Free Electrons

Embedded Linux Experts

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
/*
 *  inode.c - part of debugfs, a tiny little debug file system
 *
 *  Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
 *  Copyright (C) 2004 IBM Inc.
 *
 *	This program is free software; you can redistribute it and/or
 *	modify it under the terms of the GNU General Public License version
 *	2 as published by the Free Software Foundation.
 *
 *  debugfs is for people to use instead of /proc or /sys.
 *  See Documentation/DocBook/kernel-api for more details.
 *
 */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/kobject.h>
#include <linux/namei.h>
#include <linux/debugfs.h>
#include <linux/fsnotify.h>
#include <linux/string.h>
#include <linux/seq_file.h>
#include <linux/parser.h>
#include <linux/magic.h>
#include <linux/slab.h>
#include <linux/srcu.h>

#include "internal.h"

#define DEBUGFS_DEFAULT_MODE	0700

DEFINE_SRCU(debugfs_srcu);

static struct vfsmount *debugfs_mount;
static int debugfs_mount_count;
static bool debugfs_registered;

static struct inode *debugfs_get_inode(struct super_block *sb)
{
	struct inode *inode = new_inode(sb);
	if (inode) {
		inode->i_ino = get_next_ino();
		inode->i_atime = inode->i_mtime =
			inode->i_ctime = current_time(inode);
	}
	return inode;
}

struct debugfs_mount_opts {
	kuid_t uid;
	kgid_t gid;
	umode_t mode;
};

enum {
	Opt_uid,
	Opt_gid,
	Opt_mode,
	Opt_err
};

static const match_table_t tokens = {
	{Opt_uid, "uid=%u"},
	{Opt_gid, "gid=%u"},
	{Opt_mode, "mode=%o"},
	{Opt_err, NULL}
};

struct debugfs_fs_info {
	struct debugfs_mount_opts mount_opts;
};

static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts)
{
	substring_t args[MAX_OPT_ARGS];
	int option;
	int token;
	kuid_t uid;
	kgid_t gid;
	char *p;

	opts->mode = DEBUGFS_DEFAULT_MODE;

	while ((p = strsep(&data, ",")) != NULL) {
		if (!*p)
			continue;

		token = match_token(p, tokens, args);
		switch (token) {
		case Opt_uid:
			if (match_int(&args[0], &option))
				return -EINVAL;
			uid = make_kuid(current_user_ns(), option);
			if (!uid_valid(uid))
				return -EINVAL;
			opts->uid = uid;
			break;
		case Opt_gid:
			if (match_int(&args[0], &option))
				return -EINVAL;
			gid = make_kgid(current_user_ns(), option);
			if (!gid_valid(gid))
				return -EINVAL;
			opts->gid = gid;
			break;
		case Opt_mode:
			if (match_octal(&args[0], &option))
				return -EINVAL;
			opts->mode = option & S_IALLUGO;
			break;
		/*
		 * We might like to report bad mount options here;
		 * but traditionally debugfs has ignored all mount options
		 */
		}
	}

	return 0;
}

static int debugfs_apply_options(struct super_block *sb)
{
	struct debugfs_fs_info *fsi = sb->s_fs_info;
	struct inode *inode = d_inode(sb->s_root);
	struct debugfs_mount_opts *opts = &fsi->mount_opts;

	inode->i_mode &= ~S_IALLUGO;
	inode->i_mode |= opts->mode;

	inode->i_uid = opts->uid;
	inode->i_gid = opts->gid;

	return 0;
}

static int debugfs_remount(struct super_block *sb, int *flags, char *data)
{
	int err;
	struct debugfs_fs_info *fsi = sb->s_fs_info;

	sync_filesystem(sb);
	err = debugfs_parse_options(data, &fsi->mount_opts);
	if (err)
		goto fail;

	debugfs_apply_options(sb);

fail:
	return err;
}

static int debugfs_show_options(struct seq_file *m, struct dentry *root)
{
	struct debugfs_fs_info *fsi = root->d_sb->s_fs_info;
	struct debugfs_mount_opts *opts = &fsi->mount_opts;

	if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
		seq_printf(m, ",uid=%u",
			   from_kuid_munged(&init_user_ns, opts->uid));
	if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
		seq_printf(m, ",gid=%u",
			   from_kgid_munged(&init_user_ns, opts->gid));
	if (opts->mode != DEBUGFS_DEFAULT_MODE)
		seq_printf(m, ",mode=%o", opts->mode);

	return 0;
}

static void debugfs_evict_inode(struct inode *inode)
{
	truncate_inode_pages_final(&inode->i_data);
	clear_inode(inode);
	if (S_ISLNK(inode->i_mode))
		kfree(inode->i_link);
}

static const struct super_operations debugfs_super_operations = {
	.statfs		= simple_statfs,
	.remount_fs	= debugfs_remount,
	.show_options	= debugfs_show_options,
	.evict_inode	= debugfs_evict_inode,
};

static struct vfsmount *debugfs_automount(struct path *path)
{
	debugfs_automount_t f;
	f = (debugfs_automount_t)path->dentry->d_fsdata;
	return f(path->dentry, d_inode(path->dentry)->i_private);
}

static const struct dentry_operations debugfs_dops = {
	.d_delete = always_delete_dentry,
	.d_automount = debugfs_automount,
};

static int debug_fill_super(struct super_block *sb, void *data, int silent)
{
	static const struct tree_descr debug_files[] = {{""}};
	struct debugfs_fs_info *fsi;
	int err;

	save_mount_options(sb, data);

	fsi = kzalloc(sizeof(struct debugfs_fs_info), GFP_KERNEL);
	sb->s_fs_info = fsi;
	if (!fsi) {
		err = -ENOMEM;
		goto fail;
	}

	err = debugfs_parse_options(data, &fsi->mount_opts);
	if (err)
		goto fail;

	err  =  simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
	if (err)
		goto fail;

	sb->s_op = &debugfs_super_operations;
	sb->s_d_op = &debugfs_dops;

	debugfs_apply_options(sb);

	return 0;

fail:
	kfree(fsi);
	sb->s_fs_info = NULL;
	return err;
}

static struct dentry *debug_mount(struct file_system_type *fs_type,
			int flags, const char *dev_name,
			void *data)
{
	return mount_single(fs_type, flags, data, debug_fill_super);
}

static struct file_system_type debug_fs_type = {
	.owner =	THIS_MODULE,
	.name =		"debugfs",
	.mount =	debug_mount,
	.kill_sb =	kill_litter_super,
};
MODULE_ALIAS_FS("debugfs");

/**
 * debugfs_lookup() - look up an existing debugfs file
 * @name: a pointer to a string containing the name of the file to look up.
 * @parent: a pointer to the parent dentry of the file.
 *
 * This function will return a pointer to a dentry if it succeeds.  If the file
 * doesn't exist or an error occurs, %NULL will be returned.  The returned
 * dentry must be passed to dput() when it is no longer needed.
 *
 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 * returned.
 */
struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
{
	struct dentry *dentry;

	if (IS_ERR(parent))
		return NULL;

	if (!parent)
		parent = debugfs_mount->mnt_root;

	inode_lock(d_inode(parent));
	dentry = lookup_one_len(name, parent, strlen(name));
	inode_unlock(d_inode(parent));

	if (IS_ERR(dentry))
		return NULL;
	if (!d_really_is_positive(dentry)) {
		dput(dentry);
		return NULL;
	}
	return dentry;
}
EXPORT_SYMBOL_GPL(debugfs_lookup);

static struct dentry *start_creating(const char *name, struct dentry *parent)
{
	struct dentry *dentry;
	int error;

	pr_debug("debugfs: creating file '%s'\n",name);

	if (IS_ERR(parent))
		return parent;

	error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
			      &debugfs_mount_count);
	if (error)
		return ERR_PTR(error);

	/* If the parent is not specified, we create it in the root.
	 * We need the root dentry to do this, which is in the super
	 * block. A pointer to that is in the struct vfsmount that we
	 * have around.
	 */
	if (!parent)
		parent = debugfs_mount->mnt_root;

	inode_lock(d_inode(parent));
	dentry = lookup_one_len(name, parent, strlen(name));
	if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
		dput(dentry);
		dentry = ERR_PTR(-EEXIST);
	}

	if (IS_ERR(dentry)) {
		inode_unlock(d_inode(parent));
		simple_release_fs(&debugfs_mount, &debugfs_mount_count);
	}

	return dentry;
}

static struct dentry *failed_creating(struct dentry *dentry)
{
	inode_unlock(d_inode(dentry->d_parent));
	dput(dentry);
	simple_release_fs(&debugfs_mount, &debugfs_mount_count);
	return NULL;
}

static struct dentry *end_creating(struct dentry *dentry)
{
	inode_unlock(d_inode(dentry->d_parent));
	return dentry;
}

static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
				struct dentry *parent, void *data,
				const struct file_operations *proxy_fops,
				const struct file_operations *real_fops)
{
	struct dentry *dentry;
	struct inode *inode;

	if (!(mode & S_IFMT))
		mode |= S_IFREG;
	BUG_ON(!S_ISREG(mode));
	dentry = start_creating(name, parent);

	if (IS_ERR(dentry))
		return NULL;

	inode = debugfs_get_inode(dentry->d_sb);
	if (unlikely(!inode))
		return failed_creating(dentry);

	inode->i_mode = mode;
	inode->i_private = data;

	inode->i_fop = proxy_fops;
	dentry->d_fsdata = (void *)real_fops;

	d_instantiate(dentry, inode);
	fsnotify_create(d_inode(dentry->d_parent), dentry);
	return end_creating(dentry);
}

/**
 * debugfs_create_file - create a file in the debugfs filesystem
 * @name: a pointer to a string containing the name of the file to create.
 * @mode: the permission that the file should have.
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is NULL, then the
 *          file will be created in the root of the debugfs filesystem.
 * @data: a pointer to something that the caller will want to get to later
 *        on.  The inode.i_private pointer will point to this value on
 *        the open() call.
 * @fops: a pointer to a struct file_operations that should be used for
 *        this file.
 *
 * This is the basic "create a file" function for debugfs.  It allows for a
 * wide range of flexibility in creating a file, or a directory (if you want
 * to create a directory, the debugfs_create_dir() function is
 * recommended to be used instead.)
 *
 * This function will return a pointer to a dentry if it succeeds.  This
 * pointer must be passed to the debugfs_remove() function when the file is
 * to be removed (no automatic cleanup happens if your module is unloaded,
 * you are responsible here.)  If an error occurs, %NULL will be returned.
 *
 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 * returned.
 */
struct dentry *debugfs_create_file(const char *name, umode_t mode,
				   struct dentry *parent, void *data,
				   const struct file_operations *fops)
{

	return __debugfs_create_file(name, mode, parent, data,
				fops ? &debugfs_full_proxy_file_operations :
					&debugfs_noop_file_operations,
				fops);
}
EXPORT_SYMBOL_GPL(debugfs_create_file);

/**
 * debugfs_create_file_unsafe - create a file in the debugfs filesystem
 * @name: a pointer to a string containing the name of the file to create.
 * @mode: the permission that the file should have.
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is NULL, then the
 *          file will be created in the root of the debugfs filesystem.
 * @data: a pointer to something that the caller will want to get to later
 *        on.  The inode.i_private pointer will point to this value on
 *        the open() call.
 * @fops: a pointer to a struct file_operations that should be used for
 *        this file.
 *
 * debugfs_create_file_unsafe() is completely analogous to
 * debugfs_create_file(), the only difference being that the fops
 * handed it will not get protected against file removals by the
 * debugfs core.
 *
 * It is your responsibility to protect your struct file_operation
 * methods against file removals by means of debugfs_use_file_start()
 * and debugfs_use_file_finish(). ->open() is still protected by
 * debugfs though.
 *
 * Any struct file_operations defined by means of
 * DEFINE_DEBUGFS_ATTRIBUTE() is protected against file removals and
 * thus, may be used here.
 */
struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
				   struct dentry *parent, void *data,
				   const struct file_operations *fops)
{

	return __debugfs_create_file(name, mode, parent, data,
				fops ? &debugfs_open_proxy_file_operations :
					&debugfs_noop_file_operations,
				fops);
}
EXPORT_SYMBOL_GPL(debugfs_create_file_unsafe);

/**
 * debugfs_create_file_size - create a file in the debugfs filesystem
 * @name: a pointer to a string containing the name of the file to create.
 * @mode: the permission that the file should have.
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is NULL, then the
 *          file will be created in the root of the debugfs filesystem.
 * @data: a pointer to something that the caller will want to get to later
 *        on.  The inode.i_private pointer will point to this value on
 *        the open() call.
 * @fops: a pointer to a struct file_operations that should be used for
 *        this file.
 * @file_size: initial file size
 *
 * This is the basic "create a file" function for debugfs.  It allows for a
 * wide range of flexibility in creating a file, or a directory (if you want
 * to create a directory, the debugfs_create_dir() function is
 * recommended to be used instead.)
 *
 * This function will return a pointer to a dentry if it succeeds.  This
 * pointer must be passed to the debugfs_remove() function when the file is
 * to be removed (no automatic cleanup happens if your module is unloaded,
 * you are responsible here.)  If an error occurs, %NULL will be returned.
 *
 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 * returned.
 */
struct dentry *debugfs_create_file_size(const char *name, umode_t mode,
					struct dentry *parent, void *data,
					const struct file_operations *fops,
					loff_t file_size)
{
	struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);

	if (de)
		d_inode(de)->i_size = file_size;
	return de;
}
EXPORT_SYMBOL_GPL(debugfs_create_file_size);

/**
 * debugfs_create_dir - create a directory in the debugfs filesystem
 * @name: a pointer to a string containing the name of the directory to
 *        create.
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is NULL, then the
 *          directory will be created in the root of the debugfs filesystem.
 *
 * This function creates a directory in debugfs with the given name.
 *
 * This function will return a pointer to a dentry if it succeeds.  This
 * pointer must be passed to the debugfs_remove() function when the file is
 * to be removed (no automatic cleanup happens if your module is unloaded,
 * you are responsible here.)  If an error occurs, %NULL will be returned.
 *
 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 * returned.
 */
struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
{
	struct dentry *dentry = start_creating(name, parent);
	struct inode *inode;

	if (IS_ERR(dentry))
		return NULL;

	inode = debugfs_get_inode(dentry->d_sb);
	if (unlikely(!inode))
		return failed_creating(dentry);

	inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
	inode->i_op = &simple_dir_inode_operations;
	inode->i_fop = &simple_dir_operations;

	/* directory inodes start off with i_nlink == 2 (for "." entry) */
	inc_nlink(inode);
	d_instantiate(dentry, inode);
	inc_nlink(d_inode(dentry->d_parent));
	fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
	return end_creating(dentry);
}
EXPORT_SYMBOL_GPL(debugfs_create_dir);

/**
 * debugfs_create_automount - create automount point in the debugfs filesystem
 * @name: a pointer to a string containing the name of the file to create.
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is NULL, then the
 *          file will be created in the root of the debugfs filesystem.
 * @f: function to be called when pathname resolution steps on that one.
 * @data: opaque argument to pass to f().
 *
 * @f should return what ->d_automount() would.
 */
struct dentry *debugfs_create_automount(const char *name,
					struct dentry *parent,
					debugfs_automount_t f,
					void *data)
{
	struct dentry *dentry = start_creating(name, parent);
	struct inode *inode;

	if (IS_ERR(dentry))
		return NULL;

	inode = debugfs_get_inode(dentry->d_sb);
	if (unlikely(!inode))
		return failed_creating(dentry);

	make_empty_dir_inode(inode);
	inode->i_flags |= S_AUTOMOUNT;
	inode->i_private = data;
	dentry->d_fsdata = (void *)f;
	/* directory inodes start off with i_nlink == 2 (for "." entry) */
	inc_nlink(inode);
	d_instantiate(dentry, inode);
	inc_nlink(d_inode(dentry->d_parent));
	fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
	return end_creating(dentry);
}
EXPORT_SYMBOL(debugfs_create_automount);

/**
 * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
 * @name: a pointer to a string containing the name of the symbolic link to
 *        create.
 * @parent: a pointer to the parent dentry for this symbolic link.  This
 *          should be a directory dentry if set.  If this parameter is NULL,
 *          then the symbolic link will be created in the root of the debugfs
 *          filesystem.
 * @target: a pointer to a string containing the path to the target of the
 *          symbolic link.
 *
 * This function creates a symbolic link with the given name in debugfs that
 * links to the given target path.
 *
 * This function will return a pointer to a dentry if it succeeds.  This
 * pointer must be passed to the debugfs_remove() function when the symbolic
 * link is to be removed (no automatic cleanup happens if your module is
 * unloaded, you are responsible here.)  If an error occurs, %NULL will be
 * returned.
 *
 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 * returned.
 */
struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
				      const char *target)
{
	struct dentry *dentry;
	struct inode *inode;
	char *link = kstrdup(target, GFP_KERNEL);
	if (!link)
		return NULL;

	dentry = start_creating(name, parent);
	if (IS_ERR(dentry)) {
		kfree(link);
		return NULL;
	}

	inode = debugfs_get_inode(dentry->d_sb);
	if (unlikely(!inode)) {
		kfree(link);
		return failed_creating(dentry);
	}
	inode->i_mode = S_IFLNK | S_IRWXUGO;
	inode->i_op = &simple_symlink_inode_operations;
	inode->i_link = link;
	d_instantiate(dentry, inode);
	return end_creating(dentry);
}
EXPORT_SYMBOL_GPL(debugfs_create_symlink);

static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
{
	int ret = 0;

	if (simple_positive(dentry)) {
		dget(dentry);
		if (d_is_dir(dentry))
			ret = simple_rmdir(d_inode(parent), dentry);
		else
			simple_unlink(d_inode(parent), dentry);
		if (!ret)
			d_delete(dentry);
		dput(dentry);
	}
	return ret;
}

/**
 * debugfs_remove - removes a file or directory from the debugfs filesystem
 * @dentry: a pointer to a the dentry of the file or directory to be
 *          removed.  If this parameter is NULL or an error value, nothing
 *          will be done.
 *
 * This function removes a file or directory in debugfs that was previously
 * created with a call to another debugfs function (like
 * debugfs_create_file() or variants thereof.)
 *
 * This function is required to be called in order for the file to be
 * removed, no automatic cleanup of files will happen when a module is
 * removed, you are responsible here.
 */
void debugfs_remove(struct dentry *dentry)
{
	struct dentry *parent;
	int ret;

	if (IS_ERR_OR_NULL(dentry))
		return;

	parent = dentry->d_parent;
	inode_lock(d_inode(parent));
	ret = __debugfs_remove(dentry, parent);
	inode_unlock(d_inode(parent));
	if (!ret)
		simple_release_fs(&debugfs_mount, &debugfs_mount_count);

	synchronize_srcu(&debugfs_srcu);
}
EXPORT_SYMBOL_GPL(debugfs_remove);

/**
 * debugfs_remove_recursive - recursively removes a directory
 * @dentry: a pointer to a the dentry of the directory to be removed.  If this
 *          parameter is NULL or an error value, nothing will be done.
 *
 * This function recursively removes a directory tree in debugfs that
 * was previously created with a call to another debugfs function
 * (like debugfs_create_file() or variants thereof.)
 *
 * This function is required to be called in order for the file to be
 * removed, no automatic cleanup of files will happen when a module is
 * removed, you are responsible here.
 */
void debugfs_remove_recursive(struct dentry *dentry)
{
	struct dentry *child, *parent;

	if (IS_ERR_OR_NULL(dentry))
		return;

	parent = dentry;
 down:
	inode_lock(d_inode(parent));
 loop:
	/*
	 * The parent->d_subdirs is protected by the d_lock. Outside that
	 * lock, the child can be unlinked and set to be freed which can
	 * use the d_u.d_child as the rcu head and corrupt this list.
	 */
	spin_lock(&parent->d_lock);
	list_for_each_entry(child, &parent->d_subdirs, d_child) {
		if (!simple_positive(child))
			continue;

		/* perhaps simple_empty(child) makes more sense */
		if (!list_empty(&child->d_subdirs)) {
			spin_unlock(&parent->d_lock);
			inode_unlock(d_inode(parent));
			parent = child;
			goto down;
		}

		spin_unlock(&parent->d_lock);

		if (!__debugfs_remove(child, parent))
			simple_release_fs(&debugfs_mount, &debugfs_mount_count);

		/*
		 * The parent->d_lock protects agaist child from unlinking
		 * from d_subdirs. When releasing the parent->d_lock we can
		 * no longer trust that the next pointer is valid.
		 * Restart the loop. We'll skip this one with the
		 * simple_positive() check.
		 */
		goto loop;
	}
	spin_unlock(&parent->d_lock);

	inode_unlock(d_inode(parent));
	child = parent;
	parent = parent->d_parent;
	inode_lock(d_inode(parent));

	if (child != dentry)
		/* go up */
		goto loop;

	if (!__debugfs_remove(child, parent))
		simple_release_fs(&debugfs_mount, &debugfs_mount_count);
	inode_unlock(d_inode(parent));

	synchronize_srcu(&debugfs_srcu);
}
EXPORT_SYMBOL_GPL(debugfs_remove_recursive);

/**
 * debugfs_rename - rename a file/directory in the debugfs filesystem
 * @old_dir: a pointer to the parent dentry for the renamed object. This
 *          should be a directory dentry.
 * @old_dentry: dentry of an object to be renamed.
 * @new_dir: a pointer to the parent dentry where the object should be
 *          moved. This should be a directory dentry.
 * @new_name: a pointer to a string containing the target name.
 *
 * This function renames a file/directory in debugfs.  The target must not
 * exist for rename to succeed.
 *
 * This function will return a pointer to old_dentry (which is updated to
 * reflect renaming) if it succeeds. If an error occurs, %NULL will be
 * returned.
 *
 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 * returned.
 */
struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
		struct dentry *new_dir, const char *new_name)
{
	int error;
	struct dentry *dentry = NULL, *trap;
	const char *old_name;

	trap = lock_rename(new_dir, old_dir);
	/* Source or destination directories don't exist? */
	if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))
		goto exit;
	/* Source does not exist, cyclic rename, or mountpoint? */
	if (d_really_is_negative(old_dentry) || old_dentry == trap ||
	    d_mountpoint(old_dentry))
		goto exit;
	dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
	/* Lookup failed, cyclic rename or target exists? */
	if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
		goto exit;

	old_name = fsnotify_oldname_init(old_dentry->d_name.name);

	error = simple_rename(d_inode(old_dir), old_dentry, d_inode(new_dir),
			      dentry, 0);
	if (error) {
		fsnotify_oldname_free(old_name);
		goto exit;
	}
	d_move(old_dentry, dentry);
	fsnotify_move(d_inode(old_dir), d_inode(new_dir), old_name,
		d_is_dir(old_dentry),
		NULL, old_dentry);
	fsnotify_oldname_free(old_name);
	unlock_rename(new_dir, old_dir);
	dput(dentry);
	return old_dentry;
exit:
	if (dentry && !IS_ERR(dentry))
		dput(dentry);
	unlock_rename(new_dir, old_dir);
	return NULL;
}
EXPORT_SYMBOL_GPL(debugfs_rename);

/**
 * debugfs_initialized - Tells whether debugfs has been registered
 */
bool debugfs_initialized(void)
{
	return debugfs_registered;
}
EXPORT_SYMBOL_GPL(debugfs_initialized);

static int __init debugfs_init(void)
{
	int retval;

	retval = sysfs_create_mount_point(kernel_kobj, "debug");
	if (retval)
		return retval;

	retval = register_filesystem(&debug_fs_type);
	if (retval)
		sysfs_remove_mount_point(kernel_kobj, "debug");
	else
		debugfs_registered = true;

	return retval;
}
core_initcall(debugfs_init);