fs/open.c

   1 /*
   2  *  linux/fs/open.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 #include <linux/mm.h>
   8 #include <linux/utime.h>
   9 #include <linux/file.h>
  10 #include <linux/smp_lock.h>
  11 #include <linux/quotaops.h>
  12
  13 #include <asm/uaccess.h>
  14
  15 asmlinkage int sys_statfs(const char * path, struct statfs * buf)
  16 {
  17         struct dentry * dentry;
  18         int error;
  19
  20         lock_kernel();
  21         dentry = namei(path);
  22         error = PTR_ERR(dentry);
  23         if (!IS_ERR(dentry)) {
  24                 struct inode * inode = dentry->d_inode;
  25                 struct super_block * sb = inode->i_sb;
  26
  27                 error = -ENODEV;
  28                 if (sb && sb->s_op && sb->s_op->statfs)
  29                         error = sb->s_op->statfs(sb, buf, sizeof(struct statfs));
  30
  31                 dput(dentry);
  32         }
  33         unlock_kernel();
  34         return error;
  35 }
  36
  37 asmlinkage int sys_fstatfs(unsigned int fd, struct statfs * buf)
  38 {
  39         struct file * file;
  40         struct inode * inode;
  41         struct dentry * dentry;
  42         struct super_block * sb;
  43         int error;
  44
  45         lock_kernel();
  46         error = -EBADF;
  47         file = fget(fd);
  48         if (!file)
  49                 goto out;
  50         error = -ENOENT;
  51         if (!(dentry = file->f_dentry))
  52                 goto out_putf;
  53         if (!(inode = dentry->d_inode))
  54                 goto out_putf;
  55         error = -ENODEV;
  56         sb = inode->i_sb;
  57         if (sb && sb->s_op && sb->s_op->statfs)
  58                 error = sb->s_op->statfs(sb, buf, sizeof(struct statfs));
  59 out_putf:
  60         fput(file);
  61 out:
  62         unlock_kernel();
  63         return error;
  64 }
  65
  66 int do_truncate(struct dentry *dentry, unsigned long length)
  67 {
  68         struct inode *inode = dentry->d_inode;
  69         int error;
  70         struct iattr newattrs;
  71
  72         /* Not pretty: "inode->i_size" shouldn't really be "off_t". But it is. */
  73         if ((off_t) length < 0)
  74                 return -EINVAL;
  75
  76         down(&inode->i_sem);
  77         newattrs.ia_size = length;
  78         newattrs.ia_valid = ATTR_SIZE | ATTR_CTIME;
  79         error = notify_change(dentry, &newattrs);
  80         if (!error) {
  81                 /* truncate virtual mappings of this file */
  82                 vmtruncate(inode, length);
  83                 if (inode->i_op && inode->i_op->truncate)
  84                         inode->i_op->truncate(inode);
  85         }
  86         up(&inode->i_sem);
  87         return error;
  88 }
  89
  90 asmlinkage int sys_truncate(const char * path, unsigned long length)
  91 {
  92         struct dentry * dentry;
  93         struct inode * inode;
  94         int error;
  95
  96         lock_kernel();
  97         dentry = namei(path);
  98
  99         error = PTR_ERR(dentry);
 100         if (IS_ERR(dentry))
 101                 goto out;
 102         inode = dentry->d_inode;
 103
 104         error = -EACCES;
 105         if (S_ISDIR(inode->i_mode))
 106                 goto dput_and_out;
 107
 108         error = permission(inode,MAY_WRITE);
 109         if (error)
 110                 goto dput_and_out;
 111
 112         error = -EROFS;
 113         if (IS_RDONLY(inode))
 114                 goto dput_and_out;
 115
 116         error = -EPERM;
 117         if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
 118                 goto dput_and_out;
 119
 120         error = get_write_access(inode);
 121         if (error)
 122                 goto dput_and_out;
 123
 124         error = locks_verify_area(FLOCK_VERIFY_WRITE, inode, NULL,
 125                                   length < inode->i_size ? length : inode->i_size,
 126                                   abs(inode->i_size - length));
 127         if (!error) {
 128                 DQUOT_INIT(inode);
 129                 error = do_truncate(dentry, length);
 130         }
 131         put_write_access(inode);
 132 dput_and_out:
 133         dput(dentry);
 134 out:
 135         unlock_kernel();
 136         return error;
 137 }
 138
 139 asmlinkage int sys_ftruncate(unsigned int fd, unsigned long length)
 140 {
 141         struct inode * inode;
 142         struct dentry *dentry;
 143         struct file * file;
 144         int error;
 145
 146         lock_kernel();
 147         error = -EBADF;
 148         file = fget(fd);
 149         if (!file)
 150                 goto out;
 151         error = -ENOENT;
 152         if (!(dentry = file->f_dentry))
 153                 goto out_putf;
 154         if (!(inode = dentry->d_inode))
 155                 goto out_putf;
 156         error = -EACCES;
 157         if (S_ISDIR(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
 158                 goto out_putf;
 159         error = -EPERM;
 160         if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
 161                 goto out_putf;
 162         error = locks_verify_area(FLOCK_VERIFY_WRITE, inode, file,
 163                                   length<inode->i_size ? length : inode->i_size,
 164                                   abs(inode->i_size - length));
 165         if (!error)
 166                 error = do_truncate(dentry, length);
 167 out_putf:
 168         fput(file);
 169 out:
 170         unlock_kernel();
 171         return error;
 172 }
 173
 174 #if !(defined(__alpha__) || defined(__ia64__))
 175
 176 /*
 177  * sys_utime() can be implemented in user-level using sys_utimes().
 178  * Is this for backwards compatibility?  If so, why not move it
 179  * into the appropriate arch directory (for those architectures that
 180  * need it).
 181  */
 182
 183 /* If times==NULL, set access and modification to current time,
 184  * must be owner or have write permission.
 185  * Else, update from *times, must be owner or super user.
 186  */
 187 asmlinkage int sys_utime(char * filename, struct utimbuf * times)
 188 {
 189         int error;
 190         struct dentry * dentry;
 191         struct inode * inode;
 192         struct iattr newattrs;
 193
 194         lock_kernel();
 195         dentry = namei(filename);
 196
 197         error = PTR_ERR(dentry);
 198         if (IS_ERR(dentry))
 199                 goto out;
 200         inode = dentry->d_inode;
 201
 202         error = -EROFS;
 203         if (IS_RDONLY(inode))
 204                 goto dput_and_out;
 205
 206         /* Don't worry, the checks are done in inode_change_ok() */
 207         newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
 208         if (times) {
 209                 error = get_user(newattrs.ia_atime, &times->actime);
 210                 if (!error)
 211                         error = get_user(newattrs.ia_mtime, &times->modtime);
 212                 if (error)
 213                         goto dput_and_out;
 214
 215                 newattrs.ia_valid |= ATTR_ATIME_SET | ATTR_MTIME_SET;
 216         } else {
 217                 if (current->fsuid != inode->i_uid &&
 218                     (error = permission(inode,MAY_WRITE)) != 0)
 219                         goto dput_and_out;
 220         }
 221         error = notify_change(dentry, &newattrs);
 222 dput_and_out:
 223         dput(dentry);
 224 out:
 225         unlock_kernel();
 226         return error;
 227 }
 228
 229 #endif
 230
 231 /* If times==NULL, set access and modification to current time,
 232  * must be owner or have write permission.
 233  * Else, update from *times, must be owner or super user.
 234  */
 235 asmlinkage int sys_utimes(char * filename, struct timeval * utimes)
 236 {
 237         int error;
 238         struct dentry * dentry;
 239         struct inode * inode;
 240         struct iattr newattrs;
 241
 242         lock_kernel();
 243         dentry = namei(filename);
 244
 245         error = PTR_ERR(dentry);
 246         if (IS_ERR(dentry))
 247                 goto out;
 248         inode = dentry->d_inode;
 249
 250         error = -EROFS;
 251         if (IS_RDONLY(inode))
 252                 goto dput_and_out;
 253
 254         /* Don't worry, the checks are done in inode_change_ok() */
 255         newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
 256         if (utimes) {
 257                 struct timeval times[2];
 258                 error = -EFAULT;
 259                 if (copy_from_user(&times, utimes, sizeof(times)))
 260                         goto dput_and_out;
 261                 newattrs.ia_atime = times[0].tv_sec;
 262                 newattrs.ia_mtime = times[1].tv_sec;
 263                 newattrs.ia_valid |= ATTR_ATIME_SET | ATTR_MTIME_SET;
 264         } else {
 265                 if ((error = permission(inode,MAY_WRITE)) != 0)
 266                         goto dput_and_out;
 267         }
 268         error = notify_change(dentry, &newattrs);
 269 dput_and_out:
 270         dput(dentry);
 271 out:
 272         unlock_kernel();
 273         return error;
 274 }
 275
 276 /*
 277  * access() needs to use the real uid/gid, not the effective uid/gid.
 278  * We do this by temporarily clearing all FS-related capabilities and
 279  * switching the fsuid/fsgid around to the real ones.
 280  */
 281 asmlinkage int sys_access(const char * filename, int mode)
 282 {
 283         struct dentry * dentry;
 284         int old_fsuid, old_fsgid;
 285         kernel_cap_t old_cap;
 286         int res = -EINVAL;
 287
 288         lock_kernel();
 289         if (mode != (mode & S_IRWXO))   /* where's F_OK, X_OK, W_OK, R_OK? */
 290                 goto out;
 291         old_fsuid = current->fsuid;
 292         old_fsgid = current->fsgid;
 293         old_cap = current->cap_effective;
 294
 295         current->fsuid = current->uid;
 296         current->fsgid = current->gid;
 297
 298         /* Clear the capabilities if we switch to a non-root user */
 299         if (current->uid)
 300                 cap_clear(current->cap_effective);
 301         else
 302                 current->cap_effective = current->cap_permitted;
 303
 304         dentry = namei(filename);
 305         res = PTR_ERR(dentry);
 306         if (!IS_ERR(dentry)) {
 307                 res = permission(dentry->d_inode, mode);
 308                 /* SuS v2 requires we report a read only fs too */
 309                 if(!res && (mode & S_IWOTH) && IS_RDONLY(dentry->d_inode))
 310                         res = -EROFS;
 311                 dput(dentry);
 312         }
 313
 314         current->fsuid = old_fsuid;
 315         current->fsgid = old_fsgid;
 316         current->cap_effective = old_cap;
 317 out:
 318         unlock_kernel();
 319         return res;
 320 }
 321
 322 asmlinkage int sys_chdir(const char * filename)
 323 {
 324         int error;
 325         struct inode *inode;
 326         struct dentry *dentry, *tmp;
 327
 328         lock_kernel();
 329
 330         dentry = namei(filename);
 331         error = PTR_ERR(dentry);
 332         if (IS_ERR(dentry))
 333                 goto out;
 334
 335         inode = dentry->d_inode;
 336
 337         error = -ENOTDIR;
 338         if (!S_ISDIR(inode->i_mode))
 339                 goto dput_and_out;
 340
 341         error = permission(inode,MAY_EXEC);
 342         if (error)
 343                 goto dput_and_out;
 344
 345         /* exchange dentries */
 346         tmp = current->fs->pwd;
 347         current->fs->pwd = dentry;
 348         dentry = tmp;
 349
 350 dput_and_out:
 351         dput(dentry);
 352 out:
 353         unlock_kernel();
 354         return error;
 355 }
 356
 357 asmlinkage int sys_fchdir(unsigned int fd)
 358 {
 359         struct file *file;
 360         struct dentry *dentry;
 361         struct inode *inode;
 362         int error;
 363
 364         lock_kernel();
 365
 366         error = -EBADF;
 367         file = fget(fd);
 368         if (!file)
 369                 goto out;
 370
 371         error = -ENOENT;
 372         if (!(dentry = file->f_dentry))
 373                 goto out_putf;
 374         if (!(inode = dentry->d_inode))
 375                 goto out_putf;
 376
 377         error = -ENOTDIR;
 378         if (!S_ISDIR(inode->i_mode))
 379                 goto out_putf;
 380
 381         error = permission(inode, MAY_EXEC);
 382         if (!error) {
 383                 struct dentry *tmp = current->fs->pwd;
 384                 current->fs->pwd = dget(dentry);
 385                 dput(tmp);
 386         }
 387 out_putf:
 388         fput(file);
 389 out:
 390         unlock_kernel();
 391         return error;
 392 }
 393
 394 asmlinkage int sys_chroot(const char * filename)
 395 {
 396         int error;
 397         struct inode *inode;
 398         struct dentry *dentry, *tmp;
 399
 400         lock_kernel();
 401
 402         dentry = namei(filename);
 403         error = PTR_ERR(dentry);
 404         if (IS_ERR(dentry))
 405                 goto out;
 406
 407         inode = dentry->d_inode;
 408
 409         error = -ENOTDIR;
 410         if (!S_ISDIR(inode->i_mode))
 411                 goto dput_and_out;
 412
 413         error = permission(inode,MAY_EXEC);
 414         if (error)
 415                 goto dput_and_out;
 416
 417         error = -EPERM;
 418         if (!capable(CAP_SYS_CHROOT))
 419                 goto dput_and_out;
 420
 421         /* exchange dentries */
 422         tmp = current->fs->root;
 423         current->fs->root = dentry;
 424         dentry = tmp;
 425         error = 0;
 426
 427 dput_and_out:
 428         dput(dentry);
 429 out:
 430         unlock_kernel();
 431         return error;
 432 }
 433
 434 asmlinkage int sys_fchmod(unsigned int fd, mode_t mode)
 435 {
 436         struct inode * inode;
 437         struct dentry * dentry;
 438         struct file * file;
 439         int err = -EBADF;
 440         struct iattr newattrs;
 441
 442         lock_kernel();
 443         file = fget(fd);
 444         if (!file)
 445                 goto out;
 446
 447         err = -ENOENT;
 448         if (!(dentry = file->f_dentry))
 449                 goto out_putf;
 450         if (!(inode = dentry->d_inode))
 451                 goto out_putf;
 452
 453         err = -EROFS;
 454         if (IS_RDONLY(inode))
 455                 goto out_putf;
 456         err = -EPERM;
 457         if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
 458                 goto out_putf;
 459         if (mode == (mode_t) -1)
 460                 mode = inode->i_mode;
 461         newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
 462         newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
 463         err = notify_change(dentry, &newattrs);
 464
 465 out_putf:
 466         fput(file);
 467 out:
 468         unlock_kernel();
 469         return err;
 470 }
 471
 472 asmlinkage int sys_chmod(const char * filename, mode_t mode)
 473 {
 474         struct dentry * dentry;
 475         struct inode * inode;
 476         int error;
 477         struct iattr newattrs;
 478
 479         lock_kernel();
 480         dentry = namei(filename);
 481
 482         error = PTR_ERR(dentry);
 483         if (IS_ERR(dentry))
 484                 goto out;
 485         inode = dentry->d_inode;
 486
 487         error = -EROFS;
 488         if (IS_RDONLY(inode))
 489                 goto dput_and_out;
 490
 491         error = -EPERM;
 492         if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
 493                 goto dput_and_out;
 494
 495         if (mode == (mode_t) -1)
 496                 mode = inode->i_mode;
 497         newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
 498         newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
 499         error = notify_change(dentry, &newattrs);
 500
 501 dput_and_out:
 502         dput(dentry);
 503 out:
 504         unlock_kernel();
 505         return error;
 506 }
 507
 508 static int chown_common(struct dentry * dentry, uid_t user, gid_t group)
 509 {
 510         struct inode * inode;
 511         int error;
 512         struct iattr newattrs;
 513
 514         error = -ENOENT;
 515         if (!(inode = dentry->d_inode)) {
 516                 printk("chown_common: NULL inode\n");
 517                 goto out;
 518         }
 519         error = -EROFS;
 520         if (IS_RDONLY(inode))
 521                 goto out;
 522         error = -EPERM;
 523         if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
 524                 goto out;
 525         if (user == (uid_t) -1)
 526                 user = inode->i_uid;
 527         if (group == (gid_t) -1)
 528                 group = inode->i_gid;
 529         newattrs.ia_mode = inode->i_mode;
 530         newattrs.ia_uid = user;
 531         newattrs.ia_gid = group;
 532         newattrs.ia_valid =  ATTR_UID | ATTR_GID | ATTR_CTIME;
 533         /*
 534          * If the user or group of a non-directory has been changed by a
 535          * non-root user, remove the setuid bit.
 536          * 19981026     David C Niemi <niemi@tux.org>
 537          *
 538          */
 539         if ((inode->i_mode & S_ISUID) == S_ISUID &&
 540                 !S_ISDIR(inode->i_mode)
 541                 && current->fsuid)
 542         {
 543                 newattrs.ia_mode &= ~S_ISUID;
 544                 newattrs.ia_valid |= ATTR_MODE;
 545         }
 546         /*
 547          * Likewise, if the user or group of a non-directory has been changed
 548          * by a non-root user, remove the setgid bit UNLESS there is no group
 549          * execute bit (this would be a file marked for mandatory locking).
 550          * 19981026     David C Niemi <niemi@tux.org>
 551          */
 552         if (((inode->i_mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
 553                 && !S_ISDIR(inode->i_mode) && current->fsuid)
 554         {
 555                 newattrs.ia_mode &= ~S_ISGID;
 556                 newattrs.ia_valid |= ATTR_MODE;
 557         }
 558         error = DQUOT_TRANSFER(dentry, &newattrs);
 559 out:
 560         return error;
 561 }
 562
 563 asmlinkage int sys_chown(const char * filename, uid_t user, gid_t group)
 564 {
 565         struct dentry * dentry;
 566         int error;
 567
 568         lock_kernel();
 569         dentry = namei(filename);
 570
 571         error = PTR_ERR(dentry);
 572         if (!IS_ERR(dentry)) {
 573                 error = chown_common(dentry, user, group);
 574                 dput(dentry);
 575         }
 576         unlock_kernel();
 577         return error;
 578 }
 579
 580 asmlinkage int sys_lchown(const char * filename, uid_t user, gid_t group)
 581 {
 582         struct dentry * dentry;
 583         int error;
 584
 585         lock_kernel();
 586         dentry = lnamei(filename);
 587
 588         error = PTR_ERR(dentry);
 589         if (!IS_ERR(dentry)) {
 590                 error = chown_common(dentry, user, group);
 591                 dput(dentry);
 592         }
 593         unlock_kernel();
 594         return error;
 595 }
 596
 597
 598 asmlinkage int sys_fchown(unsigned int fd, uid_t user, gid_t group)
 599 {
 600         struct dentry * dentry;
 601         struct file * file;
 602         int error = -EBADF;
 603
 604         lock_kernel();
 605         file = fget(fd);
 606         if (!file)
 607                 goto out;
 608         error = -ENOENT;
 609         if ((dentry = file->f_dentry) != NULL)
 610                 error = chown_common(dentry, user, group);
 611         fput(file);
 612
 613 out:
 614         unlock_kernel();
 615         return error;
 616 }
 617
 618 /*
 619  * Note that while the flag value (low two bits) for sys_open means:
 620  *      00 - read-only
 621  *      01 - write-only
 622  *      10 - read-write
 623  *      11 - special
 624  * it is changed into
 625  *      00 - no permissions needed
 626  *      01 - read-permission
 627  *      10 - write-permission
 628  *      11 - read-write
 629  * for the internal routines (ie open_namei()/follow_link() etc). 00 is
 630  * used by symlinks.
 631  */
 632 struct file *filp_open(const char * filename, int flags, int mode)
 633 {
 634         struct inode * inode;
 635         struct dentry * dentry;
 636         struct file * f;
 637         int flag,error;
 638
 639         error = -ENFILE;
 640         f = get_empty_filp();
 641         if (!f)
 642                 goto out;
 643         f->f_flags = flag = flags;
 644         f->f_mode = (flag+1) & O_ACCMODE;
 645         if (f->f_mode)
 646                 flag++;
 647         if (flag & O_TRUNC)
 648                 flag |= 2;
 649         dentry = open_namei(filename,flag,mode);
 650         error = PTR_ERR(dentry);
 651         if (IS_ERR(dentry))
 652                 goto cleanup_file;
 653         inode = dentry->d_inode;
 654         if (f->f_mode & FMODE_WRITE) {
 655                 error = get_write_access(inode);
 656                 if (error)
 657                         goto cleanup_dentry;
 658         }
 659
 660         f->f_dentry = dentry;
 661         f->f_pos = 0;
 662         f->f_reada = 0;
 663         f->f_op = NULL;
 664         if (inode->i_op)
 665                 f->f_op = inode->i_op->default_file_ops;
 666         if (f->f_op && f->f_op->open) {
 667                 error = f->f_op->open(inode,f);
 668                 if (error)
 669                         goto cleanup_all;
 670         }
 671         f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 672
 673         return f;
 674
 675 cleanup_all:
 676         if (f->f_mode & FMODE_WRITE)
 677                 put_write_access(inode);
 678 cleanup_dentry:
 679         f->f_dentry = NULL;
 680         dput(dentry);
 681 cleanup_file:
 682         put_filp(f);
 683 out:
 684         return ERR_PTR(error);
 685 }
 686
 687 /*
 688  * Find an empty file descriptor entry, and mark it busy.
 689  */
 690 int get_unused_fd(void)
 691 {
 692         struct files_struct * files = current->files;
 693         int fd, error;
 694
 695         error = -EMFILE;
 696         fd = find_first_zero_bit(&files->open_fds, NR_OPEN);
 697         /*
 698          * N.B. For clone tasks sharing a files structure, this test
 699          * will limit the total number of files that can be opened.
 700          */
 701         if (fd >= current->rlim[RLIMIT_NOFILE].rlim_cur)
 702                 goto out;
 703
 704         /* Check here for fd > files->max_fds to do dynamic expansion */
 705
 706         FD_SET(fd, &files->open_fds);
 707         FD_CLR(fd, &files->close_on_exec);
 708 #if 1
 709         /* Sanity check */
 710         if (files->fd[fd] != NULL) {
 711                 printk("get_unused_fd: slot %d not NULL!\n", fd);
 712                 files->fd[fd] = NULL;
 713         }
 714 #endif
 715         error = fd;
 716
 717 out:
 718         return error;
 719 }
 720
 721 inline void put_unused_fd(unsigned int fd)
 722 {
 723         FD_CLR(fd, &current->files->open_fds);
 724 }
 725
 726 asmlinkage int sys_open(const char * filename, int flags, int mode)
 727 {
 728         char * tmp;
 729         int fd, error;
 730
 731         tmp = getname(filename);
 732         fd = PTR_ERR(tmp);
 733         if (!IS_ERR(tmp)) {
 734                 lock_kernel();
 735                 fd = get_unused_fd();
 736                 if (fd >= 0) {
 737                         struct file * f = filp_open(tmp, flags, mode);
 738                         error = PTR_ERR(f);
 739                         if (IS_ERR(f))
 740                                 goto out_error;
 741                         fd_install(fd, f);
 742                 }
 743 out:
 744                 unlock_kernel();
 745                 putname(tmp);
 746         }
 747         return fd;
 748
 749 out_error:
 750         put_unused_fd(fd);
 751         fd = error;
 752         goto out;
 753 }
 754
 755 #ifndef __alpha__
 756
 757 /*
 758  * For backward compatibility?  Maybe this should be moved
 759  * into arch/i386 instead?
 760  */
 761 asmlinkage int sys_creat(const char * pathname, int mode)
 762 {
 763         return sys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
 764 }
 765
 766 #endif
 767
 768 /*
 769  * Called when retiring the last use of a file pointer.
 770  */
 771 void __fput(struct file *filp)
 772 {
 773         struct dentry * dentry = filp->f_dentry;
 774         struct inode * inode = dentry->d_inode;
 775
 776         if (filp->f_op && filp->f_op->release)
 777                 filp->f_op->release(inode, filp);
 778         filp->f_dentry = NULL;
 779         if (filp->f_mode & FMODE_WRITE)
 780                 put_write_access(inode);
 781         dput(dentry);
 782 }
 783
 784 /*
 785  * "id" is the POSIX thread ID. We use the
 786  * files pointer for this..
 787  */
 788 int filp_close(struct file *filp, fl_owner_t id)
 789 {
 790         int retval;
 791         struct dentry *dentry = filp->f_dentry;
 792
 793         if (filp->f_count == 0) {
 794                 printk("VFS: Close: file count is 0\n");
 795                 return 0;
 796         }
 797         retval = 0;
 798         if (filp->f_op && filp->f_op->flush)
 799                 retval = filp->f_op->flush(filp);
 800         if (dentry->d_inode)
 801                 locks_remove_posix(filp, id);
 802         fput(filp);
 803         return retval;
 804 }
 805
 806 /*
 807  * Careful here! We test whether the file pointer is NULL before
 808  * releasing the fd. This ensures that one clone task can't release
 809  * an fd while another clone is opening it.
 810  */
 811 asmlinkage int sys_close(unsigned int fd)
 812 {
 813         int error;
 814         struct file * filp;
 815
 816         lock_kernel();
 817         error = -EBADF;
 818         filp = fcheck(fd);
 819         if (filp) {
 820                 struct files_struct * files = current->files;
 821                 files->fd[fd] = NULL;
 822                 put_unused_fd(fd);
 823                 FD_CLR(fd, &files->close_on_exec);
 824                 error = filp_close(filp, files);
 825         }
 826         unlock_kernel();
 827         return error;
 828 }
 829
 830 /*
 831  * This routine simulates a hangup on the tty, to arrange that users
 832  * are given clean terminals at login time.
 833  */
 834 asmlinkage int sys_vhangup(void)
 835 {
 836         int ret = -EPERM;
 837
 838         lock_kernel();
 839         if (!capable(CAP_SYS_TTY_CONFIG))
 840                 goto out;
 841         /* If there is a controlling tty, hang it up */
 842         if (current->tty)
 843                 tty_vhangup(current->tty);
 844         ret = 0;
 845 out:
 846         unlock_kernel();
 847         return ret;
 848 }