summaryrefslogtreecommitdiff
path: root/fs/ext2/xattr.c
blob: fb2e008d44069c4ab03ec1c42923c24c52d6b6c9 (plain)
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
// SPDX-License-Identifier: GPL-2.0
/*
 * linux/fs/ext2/xattr.c
 *
 * Copyright (C) 2001-2003 Andreas Gruenbacher <agruen@suse.de>
 *
 * Fix by Harrison Xing <harrison@mountainviewdata.com>.
 * Extended attributes for symlinks and special files added per
 *  suggestion of Luka Renko <luka.renko@hermes.si>.
 * xattr consolidation Copyright (c) 2004 James Morris <jmorris@redhat.com>,
 *  Red Hat Inc.
 *
 */

/*
 * Extended attributes are stored on disk blocks allocated outside of
 * any inode. The i_file_acl field is then made to point to this allocated
 * block. If all extended attributes of an inode are identical, these
 * inodes may share the same extended attribute block. Such situations
 * are automatically detected by keeping a cache of recent attribute block
 * numbers and hashes over the block's contents in memory.
 *
 *
 * Extended attribute block layout:
 *
 *   +------------------+
 *   | header           |
 *   | entry 1          | |
 *   | entry 2          | | growing downwards
 *   | entry 3          | v
 *   | four null bytes  |
 *   | . . .            |
 *   | value 1          | ^
 *   | value 3          | | growing upwards
 *   | value 2          | |
 *   +------------------+
 *
 * The block header is followed by multiple entry descriptors. These entry
 * descriptors are variable in size, and aligned to EXT2_XATTR_PAD
 * byte boundaries. The entry descriptors are sorted by attribute name,
 * so that two extended attribute blocks can be compared efficiently.
 *
 * Attribute values are aligned to the end of the block, stored in
 * no specific order. They are also padded to EXT2_XATTR_PAD byte
 * boundaries. No additional gaps are left between them.
 *
 * Locking strategy
 * ----------------
 * EXT2_I(inode)->i_file_acl is protected by EXT2_I(inode)->xattr_sem.
 * EA blocks are only changed if they are exclusive to an inode, so
 * holding xattr_sem also means that nothing but the EA block's reference
 * count will change. Multiple writers to an EA block are synchronized
 * by the bh lock. No more than a single bh lock is held at any time
 * to avoid deadlocks.
 */

#include <linux/buffer_head.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/mbcache.h>
#include <linux/quotaops.h>
#include <linux/rwsem.h>
#include <linux/security.h>
#include "ext2.h"
#include "xattr.h"
#include "acl.h"

#define HDR(bh) ((struct ext2_xattr_header *)((bh)->b_data))
#define ENTRY(ptr) ((struct ext2_xattr_entry *)(ptr))
#define FIRST_ENTRY(bh) ENTRY(HDR(bh)+1)
#define IS_LAST_ENTRY(entry) (*(__u32 *)(entry) == 0)

#ifdef EXT2_XATTR_DEBUG
# define ea_idebug(inode, f...) do { \
		printk(KERN_DEBUG "inode %s:%ld: ", \
			inode->i_sb->s_id, inode->i_ino); \
		printk(f); \
		printk("\n"); \
	} while (0)
# define ea_bdebug(bh, f...) do { \
		printk(KERN_DEBUG "block %pg:%lu: ", \
			bh->b_bdev, (unsigned long) bh->b_blocknr); \
		printk(f); \
		printk("\n"); \
	} while (0)
#else
# define ea_idebug(f...)
# define ea_bdebug(f...)
#endif

static int ext2_xattr_set2(struct inode *, struct buffer_head *,
			   struct ext2_xattr_header *);

static int ext2_xattr_cache_insert(struct mb_cache *, struct buffer_head *);
static struct buffer_head *ext2_xattr_cache_find(struct inode *,
						 struct ext2_xattr_header *);
static void ext2_xattr_rehash(struct ext2_xattr_header *,
			      struct ext2_xattr_entry *);

static const struct xattr_handler *ext2_xattr_handler_map[] = {
	[EXT2_XATTR_INDEX_USER]		     = &ext2_xattr_user_handler,
#ifdef CONFIG_EXT2_FS_POSIX_ACL
	[EXT2_XATTR_INDEX_POSIX_ACL_ACCESS]  = &posix_acl_access_xattr_handler,
	[EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT] = &posix_acl_default_xattr_handler,
#endif
	[EXT2_XATTR_INDEX_TRUSTED]	     = &ext2_xattr_trusted_handler,
#ifdef CONFIG_EXT2_FS_SECURITY
	[EXT2_XATTR_INDEX_SECURITY]	     = &ext2_xattr_security_handler,
#endif
};

const struct xattr_handler *ext2_xattr_handlers[] = {
	&ext2_xattr_user_handler,
	&ext2_xattr_trusted_handler,
#ifdef CONFIG_EXT2_FS_POSIX_ACL
	&posix_acl_access_xattr_handler,
	&posix_acl_default_xattr_handler,
#endif
#ifdef CONFIG_EXT2_FS_SECURITY
	&ext2_xattr_security_handler,
#endif
	NULL
};

#define EA_BLOCK_CACHE(inode)	(EXT2_SB(inode->i_sb)->s_ea_block_cache)

static inline const struct xattr_handler *
ext2_xattr_handler(int name_index)
{
	const struct xattr_handler *handler = NULL;

	if (name_index > 0 && name_index < ARRAY_SIZE(ext2_xattr_handler_map))
		handler = ext2_xattr_handler_map[name_index];
	return handler;
}

static bool
ext2_xattr_header_valid(struct ext2_xattr_header *header)
{
	if (header->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
	    header->h_blocks != cpu_to_le32(1))
		return false;

	return true;
}

static bool
ext2_xattr_entry_valid(struct ext2_xattr_entry *entry, size_t end_offs)
{
	size_t size;

	if (entry->e_value_block != 0)
		return false;

	size = le32_to_cpu(entry->e_value_size);
	if (size > end_offs ||
	    le16_to_cpu(entry->e_value_offs) + size > end_offs)
		return false;

	return true;
}

/*
 * ext2_xattr_get()
 *
 * Copy an extended attribute into the buffer
 * provided, or compute the buffer size required.
 * Buffer is NULL to compute the size of the buffer required.
 *
 * Returns a negative error number on failure, or the number of bytes
 * used / required on success.
 */
int
ext2_xattr_get(struct inode *inode, int name_index, const char *name,
	       void *buffer, size_t buffer_size)
{
	struct buffer_head *bh = NULL;
	struct ext2_xattr_entry *entry;
	size_t name_len, size;
	char *end;
	int error;
	struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);

	ea_idebug(inode, "name=%d.%s, buffer=%p, buffer_size=%ld",
		  name_index, name, buffer, (long)buffer_size);

	if (name == NULL)
		return -EINVAL;
	name_len = strlen(name);
	if (name_len > 255)
		return -ERANGE;

	down_read(&EXT2_I(inode)->xattr_sem);
	error = -ENODATA;
	if (!EXT2_I(inode)->i_file_acl)
		goto cleanup;
	ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
	bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
	error = -EIO;
	if (!bh)
		goto cleanup;
	ea_bdebug(bh, "b_count=%d, refcount=%d",
		atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
	end = bh->b_data + bh->b_size;
	if (!ext2_xattr_header_valid(HDR(bh))) {
bad_block:
		ext2_error(inode->i_sb, "ext2_xattr_get",
			"inode %ld: bad block %d", inode->i_ino,
			EXT2_I(inode)->i_file_acl);
		error = -EIO;
		goto cleanup;
	}

	/* find named attribute */
	entry = FIRST_ENTRY(bh);
	while (!IS_LAST_ENTRY(entry)) {
		struct ext2_xattr_entry *next =
			EXT2_XATTR_NEXT(entry);
		if ((char *)next >= end)
			goto bad_block;
		if (name_index == entry->e_name_index &&
		    name_len == entry->e_name_len &&
		    memcmp(name, entry->e_name, name_len) == 0)
			goto found;
		entry = next;
	}
	if (ext2_xattr_cache_insert(ea_block_cache, bh))
		ea_idebug(inode, "cache insert failed");
	error = -ENODATA;
	goto cleanup;
found:
	if (!ext2_xattr_entry_valid(entry, inode->i_sb->s_blocksize))
		goto bad_block;

	size = le32_to_cpu(entry->e_value_size);
	if (ext2_xattr_cache_insert(ea_block_cache, bh))
		ea_idebug(inode, "cache insert failed");
	if (buffer) {
		error = -ERANGE;
		if (size > buffer_size)
			goto cleanup;
		/* return value of attribute */
		memcpy(buffer, bh->b_data + le16_to_cpu(entry->e_value_offs),
			size);
	}
	error = size;

cleanup:
	brelse(bh);
	up_read(&EXT2_I(inode)->xattr_sem);

	return error;
}

/*
 * ext2_xattr_list()
 *
 * Copy a list of attribute names into the buffer
 * provided, or compute the buffer size required.
 * Buffer is NULL to compute the size of the buffer required.
 *
 * Returns a negative error number on failure, or the number of bytes
 * used / required on success.
 */
static int
ext2_xattr_list(struct dentry *dentry, char *buffer, size_t buffer_size)
{
	struct inode *inode = d_inode(dentry);
	struct buffer_head *bh = NULL;
	struct ext2_xattr_entry *entry;
	char *end;
	size_t rest = buffer_size;
	int error;
	struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);

	ea_idebug(inode, "buffer=%p, buffer_size=%ld",
		  buffer, (long)buffer_size);

	down_read(&EXT2_I(inode)->xattr_sem);
	error = 0;
	if (!EXT2_I(inode)->i_file_acl)
		goto cleanup;
	ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
	bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
	error = -EIO;
	if (!bh)
		goto cleanup;
	ea_bdebug(bh, "b_count=%d, refcount=%d",
		atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
	end = bh->b_data + bh->b_size;
	if (!ext2_xattr_header_valid(HDR(bh))) {
bad_block:
		ext2_error(inode->i_sb, "ext2_xattr_list",
			"inode %ld: bad block %d", inode->i_ino,
			EXT2_I(inode)->i_file_acl);
		error = -EIO;
		goto cleanup;
	}

	/* check the on-disk data structure */
	entry = FIRST_ENTRY(bh);
	while (!IS_LAST_ENTRY(entry)) {
		struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(entry);

		if ((char *)next >= end)
			goto bad_block;
		entry = next;
	}
	if (ext2_xattr_cache_insert(ea_block_cache, bh))
		ea_idebug(inode, "cache insert failed");

	/* list the attribute names */
	for (entry = FIRST_ENTRY(bh); !IS_LAST_ENTRY(entry);
	     entry = EXT2_XATTR_NEXT(entry)) {
		const struct xattr_handler *handler =
			ext2_xattr_handler(entry->e_name_index);

		if (handler && (!handler->list || handler->list(dentry))) {
			const char *prefix = handler->prefix ?: handler->name;
			size_t prefix_len = strlen(prefix);
			size_t size = prefix_len + entry->e_name_len + 1;

			if (buffer) {
				if (size > rest) {
					error = -ERANGE;
					goto cleanup;
				}
				memcpy(buffer, prefix, prefix_len);
				buffer += prefix_len;
				memcpy(buffer, entry->e_name, entry->e_name_len);
				buffer += entry->e_name_len;
				*buffer++ = 0;
			}
			rest -= size;
		}
	}
	error = buffer_size - rest;  /* total size */

cleanup:
	brelse(bh);
	up_read(&EXT2_I(inode)->xattr_sem);

	return error;
}

/*
 * Inode operation listxattr()
 *
 * d_inode(dentry)->i_mutex: don't care
 */
ssize_t
ext2_listxattr(struct dentry *dentry, char *buffer, size_t size)
{
	return ext2_xattr_list(dentry, buffer, size);
}

/*
 * If the EXT2_FEATURE_COMPAT_EXT_ATTR feature of this file system is
 * not set, set it.
 */
static void ext2_xattr_update_super_block(struct super_block *sb)
{
	if (EXT2_HAS_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR))
		return;

	spin_lock(&EXT2_SB(sb)->s_lock);
	ext2_update_dynamic_rev(sb);
	EXT2_SET_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR);
	spin_unlock(&EXT2_SB(sb)->s_lock);
	mark_buffer_dirty(EXT2_SB(sb)->s_sbh);
}

/*
 * ext2_xattr_set()
 *
 * Create, replace or remove an extended attribute for this inode.  Value
 * is NULL to remove an existing extended attribute, and non-NULL to
 * either replace an existing extended attribute, or create a new extended
 * attribute. The flags XATTR_REPLACE and XATTR_CREATE
 * specify that an extended attribute must exist and must not exist
 * previous to the call, respectively.
 *
 * Returns 0, or a negative error number on failure.
 */
int
ext2_xattr_set(struct inode *inode, int name_index, const char *name,
	       const void *value, size_t value_len, int flags)
{
	struct super_block *sb = inode->i_sb;
	struct buffer_head *bh = NULL;
	struct ext2_xattr_header *header = NULL;
	struct ext2_xattr_entry *here, *last;
	size_t name_len, free, min_offs = sb->s_blocksize;
	int not_found = 1, error;
	char *end;
	
	/*
	 * header -- Points either into bh, or to a temporarily
	 *           allocated buffer.
	 * here -- The named entry found, or the place for inserting, within
	 *         the block pointed to by header.
	 * last -- Points right after the last named entry within the block
	 *         pointed to by header.
	 * min_offs -- The offset of the first value (values are aligned
	 *             towards the end of the block).
	 * end -- Points right after the block pointed to by header.
	 */
	
	ea_idebug(inode, "name=%d.%s, value=%p, value_len=%ld",
		  name_index, name, value, (long)value_len);

	if (value == NULL)
		value_len = 0;
	if (name == NULL)
		return -EINVAL;
	name_len = strlen(name);
	if (name_len > 255 || value_len > sb->s_blocksize)
		return -ERANGE;
	down_write(&EXT2_I(inode)->xattr_sem);
	if (EXT2_I(inode)->i_file_acl) {
		/* The inode already has an extended attribute block. */
		bh = sb_bread(sb, EXT2_I(inode)->i_file_acl);
		error = -EIO;
		if (!bh)
			goto cleanup;
		ea_bdebug(bh, "b_count=%d, refcount=%d",
			atomic_read(&(bh->b_count)),
			le32_to_cpu(HDR(bh)->h_refcount));
		header = HDR(bh);
		end = bh->b_data + bh->b_size;
		if (!ext2_xattr_header_valid(header)) {
bad_block:
			ext2_error(sb, "ext2_xattr_set",
				"inode %ld: bad block %d", inode->i_ino, 
				   EXT2_I(inode)->i_file_acl);
			error = -EIO;
			goto cleanup;
		}
		/* Find the named attribute. */
		here = FIRST_ENTRY(bh);
		while (!IS_LAST_ENTRY(here)) {
			struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(here);
			if ((char *)next >= end)
				goto bad_block;
			if (!here->e_value_block && here->e_value_size) {
				size_t offs = le16_to_cpu(here->e_value_offs);
				if (offs < min_offs)
					min_offs = offs;
			}
			not_found = name_index - here->e_name_index;
			if (!not_found)
				not_found = name_len - here->e_name_len;
			if (!not_found)
				not_found = memcmp(name, here->e_name,name_len);
			if (not_found <= 0)
				break;
			here = next;
		}
		last = here;
		/* We still need to compute min_offs and last. */
		while (!IS_LAST_ENTRY(last)) {
			struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(last);
			if ((char *)next >= end)
				goto bad_block;
			if (!last->e_value_block && last->e_value_size) {
				size_t offs = le16_to_cpu(last->e_value_offs);
				if (offs < min_offs)
					min_offs = offs;
			}
			last = next;
		}

		/* Check whether we have enough space left. */
		free = min_offs - ((char*)last - (char*)header) - sizeof(__u32);
	} else {
		/* We will use a new extended attribute block. */
		free = sb->s_blocksize -
			sizeof(struct ext2_xattr_header) - sizeof(__u32);
		here = last = NULL;  /* avoid gcc uninitialized warning. */
	}

	if (not_found) {
		/* Request to remove a nonexistent attribute? */
		error = -ENODATA;
		if (flags & XATTR_REPLACE)
			goto cleanup;
		error = 0;
		if (value == NULL)
			goto cleanup;
	} else {
		/* Request to create an existing attribute? */
		error = -EEXIST;
		if (flags & XATTR_CREATE)
			goto cleanup;
		if (!here->e_value_block && here->e_value_size) {
			if (!ext2_xattr_entry_valid(here, sb->s_blocksize))
				goto bad_block;
			free += EXT2_XATTR_SIZE(
					le32_to_cpu(here->e_value_size));
		}
		free += EXT2_XATTR_LEN(name_len);
	}
	error = -ENOSPC;
	if (free < EXT2_XATTR_LEN(name_len) + EXT2_XATTR_SIZE(value_len))
		goto cleanup;

	/* Here we know that we can set the new attribute. */

	if (header) {
		/* assert(header == HDR(bh)); */
		lock_buffer(bh);
		if (header->h_refcount == cpu_to_le32(1)) {
			__u32 hash = le32_to_cpu(header->h_hash);

			ea_bdebug(bh, "modifying in-place");
			/*
			 * This must happen under buffer lock for
			 * ext2_xattr_set2() to reliably detect modified block
			 */
			mb_cache_entry_delete(EA_BLOCK_CACHE(inode), hash,
					      bh->b_blocknr);

			/* keep the buffer locked while modifying it. */
		} else {
			int offset;

			unlock_buffer(bh);
			ea_bdebug(bh, "cloning");
			header = kmalloc(bh->b_size, GFP_KERNEL);
			error = -ENOMEM;
			if (header == NULL)
				goto cleanup;
			memcpy(header, HDR(bh), bh->b_size);
			header->h_refcount = cpu_to_le32(1);

			offset = (char *)here - bh->b_data;
			here = ENTRY((char *)header + offset);
			offset = (char *)last - bh->b_data;
			last = ENTRY((char *)header + offset);
		}
	} else {
		/* Allocate a buffer where we construct the new block. */
		header = kzalloc(sb->s_blocksize, GFP_KERNEL);
		error = -ENOMEM;
		if (header == NULL)
			goto cleanup;
		end = (char *)header + sb->s_blocksize;
		header->h_magic = cpu_to_le32(EXT2_XATTR_MAGIC);
		header->h_blocks = header->h_refcount = cpu_to_le32(1);
		last = here = ENTRY(header+1);
	}

	/* Iff we are modifying the block in-place, bh is locked here. */

	if (not_found) {
		/* Insert the new name. */
		size_t size = EXT2_XATTR_LEN(name_len);
		size_t rest = (char *)last - (char *)here;
		memmove((char *)here + size, here, rest);
		memset(here, 0, size);
		here->e_name_index = name_index;
		here->e_name_len = name_len;
		memcpy(here->e_name, name, name_len);
	} else {
		if (!here->e_value_block && here->e_value_size) {
			char *first_val = (char *)header + min_offs;
			size_t offs = le16_to_cpu(here->e_value_offs);
			char *val = (char *)header + offs;
			size_t size = EXT2_XATTR_SIZE(
				le32_to_cpu(here->e_value_size));

			if (size == EXT2_XATTR_SIZE(value_len)) {
				/* The old and the new value have the same
				   size. Just replace. */
				here->e_value_size = cpu_to_le32(value_len);
				memset(val + size - EXT2_XATTR_PAD, 0,
				       EXT2_XATTR_PAD); /* Clear pad bytes. */
				memcpy(val, value, value_len);
				goto skip_replace;
			}

			/* Remove the old value. */
			memmove(first_val + size, first_val, val - first_val);
			memset(first_val, 0, size);
			here->e_value_offs = 0;
			min_offs += size;

			/* Adjust all value offsets. */
			last = ENTRY(header+1);
			while (!IS_LAST_ENTRY(last)) {
				size_t o = le16_to_cpu(last->e_value_offs);
				if (!last->e_value_block && o < offs)
					last->e_value_offs =
						cpu_to_le16(o + size);
				last = EXT2_XATTR_NEXT(last);
			}
		}
		if (value == NULL) {
			/* Remove the old name. */
			size_t size = EXT2_XATTR_LEN(name_len);
			last = ENTRY((char *)last - size);
			memmove(here, (char*)here + size,
				(char*)last - (char*)here);
			memset(last, 0, size);
		}
	}

	if (value != NULL) {
		/* Insert the new value. */
		here->e_value_size = cpu_to_le32(value_len);
		if (value_len) {
			size_t size = EXT2_XATTR_SIZE(value_len);
			char *val = (char *)header + min_offs - size;
			here->e_value_offs =
				cpu_to_le16((char *)val - (char *)header);
			memset(val + size - EXT2_XATTR_PAD, 0,
			       EXT2_XATTR_PAD); /* Clear the pad bytes. */
			memcpy(val, value, value_len);
		}
	}

skip_replace:
	if (IS_LAST_ENTRY(ENTRY(header+1))) {
		/* This block is now empty. */
		if (bh && header == HDR(bh))
			unlock_buffer(bh);  /* we were modifying in-place. */
		error = ext2_xattr_set2(inode, bh, NULL);
	} else {
		ext2_xattr_rehash(header, here);
		if (bh && header == HDR(bh))
			unlock_buffer(bh);  /* we were modifying in-place. */
		error = ext2_xattr_set2(inode, bh, header);
	}

cleanup:
	if (!(bh && header == HDR(bh)))
		kfree(header);
	brelse(bh);
	up_write(&EXT2_I(inode)->xattr_sem);

	return error;
}

/*
 * Second half of ext2_xattr_set(): Update the file system.
 */
static int
ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
		struct ext2_xattr_header *header)
{
	struct super_block *sb = inode->i_sb;
	struct buffer_head *new_bh = NULL;
	int error;
	struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);

	if (header) {
		new_bh = ext2_xattr_cache_find(inode, header);
		if (new_bh) {
			/* We found an identical block in the cache. */
			if (new_bh == old_bh) {
				ea_bdebug(new_bh, "keeping this block");
			} else {
				/* The old block is released after updating
				   the inode.  */
				ea_bdebug(new_bh, "reusing block");

				error = dquot_alloc_block(inode, 1);
				if (error) {
					unlock_buffer(new_bh);
					goto cleanup;
				}
				le32_add_cpu(&HDR(new_bh)->h_refcount, 1);
				ea_bdebug(new_bh, "refcount now=%d",
					le32_to_cpu(HDR(new_bh)->h_refcount));
			}
			unlock_buffer(new_bh);
		} else if (old_bh && header == HDR(old_bh)) {
			/* Keep this block. No need to lock the block as we
			   don't need to change the reference count. */
			new_bh = old_bh;
			get_bh(new_bh);
			ext2_xattr_cache_insert(ea_block_cache, new_bh);
		} else {
			/* We need to allocate a new block */
			ext2_fsblk_t goal = ext2_group_first_block_no(sb,
						EXT2_I(inode)->i_block_group);
			int block = ext2_new_block(inode, goal, &error);
			if (error)
				goto cleanup;
			ea_idebug(inode, "creating block %d", block);

			new_bh = sb_getblk(sb, block);
			if (unlikely(!new_bh)) {
				ext2_free_blocks(inode, block, 1);
				mark_inode_dirty(inode);
				error = -ENOMEM;
				goto cleanup;
			}
			lock_buffer(new_bh);
			memcpy(new_bh->b_data, header, new_bh->b_size);
			set_buffer_uptodate(new_bh);
			unlock_buffer(new_bh);
			ext2_xattr_cache_insert(ea_block_cache, new_bh);
			
			ext2_xattr_update_super_block(sb);
		}
		mark_buffer_dirty(new_bh);
		if (IS_SYNC(inode)) {
			sync_dirty_buffer(new_bh);
			error = -EIO;
			if (buffer_req(new_bh) && !buffer_uptodate(new_bh))
				goto cleanup;
		}
	}

	/* Update the inode. */
	EXT2_I(inode)->i_file_acl = new_bh ? new_bh->b_blocknr : 0;
	inode->i_ctime = current_time(inode);
	if (IS_SYNC(inode)) {
		error = sync_inode_metadata(inode, 1);
		/* In case sync failed due to ENOSPC the inode was actually
		 * written (only some dirty data were not) so we just proceed
		 * as if nothing happened and cleanup the unused block */
		if (error && error != -ENOSPC) {
			if (new_bh && new_bh != old_bh) {
				dquot_free_block_nodirty(inode, 1);
				mark_inode_dirty(inode);
			}
			goto cleanup;
		}
	} else
		mark_inode_dirty(inode);

	error = 0;
	if (old_bh && old_bh != new_bh) {
		/*
		 * If there was an old block and we are no longer using it,
		 * release the old block.
		 */
		lock_buffer(old_bh);
		if (HDR(old_bh)->h_refcount == cpu_to_le32(1)) {
			__u32 hash = le32_to_cpu(HDR(old_bh)->h_hash);

			/*
			 * This must happen under buffer lock for
			 * ext2_xattr_set2() to reliably detect freed block
			 */
			mb_cache_entry_delete(ea_block_cache, hash,
					      old_bh->b_blocknr);
			/* Free the old block. */
			ea_bdebug(old_bh, "freeing");
			ext2_free_blocks(inode, old_bh->b_blocknr, 1);
			mark_inode_dirty(inode);
			/* We let our caller release old_bh, so we
			 * need to duplicate the buffer before. */
			get_bh(old_bh);
			bforget(old_bh);
		} else {
			/* Decrement the refcount only. */
			le32_add_cpu(&HDR(old_bh)->h_refcount, -1);
			dquot_free_block_nodirty(inode, 1);
			mark_inode_dirty(inode);
			mark_buffer_dirty(old_bh);
			ea_bdebug(old_bh, "refcount now=%d",
				le32_to_cpu(HDR(old_bh)->h_refcount));
		}
		unlock_buffer(old_bh);
	}

cleanup:
	brelse(new_bh);

	return error;
}

/*
 * ext2_xattr_delete_inode()
 *
 * Free extended attribute resources associated with this inode. This
 * is called immediately before an inode is freed.
 */
void
ext2_xattr_delete_inode(struct inode *inode)
{
	struct buffer_head *bh = NULL;
	struct ext2_sb_info *sbi = EXT2_SB(inode->i_sb);

	down_write(&EXT2_I(inode)->xattr_sem);
	if (!EXT2_I(inode)->i_file_acl)
		goto cleanup;

	if (!ext2_data_block_valid(sbi, EXT2_I(inode)->i_file_acl, 0)) {
		ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
			"inode %ld: xattr block %d is out of data blocks range",
			inode->i_ino, EXT2_I(inode)->i_file_acl);
		goto cleanup;
	}

	bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
	if (!bh) {
		ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
			"inode %ld: block %d read error", inode->i_ino,
			EXT2_I(inode)->i_file_acl);
		goto cleanup;
	}
	ea_bdebug(bh, "b_count=%d", atomic_read(&(bh->b_count)));
	if (!ext2_xattr_header_valid(HDR(bh))) {
		ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
			"inode %ld: bad block %d", inode->i_ino,
			EXT2_I(inode)->i_file_acl);
		goto cleanup;
	}
	lock_buffer(bh);
	if (HDR(bh)->h_refcount == cpu_to_le32(1)) {
		__u32 hash = le32_to_cpu(HDR(bh)->h_hash);

		/*
		 * This must happen under buffer lock for ext2_xattr_set2() to
		 * reliably detect freed block
		 */
		mb_cache_entry_delete(EA_BLOCK_CACHE(inode), hash,
				      bh->b_blocknr);
		ext2_free_blocks(inode, EXT2_I(inode)->i_file_acl, 1);
		get_bh(bh);
		bforget(bh);
		unlock_buffer(bh);
	} else {
		le32_add_cpu(&HDR(bh)->h_refcount, -1);
		ea_bdebug(bh, "refcount now=%d",
			le32_to_cpu(HDR(bh)->h_refcount));
		unlock_buffer(bh);
		mark_buffer_dirty(bh);
		if (IS_SYNC(inode))
			sync_dirty_buffer(bh);
		dquot_free_block_nodirty(inode, 1);
	}
	EXT2_I(inode)->i_file_acl = 0;

cleanup:
	brelse(bh);
	up_write(&EXT2_I(inode)->xattr_sem);
}

/*
 * ext2_xattr_cache_insert()
 *
 * Create a new entry in the extended attribute cache, and insert
 * it unless such an entry is already in the cache.
 *
 * Returns 0, or a negative error number on failure.
 */
static int
ext2_xattr_cache_insert(struct mb_cache *cache, struct buffer_head *bh)
{
	__u32 hash = le32_to_cpu(HDR(bh)->h_hash);
	int error;

	error = mb_cache_entry_create(cache, GFP_NOFS, hash, bh->b_blocknr,
				      true);
	if (error) {
		if (error == -EBUSY) {
			ea_bdebug(bh, "already in cache (%d cache entries)",
				atomic_read(&ext2_xattr_cache->c_entry_count));
			error = 0;
		}
	} else
		ea_bdebug(bh, "inserting [%x]", (int)hash);
	return error;
}

/*
 * ext2_xattr_cmp()
 *
 * Compare two extended attribute blocks for equality.
 *
 * Returns 0 if the blocks are equal, 1 if they differ, and
 * a negative error number on errors.
 */
static int
ext2_xattr_cmp(struct ext2_xattr_header *header1,
	       struct ext2_xattr_header *header2)
{
	struct ext2_xattr_entry *entry1, *entry2;

	entry1 = ENTRY(header1+1);
	entry2 = ENTRY(header2+1);
	while (!IS_LAST_ENTRY(entry1)) {
		if (IS_LAST_ENTRY(entry2))
			return 1;
		if (entry1->e_hash != entry2->e_hash ||
		    entry1->e_name_index != entry2->e_name_index ||
		    entry1->e_name_len != entry2->e_name_len ||
		    entry1->e_value_size != entry2->e_value_size ||
		    memcmp(entry1->e_name, entry2->e_name, entry1->e_name_len))
			return 1;
		if (entry1->e_value_block != 0 || entry2->e_value_block != 0)
			return -EIO;
		if (memcmp((char *)header1 + le16_to_cpu(entry1->e_value_offs),
			   (char *)header2 + le16_to_cpu(entry2->e_value_offs),
			   le32_to_cpu(entry1->e_value_size)))
			return 1;

		entry1 = EXT2_XATTR_NEXT(entry1);
		entry2 = EXT2_XATTR_NEXT(entry2);
	}
	if (!IS_LAST_ENTRY(entry2))
		return 1;
	return 0;
}

/*
 * ext2_xattr_cache_find()
 *
 * Find an identical extended attribute block.
 *
 * Returns a locked buffer head to the block found, or NULL if such
 * a block was not found or an error occurred.
 */
static struct buffer_head *
ext2_xattr_cache_find(struct inode *inode, struct ext2_xattr_header *header)
{
	__u32 hash = le32_to_cpu(header->h_hash);
	struct mb_cache_entry *ce;
	struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);

	if (!header->h_hash)
		return NULL;  /* never share */
	ea_idebug(inode, "looking for cached blocks [%x]", (int)hash);
again:
	ce = mb_cache_entry_find_first(ea_block_cache, hash);
	while (ce) {
		struct buffer_head *bh;

		bh = sb_bread(inode->i_sb, ce->e_value);
		if (!bh) {
			ext2_error(inode->i_sb, "ext2_xattr_cache_find",
				"inode %ld: block %ld read error",
				inode->i_ino, (unsigned long) ce->e_value);
		} else {
			lock_buffer(bh);
			/*
			 * We have to be careful about races with freeing or
			 * rehashing of xattr block. Once we hold buffer lock
			 * xattr block's state is stable so we can check
			 * whether the block got freed / rehashed or not.
			 * Since we unhash mbcache entry under buffer lock when
			 * freeing / rehashing xattr block, checking whether
			 * entry is still hashed is reliable.
			 */
			if (hlist_bl_unhashed(&ce->e_hash_list)) {
				mb_cache_entry_put(ea_block_cache, ce);
				unlock_buffer(bh);
				brelse(bh);
				goto again;
			} else if (le32_to_cpu(HDR(bh)->h_refcount) >
				   EXT2_XATTR_REFCOUNT_MAX) {
				ea_idebug(inode, "block %ld refcount %d>%d",
					  (unsigned long) ce->e_value,
					  le32_to_cpu(HDR(bh)->h_refcount),
					  EXT2_XATTR_REFCOUNT_MAX);
			} else if (!ext2_xattr_cmp(header, HDR(bh))) {
				ea_bdebug(bh, "b_count=%d",
					  atomic_read(&(bh->b_count)));
				mb_cache_entry_touch(ea_block_cache, ce);
				mb_cache_entry_put(ea_block_cache, ce);
				return bh;
			}
			unlock_buffer(bh);
			brelse(bh);
		}
		ce = mb_cache_entry_find_next(ea_block_cache, ce);
	}
	return NULL;
}

#define NAME_HASH_SHIFT 5
#define VALUE_HASH_SHIFT 16

/*
 * ext2_xattr_hash_entry()
 *
 * Compute the hash of an extended attribute.
 */
static inline void ext2_xattr_hash_entry(struct ext2_xattr_header *header,
					 struct ext2_xattr_entry *entry)
{
	__u32 hash = 0;
	char *name = entry->e_name;
	int n;

	for (n=0; n < entry->e_name_len; n++) {
		hash = (hash << NAME_HASH_SHIFT) ^
		       (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
		       *name++;
	}

	if (entry->e_value_block == 0 && entry->e_value_size != 0) {
		__le32 *value = (__le32 *)((char *)header +
			le16_to_cpu(entry->e_value_offs));
		for (n = (le32_to_cpu(entry->e_value_size) +
		     EXT2_XATTR_ROUND) >> EXT2_XATTR_PAD_BITS; n; n--) {
			hash = (hash << VALUE_HASH_SHIFT) ^
			       (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
			       le32_to_cpu(*value++);
		}
	}
	entry->e_hash = cpu_to_le32(hash);
}

#undef NAME_HASH_SHIFT
#undef VALUE_HASH_SHIFT

#define BLOCK_HASH_SHIFT 16

/*
 * ext2_xattr_rehash()
 *
 * Re-compute the extended attribute hash value after an entry has changed.
 */
static void ext2_xattr_rehash(struct ext2_xattr_header *header,
			      struct ext2_xattr_entry *entry)
{
	struct ext2_xattr_entry *here;
	__u32 hash = 0;
	
	ext2_xattr_hash_entry(header, entry);
	here = ENTRY(header+1);
	while (!IS_LAST_ENTRY(here)) {
		if (!here->e_hash) {
			/* Block is not shared if an entry's hash value == 0 */
			hash = 0;
			break;
		}
		hash = (hash << BLOCK_HASH_SHIFT) ^
		       (hash >> (8*sizeof(hash) - BLOCK_HASH_SHIFT)) ^
		       le32_to_cpu(here->e_hash);
		here = EXT2_XATTR_NEXT(here);
	}
	header->h_hash = cpu_to_le32(hash);
}

#undef BLOCK_HASH_SHIFT

#define HASH_BUCKET_BITS 10

struct mb_cache *ext2_xattr_create_cache(void)
{
	return mb_cache_create(HASH_BUCKET_BITS);
}

void ext2_xattr_destroy_cache(struct mb_cache *cache)
{
	if (cache)
		mb_cache_destroy(cache);
}