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