fs/debugfs/inode.c

   1 /*
   2  *  inode.c - part of debugfs, a tiny little debug file system
   3  *
   4  *  Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
   5  *  Copyright (C) 2004 IBM Inc.
   6  *
   7  *      This program is free software; you can redistribute it and/or
   8  *      modify it under the terms of the GNU General Public License version
   9  *      2 as published by the Free Software Foundation.
  10  *
  11  *  debugfs is for people to use instead of /proc or /sys.
  12  *  See Documentation/DocBook/kernel-api for more details.
  13  *
  14  */
  15
  16 #include <linux/module.h>
  17 #include <linux/fs.h>
  18 #include <linux/mount.h>
  19 #include <linux/pagemap.h>
  20 #include <linux/init.h>
  21 #include <linux/kobject.h>
  22 #include <linux/namei.h>
  23 #include <linux/debugfs.h>
  24 #include <linux/fsnotify.h>
  25 #include <linux/string.h>
  26 #include <linux/seq_file.h>
  27 #include <linux/parser.h>
  28 #include <linux/magic.h>
  29 #include <linux/slab.h>
  30
  31 #define DEBUGFS_DEFAULT_MODE    0700
  32
  33 static struct vfsmount *debugfs_mount;
  34 static int debugfs_mount_count;
  35 static bool debugfs_registered;
  36
  37 static struct inode *debugfs_get_inode(struct super_block *sb)
  38 {
  39         struct inode *inode = new_inode(sb);
  40         if (inode) {
  41                 inode->i_ino = get_next_ino();
  42                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  43         }
  44         return inode;
  45 }
  46
  47 static inline int debugfs_positive(struct dentry *dentry)
  48 {
  49         return dentry->d_inode && !d_unhashed(dentry);
  50 }
  51
  52 struct debugfs_mount_opts {
  53         kuid_t uid;
  54         kgid_t gid;
  55         umode_t mode;
  56 };
  57
  58 enum {
  59         Opt_uid,
  60         Opt_gid,
  61         Opt_mode,
  62         Opt_err
  63 };
  64
  65 static const match_table_t tokens = {
  66         {Opt_uid, "uid=%u"},
  67         {Opt_gid, "gid=%u"},
  68         {Opt_mode, "mode=%o"},
  69         {Opt_err, NULL}
  70 };
  71
  72 struct debugfs_fs_info {
  73         struct debugfs_mount_opts mount_opts;
  74 };
  75
  76 static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
  77 {
  78         substring_t args[MAX_OPT_ARGS];
  79         int option;
  80         int token;
  81         kuid_t uid;
  82         kgid_t gid;
  83         char *p;
  84
  85         opts->mode = DEBUGFS_DEFAULT_MODE;
  86
  87         while ((p = strsep(&data, ",")) != NULL) {
  88                 if (!*p)
  89                         continue;
  90
  91                 token = match_token(p, tokens, args);
  92                 switch (token) {
  93                 case Opt_uid:
  94                         if (match_int(&args[0], &option))
  95                                 return -EINVAL;
  96                         uid = make_kuid(current_user_ns(), option);
  97                         if (!uid_valid(uid))
  98                                 return -EINVAL;
  99                         opts->uid = uid;
 100                         break;
 101                 case Opt_gid:
 102                         if (match_int(&args[0], &option))
 103                                 return -EINVAL;
 104                         gid = make_kgid(current_user_ns(), option);
 105                         if (!gid_valid(gid))
 106                                 return -EINVAL;
 107                         opts->gid = gid;
 108                         break;
 109                 case Opt_mode:
 110                         if (match_octal(&args[0], &option))
 111                                 return -EINVAL;
 112                         opts->mode = option & S_IALLUGO;
 113                         break;
 114                 /*
 115                  * We might like to report bad mount options here;
 116                  * but traditionally debugfs has ignored all mount options
 117                  */
 118                 }
 119         }
 120
 121         return 0;
 122 }
 123
 124 static int debugfs_apply_options(struct super_block *sb)
 125 {
 126         struct debugfs_fs_info *fsi = sb->s_fs_info;
 127         struct inode *inode = sb->s_root->d_inode;
 128         struct debugfs_mount_opts *opts = &fsi->mount_opts;
 129
 130         inode->i_mode &= ~S_IALLUGO;
 131         inode->i_mode |= opts->mode;
 132
 133         inode->i_uid = opts->uid;
 134         inode->i_gid = opts->gid;
 135
 136         return 0;
 137 }
 138
 139 static int debugfs_remount(struct super_block *sb, int *flags, char *data)
 140 {
 141         int err;
 142         struct debugfs_fs_info *fsi = sb->s_fs_info;
 143
 144         sync_filesystem(sb);
 145         err = debugfs_parse_options(data, &fsi->mount_opts);
 146         if (err)
 147                 goto fail;
 148
 149         debugfs_apply_options(sb);
 150
 151 fail:
 152         return err;
 153 }
 154
 155 static int debugfs_show_options(struct seq_file *m, struct dentry *root)
 156 {
 157         struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
 158         struct debugfs_mount_opts *opts = &fsi->mount_opts;
 159
 160         if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
 161                 seq_printf(m, ",uid=%u",
 162                            from_kuid_munged(&init_user_ns, opts->uid));
 163         if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
 164                 seq_printf(m, ",gid=%u",
 165                            from_kgid_munged(&init_user_ns, opts->gid));
 166         if (opts->mode != DEBUGFS_DEFAULT_MODE)
 167                 seq_printf(m, ",mode=%o", opts->mode);
 168
 169         return 0;
 170 }
 171
 172 static void debugfs_evict_inode(struct inode *inode)
 173 {
 174         truncate_inode_pages_final(&inode->i_data);
 175         clear_inode(inode);
 176         if (S_ISLNK(inode->i_mode))
 177                 kfree(inode->i_private);
 178 }
 179
 180 static const struct super_operations debugfs_super_operations = {
 181         .statfs         = simple_statfs,
 182         .remount_fs     = debugfs_remount,
 183         .show_options   = debugfs_show_options,
 184         .evict_inode    = debugfs_evict_inode,
 185 };
 186
 187 static struct vfsmount *debugfs_automount(struct path *path)
 188 {
 189         struct vfsmount *(*f)(void *);
 190         f = (struct vfsmount *(*)(void *))path->dentry->d_fsdata;
 191         return f(path->dentry->d_inode->i_private);
 192 }
 193
 194 static const struct dentry_operations debugfs_dops = {
 195         .d_delete = always_delete_dentry,
 196         .d_automount = debugfs_automount,
 197 };
 198
 199 static int debug_fill_super(struct super_block *sb, void *data, int silent)
 200 {
 201         static struct tree_descr debug_files[] = {{""}};
 202         struct debugfs_fs_info *fsi;
 203         int err;
 204
 205         save_mount_options(sb, data);
 206
 207         fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
 208         sb->s_fs_info = fsi;
 209         if (!fsi) {
 210                 err = -ENOMEM;
 211                 goto fail;
 212         }
 213
 214         err = debugfs_parse_options(data, &fsi->mount_opts);
 215         if (err)
 216                 goto fail;
 217
 218         err  =  simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
 219         if (err)
 220                 goto fail;
 221
 222         sb->s_op = &debugfs_super_operations;
 223         sb->s_d_op = &debugfs_dops;
 224
 225         debugfs_apply_options(sb);
 226
 227         return 0;
 228
 229 fail:
 230         kfree(fsi);
 231         sb->s_fs_info = NULL;
 232         return err;
 233 }
 234
 235 static struct dentry *debug_mount(struct file_system_type *fs_type,
 236                         int flags, const char *dev_name,
 237                         void *data)
 238 {
 239         return mount_single(fs_type, flags, data, debug_fill_super);
 240 }
 241
 242 static struct file_system_type debug_fs_type = {
 243         .owner =        THIS_MODULE,
 244         .name =         "debugfs",
 245         .mount =        debug_mount,
 246         .kill_sb =      kill_litter_super,
 247 };
 248 MODULE_ALIAS_FS("debugfs");
 249
 250 static struct dentry *start_creating(const char *name, struct dentry *parent)
 251 {
 252         struct dentry *dentry;
 253         int error;
 254
 255         pr_debug("debugfs: creating file '%s'\n",name);
 256
 257         error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
 258                               &debugfs_mount_count);
 259         if (error)
 260                 return ERR_PTR(error);
 261
 262         /* If the parent is not specified, we create it in the root.
 263          * We need the root dentry to do this, which is in the super
 264          * block. A pointer to that is in the struct vfsmount that we
 265          * have around.
 266          */
 267         if (!parent)
 268                 parent = debugfs_mount->mnt_root;
 269
 270         mutex_lock(&parent->d_inode->i_mutex);
 271         dentry = lookup_one_len(name, parent, strlen(name));
 272         if (!IS_ERR(dentry) && dentry->d_inode) {
 273                 dput(dentry);
 274                 dentry = ERR_PTR(-EEXIST);
 275         }
 276         if (IS_ERR(dentry))
 277                 mutex_unlock(&parent->d_inode->i_mutex);
 278         return dentry;
 279 }
 280
 281 static struct dentry *failed_creating(struct dentry *dentry)
 282 {
 283         mutex_unlock(&dentry->d_parent->d_inode->i_mutex);
 284         dput(dentry);
 285         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 286         return NULL;
 287 }
 288
 289 static struct dentry *end_creating(struct dentry *dentry)
 290 {
 291         mutex_unlock(&dentry->d_parent->d_inode->i_mutex);
 292         return dentry;
 293 }
 294
 295 /**
 296  * debugfs_create_file - create a file in the debugfs filesystem
 297  * @name: a pointer to a string containing the name of the file to create.
 298  * @mode: the permission that the file should have.
 299  * @parent: a pointer to the parent dentry for this file.  This should be a
 300  *          directory dentry if set.  If this parameter is NULL, then the
 301  *          file will be created in the root of the debugfs filesystem.
 302  * @data: a pointer to something that the caller will want to get to later
 303  *        on.  The inode.i_private pointer will point to this value on
 304  *        the open() call.
 305  * @fops: a pointer to a struct file_operations that should be used for
 306  *        this file.
 307  *
 308  * This is the basic "create a file" function for debugfs.  It allows for a
 309  * wide range of flexibility in creating a file, or a directory (if you want
 310  * to create a directory, the debugfs_create_dir() function is
 311  * recommended to be used instead.)
 312  *
 313  * This function will return a pointer to a dentry if it succeeds.  This
 314  * pointer must be passed to the debugfs_remove() function when the file is
 315  * to be removed (no automatic cleanup happens if your module is unloaded,
 316  * you are responsible here.)  If an error occurs, %NULL will be returned.
 317  *
 318  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 319  * returned.
 320  */
 321 struct dentry *debugfs_create_file(const char *name, umode_t mode,
 322                                    struct dentry *parent, void *data,
 323                                    const struct file_operations *fops)
 324 {
 325         struct dentry *dentry;
 326         struct inode *inode;
 327
 328         if (!(mode & S_IFMT))
 329                 mode |= S_IFREG;
 330         BUG_ON(!S_ISREG(mode));
 331         dentry = start_creating(name, parent);
 332
 333         if (IS_ERR(dentry))
 334                 return NULL;
 335
 336         inode = debugfs_get_inode(dentry->d_sb);
 337         if (unlikely(!inode))
 338                 return failed_creating(dentry);
 339
 340         inode->i_mode = mode;
 341         inode->i_fop = fops ? fops : &debugfs_file_operations;
 342         inode->i_private = data;
 343         d_instantiate(dentry, inode);
 344         fsnotify_create(dentry->d_parent->d_inode, dentry);
 345         return end_creating(dentry);
 346 }
 347 EXPORT_SYMBOL_GPL(debugfs_create_file);
 348
 349 /**
 350  * debugfs_create_file_size - create a file in the debugfs filesystem
 351  * @name: a pointer to a string containing the name of the file to create.
 352  * @mode: the permission that the file should have.
 353  * @parent: a pointer to the parent dentry for this file.  This should be a
 354  *          directory dentry if set.  If this parameter is NULL, then the
 355  *          file will be created in the root of the debugfs filesystem.
 356  * @data: a pointer to something that the caller will want to get to later
 357  *        on.  The inode.i_private pointer will point to this value on
 358  *        the open() call.
 359  * @fops: a pointer to a struct file_operations that should be used for
 360  *        this file.
 361  * @file_size: initial file size
 362  *
 363  * This is the basic "create a file" function for debugfs.  It allows for a
 364  * wide range of flexibility in creating a file, or a directory (if you want
 365  * to create a directory, the debugfs_create_dir() function is
 366  * recommended to be used instead.)
 367  *
 368  * This function will return a pointer to a dentry if it succeeds.  This
 369  * pointer must be passed to the debugfs_remove() function when the file is
 370  * to be removed (no automatic cleanup happens if your module is unloaded,
 371  * you are responsible here.)  If an error occurs, %NULL will be returned.
 372  *
 373  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 374  * returned.
 375  */
 376 struct dentry *debugfs_create_file_size(const char *name, umode_t mode,
 377                                         struct dentry *parent, void *data,
 378                                         const struct file_operations *fops,
 379                                         loff_t file_size)
 380 {
 381         struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
 382
 383         if (de)
 384                 de->d_inode->i_size = file_size;
 385         return de;
 386 }
 387 EXPORT_SYMBOL_GPL(debugfs_create_file_size);
 388
 389 /**
 390  * debugfs_create_dir - create a directory in the debugfs filesystem
 391  * @name: a pointer to a string containing the name of the directory to
 392  *        create.
 393  * @parent: a pointer to the parent dentry for this file.  This should be a
 394  *          directory dentry if set.  If this parameter is NULL, then the
 395  *          directory will be created in the root of the debugfs filesystem.
 396  *
 397  * This function creates a directory in debugfs with the given name.
 398  *
 399  * This function will return a pointer to a dentry if it succeeds.  This
 400  * pointer must be passed to the debugfs_remove() function when the file is
 401  * to be removed (no automatic cleanup happens if your module is unloaded,
 402  * you are responsible here.)  If an error occurs, %NULL will be returned.
 403  *
 404  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 405  * returned.
 406  */
 407 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
 408 {
 409         struct dentry *dentry = start_creating(name, parent);
 410         struct inode *inode;
 411
 412         if (IS_ERR(dentry))
 413                 return NULL;
 414
 415         inode = debugfs_get_inode(dentry->d_sb);
 416         if (unlikely(!inode))
 417                 return failed_creating(dentry);
 418
 419         inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
 420         inode->i_op = &simple_dir_inode_operations;
 421         inode->i_fop = &simple_dir_operations;
 422
 423         /* directory inodes start off with i_nlink == 2 (for "." entry) */
 424         inc_nlink(inode);
 425         d_instantiate(dentry, inode);
 426         inc_nlink(dentry->d_parent->d_inode);
 427         fsnotify_mkdir(dentry->d_parent->d_inode, dentry);
 428         return end_creating(dentry);
 429 }
 430 EXPORT_SYMBOL_GPL(debugfs_create_dir);
 431
 432 /**
 433  * debugfs_create_automount - create automount point in the debugfs filesystem
 434  * @name: a pointer to a string containing the name of the file to create.
 435  * @parent: a pointer to the parent dentry for this file.  This should be a
 436  *          directory dentry if set.  If this parameter is NULL, then the
 437  *          file will be created in the root of the debugfs filesystem.
 438  * @f: function to be called when pathname resolution steps on that one.
 439  * @data: opaque argument to pass to f().
 440  *
 441  * @f should return what ->d_automount() would.
 442  */
 443 struct dentry *debugfs_create_automount(const char *name,
 444                                         struct dentry *parent,
 445                                         struct vfsmount *(*f)(void *),
 446                                         void *data)
 447 {
 448         struct dentry *dentry = start_creating(name, parent);
 449         struct inode *inode;
 450
 451         if (IS_ERR(dentry))
 452                 return NULL;
 453
 454         inode = debugfs_get_inode(dentry->d_sb);
 455         if (unlikely(!inode))
 456                 return failed_creating(dentry);
 457
 458         inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
 459         inode->i_flags |= S_AUTOMOUNT;
 460         inode->i_private = data;
 461         dentry->d_fsdata = (void *)f;
 462         d_instantiate(dentry, inode);
 463         return end_creating(dentry);
 464 }
 465 EXPORT_SYMBOL(debugfs_create_automount);
 466
 467 /**
 468  * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
 469  * @name: a pointer to a string containing the name of the symbolic link to
 470  *        create.
 471  * @parent: a pointer to the parent dentry for this symbolic link.  This
 472  *          should be a directory dentry if set.  If this parameter is NULL,
 473  *          then the symbolic link will be created in the root of the debugfs
 474  *          filesystem.
 475  * @target: a pointer to a string containing the path to the target of the
 476  *          symbolic link.
 477  *
 478  * This function creates a symbolic link with the given name in debugfs that
 479  * links to the given target path.
 480  *
 481  * This function will return a pointer to a dentry if it succeeds.  This
 482  * pointer must be passed to the debugfs_remove() function when the symbolic
 483  * link is to be removed (no automatic cleanup happens if your module is
 484  * unloaded, you are responsible here.)  If an error occurs, %NULL will be
 485  * returned.
 486  *
 487  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 488  * returned.
 489  */
 490 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
 491                                       const char *target)
 492 {
 493         struct dentry *dentry;
 494         struct inode *inode;
 495         char *link = kstrdup(target, GFP_KERNEL);
 496         if (!link)
 497                 return NULL;
 498
 499         dentry = start_creating(name, parent);
 500         if (IS_ERR(dentry)) {
 501                 kfree(link);
 502                 return NULL;
 503         }
 504
 505         inode = debugfs_get_inode(dentry->d_sb);
 506         if (unlikely(!inode)) {
 507                 kfree(link);
 508                 return failed_creating(dentry);
 509         }
 510         inode->i_mode = S_IFLNK | S_IRWXUGO;
 511         inode->i_op = &debugfs_link_operations;
 512         inode->i_private = link;
 513         d_instantiate(dentry, inode);
 514         return end_creating(dentry);
 515 }
 516 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
 517
 518 static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
 519 {
 520         int ret = 0;
 521
 522         if (debugfs_positive(dentry)) {
 523                 dget(dentry);
 524                 if (d_is_dir(dentry))
 525                         ret = simple_rmdir(parent->d_inode, dentry);
 526                 else
 527                         simple_unlink(parent->d_inode, dentry);
 528                 if (!ret)
 529                         d_delete(dentry);
 530                 dput(dentry);
 531         }
 532         return ret;
 533 }
 534
 535 /**
 536  * debugfs_remove - removes a file or directory from the debugfs filesystem
 537  * @dentry: a pointer to a the dentry of the file or directory to be
 538  *          removed.
 539  *
 540  * This function removes a file or directory in debugfs that was previously
 541  * created with a call to another debugfs function (like
 542  * debugfs_create_file() or variants thereof.)
 543  *
 544  * This function is required to be called in order for the file to be
 545  * removed, no automatic cleanup of files will happen when a module is
 546  * removed, you are responsible here.
 547  */
 548 void debugfs_remove(struct dentry *dentry)
 549 {
 550         struct dentry *parent;
 551         int ret;
 552
 553         if (IS_ERR_OR_NULL(dentry))
 554                 return;
 555
 556         parent = dentry->d_parent;
 557         if (!parent || !parent->d_inode)
 558                 return;
 559
 560         mutex_lock(&parent->d_inode->i_mutex);
 561         ret = __debugfs_remove(dentry, parent);
 562         mutex_unlock(&parent->d_inode->i_mutex);
 563         if (!ret)
 564                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 565 }
 566 EXPORT_SYMBOL_GPL(debugfs_remove);
 567
 568 /**
 569  * debugfs_remove_recursive - recursively removes a directory
 570  * @dentry: a pointer to a the dentry of the directory to be removed.
 571  *
 572  * This function recursively removes a directory tree in debugfs that
 573  * was previously created with a call to another debugfs function
 574  * (like debugfs_create_file() or variants thereof.)
 575  *
 576  * This function is required to be called in order for the file to be
 577  * removed, no automatic cleanup of files will happen when a module is
 578  * removed, you are responsible here.
 579  */
 580 void debugfs_remove_recursive(struct dentry *dentry)
 581 {
 582         struct dentry *child, *parent;
 583
 584         if (IS_ERR_OR_NULL(dentry))
 585                 return;
 586
 587         parent = dentry->d_parent;
 588         if (!parent || !parent->d_inode)
 589                 return;
 590
 591         parent = dentry;
 592  down:
 593         mutex_lock(&parent->d_inode->i_mutex);
 594  loop:
 595         /*
 596          * The parent->d_subdirs is protected by the d_lock. Outside that
 597          * lock, the child can be unlinked and set to be freed which can
 598          * use the d_u.d_child as the rcu head and corrupt this list.
 599          */
 600         spin_lock(&parent->d_lock);
 601         list_for_each_entry(child, &parent->d_subdirs, d_child) {
 602                 if (!debugfs_positive(child))
 603                         continue;
 604
 605                 /* perhaps simple_empty(child) makes more sense */
 606                 if (!list_empty(&child->d_subdirs)) {
 607                         spin_unlock(&parent->d_lock);
 608                         mutex_unlock(&parent->d_inode->i_mutex);
 609                         parent = child;
 610                         goto down;
 611                 }
 612
 613                 spin_unlock(&parent->d_lock);
 614
 615                 if (!__debugfs_remove(child, parent))
 616                         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 617
 618                 /*
 619                  * The parent->d_lock protects agaist child from unlinking
 620                  * from d_subdirs. When releasing the parent->d_lock we can
 621                  * no longer trust that the next pointer is valid.
 622                  * Restart the loop. We'll skip this one with the
 623                  * debugfs_positive() check.
 624                  */
 625                 goto loop;
 626         }
 627         spin_unlock(&parent->d_lock);
 628
 629         mutex_unlock(&parent->d_inode->i_mutex);
 630         child = parent;
 631         parent = parent->d_parent;
 632         mutex_lock(&parent->d_inode->i_mutex);
 633
 634         if (child != dentry)
 635                 /* go up */
 636                 goto loop;
 637
 638         if (!__debugfs_remove(child, parent))
 639                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
 640         mutex_unlock(&parent->d_inode->i_mutex);
 641 }
 642 EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
 643
 644 /**
 645  * debugfs_rename - rename a file/directory in the debugfs filesystem
 646  * @old_dir: a pointer to the parent dentry for the renamed object. This
 647  *          should be a directory dentry.
 648  * @old_dentry: dentry of an object to be renamed.
 649  * @new_dir: a pointer to the parent dentry where the object should be
 650  *          moved. This should be a directory dentry.
 651  * @new_name: a pointer to a string containing the target name.
 652  *
 653  * This function renames a file/directory in debugfs.  The target must not
 654  * exist for rename to succeed.
 655  *
 656  * This function will return a pointer to old_dentry (which is updated to
 657  * reflect renaming) if it succeeds. If an error occurs, %NULL will be
 658  * returned.
 659  *
 660  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 661  * returned.
 662  */
 663 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
 664                 struct dentry *new_dir, const char *new_name)
 665 {
 666         int error;
 667         struct dentry *dentry = NULL, *trap;
 668         const char *old_name;
 669
 670         trap = lock_rename(new_dir, old_dir);
 671         /* Source or destination directories don't exist? */
 672         if (!old_dir->d_inode || !new_dir->d_inode)
 673                 goto exit;
 674         /* Source does not exist, cyclic rename, or mountpoint? */
 675         if (!old_dentry->d_inode || old_dentry == trap ||
 676             d_mountpoint(old_dentry))
 677                 goto exit;
 678         dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
 679         /* Lookup failed, cyclic rename or target exists? */
 680         if (IS_ERR(dentry) || dentry == trap || dentry->d_inode)
 681                 goto exit;
 682
 683         old_name = fsnotify_oldname_init(old_dentry->d_name.name);
 684
 685         error = simple_rename(old_dir->d_inode, old_dentry, new_dir->d_inode,
 686                 dentry);
 687         if (error) {
 688                 fsnotify_oldname_free(old_name);
 689                 goto exit;
 690         }
 691         d_move(old_dentry, dentry);
 692         fsnotify_move(old_dir->d_inode, new_dir->d_inode, old_name,
 693                 d_is_dir(old_dentry),
 694                 NULL, old_dentry);
 695         fsnotify_oldname_free(old_name);
 696         unlock_rename(new_dir, old_dir);
 697         dput(dentry);
 698         return old_dentry;
 699 exit:
 700         if (dentry && !IS_ERR(dentry))
 701                 dput(dentry);
 702         unlock_rename(new_dir, old_dir);
 703         return NULL;
 704 }
 705 EXPORT_SYMBOL_GPL(debugfs_rename);
 706
 707 /**
 708  * debugfs_initialized - Tells whether debugfs has been registered
 709  */
 710 bool debugfs_initialized(void)
 711 {
 712         return debugfs_registered;
 713 }
 714 EXPORT_SYMBOL_GPL(debugfs_initialized);
 715
 716
 717 static struct kobject *debug_kobj;
 718
 719 static int __init debugfs_init(void)
 720 {
 721         int retval;
 722
 723         debug_kobj = kobject_create_and_add("debug", kernel_kobj);
 724         if (!debug_kobj)
 725                 return -EINVAL;
 726
 727         retval = register_filesystem(&debug_fs_type);
 728         if (retval)
 729                 kobject_put(debug_kobj);
 730         else
 731                 debugfs_registered = true;
 732
 733         return retval;
 734 }
 735 core_initcall(debugfs_init);
 736