Version:  2.0.40 2.2.26 2.4.37 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7

Linux/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 #include <linux/srcu.h>
 31 
 32 #include "internal.h"
 33 
 34 #define DEBUGFS_DEFAULT_MODE    0700
 35 
 36 DEFINE_SRCU(debugfs_srcu);
 37 
 38 static struct vfsmount *debugfs_mount;
 39 static int debugfs_mount_count;
 40 static bool debugfs_registered;
 41 
 42 static struct inode *debugfs_get_inode(struct super_block *sb)
 43 {
 44         struct inode *inode = new_inode(sb);
 45         if (inode) {
 46                 inode->i_ino = get_next_ino();
 47                 inode->i_atime = inode->i_mtime =
 48                         inode->i_ctime = current_fs_time(sb);
 49         }
 50         return inode;
 51 }
 52 
 53 struct debugfs_mount_opts {
 54         kuid_t uid;
 55         kgid_t gid;
 56         umode_t mode;
 57 };
 58 
 59 enum {
 60         Opt_uid,
 61         Opt_gid,
 62         Opt_mode,
 63         Opt_err
 64 };
 65 
 66 static const match_table_t tokens = {
 67         {Opt_uid, "uid=%u"},
 68         {Opt_gid, "gid=%u"},
 69         {Opt_mode, "mode=%o"},
 70         {Opt_err, NULL}
 71 };
 72 
 73 struct debugfs_fs_info {
 74         struct debugfs_mount_opts mount_opts;
 75 };
 76 
 77 static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
 78 {
 79         substring_t args[MAX_OPT_ARGS];
 80         int option;
 81         int token;
 82         kuid_t uid;
 83         kgid_t gid;
 84         char *p;
 85 
 86         opts->mode = DEBUGFS_DEFAULT_MODE;
 87 
 88         while ((p = strsep(&data, ",")) != NULL) {
 89                 if (!*p)
 90                         continue;
 91 
 92                 token = match_token(p, tokens, args);
 93                 switch (token) {
 94                 case Opt_uid:
 95                         if (match_int(&args[0], &option))
 96                                 return -EINVAL;
 97                         uid = make_kuid(current_user_ns(), option);
 98                         if (!uid_valid(uid))
 99                                 return -EINVAL;
100                         opts->uid = uid;
101                         break;
102                 case Opt_gid:
103                         if (match_int(&args[0], &option))
104                                 return -EINVAL;
105                         gid = make_kgid(current_user_ns(), option);
106                         if (!gid_valid(gid))
107                                 return -EINVAL;
108                         opts->gid = gid;
109                         break;
110                 case Opt_mode:
111                         if (match_octal(&args[0], &option))
112                                 return -EINVAL;
113                         opts->mode = option & S_IALLUGO;
114                         break;
115                 /*
116                  * We might like to report bad mount options here;
117                  * but traditionally debugfs has ignored all mount options
118                  */
119                 }
120         }
121 
122         return 0;
123 }
124 
125 static int debugfs_apply_options(struct super_block *sb)
126 {
127         struct debugfs_fs_info *fsi = sb->s_fs_info;
128         struct inode *inode = d_inode(sb->s_root);
129         struct debugfs_mount_opts *opts = &fsi->mount_opts;
130 
131         inode->i_mode &= ~S_IALLUGO;
132         inode->i_mode |= opts->mode;
133 
134         inode->i_uid = opts->uid;
135         inode->i_gid = opts->gid;
136 
137         return 0;
138 }
139 
140 static int debugfs_remount(struct super_block *sb, int *flags, char *data)
141 {
142         int err;
143         struct debugfs_fs_info *fsi = sb->s_fs_info;
144 
145         sync_filesystem(sb);
146         err = debugfs_parse_options(data, &fsi->mount_opts);
147         if (err)
148                 goto fail;
149 
150         debugfs_apply_options(sb);
151 
152 fail:
153         return err;
154 }
155 
156 static int debugfs_show_options(struct seq_file *m, struct dentry *root)
157 {
158         struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
159         struct debugfs_mount_opts *opts = &fsi->mount_opts;
160 
161         if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
162                 seq_printf(m, ",uid=%u",
163                            from_kuid_munged(&init_user_ns, opts->uid));
164         if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
165                 seq_printf(m, ",gid=%u",
166                            from_kgid_munged(&init_user_ns, opts->gid));
167         if (opts->mode != DEBUGFS_DEFAULT_MODE)
168                 seq_printf(m, ",mode=%o", opts->mode);
169 
170         return 0;
171 }
172 
173 static void debugfs_evict_inode(struct inode *inode)
174 {
175         truncate_inode_pages_final(&inode->i_data);
176         clear_inode(inode);
177         if (S_ISLNK(inode->i_mode))
178                 kfree(inode->i_link);
179 }
180 
181 static const struct super_operations debugfs_super_operations = {
182         .statfs         = simple_statfs,
183         .remount_fs     = debugfs_remount,
184         .show_options   = debugfs_show_options,
185         .evict_inode    = debugfs_evict_inode,
186 };
187 
188 static struct vfsmount *debugfs_automount(struct path *path)
189 {
190         struct vfsmount *(*f)(void *);
191         f = (struct vfsmount *(*)(void *))path->dentry->d_fsdata;
192         return f(d_inode(path->dentry)->i_private);
193 }
194 
195 static const struct dentry_operations debugfs_dops = {
196         .d_delete = always_delete_dentry,
197         .d_automount = debugfs_automount,
198 };
199 
200 static int debug_fill_super(struct super_block *sb, void *data, int silent)
201 {
202         static struct tree_descr debug_files[] = {{""}};
203         struct debugfs_fs_info *fsi;
204         int err;
205 
206         save_mount_options(sb, data);
207 
208         fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
209         sb->s_fs_info = fsi;
210         if (!fsi) {
211                 err = -ENOMEM;
212                 goto fail;
213         }
214 
215         err = debugfs_parse_options(data, &fsi->mount_opts);
216         if (err)
217                 goto fail;
218 
219         err  =  simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
220         if (err)
221                 goto fail;
222 
223         sb->s_op = &debugfs_super_operations;
224         sb->s_d_op = &debugfs_dops;
225 
226         debugfs_apply_options(sb);
227 
228         return 0;
229 
230 fail:
231         kfree(fsi);
232         sb->s_fs_info = NULL;
233         return err;
234 }
235 
236 static struct dentry *debug_mount(struct file_system_type *fs_type,
237                         int flags, const char *dev_name,
238                         void *data)
239 {
240         return mount_single(fs_type, flags, data, debug_fill_super);
241 }
242 
243 static struct file_system_type debug_fs_type = {
244         .owner =        THIS_MODULE,
245         .name =         "debugfs",
246         .mount =        debug_mount,
247         .kill_sb =      kill_litter_super,
248 };
249 MODULE_ALIAS_FS("debugfs");
250 
251 static struct dentry *start_creating(const char *name, struct dentry *parent)
252 {
253         struct dentry *dentry;
254         int error;
255 
256         pr_debug("debugfs: creating file '%s'\n",name);
257 
258         if (IS_ERR(parent))
259                 return parent;
260 
261         error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
262                               &debugfs_mount_count);
263         if (error)
264                 return ERR_PTR(error);
265 
266         /* If the parent is not specified, we create it in the root.
267          * We need the root dentry to do this, which is in the super
268          * block. A pointer to that is in the struct vfsmount that we
269          * have around.
270          */
271         if (!parent)
272                 parent = debugfs_mount->mnt_root;
273 
274         inode_lock(d_inode(parent));
275         dentry = lookup_one_len(name, parent, strlen(name));
276         if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
277                 dput(dentry);
278                 dentry = ERR_PTR(-EEXIST);
279         }
280 
281         if (IS_ERR(dentry)) {
282                 inode_unlock(d_inode(parent));
283                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
284         }
285 
286         return dentry;
287 }
288 
289 static struct dentry *failed_creating(struct dentry *dentry)
290 {
291         inode_unlock(d_inode(dentry->d_parent));
292         dput(dentry);
293         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
294         return NULL;
295 }
296 
297 static struct dentry *end_creating(struct dentry *dentry)
298 {
299         inode_unlock(d_inode(dentry->d_parent));
300         return dentry;
301 }
302 
303 static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
304                                 struct dentry *parent, void *data,
305                                 const struct file_operations *proxy_fops,
306                                 const struct file_operations *real_fops)
307 {
308         struct dentry *dentry;
309         struct inode *inode;
310 
311         if (!(mode & S_IFMT))
312                 mode |= S_IFREG;
313         BUG_ON(!S_ISREG(mode));
314         dentry = start_creating(name, parent);
315 
316         if (IS_ERR(dentry))
317                 return NULL;
318 
319         inode = debugfs_get_inode(dentry->d_sb);
320         if (unlikely(!inode))
321                 return failed_creating(dentry);
322 
323         inode->i_mode = mode;
324         inode->i_private = data;
325 
326         inode->i_fop = proxy_fops;
327         dentry->d_fsdata = (void *)real_fops;
328 
329         d_instantiate(dentry, inode);
330         fsnotify_create(d_inode(dentry->d_parent), dentry);
331         return end_creating(dentry);
332 }
333 
334 /**
335  * debugfs_create_file - create a file in the debugfs filesystem
336  * @name: a pointer to a string containing the name of the file to create.
337  * @mode: the permission that the file should have.
338  * @parent: a pointer to the parent dentry for this file.  This should be a
339  *          directory dentry if set.  If this parameter is NULL, then the
340  *          file will be created in the root of the debugfs filesystem.
341  * @data: a pointer to something that the caller will want to get to later
342  *        on.  The inode.i_private pointer will point to this value on
343  *        the open() call.
344  * @fops: a pointer to a struct file_operations that should be used for
345  *        this file.
346  *
347  * This is the basic "create a file" function for debugfs.  It allows for a
348  * wide range of flexibility in creating a file, or a directory (if you want
349  * to create a directory, the debugfs_create_dir() function is
350  * recommended to be used instead.)
351  *
352  * This function will return a pointer to a dentry if it succeeds.  This
353  * pointer must be passed to the debugfs_remove() function when the file is
354  * to be removed (no automatic cleanup happens if your module is unloaded,
355  * you are responsible here.)  If an error occurs, %NULL will be returned.
356  *
357  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
358  * returned.
359  */
360 struct dentry *debugfs_create_file(const char *name, umode_t mode,
361                                    struct dentry *parent, void *data,
362                                    const struct file_operations *fops)
363 {
364 
365         return __debugfs_create_file(name, mode, parent, data,
366                                 fops ? &debugfs_full_proxy_file_operations :
367                                         &debugfs_noop_file_operations,
368                                 fops);
369 }
370 EXPORT_SYMBOL_GPL(debugfs_create_file);
371 
372 /**
373  * debugfs_create_file_unsafe - create a file in the debugfs filesystem
374  * @name: a pointer to a string containing the name of the file to create.
375  * @mode: the permission that the file should have.
376  * @parent: a pointer to the parent dentry for this file.  This should be a
377  *          directory dentry if set.  If this parameter is NULL, then the
378  *          file will be created in the root of the debugfs filesystem.
379  * @data: a pointer to something that the caller will want to get to later
380  *        on.  The inode.i_private pointer will point to this value on
381  *        the open() call.
382  * @fops: a pointer to a struct file_operations that should be used for
383  *        this file.
384  *
385  * debugfs_create_file_unsafe() is completely analogous to
386  * debugfs_create_file(), the only difference being that the fops
387  * handed it will not get protected against file removals by the
388  * debugfs core.
389  *
390  * It is your responsibility to protect your struct file_operation
391  * methods against file removals by means of debugfs_use_file_start()
392  * and debugfs_use_file_finish(). ->open() is still protected by
393  * debugfs though.
394  *
395  * Any struct file_operations defined by means of
396  * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
397  * thus, may be used here.
398  */
399 struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
400                                    struct dentry *parent, void *data,
401                                    const struct file_operations *fops)
402 {
403 
404         return __debugfs_create_file(name, mode, parent, data,
405                                 fops ? &debugfs_open_proxy_file_operations :
406                                         &debugfs_noop_file_operations,
407                                 fops);
408 }
409 EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);
410 
411 /**
412  * debugfs_create_file_size - create a file in the debugfs filesystem
413  * @name: a pointer to a string containing the name of the file to create.
414  * @mode: the permission that the file should have.
415  * @parent: a pointer to the parent dentry for this file.  This should be a
416  *          directory dentry if set.  If this parameter is NULL, then the
417  *          file will be created in the root of the debugfs filesystem.
418  * @data: a pointer to something that the caller will want to get to later
419  *        on.  The inode.i_private pointer will point to this value on
420  *        the open() call.
421  * @fops: a pointer to a struct file_operations that should be used for
422  *        this file.
423  * @file_size: initial file size
424  *
425  * This is the basic "create a file" function for debugfs.  It allows for a
426  * wide range of flexibility in creating a file, or a directory (if you want
427  * to create a directory, the debugfs_create_dir() function is
428  * recommended to be used instead.)
429  *
430  * This function will return a pointer to a dentry if it succeeds.  This
431  * pointer must be passed to the debugfs_remove() function when the file is
432  * to be removed (no automatic cleanup happens if your module is unloaded,
433  * you are responsible here.)  If an error occurs, %NULL will be returned.
434  *
435  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
436  * returned.
437  */
438 struct dentry *debugfs_create_file_size(const char *name, umode_t mode,
439                                         struct dentry *parent, void *data,
440                                         const struct file_operations *fops,
441                                         loff_t file_size)
442 {
443         struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
444 
445         if (de)
446                 d_inode(de)->i_size = file_size;
447         return de;
448 }
449 EXPORT_SYMBOL_GPL(debugfs_create_file_size);
450 
451 /**
452  * debugfs_create_dir - create a directory in the debugfs filesystem
453  * @name: a pointer to a string containing the name of the directory to
454  *        create.
455  * @parent: a pointer to the parent dentry for this file.  This should be a
456  *          directory dentry if set.  If this parameter is NULL, then the
457  *          directory will be created in the root of the debugfs filesystem.
458  *
459  * This function creates a directory in debugfs with the given name.
460  *
461  * This function will return a pointer to a dentry if it succeeds.  This
462  * pointer must be passed to the debugfs_remove() function when the file is
463  * to be removed (no automatic cleanup happens if your module is unloaded,
464  * you are responsible here.)  If an error occurs, %NULL will be returned.
465  *
466  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
467  * returned.
468  */
469 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
470 {
471         struct dentry *dentry = start_creating(name, parent);
472         struct inode *inode;
473 
474         if (IS_ERR(dentry))
475                 return NULL;
476 
477         inode = debugfs_get_inode(dentry->d_sb);
478         if (unlikely(!inode))
479                 return failed_creating(dentry);
480 
481         inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
482         inode->i_op = &simple_dir_inode_operations;
483         inode->i_fop = &simple_dir_operations;
484 
485         /* directory inodes start off with i_nlink == 2 (for "." entry) */
486         inc_nlink(inode);
487         d_instantiate(dentry, inode);
488         inc_nlink(d_inode(dentry->d_parent));
489         fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
490         return end_creating(dentry);
491 }
492 EXPORT_SYMBOL_GPL(debugfs_create_dir);
493 
494 /**
495  * debugfs_create_automount - create automount point in the debugfs filesystem
496  * @name: a pointer to a string containing the name of the file to create.
497  * @parent: a pointer to the parent dentry for this file.  This should be a
498  *          directory dentry if set.  If this parameter is NULL, then the
499  *          file will be created in the root of the debugfs filesystem.
500  * @f: function to be called when pathname resolution steps on that one.
501  * @data: opaque argument to pass to f().
502  *
503  * @f should return what ->d_automount() would.
504  */
505 struct dentry *debugfs_create_automount(const char *name,
506                                         struct dentry *parent,
507                                         struct vfsmount *(*f)(void *),
508                                         void *data)
509 {
510         struct dentry *dentry = start_creating(name, parent);
511         struct inode *inode;
512 
513         if (IS_ERR(dentry))
514                 return NULL;
515 
516         inode = debugfs_get_inode(dentry->d_sb);
517         if (unlikely(!inode))
518                 return failed_creating(dentry);
519 
520         make_empty_dir_inode(inode);
521         inode->i_flags |= S_AUTOMOUNT;
522         inode->i_private = data;
523         dentry->d_fsdata = (void *)f;
524         /* directory inodes start off with i_nlink == 2 (for "." entry) */
525         inc_nlink(inode);
526         d_instantiate(dentry, inode);
527         inc_nlink(d_inode(dentry->d_parent));
528         fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
529         return end_creating(dentry);
530 }
531 EXPORT_SYMBOL(debugfs_create_automount);
532 
533 /**
534  * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
535  * @name: a pointer to a string containing the name of the symbolic link to
536  *        create.
537  * @parent: a pointer to the parent dentry for this symbolic link.  This
538  *          should be a directory dentry if set.  If this parameter is NULL,
539  *          then the symbolic link will be created in the root of the debugfs
540  *          filesystem.
541  * @target: a pointer to a string containing the path to the target of the
542  *          symbolic link.
543  *
544  * This function creates a symbolic link with the given name in debugfs that
545  * links to the given target path.
546  *
547  * This function will return a pointer to a dentry if it succeeds.  This
548  * pointer must be passed to the debugfs_remove() function when the symbolic
549  * link is to be removed (no automatic cleanup happens if your module is
550  * unloaded, you are responsible here.)  If an error occurs, %NULL will be
551  * returned.
552  *
553  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
554  * returned.
555  */
556 struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
557                                       const char *target)
558 {
559         struct dentry *dentry;
560         struct inode *inode;
561         char *link = kstrdup(target, GFP_KERNEL);
562         if (!link)
563                 return NULL;
564 
565         dentry = start_creating(name, parent);
566         if (IS_ERR(dentry)) {
567                 kfree(link);
568                 return NULL;
569         }
570 
571         inode = debugfs_get_inode(dentry->d_sb);
572         if (unlikely(!inode)) {
573                 kfree(link);
574                 return failed_creating(dentry);
575         }
576         inode->i_mode = S_IFLNK | S_IRWXUGO;
577         inode->i_op = &simple_symlink_inode_operations;
578         inode->i_link = link;
579         d_instantiate(dentry, inode);
580         return end_creating(dentry);
581 }
582 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
583 
584 static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
585 {
586         int ret = 0;
587 
588         if (simple_positive(dentry)) {
589                 dget(dentry);
590                 if (d_is_dir(dentry))
591                         ret = simple_rmdir(d_inode(parent), dentry);
592                 else
593                         simple_unlink(d_inode(parent), dentry);
594                 if (!ret)
595                         d_delete(dentry);
596                 dput(dentry);
597         }
598         return ret;
599 }
600 
601 /**
602  * debugfs_remove - removes a file or directory from the debugfs filesystem
603  * @dentry: a pointer to a the dentry of the file or directory to be
604  *          removed.  If this parameter is NULL or an error value, nothing
605  *          will be done.
606  *
607  * This function removes a file or directory in debugfs that was previously
608  * created with a call to another debugfs function (like
609  * debugfs_create_file() or variants thereof.)
610  *
611  * This function is required to be called in order for the file to be
612  * removed, no automatic cleanup of files will happen when a module is
613  * removed, you are responsible here.
614  */
615 void debugfs_remove(struct dentry *dentry)
616 {
617         struct dentry *parent;
618         int ret;
619 
620         if (IS_ERR_OR_NULL(dentry))
621                 return;
622 
623         parent = dentry->d_parent;
624         if (!parent || d_really_is_negative(parent))
625                 return;
626 
627         inode_lock(d_inode(parent));
628         ret = __debugfs_remove(dentry, parent);
629         inode_unlock(d_inode(parent));
630         if (!ret)
631                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
632 
633         synchronize_srcu(&debugfs_srcu);
634 }
635 EXPORT_SYMBOL_GPL(debugfs_remove);
636 
637 /**
638  * debugfs_remove_recursive - recursively removes a directory
639  * @dentry: a pointer to a the dentry of the directory to be removed.  If this
640  *          parameter is NULL or an error value, nothing will be done.
641  *
642  * This function recursively removes a directory tree in debugfs that
643  * was previously created with a call to another debugfs function
644  * (like debugfs_create_file() or variants thereof.)
645  *
646  * This function is required to be called in order for the file to be
647  * removed, no automatic cleanup of files will happen when a module is
648  * removed, you are responsible here.
649  */
650 void debugfs_remove_recursive(struct dentry *dentry)
651 {
652         struct dentry *child, *parent;
653 
654         if (IS_ERR_OR_NULL(dentry))
655                 return;
656 
657         parent = dentry->d_parent;
658         if (!parent || d_really_is_negative(parent))
659                 return;
660 
661         parent = dentry;
662  down:
663         inode_lock(d_inode(parent));
664  loop:
665         /*
666          * The parent->d_subdirs is protected by the d_lock. Outside that
667          * lock, the child can be unlinked and set to be freed which can
668          * use the d_u.d_child as the rcu head and corrupt this list.
669          */
670         spin_lock(&parent->d_lock);
671         list_for_each_entry(child, &parent->d_subdirs, d_child) {
672                 if (!simple_positive(child))
673                         continue;
674 
675                 /* perhaps simple_empty(child) makes more sense */
676                 if (!list_empty(&child->d_subdirs)) {
677                         spin_unlock(&parent->d_lock);
678                         inode_unlock(d_inode(parent));
679                         parent = child;
680                         goto down;
681                 }
682 
683                 spin_unlock(&parent->d_lock);
684 
685                 if (!__debugfs_remove(child, parent))
686                         simple_release_fs(&debugfs_mount, &debugfs_mount_count);
687 
688                 /*
689                  * The parent->d_lock protects agaist child from unlinking
690                  * from d_subdirs. When releasing the parent->d_lock we can
691                  * no longer trust that the next pointer is valid.
692                  * Restart the loop. We'll skip this one with the
693                  * simple_positive() check.
694                  */
695                 goto loop;
696         }
697         spin_unlock(&parent->d_lock);
698 
699         inode_unlock(d_inode(parent));
700         child = parent;
701         parent = parent->d_parent;
702         inode_lock(d_inode(parent));
703 
704         if (child != dentry)
705                 /* go up */
706                 goto loop;
707 
708         if (!__debugfs_remove(child, parent))
709                 simple_release_fs(&debugfs_mount, &debugfs_mount_count);
710         inode_unlock(d_inode(parent));
711 
712         synchronize_srcu(&debugfs_srcu);
713 }
714 EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
715 
716 /**
717  * debugfs_rename - rename a file/directory in the debugfs filesystem
718  * @old_dir: a pointer to the parent dentry for the renamed object. This
719  *          should be a directory dentry.
720  * @old_dentry: dentry of an object to be renamed.
721  * @new_dir: a pointer to the parent dentry where the object should be
722  *          moved. This should be a directory dentry.
723  * @new_name: a pointer to a string containing the target name.
724  *
725  * This function renames a file/directory in debugfs.  The target must not
726  * exist for rename to succeed.
727  *
728  * This function will return a pointer to old_dentry (which is updated to
729  * reflect renaming) if it succeeds. If an error occurs, %NULL will be
730  * returned.
731  *
732  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
733  * returned.
734  */
735 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
736                 struct dentry *new_dir, const char *new_name)
737 {
738         int error;
739         struct dentry *dentry = NULL, *trap;
740         const char *old_name;
741 
742         trap = lock_rename(new_dir, old_dir);
743         /* Source or destination directories don't exist? */
744         if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))
745                 goto exit;
746         /* Source does not exist, cyclic rename, or mountpoint? */
747         if (d_really_is_negative(old_dentry) || old_dentry == trap ||
748             d_mountpoint(old_dentry))
749                 goto exit;
750         dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
751         /* Lookup failed, cyclic rename or target exists? */
752         if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
753                 goto exit;
754 
755         old_name = fsnotify_oldname_init(old_dentry->d_name.name);
756 
757         error = simple_rename(d_inode(old_dir), old_dentry, d_inode(new_dir),
758                 dentry);
759         if (error) {
760                 fsnotify_oldname_free(old_name);
761                 goto exit;
762         }
763         d_move(old_dentry, dentry);
764         fsnotify_move(d_inode(old_dir), d_inode(new_dir), old_name,
765                 d_is_dir(old_dentry),
766                 NULL, old_dentry);
767         fsnotify_oldname_free(old_name);
768         unlock_rename(new_dir, old_dir);
769         dput(dentry);
770         return old_dentry;
771 exit:
772         if (dentry && !IS_ERR(dentry))
773                 dput(dentry);
774         unlock_rename(new_dir, old_dir);
775         return NULL;
776 }
777 EXPORT_SYMBOL_GPL(debugfs_rename);
778 
779 /**
780  * debugfs_initialized - Tells whether debugfs has been registered
781  */
782 bool debugfs_initialized(void)
783 {
784         return debugfs_registered;
785 }
786 EXPORT_SYMBOL_GPL(debugfs_initialized);
787 
788 static int __init debugfs_init(void)
789 {
790         int retval;
791 
792         retval = sysfs_create_mount_point(kernel_kobj, "debug");
793         if (retval)
794                 return retval;
795 
796         retval = register_filesystem(&debug_fs_type);
797         if (retval)
798                 sysfs_remove_mount_point(kernel_kobj, "debug");
799         else
800                 debugfs_registered = true;
801 
802         return retval;
803 }
804 core_initcall(debugfs_init);
805 
806 

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