157static LIST_HEAD(blocked_list);
 158static DEFINE_SPINLOCK(file_lock_lock);
 159
 160/*
 161 * Protects the two list heads above, plus the inode->i_flock list
 162 */
 163void lock_flocks(void)
 164{
 165        spin_lock(&file_lock_lock);
 166}
 167EXPORT_SYMBOL_GPL(lock_flocks);
 168
 169void unlock_flocks(void)
 170{
 171        spin_unlock(&file_lock_lock);
 172}
 173EXPORT_SYMBOL_GPL(unlock_flocks);
 174
 175static struct kmem_cache *filelock_cache __read_mostly;
 176
 177static void locks_init_lock_heads(struct file_lock *fl)
 178{
 179        INIT_LIST_HEAD(&fl->fl_link);
 180        INIT_LIST_HEAD(&fl->fl_block);
 181        init_waitqueue_head(&fl->fl_wait);
 182}
 183
 184/* Allocate an empty lock structure. */
 185struct file_lock *locks_alloc_lock(void)
 186{
 187        struct file_lock *fl = kmem_cache_zalloc(filelock_cache, GFP_KERNEL);
 188
 189        if (fl)
 190                locks_init_lock_heads(fl);
 191
 192        return fl;
 193}
 194EXPORT_SYMBOL_GPL(locks_alloc_lock);
 195
 196void locks_release_private(struct file_lock *fl)
 197{
 198        if (fl->fl_ops) {
 199                if (fl->fl_ops->fl_release_private)
 200                        fl->fl_ops->fl_release_private(fl);
 201                fl->fl_ops = NULL;
 202        }
 203        fl->fl_lmops = NULL;
 204
 205}
 206EXPORT_SYMBOL_GPL(locks_release_private);
 207
 208/* Free a lock which is not in use. */
 209void locks_free_lock(struct file_lock *fl)
 210{
 211        BUG_ON(waitqueue_active(&fl->fl_wait));
 212        BUG_ON(!list_empty(&fl->fl_block));
 213        BUG_ON(!list_empty(&fl->fl_link));
 214
 215        locks_release_private(fl);
 216        kmem_cache_free(filelock_cache, fl);
 217}
 218EXPORT_SYMBOL(locks_free_lock);
 219
 220void locks_init_lock(struct file_lock *fl)
 221{
 222        memset(fl, 0, sizeof(struct file_lock));
 223        locks_init_lock_heads(fl);
 224}
 225
 226EXPORT_SYMBOL(locks_init_lock);
 227
 228static void locks_copy_private(struct file_lock *new, struct file_lock *fl)
 229{
 230        if (fl->fl_ops) {
 231                if (fl->fl_ops->fl_copy_lock)
 232                        fl->fl_ops->fl_copy_lock(new, fl);
 233                new->fl_ops = fl->fl_ops;
 234        }
 235        if (fl->fl_lmops)
 236                new->fl_lmops = fl->fl_lmops;
 237}
 238
 239/*
 240 * Initialize a new lock from an existing file_lock structure.
 241 */
 242void __locks_copy_lock(struct file_lock *new, const struct file_lock *fl)
 243{
 244        new->fl_owner = fl->fl_owner;
 245        new->fl_pid = fl->fl_pid;
 246        new->fl_file = NULL;
 247        new->fl_flags = fl->fl_flags;
 248        new->fl_type = fl->fl_type;
 249        new->fl_start = fl->fl_start;
 250        new->fl_end = fl->fl_end;
 251        new->fl_ops = NULL;
 252        new->fl_lmops = NULL;
 253}
 254EXPORT_SYMBOL(__locks_copy_lock);
 255
 256void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
 257{
 258        locks_release_private(new);
 259
 260        __locks_copy_lock(new, fl);
 261        new->fl_file = fl->fl_file;
 262        new->fl_ops = fl->fl_ops;
 263        new->fl_lmops = fl->fl_lmops;
 264
 265        locks_copy_private(new, fl);
 266}
 267
 268EXPORT_SYMBOL(locks_copy_lock);
 269
 270static inline int flock_translate_cmd(int cmd) {
 271        if (cmd & LOCK_MAND)
 272                return cmd & (LOCK_MAND | LOCK_RW);
 273        switch (cmd) {
 274        case LOCK_SH:
 275                return F_RDLCK;
 276        case LOCK_EX:
 277                return F_WRLCK;
 278        case LOCK_UN:
 279                return F_UNLCK;
 280        }
 281        return -EINVAL;
 282}
 283
 284/* Fill in a file_lock structure with an appropriate FLOCK lock. */
 285static int flock_make_lock(struct file *filp, struct file_lock **lock,
 286                unsigned int cmd)
 287{
 288        struct file_lock *fl;
 289        int type = flock_translate_cmd(cmd);
 290        if (type < 0)
 291                return type;
 292        
 293        fl = locks_alloc_lock();
 294        if (fl == NULL)
 295                return -ENOMEM;
 296
 297        fl->fl_file = filp;
 298        fl->fl_pid = current->tgid;
 299        fl->fl_flags = FL_FLOCK;
 300        fl->fl_type = type;
 301        fl->fl_end = OFFSET_MAX;
 302        
 303        *lock = fl;
 304        return 0;
 305}
 306
 307static int assign_type(struct file_lock *fl, long type)
 308{
 309        switch (type) {
 310        case F_RDLCK:
 311        case F_WRLCK:
 312        case F_UNLCK:
 313                fl->fl_type = type;
 314                break;
 315        default:
 316                return -EINVAL;
 317        }
 318        return 0;
 319}
 320
 321/* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX
 322 * style lock.
 323 */
 324static int flock_to_posix_lock(struct file *filp, struct file_lock *fl,
 325                               struct flock *l)
 326{
 327        off_t start, end;
 328
 329        switch (l->l_whence) {
 330        case SEEK_SET:
 331                start = 0;
 332                break;
 333        case SEEK_CUR:
 334                start = filp->f_pos;
 335                break;
 336        case SEEK_END:
 337                start = i_size_read(filp->f_path.dentry->d_inode);
 338                break;
 339        default:
 340                return -EINVAL;
 341        }
 342
 343        /* POSIX-1996 leaves the case l->l_len < 0 undefined;
 344           POSIX-2001 defines it. */
 345        start += l->l_start;
 346        if (start < 0)
 347                return -EINVAL;
 348        fl->fl_end = OFFSET_MAX;
 349        if (l->l_len > 0) {
 350                end = start + l->l_len - 1;
 351                fl->fl_end = end;
 352        } else if (l->l_len < 0) {
 353                end = start - 1;
 354                fl->fl_end = end;
 355                start += l->l_len;
 356                if (start < 0)
 357                        return -EINVAL;
 358        }
 359        fl->fl_start = start;   /* we record the absolute position */
 360        if (fl->fl_end < fl->fl_start)
 361                return -EOVERFLOW;
 362        
 363        fl->fl_owner = current->files;
 364        fl->fl_pid = current->tgid;
 365        fl->fl_file = filp;
 366        fl->fl_flags = FL_POSIX;
 367        fl->fl_ops = NULL;
 368        fl->fl_lmops = NULL;
 369
 370        return assign_type(fl, l->l_type);
 371}
 372
 373#if BITS_PER_LONG == 32
 374static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
 375                                 struct flock64 *l)
 376{
 377        loff_t start;
 378
 379        switch (l->l_whence) {
 380        case SEEK_SET:
 381                start = 0;
 382                break;
 383        case SEEK_CUR:
 384                start = filp->f_pos;
 385                break;
 386        case SEEK_END:
 387                start = i_size_read(filp->f_path.dentry->d_inode);
 388                break;
 389        default:
 390                return -EINVAL;
 391        }
 392
 393        start += l->l_start;
 394        if (start < 0)
 395                return -EINVAL;
 396        fl->fl_end = OFFSET_MAX;
 397        if (l->l_len > 0) {
 398                fl->fl_end = start + l->l_len - 1;
 399        } else if (l->l_len < 0) {
 400                fl->fl_end = start - 1;
 401                start += l->l_len;
 402                if (start < 0)
 403                        return -EINVAL;
 404        }
 405        fl->fl_start = start;   /* we record the absolute position */
 406        if (fl->fl_end < fl->fl_start)
 407                return -EOVERFLOW;
 408        
 409        fl->fl_owner = current->files;
 410        fl->fl_pid = current->tgid;
 411        fl->fl_file = filp;
 412        fl->fl_flags = FL_POSIX;
 413        fl->fl_ops = NULL;
 414        fl->fl_lmops = NULL;
 415
 416        return assign_type(fl, l->l_type);
 417}
 418#endif
 419
 420/* default lease lock manager operations */
 421static void lease_break_callback(struct file_lock *fl)
 422{
 423        kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG);
 424}
 425
 426static const struct lock_manager_operations lease_manager_ops = {
 427        .lm_break = lease_break_callback,
 428        .lm_change = lease_modify,
 429};
 430
 431/*
 432 * Initialize a lease, use the default lock manager operations
 433 */
 434static int lease_init(struct file *filp, long type, struct file_lock *fl)
 435 {
 436        if (assign_type(fl, type) != 0)
 437                return -EINVAL;
 438
 439        fl->fl_owner = current->files;
 440        fl->fl_pid = current->tgid;
 441
 442        fl->fl_file = filp;
 443        fl->fl_flags = FL_LEASE;
 444        fl->fl_start = 0;
 445        fl->fl_end = OFFSET_MAX;
 446        fl->fl_ops = NULL;
 447        fl->fl_lmops = &lease_manager_ops;
 448        return 0;
 449}
 450
 451/* Allocate a file_lock initialised to this type of lease */
 452static struct file_lock *lease_alloc(struct file *filp, long type)
 453{
 454        struct file_lock *fl = locks_alloc_lock();
 455        int error = -ENOMEM;
 456
 457        if (fl == NULL)
 458                return ERR_PTR(error);
 459
 460        error = lease_init(filp, type, fl);
 461        if (error) {
 462                locks_free_lock(fl);
 463                return ERR_PTR(error);
 464        }
 465        return fl;
 466}
 467
 468/* Check if two locks overlap each other.
 469 */
 470static inline int locks_overlap(struct file_lock *fl1, struct file_lock *fl2)
 471{
 472        return ((fl1->fl_end >= fl2->fl_start) &&
 473                (fl2->fl_end >= fl1->fl_start));
 474}
 475
 476/*
 477 * Check whether two locks have the same owner.
 478 */
 479static int posix_same_owner(struct file_lock *fl1, struct file_lock *fl2)
 480{
 481        if (fl1->fl_lmops && fl1->fl_lmops->lm_compare_owner)
 482                return fl2->fl_lmops == fl1->fl_lmops &&
 483                        fl1->fl_lmops->lm_compare_owner(fl1, fl2);
 484        return fl1->fl_owner == fl2->fl_owner;
 485}
 486
 487/* Remove waiter from blocker's block list.
 488 * When blocker ends up pointing to itself then the list is empty.
 489 */
 490static void __locks_delete_block(struct file_lock *waiter)
 491{
 492        list_del_init(&waiter->fl_block);
 493        list_del_init(&waiter->fl_link);
 494        waiter->fl_next = NULL;
 495}
 496
 497/*
 498 */
 499void locks_delete_block(struct file_lock *waiter)
 500{
 501        lock_flocks();
 502        __locks_delete_block(waiter);
 503        unlock_flocks();
 504}
 505EXPORT_SYMBOL(locks_delete_block);
 506
 507/* Insert waiter into blocker's block list.
 508 * We use a circular list so that processes can be easily woken up in
 509 * the order they blocked. The documentation doesn't require this but
 510 * it seems like the reasonable thing to do.
 511 */
 512static void locks_insert_block(struct file_lock *blocker, 
 513                               struct file_lock *waiter)
 514{
 515        BUG_ON(!list_empty(&waiter->fl_block));
 516        list_add_tail(&waiter->fl_block, &blocker->fl_block);
 517        waiter->fl_next = blocker;
 518        if (IS_POSIX(blocker))
 519                list_add(&waiter->fl_link, &blocked_list);
 520}
 521
 522/* Wake up processes blocked waiting for blocker.
 523 * If told to wait then schedule the processes until the block list
 524 * is empty, otherwise empty the block list ourselves.
 525 */
 526static void locks_wake_up_blocks(struct file_lock *blocker)
 527{
 528        while (!list_empty(&blocker->fl_block)) {
 529                struct file_lock *waiter;
 530
 531                waiter = list_first_entry(&blocker->fl_block,
 532                                struct file_lock, fl_block);
 533                __locks_delete_block(waiter);
 534                if (waiter->fl_lmops && waiter->fl_lmops->lm_notify)
 535                        waiter->fl_lmops->lm_notify(waiter);
 536                else
 537                        wake_up(&waiter->fl_wait);
 538        }
 539}
 540
 541/* Insert file lock fl into an inode's lock list at the position indicated
 542 * by pos. At the same time add the lock to the global file lock list.
 543 */
 544static void locks_insert_lock(struct file_lock **pos, struct file_lock *fl)
 545{
 546        list_add(&fl->fl_link, &file_lock_list);
 547
 548        fl->fl_nspid = get_pid(task_tgid(current));
 549
 550        /* insert into file's list */
 551        fl->fl_next = *pos;
 552        *pos = fl;
 553}
 554
 555/*
 556 * Delete a lock and then free it.
 557 * Wake up processes that are blocked waiting for this lock,
 558 * notify the FS that the lock has been cleared and
 559 * finally free the lock.
 560 */
 561static void locks_delete_lock(struct file_lock **thisfl_p)
 562{
 563        struct file_lock *fl = *thisfl_p;
 564
 565        *thisfl_p = fl->fl_next;
 566        fl->fl_next = NULL;
 567        list_del_init(&fl->fl_link);
 568
 569        if (fl->fl_nspid) {
 570                put_pid(fl->fl_nspid);
 571                fl->fl_nspid = NULL;
 572        }
 573
 574        locks_wake_up_blocks(fl);
 575        locks_free_lock(fl);
 576}
 577
 578/* Determine if lock sys_fl blocks lock caller_fl. Common functionality
 579 * checks for shared/exclusive status of overlapping locks.
 580 */
 581static int locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
 582{
 583        if (sys_fl->fl_type == F_WRLCK)
 584                return 1;
 585        if (caller_fl->fl_type == F_WRLCK)
 586                return 1;
 587        return 0;
 588}
 589
 590/* Determine if lock sys_fl blocks lock caller_fl. POSIX specific
 591 * checking before calling the locks_conflict().
 592 */
 593static int posix_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
 594{
 595        /* POSIX locks owned by the same process do not conflict with
 596         * each other.
 597         */
 598        if (!IS_POSIX(sys_fl) || posix_same_owner(caller_fl, sys_fl))
 599                return (0);
 600
 601        /* Check whether they overlap */
 602        if (!locks_overlap(caller_fl, sys_fl))
 603                return 0;
 604
 605        return (locks_conflict(caller_fl, sys_fl));
 606}
 607
 608/* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific
 609 * checking before calling the locks_conflict().
 610 */
 611static int flock_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
 612{
 613        /* FLOCK locks referring to the same filp do not conflict with
 614         * each other.
 615         */
 616        if (!IS_FLOCK(sys_fl) || (caller_fl->fl_file == sys_fl->fl_file))
 617                return (0);
 618        if ((caller_fl->fl_type & LOCK_MAND) || (sys_fl->fl_type & LOCK_MAND))
 619                return 0;
 620
 621        return (locks_conflict(caller_fl, sys_fl));
 622}
 623
 624void
 625posix_test_lock(struct file *filp, struct file_lock *fl)
 626{
 627        struct file_lock *cfl;
 628
 629        lock_flocks();
 630        for (cfl = filp->f_path.dentry->d_inode->i_flock; cfl; cfl = cfl->fl_next) {
 631                if (!IS_POSIX(cfl))
 632                        continue;
 633                if (posix_locks_conflict(fl, cfl))
 634                        break;
 635        }
 636        if (cfl) {
 637                __locks_copy_lock(fl, cfl);
 638                if (cfl->fl_nspid)
 639                        fl->fl_pid = pid_vnr(cfl->fl_nspid);
 640        } else
 641                fl->fl_type = F_UNLCK;
 642        unlock_flocks();
 643        return;
 644}
 645EXPORT_SYMBOL(posix_test_lock);
 646
 647/*
 648 * Deadlock detection:
 649 *
 650 * We attempt to detect deadlocks that are due purely to posix file
 651 * locks.
 652 *
 653 * We assume that a task can be waiting for at most one lock at a time.
 654 * So for any acquired lock, the process holding that lock may be
 655 * waiting on at most one other lock.  That lock in turns may be held by
 656 * someone waiting for at most one other lock.  Given a requested lock
 657 * caller_fl which is about to wait for a conflicting lock block_fl, we
 658 * follow this chain of waiters to ensure we are not about to create a
 659 * cycle.
 660 *
 661 * Since we do this before we ever put a process to sleep on a lock, we
 662 * are ensured that there is never a cycle; that is what guarantees that
 663 * the while() loop in posix_locks_deadlock() eventually completes.
 664 *
 665 * Note: the above assumption may not be true when handling lock
 666 * requests from a broken NFS client. It may also fail in the presence
 667 * of tasks (such as posix threads) sharing the same open file table.
 668 *
 669 * To handle those cases, we just bail out after a few iterations.
 670 */
 671
 672#define MAX_DEADLK_ITERATIONS 10
 673
 674/* Find a lock that the owner of the given block_fl is blocking on. */
 675static struct file_lock *what_owner_is_waiting_for(struct file_lock *block_fl)
 676{
 677        struct file_lock *fl;
 678
 679        list_for_each_entry(fl, &blocked_list, fl_link) {
 680                if (posix_same_owner(fl, block_fl))
 681                        return fl->fl_next;
 682        }
 683        return NULL;
 684}
 685
 686static int posix_locks_deadlock(struct file_lock *caller_fl,
 687                                struct file_lock *block_fl)
 688{
 689        int i = 0;
 690
 691        while ((block_fl = what_owner_is_waiting_for(block_fl))) {
 692                if (i++ > MAX_DEADLK_ITERATIONS)
 693                        return 0;
 694                if (posix_same_owner(caller_fl, block_fl))
 695                        return 1;
 696        }
 697        return 0;
 698}
 699
 700/* Try to create a FLOCK lock on filp. We always insert new FLOCK locks
 701 * after any leases, but before any posix locks.
 702 *
 703 * Note that if called with an FL_EXISTS argument, the caller may determine
 704 * whether or not a lock was successfully freed by testing the return
 705 * value for -ENOENT.
 706 */
 707static int flock_lock_file(struct file *filp, struct file_lock *request)
 708{
 709        struct file_lock *new_fl = NULL;
 710        struct file_lock **before;
 711        struct inode * inode = filp->f_path.dentry->d_inode;
 712        int error = 0;
 713        int found = 0;
 714
 715        if (!(request->fl_flags & FL_ACCESS) && (request->fl_type != F_UNLCK)) {
 716                new_fl = locks_alloc_lock();
 717                if (!new_fl)
 718                        return -ENOMEM;
 719        }
 720
 721        lock_flocks();
 722        if (request->fl_flags & FL_ACCESS)
 723                goto find_conflict;
 724
 725        for_each_lock(inode, before) {
 726                struct file_lock *fl = *before;
 727                if (IS_POSIX(fl))
 728                        break;
 729                if (IS_LEASE(fl))
 730                        continue;
 731                if (filp != fl->fl_file)
 732                        continue;
 733                if (request->fl_type == fl->fl_type)
 734                        goto out;
 735                found = 1;
 736                locks_delete_lock(before);
 737                break;
 738        }
 739
 740        if (request->fl_type == F_UNLCK) {
 741                if ((request->fl_flags & FL_EXISTS) && !found)
 742                        error = -ENOENT;
 743                goto out;
 744        }
 745
 746        /*
 747         * If a higher-priority process was blocked on the old file lock,
 748         * give it the opportunity to lock the file.
 749         */
 750        if (found) {
 751                unlock_flocks();
 752                cond_resched();
 753                lock_flocks();
 754        }
 755
 756find_conflict:
 757        for_each_lock(inode, before) {
 758                struct file_lock *fl = *before;
 759                if (IS_POSIX(fl))
 760                        break;
 761                if (IS_LEASE(fl))
 762                        continue;
 763                if (!flock_locks_conflict(request, fl))
 764                        continue;
 765                error = -EAGAIN;
 766                if (!(request->fl_flags & FL_SLEEP))
 767                        goto out;
 768                error = FILE_LOCK_DEFERRED;
 769                locks_insert_block(fl, request);
 770                goto out;
 771        }
 772        if (request->fl_flags & FL_ACCESS)
 773                goto out;
 774        locks_copy_lock(new_fl, request);
 775        locks_insert_lock(before, new_fl);
 776        new_fl = NULL;
 777        error = 0;
 778
 779out:
 780        unlock_flocks();
 781        if (new_fl)
 782                locks_free_lock(new_fl);
 783        return error;
 784}
 785
 786static int __posix_lock_file(struct inode *inode, struct file_lock *request, struct file_lock *conflock)
 787{
 788        struct file_lock *fl;
 789        struct file_lock *new_fl = NULL;
 790        struct file_lock *new_fl2 = NULL;
 791        struct file_lock *left = NULL;
 792        struct file_lock *right = NULL;
 793        struct file_lock **before;
 794        int error, added = 0;
 795
 796        /*
 797         * We may need two file_lock structures for this operation,
 798         * so we get them in advance to avoid races.
 799         *
 800         * In some cases we can be sure, that no new locks will be needed
 801         */
 802        if (!(request->fl_flags & FL_ACCESS) &&
 803            (request->fl_type != F_UNLCK ||
 804             request->fl_start != 0 || request->fl_end != OFFSET_MAX)) {
 805                new_fl = locks_alloc_lock();
 806                new_fl2 = locks_alloc_lock();
 807        }
 808
 809        lock_flocks();
 810        if (request->fl_type != F_UNLCK) {
 811                for_each_lock(inode, before) {
 812                        fl = *before;
 813                        if (!IS_POSIX(fl))
 814                                continue;
 815                        if (!posix_locks_conflict(request, fl))
 816                                continue;
 817                        if (conflock)
 818                                __locks_copy_lock(conflock, fl);
 819                        error = -EAGAIN;
 820                        if (!(request->fl_flags & FL_SLEEP))
 821                                goto out;
 822                        error = -EDEADLK;
 823                        if (posix_locks_deadlock(request, fl))
 824                                goto out;
 825                        error = FILE_LOCK_DEFERRED;
 826                        locks_insert_block(fl, request);
 827                        goto out;
 828                }
 829        }
 830
 831        /* If we're just looking for a conflict, we're done. */
 832        error = 0;
 833        if (request->fl_flags & FL_ACCESS)
 834                goto out;
 835
 836        /*
 837         * Find the first old lock with the same owner as the new lock.
 838         */
 839        
 840        before = &inode->i_flock;
 841
 842        /* First skip locks owned by other processes.  */
 843        while ((fl = *before) && (!IS_POSIX(fl) ||
 844                                  !posix_same_owner(request, fl))) {
 845                before = &fl->fl_next;
 846        }
 847
 848        /* Process locks with this owner.  */
 849        while ((fl = *before) && posix_same_owner(request, fl)) {
 850                /* Detect adjacent or overlapping regions (if same lock type)
 851                 */
 852                if (request->fl_type == fl->fl_type) {
 853                        /* In all comparisons of start vs end, use
 854                         * "start - 1" rather than "end + 1". If end
 855                         * is OFFSET_MAX, end + 1 will become negative.
 856                         */
 857                        if (fl->fl_end < request->fl_start - 1)
 858                                goto next_lock;
 859                        /* If the next lock in the list has entirely bigger
 860                         * addresses than the new one, insert the lock here.
 861                         */
 862                        if (fl->fl_start - 1 > request->fl_end)
 863                                break;
 864
 865                        /* If we come here, the new and old lock are of the
 866                         * same type and adjacent or overlapping. Make one
 867                         * lock yielding from the lower start address of both
 868                         * locks to the higher end address.
 869                         */
 870                        if (fl->fl_start > request->fl_start)
 871                                fl->fl_start = request->fl_start;
 872                        else
 873                                request->fl_start = fl->fl_start;
 874                        if (fl->fl_end < request->fl_end)
 875                                fl->fl_end = request->fl_end;
 876                        else
 877                                request->fl_end = fl->fl_end;
 878                        if (added) {
 879                                locks_delete_lock(before);
 880                                continue;
 881                        }
 882                        request = fl;
 883                        added = 1;
 884                }
 885                else {
 886                        /* Processing for different lock types is a bit
 887                         * more complex.
 888                         */
 889                        if (fl->fl_end < request->fl_start)
 890                                goto next_lock;
 891                        if (fl->fl_start > request->fl_end)
 892                                break;
 893                        if (request->fl_type == F_UNLCK)
 894                                added = 1;
 895                        if (fl->fl_start < request->fl_start)
 896                                left = fl;
 897                        /* If the next lock in the list has a higher end
 898                         * address than the new one, insert the new one here.
 899                         */
 900                        if (fl->fl_end > request->fl_end) {
 901                                right = fl;
 902                                break;
 903                        }
 904                        if (fl->fl_start >= request->fl_start) {
 905                                /* The new lock completely replaces an old
 906                                 * one (This may happen several times).
 907                                 */
 908                                if (added) {
 909                                        locks_delete_lock(before);
 910                                        continue;
 911                                }
 912                                /* Replace the old lock with the new one.
 913                                 * Wake up anybody waiting for the old one,
 914                                 * as the change in lock type might satisfy
 915                                 * their needs.
 916                                 */
 917                                locks_wake_up_blocks(fl);
 918                                fl->fl_start = request->fl_start;
 919                                fl->fl_end = request->fl_end;
 920                                fl->fl_type = request->fl_type;
 921                                locks_release_private(fl);
 922                                locks_copy_private(fl, request);
 923                                request = fl;
 924                                added = 1;
 925                        }
 926                }
 927                /* Go on to next lock.
 928                 */
 929        next_lock:
 930                before = &fl->fl_next;
 931        }
 932
 933        /*
 934         * The above code only modifies existing locks in case of
 935         * merging or replacing.  If new lock(s) need to be inserted
 936         * all modifications are done bellow this, so it's safe yet to
 937         * bail out.
 938         */
 939        error = -ENOLCK; /* "no luck" */
 940        if (right && left == right && !new_fl2)
 941                goto out;
 942
 943        error = 0;
 944        if (!added) {
 945                if (request->fl_type == F_UNLCK) {
 946                        if (request->fl_flags & FL_EXISTS)
 947                                error = -ENOENT;
 948                        goto out;
 949                }
 950
 951                if (!new_fl) {
 952                        error = -ENOLCK;
 953                        goto out;
 954                }
 955                locks_copy_lock(new_fl, request);
 956                locks_insert_lock(before, new_fl);
 957                new_fl = NULL;
 958        }
 959        if (right) {
 960                if (left == right) {
 961                        /* The new lock breaks the old one in two pieces,
 962                         * so we have to use the second new lock.
 963                         */
 964                        left = new_fl2;
 965                        new_fl2 = NULL;
 966                        locks_copy_lock(left, right);
 967                        locks_insert_lock(before, left);
 968                }
 969                right->fl_start = request->fl_end + 1;
 970                locks_wake_up_blocks(right);
 971        }
 972        if (left) {
 973                left->fl_end = request->fl_start - 1;
 974                locks_wake_up_blocks(left);
 975        }
 976 out:
 977        unlock_flocks();
 978        /*
 979         * Free any unused locks.
 980         */
 981        if (new_fl)
 982                locks_free_lock(new_fl);
 983        if (new_fl2)
 984                locks_free_lock(new_fl2);
 985        return error;
 986}
 987
 988/**
 989 * posix_lock_file - Apply a POSIX-style lock to a file
 990 * @filp: The file to apply the lock to
 991 * @fl: The lock to be applied
 992 * @conflock: Place to return a copy of the conflicting lock, if found.
 993 *
 994 * Add a POSIX style lock to a file.
 995 * We merge adjacent & overlapping locks whenever possible.
 996 * POSIX locks are sorted by owner task, then by starting address
 997 *
 998 * Note that if called with an FL_EXISTS argument, the caller may determine
 999 * whether or not a lock was successfully freed by testing the return
1000 * value for -ENOENT.
1001 */
1002int posix_lock_file(struct file *filp, struct file_lock *fl,
1003                        struct file_lock *conflock)
1004{
1005        return __posix_lock_file(filp->f_path.dentry->d_inode, fl, conflock);
1006}
1007EXPORT_SYMBOL(posix_lock_file);
1008
1009/**
1010 * posix_lock_file_wait - Apply a POSIX-style lock to a file
1011 * @filp: The file to apply the lock to
1012 * @fl: The lock to be applied
1013 *
1014 * Add a POSIX style lock to a file.
1015 * We merge adjacent & overlapping locks whenever possible.
1016 * POSIX locks are sorted by owner task, then by starting address
1017 */
1018int posix_lock_file_wait(struct file *filp, struct file_lock *fl)
1019{
1020        int error;
1021        might_sleep ();
1022        for (;;) {
1023                error = posix_lock_file(filp, fl, NULL);
1024                if (error != FILE_LOCK_DEFERRED)
1025                        break;
1026                error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
1027                if (!error)
1028                        continue;
1029
1030                locks_delete_block(fl);
1031                break;
1032        }
1033        return error;
1034}
1035EXPORT_SYMBOL(posix_lock_file_wait);
1036
1037/**
1038 * locks_mandatory_locked - Check for an active lock
1039 * @inode: the file to check
1040 *
1041 * Searches the inode's list of locks to find any POSIX locks which conflict.
1042 * This function is called from locks_verify_locked() only.
1043 */
1044int locks_mandatory_locked(struct inode *inode)
1045{
1046        fl_owner_t owner = current->files;
1047        struct file_lock *fl;
1048
1049        /*
1050         * Search the lock list for this inode for any POSIX locks.
1051         */
1052        lock_flocks();
1053        for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
1054                if (!IS_POSIX(fl))
1055                        continue;
1056                if (fl->fl_owner != owner)
1057                        break;
1058        }
1059        unlock_flocks();
1060        return fl ? -EAGAIN : 0;
1061}
1062
1063/**
1064 * locks_mandatory_area - Check for a conflicting lock
1065 * @read_write: %FLOCK_VERIFY_WRITE for exclusive access, %FLOCK_VERIFY_READ
1066 *              for shared
1067 * @inode:      the file to check
1068 * @filp:       how the file was opened (if it was)
1069 * @offset:     start of area to check
1070 * @count:      length of area to check
1071 *
1072 * Searches the inode's list of locks to find any POSIX locks which conflict.
1073 * This function is called from rw_verify_area() and
1074 * locks_verify_truncate().
1075 */
1076int locks_mandatory_area(int read_write, struct inode *inode,
1077                         struct file *filp, loff_t offset,
1078                         size_t count)
1079{
1080        struct file_lock fl;
1081        int error;
1082
1083        locks_init_lock(&fl);
1084        fl.fl_owner = current->files;
1085        fl.fl_pid = current->tgid;
1086        fl.fl_file = filp;
1087        fl.fl_flags = FL_POSIX | FL_ACCESS;
1088        if (filp && !(filp->f_flags & O_NONBLOCK))
1089                fl.fl_flags |= FL_SLEEP;
1090        fl.fl_type = (read_write == FLOCK_VERIFY_WRITE) ? F_WRLCK : F_RDLCK;
1091        fl.fl_start = offset;
1092        fl.fl_end = offset + count - 1;
1093
1094        for (;;) {
1095                error = __posix_lock_file(inode, &fl, NULL);
1096                if (error != FILE_LOCK_DEFERRED)
1097                        break;
1098                error = wait_event_interruptible(fl.fl_wait, !fl.fl_next);
1099                if (!error) {
1100                        /*
1101                         * If we've been sleeping someone might have
1102                         * changed the permissions behind our back.
1103                         */
1104                        if (__mandatory_lock(inode))
1105                                continue;
1106                }
1107
1108                locks_delete_block(&fl);
1109                break;
1110        }
1111
1112        return error;
1113}
1114
1115EXPORT_SYMBOL(locks_mandatory_area);
1116
1117static void lease_clear_pending(struct file_lock *fl, int arg)
1118{
1119        switch (arg) {
1120        case F_UNLCK:
1121                fl->fl_flags &= ~FL_UNLOCK_PENDING;
1122                /* fall through: */
1123        case F_RDLCK:
1124                fl->fl_flags &= ~FL_DOWNGRADE_PENDING;
1125        }
1126}
1127
1128/* We already had a lease on this file; just change its type */
1129int lease_modify(struct file_lock **before, int arg)
1130{
1131        struct file_lock *fl = *before;
1132        int error = assign_type(fl, arg);
1133
1134        if (error)
1135                return error;
1136        lease_clear_pending(fl, arg);
1137        locks_wake_up_blocks(fl);
1138        if (arg == F_UNLCK) {
1139                struct file *filp = fl->fl_file;
1140
1141                f_delown(filp);
1142                filp->f_owner.signum = 0;
1143                fasync_helper(0, fl->fl_file, 0, &fl->fl_fasync);
1144                if (fl->fl_fasync != NULL) {
1145                        printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync);
1146                        fl->fl_fasync = NULL;
1147                }
1148                locks_delete_lock(before);
1149        }
1150        return 0;
1151}
1152
1153EXPORT_SYMBOL(lease_modify);
1154
1155static bool past_time(unsigned long then)
1156{
1157        if (!then)
1158                /* 0 is a special value meaning "this never expires": */
1159                return false;
1160        return time_after(jiffies, then);
1161}
1162
1163static void time_out_leases(struct inode *inode)
1164{
1165        struct file_lock **before;
1166        struct file_lock *fl;
1167
1168        before = &inode->i_flock;
1169        while ((fl = *before) && IS_LEASE(fl) && lease_breaking(fl)) {
1170                if (past_time(fl->fl_downgrade_time))
1171                        lease_modify(before, F_RDLCK);
1172                if (past_time(fl->fl_break_time))
1173                        lease_modify(before, F_UNLCK);
1174                if (fl == *before)      /* lease_modify may have freed fl */
1175                        before = &fl->fl_next;
1176        }
1177}
1178
1179/**
1180 *      __break_lease   -       revoke all outstanding leases on file
1181 *      @inode: the inode of the file to return
1182 *      @mode: the open mode (read or write)
1183 *
1184 *      break_lease (inlined for speed) has checked there already is at least
1185 *      some kind of lock (maybe a lease) on this file.  Leases are broken on
1186 *      a call to open() or truncate().  This function can sleep unless you
1187 *      specified %O_NONBLOCK to your open().
1188 */
1189int __break_lease(struct inode *inode, unsigned int mode)
1190{
1191        int error = 0;
1192        struct file_lock *new_fl, *flock;
1193        struct file_lock *fl;
1194        unsigned long break_time;
1195        int i_have_this_lease = 0;
1196        int want_write = (mode & O_ACCMODE) != O_RDONLY;
1197
1198        new_fl = lease_alloc(NULL, want_write ? F_WRLCK : F_RDLCK);
1199        if (IS_ERR(new_fl))
1200                return PTR_ERR(new_fl);
1201
1202        lock_flocks();
1203
1204        time_out_leases(inode);
1205
1206        flock = inode->i_flock;
1207        if ((flock == NULL) || !IS_LEASE(flock))
1208                goto out;
1209
1210        if (!locks_conflict(flock, new_fl))
1211                goto out;
1212
1213        for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next)
1214                if (fl->fl_owner == current->files)
1215                        i_have_this_lease = 1;
1216
1217        break_time = 0;
1218        if (lease_break_time > 0) {
1219                break_time = jiffies + lease_break_time * HZ;
1220                if (break_time == 0)
1221                        break_time++;   /* so that 0 means no break time */
1222        }
1223
1224        for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next) {
1225                if (want_write) {
1226                        if (fl->fl_flags & FL_UNLOCK_PENDING)
1227                                continue;
1228                        fl->fl_flags |= FL_UNLOCK_PENDING;
1229                        fl->fl_break_time = break_time;
1230                } else {
1231                        if (lease_breaking(flock))
1232                                continue;
1233                        fl->fl_flags |= FL_DOWNGRADE_PENDING;
1234                        fl->fl_downgrade_time = break_time;
1235                }
1236                fl->fl_lmops->lm_break(fl);
1237        }
1238
1239        if (i_have_this_lease || (mode & O_NONBLOCK)) {
1240                error = -EWOULDBLOCK;
1241                goto out;
1242        }
1243
1244restart:
1245        break_time = flock->fl_break_time;
1246        if (break_time != 0) {
1247                break_time -= jiffies;
1248                if (break_time == 0)
1249                        break_time++;
1250        }
1251        locks_insert_block(flock, new_fl);
1252        unlock_flocks();
1253        error = wait_event_interruptible_timeout(new_fl->fl_wait,
1254                                                !new_fl->fl_next, break_time);
1255        lock_flocks();
1256        __locks_delete_block(new_fl);
1257        if (error >= 0) {
1258                if (error == 0)
1259                        time_out_leases(inode);
1260                /*
1261                 * Wait for the next conflicting lease that has not been
1262                 * broken yet
1263                 */
1264                for (flock = inode->i_flock; flock && IS_LEASE(flock);
1265                                flock = flock->fl_next) {
1266                        if (locks_conflict(new_fl, flock))
1267                                goto restart;
1268                }
1269                error = 0;
1270        }
1271
1272out:
1273        unlock_flocks();
1274        locks_free_lock(new_fl);
1275        return error;
1276}
1277
1278EXPORT_SYMBOL(__break_lease);
1279
1280/**
1281 *      lease_get_mtime - get the last modified time of an inode
1282 *      @inode: the inode
1283 *      @time:  pointer to a timespec which will contain the last modified time
1284 *
1285 * This is to force NFS clients to flush their caches for files with
1286 * exclusive leases.  The justification is that if someone has an
1287 * exclusive lease, then they could be modifying it.
1288 */
1289void lease_get_mtime(struct inode *inode, struct timespec *time)
1290{
1291        struct file_lock *flock = inode->i_flock;
1292        if (flock && IS_LEASE(flock) && (flock->fl_type == F_WRLCK))
1293                *time = current_fs_time(inode->i_sb);
1294        else
1295                *time = inode->i_mtime;
1296}
1297
1298EXPORT_SYMBOL(lease_get_mtime);
1299
1300/**
1301 *      fcntl_getlease - Enquire what lease is currently active
1302 *      @filp: the file
1303 *
1304 *      The value returned by this function will be one of
1305 *      (if no lease break is pending):
1306 *
1307 *      %F_RDLCK to indicate a shared lease is held.
1308 *
1309 *      %F_WRLCK to indicate an exclusive lease is held.
1310 *
1311 *      %F_UNLCK to indicate no lease is held.
1312 *
1313 *      (if a lease break is pending):
1314 *
1315 *      %F_RDLCK to indicate an exclusive lease needs to be
1316 *              changed to a shared lease (or removed).
1317 *
1318 *      %F_UNLCK to indicate the lease needs to be removed.
1319 *
1320 *      XXX: sfr & willy disagree over whether F_INPROGRESS
1321 *      should be returned to userspace.
1322 */
1323int fcntl_getlease(struct file *filp)
1324{
1325        struct file_lock *fl;
1326        int type = F_UNLCK;
1327
1328        lock_flocks();
1329        time_out_leases(filp->f_path.dentry->d_inode);
1330        for (fl = filp->f_path.dentry->d_inode->i_flock; fl && IS_LEASE(fl);
1331                        fl = fl->fl_next) {
1332                if (fl->fl_file == filp) {
1333                        type = target_leasetype(fl);
1334                        break;
1335                }
1336        }
1337        unlock_flocks();
1338        return type;
1339}
1340
1341int generic_add_lease(struct file *filp, long arg, struct file_lock **flp)
1342{
1343        struct file_lock *fl, **before, **my_before = NULL, *lease;
1344        struct dentry *dentry = filp->f_path.dentry;
1345        struct inode *inode = dentry->d_inode;
1346        int error;
1347
1348        lease = *flp;
1349
1350        error = -EAGAIN;
1351        if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0))
1352                goto out;
1353        if ((arg == F_WRLCK)
1354            && ((dentry->d_count > 1)
1355                || (atomic_read(&inode->i_count) > 1)))
1356                goto out;
1357
1358        /*
1359         * At this point, we know that if there is an exclusive
1360         * lease on this file, then we hold it on this filp
1361         * (otherwise our open of this file would have blocked).
1362         * And if we are trying to acquire an exclusive lease,
1363         * then the file is not open by anyone (including us)
1364         * except for this filp.
1365         */
1366        error = -EAGAIN;
1367        for (before = &inode->i_flock;
1368                        ((fl = *before) != NULL) && IS_LEASE(fl);
1369                        before = &fl->fl_next) {
1370                if (fl->fl_file == filp) {
1371                        my_before = before;
1372                        continue;
1373                }
1374                /*
1375                 * No exclusive leases if someone else has a lease on
1376                 * this file:
1377                 */
1378                if (arg == F_WRLCK)
1379                        goto out;
1380                /*
1381                 * Modifying our existing lease is OK, but no getting a
1382                 * new lease if someone else is opening for write:
1383                 */
1384                if (fl->fl_flags & FL_UNLOCK_PENDING)
1385                        goto out;
1386        }
1387
1388        if (my_before != NULL) {
1389                error = lease->fl_lmops->lm_change(my_before, arg);
1390                if (!error)
1391                        *flp = *my_before;
1392                goto out;
1393        }
1394
1395        error = -EINVAL;
1396        if (!leases_enable)
1397                goto out;
1398
1399        locks_insert_lock(before, lease);
1400        return 0;
1401
1402out:
1403        return error;
1404}
1405
1406int generic_delete_lease(struct file *filp, struct file_lock **flp)
1407{
1408        struct file_lock *fl, **before;
1409        struct dentry *dentry = filp->f_path.dentry;
1410        struct inode *inode = dentry->d_inode;
1411
1412        for (before = &inode->i_flock;
1413                        ((fl = *before) != NULL) && IS_LEASE(fl);
1414                        before = &fl->fl_next) {
1415                if (fl->fl_file != filp)
1416                        continue;
1417                return (*flp)->fl_lmops->lm_change(before, F_UNLCK);
1418        }
1419        return -EAGAIN;
1420}
1421
1422/**
1423 *      generic_setlease        -       sets a lease on an open file
1424 *      @filp: file pointer
1425 *      @arg: type of lease to obtain
1426 *      @flp: input - file_lock to use, output - file_lock inserted
1427 *
1428 *      The (input) flp->fl_lmops->lm_break function is required
1429 *      by break_lease().
1430 *
1431 *      Called with file_lock_lock held.
1432 */
1433int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
1434{
1435        struct dentry *dentry = filp->f_path.dentry;
1436        struct inode *inode = dentry->d_inode;
1437        int error;
1438
1439        if ((!uid_eq(current_fsuid(), inode->i_uid)) && !capable(CAP_LEASE))
1440                return -EACCES;
1441        if (!S_ISREG(inode->i_mode))
1442                return -EINVAL;
1443        error = security_file_lock(filp, arg);
1444        if (error)
1445                return error;
1446
1447        time_out_leases(inode);
1448
1449        BUG_ON(!(*flp)->fl_lmops->lm_break);
1450
1451        switch (arg) {
1452        case F_UNLCK:
1453                return generic_delete_lease(filp, flp);
1454        case F_RDLCK:
1455        case F_WRLCK:
1456                return generic_add_lease(filp, arg, flp);
1457        default:
1458                return -EINVAL;
1459        }
1460}
1461EXPORT_SYMBOL(generic_setlease);
1462
1463static int __vfs_setlease(struct file *filp, long arg, struct file_lock **lease)
1464{
1465        if (filp->f_op && filp->f_op->setlease)
1466                return filp->f_op->setlease(filp, arg, lease);
1467        else
1468                return generic_setlease(filp, arg, lease);
1469}
1470
1471/**
1472 *      vfs_setlease        -       sets a lease on an open file
1473 *      @filp: file pointer
1474 *      @arg: type of lease to obtain
1475 *      @lease: file_lock to use
1476 *
1477 *      Call this to establish a lease on the file.
1478 *      The (*lease)->fl_lmops->lm_break operation must be set; if not,
1479 *      break_lease will oops!
1480 *
1481 *      This will call the filesystem's setlease file method, if
1482 *      defined.  Note that there is no getlease method; instead, the
1483 *      filesystem setlease method should call back to setlease() to
1484 *      add a lease to the inode's lease list, where fcntl_getlease() can
1485 *      find it.  Since fcntl_getlease() only reports whether the current
1486 *      task holds a lease, a cluster filesystem need only do this for
1487 *      leases held by processes on this node.
1488 *
1489 *      There is also no break_lease method; filesystems that
1490 *      handle their own leases should break leases themselves from the
1491 *      filesystem's open, create, and (on truncate) setattr methods.
1492 *
1493 *      Warning: the only current setlease methods exist only to disable
1494 *      leases in certain cases.  More vfs changes may be required to
1495 *      allow a full filesystem lease implementation.
1496 */
1497
1498int vfs_setlease(struct file *filp, long arg, struct file_lock **lease)
1499{
1500        int error;
1501
1502        lock_flocks();
1503        error = __vfs_setlease(filp, arg, lease);
1504        unlock_flocks();
1505
1506        return error;
1507}
1508EXPORT_SYMBOL_GPL(vfs_setlease);
1509
1510static int do_fcntl_delete_lease(struct file *filp)
1511{
1512        struct file_lock fl, *flp = &fl;
1513
1514        lease_init(filp, F_UNLCK, flp);
1515
1516        return vfs_setlease(filp, F_UNLCK, &flp);
1517}
1518
1519static int do_fcntl_add_lease(unsigned int fd, struct file *filp, long arg)
1520{
1521        struct file_lock *fl, *ret;
1522        struct fasync_struct *new;
1523        int error;
1524
1525        fl = lease_alloc(filp, arg);
1526        if (IS_ERR(fl))
1527                return PTR_ERR(fl);
1528
1529        new = fasync_alloc();
1530        if (!new) {
1531                locks_free_lock(fl);
1532                return -ENOMEM;
1533        }
1534        ret = fl;
1535        lock_flocks();
1536        error = __vfs_setlease(filp, arg, &ret);
1537        if (error) {
1538                unlock_flocks();
1539                locks_free_lock(fl);
1540                goto out_free_fasync;
1541        }
1542        if (ret != fl)
1543                locks_free_lock(fl);
1544
1545        /*
1546         * fasync_insert_entry() returns the old entry if any.
1547         * If there was no old entry, then it used 'new' and
1548         * inserted it into the fasync list. Clear new so that
1549         * we don't release it here.
1550         */
1551        if (!fasync_insert_entry(fd, filp, &ret->fl_fasync, new))
1552                new = NULL;
1553
1554        error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
1555        unlock_flocks();
1556
1557out_free_fasync:
1558        if (new)
1559                fasync_free(new);
1560        return error;
1561}
1562
1563/**
1564 *      fcntl_setlease  -       sets a lease on an open file
1565 *      @fd: open file descriptor
1566 *      @filp: file pointer
1567 *      @arg: type of lease to obtain
1568 *
1569 *      Call this fcntl to establish a lease on the file.
1570 *      Note that you also need to call %F_SETSIG to
1571 *      receive a signal when the lease is broken.
1572 */
1573int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
1574{
1575        if (arg == F_UNLCK)
1576                return do_fcntl_delete_lease(filp);
1577        return do_fcntl_add_lease(fd, filp, arg);
1578}
1579
1580/**
1581 * flock_lock_file_wait - Apply a FLOCK-style lock to a file
1582 * @filp: The file to apply the lock to
1583 * @fl: The lock to be applied
1584 *
1585 * Add a FLOCK style lock to a file.
1586 */
1587int flock_lock_file_wait(struct file *filp, struct file_lock *fl)
1588{
1589        int error;
1590        might_sleep();
1591        for (;;) {
1592                error = flock_lock_file(filp, fl);
1593                if (error != FILE_LOCK_DEFERRED)
1594                        break;
1595                error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
1596                if (!error)
1597                        continue;
1598
1599                locks_delete_block(fl);
1600                break;
1601        }
1602        return error;
1603}
1604
1605EXPORT_SYMBOL(flock_lock_file_wait);
1606
1607/**
1608 *      sys_flock: - flock() system call.
1609 *      @fd: the file descriptor to lock.
1610 *      @cmd: the type of lock to apply.
1611 *
1612 *      Apply a %FL_FLOCK style lock to an open file descriptor.
1613 *      The @cmd can be one of
1614 *
1615 *      %LOCK_SH -- a shared lock.
1616 *
1617 *      %LOCK_EX -- an exclusive lock.
1618 *
1619 *      %LOCK_UN -- remove an existing lock.
1620 *
1621 *      %LOCK_MAND -- a `mandatory' flock.  This exists to emulate Windows Share Modes.
1622 *
1623 *      %LOCK_MAND can be combined with %LOCK_READ or %LOCK_WRITE to allow other
1624 *      processes read and write access respectively.
1625 */
1626SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd)
1627{
1628        struct fd f = fdget(fd);
1629        struct file_lock *lock;
1630        int can_sleep, unlock;
1631        int error;
1632
1633        error = -EBADF;
1634        if (!f.file)
1635                goto out;
1636
1637        can_sleep = !(cmd & LOCK_NB);
1638        cmd &= ~LOCK_NB;
1639        unlock = (cmd == LOCK_UN);
1640
1641        if (!unlock && !(cmd & LOCK_MAND) &&
1642            !(f.file->f_mode & (FMODE_READ|FMODE_WRITE)))
1643                goto out_putf;
1644
1645        error = flock_make_lock(f.file, &lock, cmd);
1646        if (error)
1647                goto out_putf;
1648        if (can_sleep)
1649                lock->fl_flags |= FL_SLEEP;
1650
1651        error = security_file_lock(f.file, lock->fl_type);
1652        if (error)
1653                goto out_free;
1654
1655        if (f.file->f_op && f.file->f_op->flock)
1656                error = f.file->f_op->flock(f.file,
1657                                          (can_sleep) ? F_SETLKW : F_SETLK,
1658                                          lock);
1659        else
1660                error = flock_lock_file_wait(f.file, lock);
1661
1662 out_free:
1663        locks_free_lock(lock);
1664
1665 out_putf:
1666        fdput(f);
1667 out:
1668        return error;
1669}
1670
1671/**
1672 * vfs_test_lock - test file byte range lock
1673 * @filp: The file to test lock for
1674 * @fl: The lock to test; also used to hold result
1675 *
1676 * Returns -ERRNO on failure.  Indicates presence of conflicting lock by
1677 * setting conf->fl_type to something other than F_UNLCK.
1678 */
1679int vfs_test_lock(struct file *filp, struct file_lock *fl)
1680{
1681        if (filp->f_op && filp->f_op->lock)
1682                return filp->f_op->lock(filp, F_GETLK, fl);
1683        posix_test_lock(filp, fl);
1684        return 0;
1685}
1686EXPORT_SYMBOL_GPL(vfs_test_lock);
1687
1688static int posix_lock_to_flock(struct flock *flock, struct file_lock *fl)
1689{
1690        flock->l_pid = fl->fl_pid;
1691#if BITS_PER_LONG == 32
1692        /*
1693         * Make sure we can represent the posix lock via
1694         * legacy 32bit flock.
1695         */
1696        if (fl->fl_start > OFFT_OFFSET_MAX)
1697                return -EOVERFLOW;
1698        if (fl->fl_end != OFFSET_MAX && fl->fl_end > OFFT_OFFSET_MAX)
1699                return -EOVERFLOW;
1700#endif
1701        flock->l_start = fl->fl_start;
1702        flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
1703                fl->fl_end - fl->fl_start + 1;
1704        flock->l_whence = 0;
1705        flock->l_type = fl->fl_type;
1706        return 0;
1707}
1708
1709#if BITS_PER_LONG == 32
1710static void posix_lock_to_flock64(struct flock64 *flock, struct file_lock *fl)
1711{
1712        flock->l_pid = fl->fl_pid;
1713        flock->l_start = fl->fl_start;
1714        flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
1715                fl->fl_end - fl->fl_start + 1;
1716        flock->l_whence = 0;
1717        flock->l_type = fl->fl_type;
1718}
1719#endif
1720
1721/* Report the first existing lock that would conflict with l.
1722 * This implements the F_GETLK command of fcntl().
1723 */
1724int fcntl_getlk(struct file *filp, struct flock __user *l)
1725{
1726        struct file_lock file_lock;
1727        struct flock flock;
1728        int error;
1729
1730        error = -EFAULT;
1731        if (copy_from_user(&flock, l, sizeof(flock)))
1732                goto out;
1733        error = -EINVAL;
1734        if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
1735                goto out;
1736
1737        error = flock_to_posix_lock(filp, &file_lock, &flock);
1738        if (error)
1739                goto out;
1740
1741        error = vfs_test_lock(filp, &file_lock);
1742        if (error)
1743                goto out;
1744 
1745        flock.l_type = file_lock.fl_type;
1746        if (file_lock.fl_type != F_UNLCK) {
1747                error = posix_lock_to_flock(&flock, &file_lock);
1748                if (error)
1749                        goto out;
1750        }
1751        error = -EFAULT;
1752        if (!copy_to_user(l, &flock, sizeof(flock)))
1753                error = 0;
1754out:
1755        return error;
1756}
1757
1758/**
1759 * vfs_lock_file - file byte range lock
1760 * @filp: The file to apply the lock to
1761 * @cmd: type of locking operation (F_SETLK, F_GETLK, etc.)
1762 * @fl: The lock to be applied
1763 * @conf: Place to return a copy of the conflicting lock, if found.
1764 *
1765 * A caller that doesn't care about the conflicting lock may pass NULL
1766 * as the final argument.
1767 *
1768 * If the filesystem defines a private ->lock() method, then @conf will
1769 * be left unchanged; so a caller that cares should initialize it to
1770 * some acceptable default.
1771 *
1772 * To avoid blocking kernel daemons, such as lockd, that need to acquire POSIX
1773 * locks, the ->lock() interface may return asynchronously, before the lock has
1774 * been granted or denied by the underlying filesystem, if (and only if)
1775 * lm_grant is set. Callers expecting ->lock() to return asynchronously
1776 * will only use F_SETLK, not F_SETLKW; they will set FL_SLEEP if (and only if)
1777 * the request is for a blocking lock. When ->lock() does return asynchronously,
1778 * it must return FILE_LOCK_DEFERRED, and call ->lm_grant() when the lock
1779 * request completes.
1780 * If the request is for non-blocking lock the file system should return
1781 * FILE_LOCK_DEFERRED then try to get the lock and call the callback routine
1782 * with the result. If the request timed out the callback routine will return a
1783 * nonzero return code and the file system should release the lock. The file
1784 * system is also responsible to keep a corresponding posix lock when it
1785 * grants a lock so the VFS can find out which locks are locally held and do
1786 * the correct lock cleanup when required.
1787 * The underlying filesystem must not drop the kernel lock or call
1788 * ->lm_grant() before returning to the caller with a FILE_LOCK_DEFERRED
1789 * return code.
1790 */
1791int vfs_lock_file(struct file *filp, unsigned int cmd, struct file_lock *fl, struct file_lock *conf)
1792{
1793        if (filp->f_op && filp->f_op->lock)
1794                return filp->f_op->lock(filp, cmd, fl);
1795        else
1796                return posix_lock_file(filp, fl, conf);
1797}
1798EXPORT_SYMBOL_GPL(vfs_lock_file);
1799
1800static int do_lock_file_wait(struct file *filp, unsigned int cmd,
1801                             struct file_lock *fl)
1802{
1803        int error;
1804
1805        error = security_file_lock(filp, fl->fl_type);
1806        if (error)
1807                return error;
1808
1809        for (;;) {
1810                error = vfs_lock_file(filp, cmd, fl, NULL);
1811                if (error != FILE_LOCK_DEFERRED)
1812                        break;
1813                error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
1814                if (!error)
1815                        continue;
1816
1817                locks_delete_block(fl);
1818                break;
1819        }
1820
1821        return error;
1822}
1823
1824/* Apply the lock described by l to an open file descriptor.
1825 * This implements both the F_SETLK and F_SETLKW commands of fcntl().
1826 */
1827int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
1828                struct flock __user *l)
1829{
1830        struct file_lock *file_lock = locks_alloc_lock();
1831        struct flock flock;
1832        struct inode *inode;
1833        struct file *f;
1834        int error;
1835
1836        if (file_lock == NULL)
1837                return -ENOLCK;
1838
1839        /*
1840         * This might block, so we do it before checking the inode.
1841         */
1842        error = -EFAULT;
1843        if (copy_from_user(&flock, l, sizeof(flock)))
1844                goto out;
1845
1846        inode = filp->f_path.dentry->d_inode;
1847
1848        /* Don't allow mandatory locks on files that may be memory mapped
1849         * and shared.
1850         */
1851        if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) {
1852                error = -EAGAIN;
1853                goto out;
1854        }
1855
1856again:
1857        error = flock_to_posix_lock(filp, file_lock, &flock);
1858        if (error)
1859                goto out;
1860        if (cmd == F_SETLKW) {
1861                file_lock->fl_flags |= FL_SLEEP;
1862        }
1863        
1864        error = -EBADF;
1865        switch (flock.l_type) {
1866        case F_RDLCK:
1867                if (!(filp->f_mode & FMODE_READ))
1868                        goto out;
1869                break;
1870        case F_WRLCK:
1871                if (!(filp->f_mode & FMODE_WRITE))
1872                        goto out;
1873                break;
1874        case F_UNLCK:
1875                break;
1876        default:
1877                error = -EINVAL;
1878                goto out;
1879        }
1880
1881        error = do_lock_file_wait(filp, cmd, file_lock);
1882
1883        /*
1884         * Attempt to detect a close/fcntl race and recover by
1885         * releasing the lock that was just acquired.
1886         */
1887        /*
1888         * we need that spin_lock here - it prevents reordering between
1889         * update of inode->i_flock and check for it done in close().
1890         * rcu_read_lock() wouldn't do.
1891         */
1892        spin_lock(&current->files->file_lock);
1893        f = fcheck(fd);
1894        spin_unlock(&current->files->file_lock);
1895        if (!error && f != filp && flock.l_type != F_UNLCK) {
1896                flock.l_type = F_UNLCK;
1897                goto again;
1898        }
1899
1900out:
1901        locks_free_lock(file_lock);
1902        return error;
1903}
1904
1905#if BITS_PER_LONG == 32
1906/* Report the first existing lock that would conflict with l.
1907 * This implements the F_GETLK command of fcntl().
1908 */
1909int fcntl_getlk64(struct file *filp, struct flock64 __user *l)
1910{
1911        struct file_lock file_lock;
1912        struct flock64 flock;
1913        int error;
1914
1915        error = -EFAULT;
1916        if (copy_from_user(&flock, l, sizeof(flock)))
1917                goto out;
1918        error = -EINVAL;
1919        if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
1920                goto out;
1921
1922        error = flock64_to_posix_lock(filp, &file_lock, &flock);
1923        if (error)
1924                goto out;
1925
1926        error = vfs_test_lock(filp, &file_lock);
1927        if (error)
1928                goto out;
1929
1930        flock.l_type = file_lock.fl_type;
1931        if (file_lock.fl_type != F_UNLCK)
1932                posix_lock_to_flock64(&flock, &file_lock);
1933
1934        error = -EFAULT;
1935        if (!copy_to_user(l, &flock, sizeof(flock)))
1936                error = 0;
1937  
1938out:
1939        return error;
1940}
1941
1942/* Apply the lock described by l to an open file descriptor.
1943 * This implements both the F_SETLK and F_SETLKW commands of fcntl().
1944 */
1945int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
1946                struct flock64 __user *l)
1947{
1948        struct file_lock *file_lock = locks_alloc_lock();
1949        struct flock64 flock;
1950        struct inode *inode;
1951        struct file *f;
1952        int error;
1953
1954        if (file_lock == NULL)
1955                return -ENOLCK;
1956
1957        /*
1958         * This might block, so we do it before checking the inode.
1959         */
1960        error = -EFAULT;
1961        if (copy_from_user(&flock, l, sizeof(flock)))
1962                goto out;
1963
1964        inode = filp->f_path.dentry->d_inode;
1965
1966        /* Don't allow mandatory locks on files that may be memory mapped
1967         * and shared.
1968         */
1969        if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) {
1970                error = -EAGAIN;
1971                goto out;
1972        }
1973
1974again:
1975        error = flock64_to_posix_lock(filp, file_lock, &flock);
1976        if (error)
1977                goto out;
1978        if (cmd == F_SETLKW64) {
1979                file_lock->fl_flags |= FL_SLEEP;
1980        }
1981        
1982        error = -EBADF;
1983        switch (flock.l_type) {
1984        case F_RDLCK:
1985                if (!(filp->f_mode & FMODE_READ))
1986                        goto out;
1987                break;
1988        case F_WRLCK:
1989                if (!(filp->f_mode & FMODE_WRITE))
1990                        goto out;
1991                break;
1992        case F_UNLCK:
1993                break;
1994        default:
1995                error = -EINVAL;
1996                goto out;
1997        }
1998
1999        error = do_lock_file_wait(filp, cmd, file_lock);
2000
2001        /*
2002         * Attempt to detect a close/fcntl race and recover by
2003         * releasing the lock that was just acquired.
2004         */
2005        spin_lock(&current->files->file_lock);
2006        f = fcheck(fd);
2007        spin_unlock(&current->files->file_lock);
2008        if (!error && f != filp && flock.l_type != F_UNLCK) {
2009                flock.l_type = F_UNLCK;
2010                goto again;
2011        }
2012
2013out:
2014        locks_free_lock(file_lock);
2015        return error;
2016}
2017#endif /* BITS_PER_LONG == 32 */
2018
2019/*
2020 * This function is called when the file is being removed
2021 * from the task's fd array.  POSIX locks belonging to this task
2022 * are deleted at this time.
2023 */
2024void locks_remove_posix(struct file *filp, fl_owner_t owner)
2025{
2026        struct file_lock lock;
2027
2028        /*
2029         * If there are no locks held on this file, we don't need to call
2030         * posix_lock_file().  Another process could be setting a lock on this
2031         * file at the same time, but we wouldn't remove that lock anyway.
2032         */
2033        if (!filp->f_path.dentry->d_inode->i_flock)
2034                return;
2035
2036        lock.fl_type = F_UNLCK;
2037        lock.fl_flags = FL_POSIX | FL_CLOSE;
2038        lock.fl_start = 0;
2039        lock.fl_end = OFFSET_MAX;
2040        lock.fl_owner = owner;
2041        lock.fl_pid = current->tgid;
2042        lock.fl_file = filp;
2043        lock.fl_ops = NULL;
2044        lock.fl_lmops = NULL;
2045
2046        vfs_lock_file(filp, F_SETLK, &lock, NULL);
2047
2048        if (lock.fl_ops && lock.fl_ops->fl_release_private)
2049                lock.fl_ops->fl_release_private(&lock);
2050}
2051
2052EXPORT_SYMBOL(locks_remove_posix);
2053
2054/*
2055 * This function is called on the last close of an open file.
2056 */
2057void locks_remove_flock(struct file *filp)
2058{
2059        struct inode * inode = filp->f_path.dentry->d_inode;
2060        struct file_lock *fl;
2061        struct file_lock **before;
2062
2063        if (!inode->i_flock)
2064                return;
2065
2066        if (filp->f_op && filp->f_op->flock) {
2067                struct file_lock fl = {
2068                        .fl_pid = current->tgid,
2069                        .fl_file = filp,
2070                        .fl_flags = FL_FLOCK,
2071                        .fl_type = F_UNLCK,
2072                        .fl_end = OFFSET_MAX,
2073                };
2074                filp->f_op->flock(filp, F_SETLKW, &fl);
2075                if (fl.fl_ops && fl.fl_ops->fl_release_private)
2076                        fl.fl_ops->fl_release_private(&fl);
2077        }
2078
2079        lock_flocks();
2080        before = &inode->i_flock;
2081
2082        while ((fl = *before) != NULL) {
2083                if (fl->fl_file == filp) {
2084                        if (IS_FLOCK(fl)) {
2085                                locks_delete_lock(before);
2086                                continue;
2087                        }
2088                        if (IS_LEASE(fl)) {
2089                                lease_modify(before, F_UNLCK);
2090                                continue;
2091                        }
2092                        /* What? */
2093                        BUG();
2094                }
2095                before = &fl->fl_next;
2096        }
2097        unlock_flocks();
2098}
2099
2100/**
2101 *      posix_unblock_lock - stop waiting for a file lock
2102 *      @filp:   how the file was opened
2103 *      @waiter: the lock which was waiting
2104 *
2105 *      lockd needs to block waiting for locks.
2106 */
2107int
2108posix_unblock_lock(struct file *filp, struct file_lock *waiter)
2109{
2110        int status = 0;
2111
2112        lock_flocks();
2113        if (waiter->fl_next)
2114                __locks_delete_block(waiter);
2115        else
2116                status = -ENOENT;
2117        unlock_flocks();
2118        return status;
2119}
2120
2121EXPORT_SYMBOL(posix_unblock_lock);
2122
2123/**
2124 * vfs_cancel_lock - file byte range unblock lock
2125 * @filp: The file to apply the unblock to
2126 * @fl: The lock to be unblocked
2127 *
2128 * Used by lock managers to cancel blocked requests
2129 */
2130int vfs_cancel_lock(struct file *filp, struct file_lock *fl)
2131{
2132        if (filp->f_op && filp->f_op->lock)
2133                return filp->f_op->lock(filp, F_CANCELLK, fl);
2134        return 0;
2135}
2136
2137EXPORT_SYMBOL_GPL(vfs_cancel_lock);
2138
2139#ifdef CONFIG_PROC_FS
2140#include <linux/proc_fs.h>
2141#include <linux/seq_file.h>
2142
2143static void lock_get_status(struct seq_file *f, struct file_lock *fl,
2144                            loff_t id, char *pfx)
2145{
2146        struct inode *inode = NULL;
2147        unsigned int fl_pid;
2148
2149        if (fl->fl_nspid)
2150                fl_pid = pid_vnr(fl->fl_nspid);
2151        else
2152                fl_pid = fl->fl_pid;
2153
2154        if (fl->fl_file != NULL)
2155                inode = fl->fl_file->f_path.dentry->d_inode;
2156
2157        seq_printf(f, "%lld:%s ", id, pfx);
2158        if (IS_POSIX(fl)) {
2159                seq_printf(f, "%6s %s ",
2160                             (fl->fl_flags & FL_ACCESS) ? "ACCESS" : "POSIX ",
2161                             (inode == NULL) ? "*NOINODE*" :
2162                             mandatory_lock(inode) ? "MANDATORY" : "ADVISORY ");
2163        } else if (IS_FLOCK(fl)) {
2164                if (fl->fl_type & LOCK_MAND) {
2165                        seq_printf(f, "FLOCK  MSNFS     ");
2166                } else {
2167                        seq_printf(f, "FLOCK  ADVISORY  ");
2168                }
2169        } else if (IS_LEASE(fl)) {
2170                seq_printf(f, "LEASE  ");
2171                if (lease_breaking(fl))
2172                        seq_printf(f, "BREAKING  ");
2173                else if (fl->fl_file)
2174                        seq_printf(f, "ACTIVE    ");
2175                else
2176                        seq_printf(f, "BREAKER   ");
2177        } else {
2178                seq_printf(f, "UNKNOWN UNKNOWN  ");
2179        }
2180        if (fl->fl_type & LOCK_MAND) {
2181                seq_printf(f, "%s ",
2182                               (fl->fl_type & LOCK_READ)
2183                               ? (fl->fl_type & LOCK_WRITE) ? "RW   " : "READ "
2184                               : (fl->fl_type & LOCK_WRITE) ? "WRITE" : "NONE ");
2185        } else {
2186                seq_printf(f, "%s ",
2187                               (lease_breaking(fl))
2188                               ? (fl->fl_type == F_UNLCK) ? "UNLCK" : "READ "
2189                               : (fl->fl_type == F_WRLCK) ? "WRITE" : "READ ");
2190        }
2191        if (inode) {
2192#ifdef WE_CAN_BREAK_LSLK_NOW
2193                seq_printf(f, "%d %s:%ld ", fl_pid,
2194                                inode->i_sb->s_id, inode->i_ino);
2195#else
2196                /* userspace relies on this representation of dev_t ;-( */
2197                seq_printf(f, "%d %02x:%02x:%ld ", fl_pid,
2198                                MAJOR(inode->i_sb->s_dev),
2199                                MINOR(inode->i_sb->s_dev), inode->i_ino);
2200#endif
2201        } else {
2202                seq_printf(f, "%d <none>:0 ", fl_pid);
2203        }
2204        if (IS_POSIX(fl)) {
2205                if (fl->fl_end == OFFSET_MAX)
2206                        seq_printf(f, "%Ld EOF\n", fl->fl_start);
2207                else
2208                        seq_printf(f, "%Ld %Ld\n", fl->fl_start, fl->fl_end);
2209        } else {
2210                seq_printf(f, "0 EOF\n");
2211        }
2212}
2213
2214static int locks_show(struct seq_file *f, void *v)
2215{
2216        struct file_lock *fl, *bfl;
2217
2218        fl = list_entry(v, struct file_lock, fl_link);
2219
2220        lock_get_status(f, fl, *((loff_t *)f->private), "");
2221
2222        list_for_each_entry(bfl, &fl->fl_block, fl_block)
2223                lock_get_status(f, bfl, *((loff_t *)f->private), " ->");
2224
2225        return 0;
2226}
2227
2228static void *locks_start(struct seq_file *f, loff_t *pos)
2229{
2230        loff_t *p = f->private;
2231
2232        lock_flocks();
2233        *p = (*pos + 1);
2234        return seq_list_start(&file_lock_list, *pos);
2235}
2236
2237static void *locks_next(struct seq_file *f, void *v, loff_t *pos)
2238{
2239        loff_t *p = f->private;
2240        ++*p;
2241        return seq_list_next(v, &file_lock_list, pos);
2242}
2243
2244static void locks_stop(struct seq_file *f, void *v)
2245{
2246        unlock_flocks();
2247}
2248
2249static const struct seq_operations locks_seq_operations = {
2250        .start  = locks_start,
2251        .next   = locks_next,
2252        .stop   = locks_stop,
2253        .show   = locks_show,
2254};
2255
2256static int locks_open(struct inode *inode, struct file *filp)
2257{
2258        return seq_open_private(filp, &locks_seq_operations, sizeof(loff_t));
2259}
2260
2261static const struct file_operations proc_locks_operations = {
2262        .open           = locks_open,
2263        .read           = seq_read,
2264        .llseek         = seq_lseek,
2265        .release        = seq_release_private,
2266};
2267
2268static int __init proc_locks_init(void)
2269{
2270        proc_create("locks", 0, NULL, &proc_locks_operations);
2271        return 0;
2272}
2273module_init(proc_locks_init);
2274#endif
2275
2276/**
2277 *      lock_may_read - checks that the region is free of locks
2278 *      @inode: the inode that is being read
2279 *      @start: the first byte to read
2280 *      @len: the number of bytes to read
2281 *
2282 *      Emulates Windows locking requirements.  Whole-file
2283 *      mandatory locks (share modes) can prohibit a read and
2284 *      byte-range POSIX locks can prohibit a read if they overlap.
2285 *
2286 *      N.B. this function is only ever called
2287 *      from knfsd and ownership of locks is never checked.
2288 */
2289int lock_may_read(struct inode *inode, loff_t start, unsigned long len)
2290{
2291        struct file_lock *fl;
2292        int result = 1;
2293        lock_flocks();
2294        for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
2295                if (IS_POSIX(fl)) {
2296                        if (fl->fl_type == F_RDLCK)
2297                                continue;
2298                        if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
2299                                continue;
2300                } else if (IS_FLOCK(fl)) {
2301                        if (!(fl->fl_type & LOCK_MAND))
2302                                continue;
2303                        if (fl->fl_type & LOCK_READ)
2304                                continue;
2305                } else
2306                        continue;
2307                result = 0;
2308                break;
2309        }
2310        unlock_flocks();
2311        return result;
2312}
2313
2314EXPORT_SYMBOL(lock_may_read);
2315
2316/**
2317 *      lock_may_write - checks that the region is free of locks
2318 *      @inode: the inode that is being written
2319 *      @start: the first byte to write
2320 *      @len: the number of bytes to write
2321 *
2322 *      Emulates Windows locking requirements.  Whole-file
2323 *      mandatory locks (share modes) can prohibit a write and
2324 *      byte-range POSIX locks can prohibit a write if they overlap.
2325 *
2326 *      N.B. this function is only ever called
2327 *      from knfsd and ownership of locks is never checked.
2328 */
2329int lock_may_write(struct inode *inode, loff_t start, unsigned long len)
2330{
2331        struct file_lock *fl;
2332        int result = 1;
2333        lock_flocks();
2334        for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
2335                if (IS_POSIX(fl)) {
2336                        if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
2337                                continue;
2338                } else if (IS_FLOCK(fl)) {
2339                        if (!(fl->fl_type & LOCK_MAND))
2340                                continue;
2341                        if (fl->fl_type & LOCK_WRITE)
2342                                continue;
2343                } else
2344                        continue;
2345                result = 0;
2346                break;
2347        }
2348        unlock_flocks();
2349        return result;
2350}
2351
2352EXPORT_SYMBOL(lock_may_write);
2353
2354static int __init filelock_init(void)
2355{
2356        filelock_cache = kmem_cache_create("file_lock_cache",
2357                        sizeof(struct file_lock), 0, SLAB_PANIC, NULL);
2358
2359        return 0;
2360}
2361
2362core_initcall(filelock_init);
2363
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