Linux Audio

Check our new training course

Embedded Linux Audio

Check our new training course
with Creative Commons CC-BY-SA
lecture materials

Bootlin logo

Elixir Cross Referencer

Loading...
   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
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
/*
 * fs/sysfs/dir.c - sysfs core and dir operation implementation
 *
 * Copyright (c) 2001-3 Patrick Mochel
 * Copyright (c) 2007 SUSE Linux Products GmbH
 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
 *
 * This file is released under the GPLv2.
 *
 * Please see Documentation/filesystems/sysfs.txt for more information.
 */

#undef DEBUG

#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/module.h>
#include <linux/kobject.h>
#include <linux/namei.h>
#include <linux/idr.h>
#include <linux/completion.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/security.h>
#include <linux/hash.h>
#include "sysfs.h"

DEFINE_MUTEX(sysfs_mutex);
DEFINE_SPINLOCK(sysfs_assoc_lock);

#define to_sysfs_dirent(X) rb_entry((X), struct sysfs_dirent, s_rb);

static DEFINE_SPINLOCK(sysfs_ino_lock);
static DEFINE_IDA(sysfs_ino_ida);

/**
 *	sysfs_name_hash
 *	@ns:   Namespace tag to hash
 *	@name: Null terminated string to hash
 *
 *	Returns 31 bit hash of ns + name (so it fits in an off_t )
 */
static unsigned int sysfs_name_hash(const void *ns, const char *name)
{
	unsigned long hash = init_name_hash();
	unsigned int len = strlen(name);
	while (len--)
		hash = partial_name_hash(*name++, hash);
	hash = ( end_name_hash(hash) ^ hash_ptr( (void *)ns, 31 ) );
	hash &= 0x7fffffffU;
	/* Reserve hash numbers 0, 1 and INT_MAX for magic directory entries */
	if (hash < 1)
		hash += 2;
	if (hash >= INT_MAX)
		hash = INT_MAX - 1;
	return hash;
}

static int sysfs_name_compare(unsigned int hash, const void *ns,
	const char *name, const struct sysfs_dirent *sd)
{
	if (hash != sd->s_hash)
		return hash - sd->s_hash;
	if (ns != sd->s_ns)
		return ns - sd->s_ns;
	return strcmp(name, sd->s_name);
}

static int sysfs_sd_compare(const struct sysfs_dirent *left,
			    const struct sysfs_dirent *right)
{
	return sysfs_name_compare(left->s_hash, left->s_ns, left->s_name,
				  right);
}

/**
 *	sysfs_link_subling - link sysfs_dirent into sibling rbtree
 *	@sd: sysfs_dirent of interest
 *
 *	Link @sd into its sibling rbtree which starts from
 *	sd->s_parent->s_dir.children.
 *
 *	Locking:
 *	mutex_lock(sysfs_mutex)
 *
 *	RETURNS:
 *	0 on susccess -EEXIST on failure.
 */
static int sysfs_link_sibling(struct sysfs_dirent *sd)
{
	struct rb_node **node = &sd->s_parent->s_dir.children.rb_node;
	struct rb_node *parent = NULL;

	if (sysfs_type(sd) == SYSFS_DIR)
		sd->s_parent->s_dir.subdirs++;

	while (*node) {
		struct sysfs_dirent *pos;
		int result;

		pos = to_sysfs_dirent(*node);
		parent = *node;
		result = sysfs_sd_compare(sd, pos);
		if (result < 0)
			node = &pos->s_rb.rb_left;
		else if (result > 0)
			node = &pos->s_rb.rb_right;
		else
			return -EEXIST;
	}
	/* add new node and rebalance the tree */
	rb_link_node(&sd->s_rb, parent, node);
	rb_insert_color(&sd->s_rb, &sd->s_parent->s_dir.children);
	return 0;
}

/**
 *	sysfs_unlink_sibling - unlink sysfs_dirent from sibling rbtree
 *	@sd: sysfs_dirent of interest
 *
 *	Unlink @sd from its sibling rbtree which starts from
 *	sd->s_parent->s_dir.children.
 *
 *	Locking:
 *	mutex_lock(sysfs_mutex)
 */
static void sysfs_unlink_sibling(struct sysfs_dirent *sd)
{
	if (sysfs_type(sd) == SYSFS_DIR)
		sd->s_parent->s_dir.subdirs--;

	rb_erase(&sd->s_rb, &sd->s_parent->s_dir.children);
}

#ifdef CONFIG_DEBUG_LOCK_ALLOC

/* Test for attributes that want to ignore lockdep for read-locking */
static bool ignore_lockdep(struct sysfs_dirent *sd)
{
	return sysfs_type(sd) == SYSFS_KOBJ_ATTR &&
			sd->s_attr.attr->ignore_lockdep;
}

#else

static inline bool ignore_lockdep(struct sysfs_dirent *sd)
{
	return true;
}

#endif

/**
 *	sysfs_get_active - get an active reference to sysfs_dirent
 *	@sd: sysfs_dirent to get an active reference to
 *
 *	Get an active reference of @sd.  This function is noop if @sd
 *	is NULL.
 *
 *	RETURNS:
 *	Pointer to @sd on success, NULL on failure.
 */
struct sysfs_dirent *sysfs_get_active(struct sysfs_dirent *sd)
{
	if (unlikely(!sd))
		return NULL;

	if (!atomic_inc_unless_negative(&sd->s_active))
		return NULL;

	if (likely(!ignore_lockdep(sd)))
		rwsem_acquire_read(&sd->dep_map, 0, 1, _RET_IP_);
	return sd;
}

/**
 *	sysfs_put_active - put an active reference to sysfs_dirent
 *	@sd: sysfs_dirent to put an active reference to
 *
 *	Put an active reference to @sd.  This function is noop if @sd
 *	is NULL.
 */
void sysfs_put_active(struct sysfs_dirent *sd)
{
	int v;

	if (unlikely(!sd))
		return;

	if (likely(!ignore_lockdep(sd)))
		rwsem_release(&sd->dep_map, 1, _RET_IP_);
	v = atomic_dec_return(&sd->s_active);
	if (likely(v != SD_DEACTIVATED_BIAS))
		return;

	/* atomic_dec_return() is a mb(), we'll always see the updated
	 * sd->u.completion.
	 */
	complete(sd->u.completion);
}

/**
 *	sysfs_deactivate - deactivate sysfs_dirent
 *	@sd: sysfs_dirent to deactivate
 *
 *	Deny new active references and drain existing ones.
 */
static void sysfs_deactivate(struct sysfs_dirent *sd)
{
	DECLARE_COMPLETION_ONSTACK(wait);
	int v;

	BUG_ON(!(sd->s_flags & SYSFS_FLAG_REMOVED));

	if (!(sysfs_type(sd) & SYSFS_ACTIVE_REF))
		return;

	sd->u.completion = (void *)&wait;

	rwsem_acquire(&sd->dep_map, 0, 0, _RET_IP_);
	/* atomic_add_return() is a mb(), put_active() will always see
	 * the updated sd->u.completion.
	 */
	v = atomic_add_return(SD_DEACTIVATED_BIAS, &sd->s_active);

	if (v != SD_DEACTIVATED_BIAS) {
		lock_contended(&sd->dep_map, _RET_IP_);
		wait_for_completion(&wait);
	}

	lock_acquired(&sd->dep_map, _RET_IP_);
	rwsem_release(&sd->dep_map, 1, _RET_IP_);
}

static int sysfs_alloc_ino(unsigned int *pino)
{
	int ino, rc;

 retry:
	spin_lock(&sysfs_ino_lock);
	rc = ida_get_new_above(&sysfs_ino_ida, 2, &ino);
	spin_unlock(&sysfs_ino_lock);

	if (rc == -EAGAIN) {
		if (ida_pre_get(&sysfs_ino_ida, GFP_KERNEL))
			goto retry;
		rc = -ENOMEM;
	}

	*pino = ino;
	return rc;
}

static void sysfs_free_ino(unsigned int ino)
{
	spin_lock(&sysfs_ino_lock);
	ida_remove(&sysfs_ino_ida, ino);
	spin_unlock(&sysfs_ino_lock);
}

void release_sysfs_dirent(struct sysfs_dirent * sd)
{
	struct sysfs_dirent *parent_sd;

 repeat:
	/* Moving/renaming is always done while holding reference.
	 * sd->s_parent won't change beneath us.
	 */
	parent_sd = sd->s_parent;

	WARN(!(sd->s_flags & SYSFS_FLAG_REMOVED),
		"sysfs: free using entry: %s/%s\n",
		parent_sd ? parent_sd->s_name : "", sd->s_name);

	if (sysfs_type(sd) == SYSFS_KOBJ_LINK)
		sysfs_put(sd->s_symlink.target_sd);
	if (sysfs_type(sd) & SYSFS_COPY_NAME)
		kfree(sd->s_name);
	if (sd->s_iattr && sd->s_iattr->ia_secdata)
		security_release_secctx(sd->s_iattr->ia_secdata,
					sd->s_iattr->ia_secdata_len);
	kfree(sd->s_iattr);
	sysfs_free_ino(sd->s_ino);
	kmem_cache_free(sysfs_dir_cachep, sd);

	sd = parent_sd;
	if (sd && atomic_dec_and_test(&sd->s_count))
		goto repeat;
}

static int sysfs_dentry_delete(const struct dentry *dentry)
{
	struct sysfs_dirent *sd = dentry->d_fsdata;
	return !(sd && !(sd->s_flags & SYSFS_FLAG_REMOVED));
}

static int sysfs_dentry_revalidate(struct dentry *dentry, unsigned int flags)
{
	struct sysfs_dirent *sd;
	int is_dir;
	int type;

	if (flags & LOOKUP_RCU)
		return -ECHILD;

	sd = dentry->d_fsdata;
	mutex_lock(&sysfs_mutex);

	/* The sysfs dirent has been deleted */
	if (sd->s_flags & SYSFS_FLAG_REMOVED)
		goto out_bad;

	/* The sysfs dirent has been moved? */
	if (dentry->d_parent->d_fsdata != sd->s_parent)
		goto out_bad;

	/* The sysfs dirent has been renamed */
	if (strcmp(dentry->d_name.name, sd->s_name) != 0)
		goto out_bad;

	/* The sysfs dirent has been moved to a different namespace */
	type = KOBJ_NS_TYPE_NONE;
	if (sd->s_parent) {
		type = sysfs_ns_type(sd->s_parent);
		if (type != KOBJ_NS_TYPE_NONE &&
				sysfs_info(dentry->d_sb)->ns[type] != sd->s_ns)
			goto out_bad;
	}

	mutex_unlock(&sysfs_mutex);
out_valid:
	return 1;
out_bad:
	/* Remove the dentry from the dcache hashes.
	 * If this is a deleted dentry we use d_drop instead of d_delete
	 * so sysfs doesn't need to cope with negative dentries.
	 *
	 * If this is a dentry that has simply been renamed we
	 * use d_drop to remove it from the dcache lookup on its
	 * old parent.  If this dentry persists later when a lookup
	 * is performed at its new name the dentry will be readded
	 * to the dcache hashes.
	 */
	is_dir = (sysfs_type(sd) == SYSFS_DIR);
	mutex_unlock(&sysfs_mutex);
	if (is_dir) {
		/* If we have submounts we must allow the vfs caches
		 * to lie about the state of the filesystem to prevent
		 * leaks and other nasty things.
		 */
		if (have_submounts(dentry))
			goto out_valid;
		shrink_dcache_parent(dentry);
	}
	d_drop(dentry);
	return 0;
}

static void sysfs_dentry_release(struct dentry *dentry)
{
	sysfs_put(dentry->d_fsdata);
}

const struct dentry_operations sysfs_dentry_ops = {
	.d_revalidate	= sysfs_dentry_revalidate,
	.d_delete	= sysfs_dentry_delete,
	.d_release	= sysfs_dentry_release,
};

struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type)
{
	char *dup_name = NULL;
	struct sysfs_dirent *sd;

	if (type & SYSFS_COPY_NAME) {
		name = dup_name = kstrdup(name, GFP_KERNEL);
		if (!name)
			return NULL;
	}

	sd = kmem_cache_zalloc(sysfs_dir_cachep, GFP_KERNEL);
	if (!sd)
		goto err_out1;

	if (sysfs_alloc_ino(&sd->s_ino))
		goto err_out2;

	atomic_set(&sd->s_count, 1);
	atomic_set(&sd->s_active, 0);

	sd->s_name = name;
	sd->s_mode = mode;
	sd->s_flags = type | SYSFS_FLAG_REMOVED;

	return sd;

 err_out2:
	kmem_cache_free(sysfs_dir_cachep, sd);
 err_out1:
	kfree(dup_name);
	return NULL;
}

/**
 *	sysfs_addrm_start - prepare for sysfs_dirent add/remove
 *	@acxt: pointer to sysfs_addrm_cxt to be used
 *	@parent_sd: parent sysfs_dirent
 *
 *	This function is called when the caller is about to add or
 *	remove sysfs_dirent under @parent_sd.  This function acquires
 *	sysfs_mutex.  @acxt is used to keep and pass context to
 *	other addrm functions.
 *
 *	LOCKING:
 *	Kernel thread context (may sleep).  sysfs_mutex is locked on
 *	return.
 */
void sysfs_addrm_start(struct sysfs_addrm_cxt *acxt,
		       struct sysfs_dirent *parent_sd)
{
	memset(acxt, 0, sizeof(*acxt));
	acxt->parent_sd = parent_sd;

	mutex_lock(&sysfs_mutex);
}

/**
 *	__sysfs_add_one - add sysfs_dirent to parent without warning
 *	@acxt: addrm context to use
 *	@sd: sysfs_dirent to be added
 *
 *	Get @acxt->parent_sd and set sd->s_parent to it and increment
 *	nlink of parent inode if @sd is a directory and link into the
 *	children list of the parent.
 *
 *	This function should be called between calls to
 *	sysfs_addrm_start() and sysfs_addrm_finish() and should be
 *	passed the same @acxt as passed to sysfs_addrm_start().
 *
 *	LOCKING:
 *	Determined by sysfs_addrm_start().
 *
 *	RETURNS:
 *	0 on success, -EEXIST if entry with the given name already
 *	exists.
 */
int __sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
{
	struct sysfs_inode_attrs *ps_iattr;
	int ret;

	if (!!sysfs_ns_type(acxt->parent_sd) != !!sd->s_ns) {
		WARN(1, KERN_WARNING "sysfs: ns %s in '%s' for '%s'\n",
			sysfs_ns_type(acxt->parent_sd)? "required": "invalid",
			acxt->parent_sd->s_name, sd->s_name);
		return -EINVAL;
	}

	sd->s_hash = sysfs_name_hash(sd->s_ns, sd->s_name);
	sd->s_parent = sysfs_get(acxt->parent_sd);

	ret = sysfs_link_sibling(sd);
	if (ret)
		return ret;

	/* Update timestamps on the parent */
	ps_iattr = acxt->parent_sd->s_iattr;
	if (ps_iattr) {
		struct iattr *ps_iattrs = &ps_iattr->ia_iattr;
		ps_iattrs->ia_ctime = ps_iattrs->ia_mtime = CURRENT_TIME;
	}

	/* Mark the entry added into directory tree */
	sd->s_flags &= ~SYSFS_FLAG_REMOVED;

	return 0;
}

/**
 *	sysfs_pathname - return full path to sysfs dirent
 *	@sd: sysfs_dirent whose path we want
 *	@path: caller allocated buffer of size PATH_MAX
 *
 *	Gives the name "/" to the sysfs_root entry; any path returned
 *	is relative to wherever sysfs is mounted.
 */
static char *sysfs_pathname(struct sysfs_dirent *sd, char *path)
{
	if (sd->s_parent) {
		sysfs_pathname(sd->s_parent, path);
		strlcat(path, "/", PATH_MAX);
	}
	strlcat(path, sd->s_name, PATH_MAX);
	return path;
}

/**
 *	sysfs_add_one - add sysfs_dirent to parent
 *	@acxt: addrm context to use
 *	@sd: sysfs_dirent to be added
 *
 *	Get @acxt->parent_sd and set sd->s_parent to it and increment
 *	nlink of parent inode if @sd is a directory and link into the
 *	children list of the parent.
 *
 *	This function should be called between calls to
 *	sysfs_addrm_start() and sysfs_addrm_finish() and should be
 *	passed the same @acxt as passed to sysfs_addrm_start().
 *
 *	LOCKING:
 *	Determined by sysfs_addrm_start().
 *
 *	RETURNS:
 *	0 on success, -EEXIST if entry with the given name already
 *	exists.
 */
int sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
{
	int ret;

	ret = __sysfs_add_one(acxt, sd);
	if (ret == -EEXIST) {
		char *path = kzalloc(PATH_MAX, GFP_KERNEL);
		WARN(1, KERN_WARNING
		     "sysfs: cannot create duplicate filename '%s'\n",
		     (path == NULL) ? sd->s_name
				    : (sysfs_pathname(acxt->parent_sd, path),
				       strlcat(path, "/", PATH_MAX),
				       strlcat(path, sd->s_name, PATH_MAX),
				       path));
		kfree(path);
	}

	return ret;
}

/**
 *	sysfs_remove_one - remove sysfs_dirent from parent
 *	@acxt: addrm context to use
 *	@sd: sysfs_dirent to be removed
 *
 *	Mark @sd removed and drop nlink of parent inode if @sd is a
 *	directory.  @sd is unlinked from the children list.
 *
 *	This function should be called between calls to
 *	sysfs_addrm_start() and sysfs_addrm_finish() and should be
 *	passed the same @acxt as passed to sysfs_addrm_start().
 *
 *	LOCKING:
 *	Determined by sysfs_addrm_start().
 */
void sysfs_remove_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
{
	struct sysfs_inode_attrs *ps_iattr;

	BUG_ON(sd->s_flags & SYSFS_FLAG_REMOVED);

	sysfs_unlink_sibling(sd);

	/* Update timestamps on the parent */
	ps_iattr = acxt->parent_sd->s_iattr;
	if (ps_iattr) {
		struct iattr *ps_iattrs = &ps_iattr->ia_iattr;
		ps_iattrs->ia_ctime = ps_iattrs->ia_mtime = CURRENT_TIME;
	}

	sd->s_flags |= SYSFS_FLAG_REMOVED;
	sd->u.removed_list = acxt->removed;
	acxt->removed = sd;
}

/**
 *	sysfs_addrm_finish - finish up sysfs_dirent add/remove
 *	@acxt: addrm context to finish up
 *
 *	Finish up sysfs_dirent add/remove.  Resources acquired by
 *	sysfs_addrm_start() are released and removed sysfs_dirents are
 *	cleaned up.
 *
 *	LOCKING:
 *	sysfs_mutex is released.
 */
void sysfs_addrm_finish(struct sysfs_addrm_cxt *acxt)
{
	/* release resources acquired by sysfs_addrm_start() */
	mutex_unlock(&sysfs_mutex);

	/* kill removed sysfs_dirents */
	while (acxt->removed) {
		struct sysfs_dirent *sd = acxt->removed;

		acxt->removed = sd->u.removed_list;

		sysfs_deactivate(sd);
		unmap_bin_file(sd);
		sysfs_put(sd);
	}
}

/**
 *	sysfs_find_dirent - find sysfs_dirent with the given name
 *	@parent_sd: sysfs_dirent to search under
 *	@name: name to look for
 *
 *	Look for sysfs_dirent with name @name under @parent_sd.
 *
 *	LOCKING:
 *	mutex_lock(sysfs_mutex)
 *
 *	RETURNS:
 *	Pointer to sysfs_dirent if found, NULL if not.
 */
struct sysfs_dirent *sysfs_find_dirent(struct sysfs_dirent *parent_sd,
				       const void *ns,
				       const unsigned char *name)
{
	struct rb_node *node = parent_sd->s_dir.children.rb_node;
	unsigned int hash;

	if (!!sysfs_ns_type(parent_sd) != !!ns) {
		WARN(1, KERN_WARNING "sysfs: ns %s in '%s' for '%s'\n",
			sysfs_ns_type(parent_sd)? "required": "invalid",
			parent_sd->s_name, name);
		return NULL;
	}

	hash = sysfs_name_hash(ns, name);
	while (node) {
		struct sysfs_dirent *sd;
		int result;

		sd = to_sysfs_dirent(node);
		result = sysfs_name_compare(hash, ns, name, sd);
		if (result < 0)
			node = node->rb_left;
		else if (result > 0)
			node = node->rb_right;
		else
			return sd;
	}
	return NULL;
}

/**
 *	sysfs_get_dirent - find and get sysfs_dirent with the given name
 *	@parent_sd: sysfs_dirent to search under
 *	@name: name to look for
 *
 *	Look for sysfs_dirent with name @name under @parent_sd and get
 *	it if found.
 *
 *	LOCKING:
 *	Kernel thread context (may sleep).  Grabs sysfs_mutex.
 *
 *	RETURNS:
 *	Pointer to sysfs_dirent if found, NULL if not.
 */
struct sysfs_dirent *sysfs_get_dirent(struct sysfs_dirent *parent_sd,
				      const void *ns,
				      const unsigned char *name)
{
	struct sysfs_dirent *sd;

	mutex_lock(&sysfs_mutex);
	sd = sysfs_find_dirent(parent_sd, ns, name);
	sysfs_get(sd);
	mutex_unlock(&sysfs_mutex);

	return sd;
}
EXPORT_SYMBOL_GPL(sysfs_get_dirent);

static int create_dir(struct kobject *kobj, struct sysfs_dirent *parent_sd,
	enum kobj_ns_type type, const void *ns, const char *name,
	struct sysfs_dirent **p_sd)
{
	umode_t mode = S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO;
	struct sysfs_addrm_cxt acxt;
	struct sysfs_dirent *sd;
	int rc;

	/* allocate */
	sd = sysfs_new_dirent(name, mode, SYSFS_DIR);
	if (!sd)
		return -ENOMEM;

	sd->s_flags |= (type << SYSFS_NS_TYPE_SHIFT);
	sd->s_ns = ns;
	sd->s_dir.kobj = kobj;

	/* link in */
	sysfs_addrm_start(&acxt, parent_sd);
	rc = sysfs_add_one(&acxt, sd);
	sysfs_addrm_finish(&acxt);

	if (rc == 0)
		*p_sd = sd;
	else
		sysfs_put(sd);

	return rc;
}

int sysfs_create_subdir(struct kobject *kobj, const char *name,
			struct sysfs_dirent **p_sd)
{
	return create_dir(kobj, kobj->sd,
			  KOBJ_NS_TYPE_NONE, NULL, name, p_sd);
}

/**
 *	sysfs_read_ns_type: return associated ns_type
 *	@kobj: the kobject being queried
 *
 *	Each kobject can be tagged with exactly one namespace type
 *	(i.e. network or user).  Return the ns_type associated with
 *	this object if any
 */
static enum kobj_ns_type sysfs_read_ns_type(struct kobject *kobj)
{
	const struct kobj_ns_type_operations *ops;
	enum kobj_ns_type type;

	ops = kobj_child_ns_ops(kobj);
	if (!ops)
		return KOBJ_NS_TYPE_NONE;

	type = ops->type;
	BUG_ON(type <= KOBJ_NS_TYPE_NONE);
	BUG_ON(type >= KOBJ_NS_TYPES);
	BUG_ON(!kobj_ns_type_registered(type));

	return type;
}

/**
 *	sysfs_create_dir - create a directory for an object.
 *	@kobj:		object we're creating directory for. 
 */
int sysfs_create_dir(struct kobject * kobj)
{
	enum kobj_ns_type type;
	struct sysfs_dirent *parent_sd, *sd;
	const void *ns = NULL;
	int error = 0;

	BUG_ON(!kobj);

	if (kobj->parent)
		parent_sd = kobj->parent->sd;
	else
		parent_sd = &sysfs_root;

	if (!parent_sd)
		return -ENOENT;

	if (sysfs_ns_type(parent_sd))
		ns = kobj->ktype->namespace(kobj);
	type = sysfs_read_ns_type(kobj);

	error = create_dir(kobj, parent_sd, type, ns, kobject_name(kobj), &sd);
	if (!error)
		kobj->sd = sd;
	return error;
}

static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry,
				unsigned int flags)
{
	struct dentry *ret = NULL;
	struct dentry *parent = dentry->d_parent;
	struct sysfs_dirent *parent_sd = parent->d_fsdata;
	struct sysfs_dirent *sd;
	struct inode *inode;
	enum kobj_ns_type type;
	const void *ns;

	mutex_lock(&sysfs_mutex);

	type = sysfs_ns_type(parent_sd);
	ns = sysfs_info(dir->i_sb)->ns[type];

	sd = sysfs_find_dirent(parent_sd, ns, dentry->d_name.name);

	/* no such entry */
	if (!sd) {
		ret = ERR_PTR(-ENOENT);
		goto out_unlock;
	}
	dentry->d_fsdata = sysfs_get(sd);

	/* attach dentry and inode */
	inode = sysfs_get_inode(dir->i_sb, sd);
	if (!inode) {
		ret = ERR_PTR(-ENOMEM);
		goto out_unlock;
	}

	/* instantiate and hash dentry */
	ret = d_materialise_unique(dentry, inode);
 out_unlock:
	mutex_unlock(&sysfs_mutex);
	return ret;
}

const struct inode_operations sysfs_dir_inode_operations = {
	.lookup		= sysfs_lookup,
	.permission	= sysfs_permission,
	.setattr	= sysfs_setattr,
	.getattr	= sysfs_getattr,
	.setxattr	= sysfs_setxattr,
};

static void remove_dir(struct sysfs_dirent *sd)
{
	struct sysfs_addrm_cxt acxt;

	sysfs_addrm_start(&acxt, sd->s_parent);
	sysfs_remove_one(&acxt, sd);
	sysfs_addrm_finish(&acxt);
}

void sysfs_remove_subdir(struct sysfs_dirent *sd)
{
	remove_dir(sd);
}


static void __sysfs_remove_dir(struct sysfs_dirent *dir_sd)
{
	struct sysfs_addrm_cxt acxt;
	struct rb_node *pos;

	if (!dir_sd)
		return;

	pr_debug("sysfs %s: removing dir\n", dir_sd->s_name);
	sysfs_addrm_start(&acxt, dir_sd);
	pos = rb_first(&dir_sd->s_dir.children);
	while (pos) {
		struct sysfs_dirent *sd = to_sysfs_dirent(pos);
		pos = rb_next(pos);
		if (sysfs_type(sd) != SYSFS_DIR)
			sysfs_remove_one(&acxt, sd);
	}
	sysfs_addrm_finish(&acxt);

	remove_dir(dir_sd);
}

/**
 *	sysfs_remove_dir - remove an object's directory.
 *	@kobj:	object.
 *
 *	The only thing special about this is that we remove any files in
 *	the directory before we remove the directory, and we've inlined
 *	what used to be sysfs_rmdir() below, instead of calling separately.
 */

void sysfs_remove_dir(struct kobject * kobj)
{
	struct sysfs_dirent *sd = kobj->sd;

	spin_lock(&sysfs_assoc_lock);
	kobj->sd = NULL;
	spin_unlock(&sysfs_assoc_lock);

	__sysfs_remove_dir(sd);
}

int sysfs_rename(struct sysfs_dirent *sd,
	struct sysfs_dirent *new_parent_sd, const void *new_ns,
	const char *new_name)
{
	int error;

	mutex_lock(&sysfs_mutex);

	error = 0;
	if ((sd->s_parent == new_parent_sd) && (sd->s_ns == new_ns) &&
	    (strcmp(sd->s_name, new_name) == 0))
		goto out;	/* nothing to rename */

	error = -EEXIST;
	if (sysfs_find_dirent(new_parent_sd, new_ns, new_name))
		goto out;

	/* rename sysfs_dirent */
	if (strcmp(sd->s_name, new_name) != 0) {
		error = -ENOMEM;
		new_name = kstrdup(new_name, GFP_KERNEL);
		if (!new_name)
			goto out;

		kfree(sd->s_name);
		sd->s_name = new_name;
	}

	/* Move to the appropriate place in the appropriate directories rbtree. */
	sysfs_unlink_sibling(sd);
	sysfs_get(new_parent_sd);
	sysfs_put(sd->s_parent);
	sd->s_ns = new_ns;
	sd->s_hash = sysfs_name_hash(sd->s_ns, sd->s_name);
	sd->s_parent = new_parent_sd;
	sysfs_link_sibling(sd);

	error = 0;
 out:
	mutex_unlock(&sysfs_mutex);
	return error;
}

int sysfs_rename_dir(struct kobject *kobj, const char *new_name)
{
	struct sysfs_dirent *parent_sd = kobj->sd->s_parent;
	const void *new_ns = NULL;

	if (sysfs_ns_type(parent_sd))
		new_ns = kobj->ktype->namespace(kobj);

	return sysfs_rename(kobj->sd, parent_sd, new_ns, new_name);
}

int sysfs_move_dir(struct kobject *kobj, struct kobject *new_parent_kobj)
{
	struct sysfs_dirent *sd = kobj->sd;
	struct sysfs_dirent *new_parent_sd;
	const void *new_ns = NULL;

	BUG_ON(!sd->s_parent);
	if (sysfs_ns_type(sd->s_parent))
		new_ns = kobj->ktype->namespace(kobj);
	new_parent_sd = new_parent_kobj && new_parent_kobj->sd ?
		new_parent_kobj->sd : &sysfs_root;

	return sysfs_rename(sd, new_parent_sd, new_ns, sd->s_name);
}

/* Relationship between s_mode and the DT_xxx types */
static inline unsigned char dt_type(struct sysfs_dirent *sd)
{
	return (sd->s_mode >> 12) & 15;
}

static int sysfs_dir_release(struct inode *inode, struct file *filp)
{
	sysfs_put(filp->private_data);
	return 0;
}

static struct sysfs_dirent *sysfs_dir_pos(const void *ns,
	struct sysfs_dirent *parent_sd,	loff_t hash, struct sysfs_dirent *pos)
{
	if (pos) {
		int valid = !(pos->s_flags & SYSFS_FLAG_REMOVED) &&
			pos->s_parent == parent_sd &&
			hash == pos->s_hash;
		sysfs_put(pos);
		if (!valid)
			pos = NULL;
	}
	if (!pos && (hash > 1) && (hash < INT_MAX)) {
		struct rb_node *node = parent_sd->s_dir.children.rb_node;
		while (node) {
			pos = to_sysfs_dirent(node);

			if (hash < pos->s_hash)
				node = node->rb_left;
			else if (hash > pos->s_hash)
				node = node->rb_right;
			else
				break;
		}
	}
	/* Skip over entries in the wrong namespace */
	while (pos && pos->s_ns != ns) {
		struct rb_node *node = rb_next(&pos->s_rb);
		if (!node)
			pos = NULL;
		else
			pos = to_sysfs_dirent(node);
	}
	return pos;
}

static struct sysfs_dirent *sysfs_dir_next_pos(const void *ns,
	struct sysfs_dirent *parent_sd,	ino_t ino, struct sysfs_dirent *pos)
{
	pos = sysfs_dir_pos(ns, parent_sd, ino, pos);
	if (pos) do {
		struct rb_node *node = rb_next(&pos->s_rb);
		if (!node)
			pos = NULL;
		else
			pos = to_sysfs_dirent(node);
	} while (pos && pos->s_ns != ns);
	return pos;
}

static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
{
	struct dentry *dentry = filp->f_path.dentry;
	struct sysfs_dirent * parent_sd = dentry->d_fsdata;
	struct sysfs_dirent *pos = filp->private_data;
	enum kobj_ns_type type;
	const void *ns;
	ino_t ino;
	loff_t off;

	type = sysfs_ns_type(parent_sd);
	ns = sysfs_info(dentry->d_sb)->ns[type];

	if (filp->f_pos == 0) {
		ino = parent_sd->s_ino;
		if (filldir(dirent, ".", 1, filp->f_pos, ino, DT_DIR) == 0)
			filp->f_pos++;
		else
			return 0;
	}
	if (filp->f_pos == 1) {
		if (parent_sd->s_parent)
			ino = parent_sd->s_parent->s_ino;
		else
			ino = parent_sd->s_ino;
		if (filldir(dirent, "..", 2, filp->f_pos, ino, DT_DIR) == 0)
			filp->f_pos++;
		else
			return 0;
	}
	mutex_lock(&sysfs_mutex);
	off = filp->f_pos;
	for (pos = sysfs_dir_pos(ns, parent_sd, filp->f_pos, pos);
	     pos;
	     pos = sysfs_dir_next_pos(ns, parent_sd, filp->f_pos, pos)) {
		const char * name;
		unsigned int type;
		int len, ret;

		name = pos->s_name;
		len = strlen(name);
		ino = pos->s_ino;
		type = dt_type(pos);
		off = filp->f_pos = pos->s_hash;
		filp->private_data = sysfs_get(pos);

		mutex_unlock(&sysfs_mutex);
		ret = filldir(dirent, name, len, off, ino, type);
		mutex_lock(&sysfs_mutex);
		if (ret < 0)
			break;
	}
	mutex_unlock(&sysfs_mutex);

	/* don't reference last entry if its refcount is dropped */
	if (!pos) {
		filp->private_data = NULL;

		/* EOF and not changed as 0 or 1 in read/write path */
		if (off == filp->f_pos && off > 1)
			filp->f_pos = INT_MAX;
	}
	return 0;
}

static loff_t sysfs_dir_llseek(struct file *file, loff_t offset, int whence)
{
	struct inode *inode = file_inode(file);
	loff_t ret;

	mutex_lock(&inode->i_mutex);
	ret = generic_file_llseek(file, offset, whence);
	mutex_unlock(&inode->i_mutex);

	return ret;
}

const struct file_operations sysfs_dir_operations = {
	.read		= generic_read_dir,
	.readdir	= sysfs_readdir,
	.release	= sysfs_dir_release,
	.llseek		= sysfs_dir_llseek,
};