summaryrefslogtreecommitdiff
path: root/fs/xfs/xfs_da_format.h
blob: aeca0038a013689f7f160fcda349f7882d2a8d60 (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
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
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
/*
 * Copyright (c) 2000-2001,2005 Silicon Graphics, Inc.
 * Copyright (c) 2013 Red Hat, Inc.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#ifndef __XFS_DA_FORMAT_H__
#define __XFS_DA_FORMAT_H__

/*========================================================================
 * Directory Structure when greater than XFS_LBSIZE(mp) bytes.
 *========================================================================*/

/*
 * This structure is common to both leaf nodes and non-leaf nodes in the Btree.
 *
 * It is used to manage a doubly linked list of all blocks at the same
 * level in the Btree, and to identify which type of block this is.
 */
#define XFS_DA_NODE_MAGIC	0xfebe	/* magic number: non-leaf blocks */
#define XFS_ATTR_LEAF_MAGIC	0xfbee	/* magic number: attribute leaf blks */
#define	XFS_DIR2_LEAF1_MAGIC	0xd2f1	/* magic number: v2 dirlf single blks */
#define	XFS_DIR2_LEAFN_MAGIC	0xd2ff	/* magic number: v2 dirlf multi blks */

typedef struct xfs_da_blkinfo {
	__be32		forw;			/* previous block in list */
	__be32		back;			/* following block in list */
	__be16		magic;			/* validity check on block */
	__be16		pad;			/* unused */
} xfs_da_blkinfo_t;

/*
 * CRC enabled directory structure types
 *
 * The headers change size for the additional verification information, but
 * otherwise the tree layouts and contents are unchanged. Hence the da btree
 * code can use the struct xfs_da_blkinfo for manipulating the tree links and
 * magic numbers without modification for both v2 and v3 nodes.
 */
#define XFS_DA3_NODE_MAGIC	0x3ebe	/* magic number: non-leaf blocks */
#define XFS_ATTR3_LEAF_MAGIC	0x3bee	/* magic number: attribute leaf blks */
#define	XFS_DIR3_LEAF1_MAGIC	0x3df1	/* magic number: v2 dirlf single blks */
#define	XFS_DIR3_LEAFN_MAGIC	0x3dff	/* magic number: v2 dirlf multi blks */

struct xfs_da3_blkinfo {
	/*
	 * the node link manipulation code relies on the fact that the first
	 * element of this structure is the struct xfs_da_blkinfo so it can
	 * ignore the differences in the rest of the structures.
	 */
	struct xfs_da_blkinfo	hdr;
	__be32			crc;	/* CRC of block */
	__be64			blkno;	/* first block of the buffer */
	__be64			lsn;	/* sequence number of last write */
	uuid_t			uuid;	/* filesystem we belong to */
	__be64			owner;	/* inode that owns the block */
};

/*
 * This is the structure of the root and intermediate nodes in the Btree.
 * The leaf nodes are defined above.
 *
 * Entries are not packed.
 *
 * Since we have duplicate keys, use a binary search but always follow
 * all match in the block, not just the first match found.
 */
#define	XFS_DA_NODE_MAXDEPTH	5	/* max depth of Btree */

typedef struct xfs_da_node_hdr {
	struct xfs_da_blkinfo	info;	/* block type, links, etc. */
	__be16			__count; /* count of active entries */
	__be16			__level; /* level above leaves (leaf == 0) */
} xfs_da_node_hdr_t;

struct xfs_da3_node_hdr {
	struct xfs_da3_blkinfo	info;	/* block type, links, etc. */
	__be16			__count; /* count of active entries */
	__be16			__level; /* level above leaves (leaf == 0) */
	__be32			__pad32;
};

#define XFS_DA3_NODE_CRC_OFF	(offsetof(struct xfs_da3_node_hdr, info.crc))

typedef struct xfs_da_node_entry {
	__be32	hashval;	/* hash value for this descendant */
	__be32	before;		/* Btree block before this key */
} xfs_da_node_entry_t;

typedef struct xfs_da_intnode {
	struct xfs_da_node_hdr	hdr;
	struct xfs_da_node_entry __btree[];
} xfs_da_intnode_t;

struct xfs_da3_intnode {
	struct xfs_da3_node_hdr	hdr;
	struct xfs_da_node_entry __btree[];
};

/*
 * In-core version of the node header to abstract the differences in the v2 and
 * v3 disk format of the headers. Callers need to convert to/from disk format as
 * appropriate.
 */
struct xfs_da3_icnode_hdr {
	__uint32_t	forw;
	__uint32_t	back;
	__uint16_t	magic;
	__uint16_t	count;
	__uint16_t	level;
};

extern void xfs_da3_node_hdr_from_disk(struct xfs_da3_icnode_hdr *to,
				       struct xfs_da_intnode *from);
extern void xfs_da3_node_hdr_to_disk(struct xfs_da_intnode *to,
				     struct xfs_da3_icnode_hdr *from);

static inline int
__xfs_da3_node_hdr_size(bool v3)
{
	if (v3)
		return sizeof(struct xfs_da3_node_hdr);
	return sizeof(struct xfs_da_node_hdr);
}
static inline int
xfs_da3_node_hdr_size(struct xfs_da_intnode *dap)
{
	bool	v3 = dap->hdr.info.magic == cpu_to_be16(XFS_DA3_NODE_MAGIC);

	return __xfs_da3_node_hdr_size(v3);
}

static inline struct xfs_da_node_entry *
xfs_da3_node_tree_p(struct xfs_da_intnode *dap)
{
	if (dap->hdr.info.magic == cpu_to_be16(XFS_DA3_NODE_MAGIC)) {
		struct xfs_da3_intnode *dap3 = (struct xfs_da3_intnode *)dap;
		return dap3->__btree;
	}
	return dap->__btree;
}

extern void xfs_da3_intnode_from_disk(struct xfs_da3_icnode_hdr *to,
				      struct xfs_da_intnode *from);
extern void xfs_da3_intnode_to_disk(struct xfs_da_intnode *to,
				    struct xfs_da3_icnode_hdr *from);

#define	XFS_LBSIZE(mp)	(mp)->m_sb.sb_blocksize

/*
 * Directory version 2.
 *
 * There are 4 possible formats:
 *  - shortform - embedded into the inode
 *  - single block - data with embedded leaf at the end
 *  - multiple data blocks, single leaf+freeindex block
 *  - data blocks, node and leaf blocks (btree), freeindex blocks
 *
 * Note: many node blocks structures and constants are shared with the attr
 * code and defined in xfs_da_btree.h.
 */

#define	XFS_DIR2_BLOCK_MAGIC	0x58443242	/* XD2B: single block dirs */
#define	XFS_DIR2_DATA_MAGIC	0x58443244	/* XD2D: multiblock dirs */
#define	XFS_DIR2_FREE_MAGIC	0x58443246	/* XD2F: free index blocks */

/*
 * Directory Version 3 With CRCs.
 *
 * The tree formats are the same as for version 2 directories.  The difference
 * is in the block header and dirent formats. In many cases the v3 structures
 * use v2 definitions as they are no different and this makes code sharing much
 * easier.
 *
 * Also, the xfs_dir3_*() functions handle both v2 and v3 formats - if the
 * format is v2 then they switch to the existing v2 code, or the format is v3
 * they implement the v3 functionality. This means the existing dir2 is a mix of
 * xfs_dir2/xfs_dir3 calls and functions. The xfs_dir3 functions are called
 * where there is a difference in the formats, otherwise the code is unchanged.
 *
 * Where it is possible, the code decides what to do based on the magic numbers
 * in the blocks rather than feature bits in the superblock. This means the code
 * is as independent of the external XFS code as possible as doesn't require
 * passing struct xfs_mount pointers into places where it isn't really
 * necessary.
 *
 * Version 3 includes:
 *
 *	- a larger block header for CRC and identification purposes and so the
 *	offsets of all the structures inside the blocks are different.
 *
 *	- new magic numbers to be able to detect the v2/v3 types on the fly.
 */

#define	XFS_DIR3_BLOCK_MAGIC	0x58444233	/* XDB3: single block dirs */
#define	XFS_DIR3_DATA_MAGIC	0x58444433	/* XDD3: multiblock dirs */
#define	XFS_DIR3_FREE_MAGIC	0x58444633	/* XDF3: free index blocks */

/*
 * Dirents in version 3 directories have a file type field. Additions to this
 * list are an on-disk format change, requiring feature bits. Valid values
 * are as follows:
 */
#define XFS_DIR3_FT_UNKNOWN		0
#define XFS_DIR3_FT_REG_FILE		1
#define XFS_DIR3_FT_DIR			2
#define XFS_DIR3_FT_CHRDEV		3
#define XFS_DIR3_FT_BLKDEV		4
#define XFS_DIR3_FT_FIFO		5
#define XFS_DIR3_FT_SOCK		6
#define XFS_DIR3_FT_SYMLINK		7
#define XFS_DIR3_FT_WHT			8

#define XFS_DIR3_FT_MAX			9

/*
 * Byte offset in data block and shortform entry.
 */
typedef	__uint16_t	xfs_dir2_data_off_t;
#define	NULLDATAOFF	0xffffU
typedef uint		xfs_dir2_data_aoff_t;	/* argument form */

/*
 * Normalized offset (in a data block) of the entry, really xfs_dir2_data_off_t.
 * Only need 16 bits, this is the byte offset into the single block form.
 */
typedef struct { __uint8_t i[2]; } __arch_pack xfs_dir2_sf_off_t;

/*
 * Offset in data space of a data entry.
 */
typedef	__uint32_t	xfs_dir2_dataptr_t;
#define	XFS_DIR2_MAX_DATAPTR	((xfs_dir2_dataptr_t)0xffffffff)
#define	XFS_DIR2_NULL_DATAPTR	((xfs_dir2_dataptr_t)0)

/*
 * Byte offset in a directory.
 */
typedef	xfs_off_t	xfs_dir2_off_t;

/*
 * Directory block number (logical dirblk in file)
 */
typedef	__uint32_t	xfs_dir2_db_t;

/*
 * Inode number stored as 8 8-bit values.
 */
typedef	struct { __uint8_t i[8]; } xfs_dir2_ino8_t;

/*
 * Inode number stored as 4 8-bit values.
 * Works a lot of the time, when all the inode numbers in a directory
 * fit in 32 bits.
 */
typedef struct { __uint8_t i[4]; } xfs_dir2_ino4_t;

typedef union {
	xfs_dir2_ino8_t	i8;
	xfs_dir2_ino4_t	i4;
} xfs_dir2_inou_t;
#define	XFS_DIR2_MAX_SHORT_INUM	((xfs_ino_t)0xffffffffULL)

/*
 * Directory layout when stored internal to an inode.
 *
 * Small directories are packed as tightly as possible so as to fit into the
 * literal area of the inode.  These "shortform" directories consist of a
 * single xfs_dir2_sf_hdr header followed by zero or more xfs_dir2_sf_entry
 * structures.  Due the different inode number storage size and the variable
 * length name field in the xfs_dir2_sf_entry all these structure are
 * variable length, and the accessors in this file should be used to iterate
 * over them.
 */
typedef struct xfs_dir2_sf_hdr {
	__uint8_t		count;		/* count of entries */
	__uint8_t		i8count;	/* count of 8-byte inode #s */
	xfs_dir2_inou_t		parent;		/* parent dir inode number */
} __arch_pack xfs_dir2_sf_hdr_t;

typedef struct xfs_dir2_sf_entry {
	__u8			namelen;	/* actual name length */
	xfs_dir2_sf_off_t	offset;		/* saved offset */
	__u8			name[];		/* name, variable size */
	/*
	 * A single byte containing the file type field follows the inode
	 * number for version 3 directory entries.
	 *
	 * A xfs_dir2_ino8_t or xfs_dir2_ino4_t follows here, at a
	 * variable offset after the name.
	 */
} __arch_pack xfs_dir2_sf_entry_t;

static inline int xfs_dir2_sf_hdr_size(int i8count)
{
	return sizeof(struct xfs_dir2_sf_hdr) -
		(i8count == 0) *
		(sizeof(xfs_dir2_ino8_t) - sizeof(xfs_dir2_ino4_t));
}

static inline xfs_dir2_data_aoff_t
xfs_dir2_sf_get_offset(xfs_dir2_sf_entry_t *sfep)
{
	return get_unaligned_be16(&sfep->offset.i);
}

static inline void
xfs_dir2_sf_put_offset(xfs_dir2_sf_entry_t *sfep, xfs_dir2_data_aoff_t off)
{
	put_unaligned_be16(off, &sfep->offset.i);
}

static inline struct xfs_dir2_sf_entry *
xfs_dir2_sf_firstentry(struct xfs_dir2_sf_hdr *hdr)
{
	return (struct xfs_dir2_sf_entry *)
		((char *)hdr + xfs_dir2_sf_hdr_size(hdr->i8count));
}

/*
 * Data block structures.
 *
 * A pure data block looks like the following drawing on disk:
 *
 *    +-------------------------------------------------+
 *    | xfs_dir2_data_hdr_t                             |
 *    +-------------------------------------------------+
 *    | xfs_dir2_data_entry_t OR xfs_dir2_data_unused_t |
 *    | xfs_dir2_data_entry_t OR xfs_dir2_data_unused_t |
 *    | xfs_dir2_data_entry_t OR xfs_dir2_data_unused_t |
 *    | ...                                             |
 *    +-------------------------------------------------+
 *    | unused space                                    |
 *    +-------------------------------------------------+
 *
 * As all the entries are variable size structures the accessors below should
 * be used to iterate over them.
 *
 * In addition to the pure data blocks for the data and node formats,
 * most structures are also used for the combined data/freespace "block"
 * format below.
 */

#define	XFS_DIR2_DATA_ALIGN_LOG	3		/* i.e., 8 bytes */
#define	XFS_DIR2_DATA_ALIGN	(1 << XFS_DIR2_DATA_ALIGN_LOG)
#define	XFS_DIR2_DATA_FREE_TAG	0xffff
#define	XFS_DIR2_DATA_FD_COUNT	3

/*
 * Directory address space divided into sections,
 * spaces separated by 32GB.
 */
#define	XFS_DIR2_SPACE_SIZE	(1ULL << (32 + XFS_DIR2_DATA_ALIGN_LOG))
#define	XFS_DIR2_DATA_SPACE	0
#define	XFS_DIR2_DATA_OFFSET	(XFS_DIR2_DATA_SPACE * XFS_DIR2_SPACE_SIZE)
#define	XFS_DIR2_DATA_FIRSTDB(mp)	\
	xfs_dir2_byte_to_db(mp, XFS_DIR2_DATA_OFFSET)

/*
 * Describe a free area in the data block.
 *
 * The freespace will be formatted as a xfs_dir2_data_unused_t.
 */
typedef struct xfs_dir2_data_free {
	__be16			offset;		/* start of freespace */
	__be16			length;		/* length of freespace */
} xfs_dir2_data_free_t;

/*
 * Header for the data blocks.
 *
 * The code knows that XFS_DIR2_DATA_FD_COUNT is 3.
 */
typedef struct xfs_dir2_data_hdr {
	__be32			magic;		/* XFS_DIR2_DATA_MAGIC or */
						/* XFS_DIR2_BLOCK_MAGIC */
	xfs_dir2_data_free_t	bestfree[XFS_DIR2_DATA_FD_COUNT];
} xfs_dir2_data_hdr_t;

/*
 * define a structure for all the verification fields we are adding to the
 * directory block structures. This will be used in several structures.
 * The magic number must be the first entry to align with all the dir2
 * structures so we determine how to decode them just by the magic number.
 */
struct xfs_dir3_blk_hdr {
	__be32			magic;	/* magic number */
	__be32			crc;	/* CRC of block */
	__be64			blkno;	/* first block of the buffer */
	__be64			lsn;	/* sequence number of last write */
	uuid_t			uuid;	/* filesystem we belong to */
	__be64			owner;	/* inode that owns the block */
};

struct xfs_dir3_data_hdr {
	struct xfs_dir3_blk_hdr	hdr;
	xfs_dir2_data_free_t	best_free[XFS_DIR2_DATA_FD_COUNT];
	__be32			pad;	/* 64 bit alignment */
};

#define XFS_DIR3_DATA_CRC_OFF  offsetof(struct xfs_dir3_data_hdr, hdr.crc)

/*
 * Active entry in a data block.
 *
 * Aligned to 8 bytes.  After the variable length name field there is a
 * 2 byte tag field, which can be accessed using xfs_dir3_data_entry_tag_p.
 *
 * For dir3 structures, there is file type field between the name and the tag.
 * This can only be manipulated by helper functions. It is packed hard against
 * the end of the name so any padding for rounding is between the file type and
 * the tag.
 */
typedef struct xfs_dir2_data_entry {
	__be64			inumber;	/* inode number */
	__u8			namelen;	/* name length */
	__u8			name[];		/* name bytes, no null */
     /* __u8			filetype; */	/* type of inode we point to */
     /*	__be16                  tag; */		/* starting offset of us */
} xfs_dir2_data_entry_t;

/*
 * Unused entry in a data block.
 *
 * Aligned to 8 bytes.  Tag appears as the last 2 bytes and must be accessed
 * using xfs_dir2_data_unused_tag_p.
 */
typedef struct xfs_dir2_data_unused {
	__be16			freetag;	/* XFS_DIR2_DATA_FREE_TAG */
	__be16			length;		/* total free length */
						/* variable offset */
	__be16			tag;		/* starting offset of us */
} xfs_dir2_data_unused_t;

/*
 * Pointer to a freespace's tag word.
 */
static inline __be16 *
xfs_dir2_data_unused_tag_p(struct xfs_dir2_data_unused *dup)
{
	return (__be16 *)((char *)dup +
			be16_to_cpu(dup->length) - sizeof(__be16));
}

/*
 * Leaf block structures.
 *
 * A pure leaf block looks like the following drawing on disk:
 *
 *    +---------------------------+
 *    | xfs_dir2_leaf_hdr_t       |
 *    +---------------------------+
 *    | xfs_dir2_leaf_entry_t     |
 *    | xfs_dir2_leaf_entry_t     |
 *    | xfs_dir2_leaf_entry_t     |
 *    | xfs_dir2_leaf_entry_t     |
 *    | ...                       |
 *    +---------------------------+
 *    | xfs_dir2_data_off_t       |
 *    | xfs_dir2_data_off_t       |
 *    | xfs_dir2_data_off_t       |
 *    | ...                       |
 *    +---------------------------+
 *    | xfs_dir2_leaf_tail_t      |
 *    +---------------------------+
 *
 * The xfs_dir2_data_off_t members (bests) and tail are at the end of the block
 * for single-leaf (magic = XFS_DIR2_LEAF1_MAGIC) blocks only, but not present
 * for directories with separate leaf nodes and free space blocks
 * (magic = XFS_DIR2_LEAFN_MAGIC).
 *
 * As all the entries are variable size structures the accessors below should
 * be used to iterate over them.
 */

/*
 * Offset of the leaf/node space.  First block in this space
 * is the btree root.
 */
#define	XFS_DIR2_LEAF_SPACE	1
#define	XFS_DIR2_LEAF_OFFSET	(XFS_DIR2_LEAF_SPACE * XFS_DIR2_SPACE_SIZE)
#define	XFS_DIR2_LEAF_FIRSTDB(mp)	\
	xfs_dir2_byte_to_db(mp, XFS_DIR2_LEAF_OFFSET)

/*
 * Leaf block header.
 */
typedef struct xfs_dir2_leaf_hdr {
	xfs_da_blkinfo_t	info;		/* header for da routines */
	__be16			count;		/* count of entries */
	__be16			stale;		/* count of stale entries */
} xfs_dir2_leaf_hdr_t;

struct xfs_dir3_leaf_hdr {
	struct xfs_da3_blkinfo	info;		/* header for da routines */
	__be16			count;		/* count of entries */
	__be16			stale;		/* count of stale entries */
	__be32			pad;		/* 64 bit alignment */
};

struct xfs_dir3_icleaf_hdr {
	__uint32_t		forw;
	__uint32_t		back;
	__uint16_t		magic;
	__uint16_t		count;
	__uint16_t		stale;
};

/*
 * Leaf block entry.
 */
typedef struct xfs_dir2_leaf_entry {
	__be32			hashval;	/* hash value of name */
	__be32			address;	/* address of data entry */
} xfs_dir2_leaf_entry_t;

/*
 * Leaf block tail.
 */
typedef struct xfs_dir2_leaf_tail {
	__be32			bestcount;
} xfs_dir2_leaf_tail_t;

/*
 * Leaf block.
 */
typedef struct xfs_dir2_leaf {
	xfs_dir2_leaf_hdr_t	hdr;			/* leaf header */
	xfs_dir2_leaf_entry_t	__ents[];		/* entries */
} xfs_dir2_leaf_t;

struct xfs_dir3_leaf {
	struct xfs_dir3_leaf_hdr	hdr;		/* leaf header */
	struct xfs_dir2_leaf_entry	__ents[];	/* entries */
};

#define XFS_DIR3_LEAF_CRC_OFF  offsetof(struct xfs_dir3_leaf_hdr, info.crc)

extern void xfs_dir3_leaf_hdr_from_disk(struct xfs_dir3_icleaf_hdr *to,
					struct xfs_dir2_leaf *from);

static inline int
xfs_dir3_leaf_hdr_size(struct xfs_dir2_leaf *lp)
{
	if (lp->hdr.info.magic == cpu_to_be16(XFS_DIR3_LEAF1_MAGIC) ||
	    lp->hdr.info.magic == cpu_to_be16(XFS_DIR3_LEAFN_MAGIC))
		return sizeof(struct xfs_dir3_leaf_hdr);
	return sizeof(struct xfs_dir2_leaf_hdr);
}

static inline int
xfs_dir3_max_leaf_ents(struct xfs_mount *mp, struct xfs_dir2_leaf *lp)
{
	return (mp->m_dirblksize - xfs_dir3_leaf_hdr_size(lp)) /
		(uint)sizeof(struct xfs_dir2_leaf_entry);
}

/*
 * Get address of the bestcount field in the single-leaf block.
 */
static inline struct xfs_dir2_leaf_entry *
xfs_dir3_leaf_ents_p(struct xfs_dir2_leaf *lp)
{
	if (lp->hdr.info.magic == cpu_to_be16(XFS_DIR3_LEAF1_MAGIC) ||
	    lp->hdr.info.magic == cpu_to_be16(XFS_DIR3_LEAFN_MAGIC)) {
		struct xfs_dir3_leaf *lp3 = (struct xfs_dir3_leaf *)lp;
		return lp3->__ents;
	}
	return lp->__ents;
}

/*
 * Get address of the bestcount field in the single-leaf block.
 */
static inline struct xfs_dir2_leaf_tail *
xfs_dir2_leaf_tail_p(struct xfs_mount *mp, struct xfs_dir2_leaf *lp)
{
	return (struct xfs_dir2_leaf_tail *)
		((char *)lp + mp->m_dirblksize -
		  sizeof(struct xfs_dir2_leaf_tail));
}

/*
 * Get address of the bests array in the single-leaf block.
 */
static inline __be16 *
xfs_dir2_leaf_bests_p(struct xfs_dir2_leaf_tail *ltp)
{
	return (__be16 *)ltp - be32_to_cpu(ltp->bestcount);
}

/*
 * DB blocks here are logical directory block numbers, not filesystem blocks.
 */

/*
 * Convert dataptr to byte in file space
 */
static inline xfs_dir2_off_t
xfs_dir2_dataptr_to_byte(struct xfs_mount *mp, xfs_dir2_dataptr_t dp)
{
	return (xfs_dir2_off_t)dp << XFS_DIR2_DATA_ALIGN_LOG;
}

/*
 * Convert byte in file space to dataptr.  It had better be aligned.
 */
static inline xfs_dir2_dataptr_t
xfs_dir2_byte_to_dataptr(struct xfs_mount *mp, xfs_dir2_off_t by)
{
	return (xfs_dir2_dataptr_t)(by >> XFS_DIR2_DATA_ALIGN_LOG);
}

/*
 * Convert byte in space to (DB) block
 */
static inline xfs_dir2_db_t
xfs_dir2_byte_to_db(struct xfs_mount *mp, xfs_dir2_off_t by)
{
	return (xfs_dir2_db_t)
		(by >> (mp->m_sb.sb_blocklog + mp->m_sb.sb_dirblklog));
}

/*
 * Convert dataptr to a block number
 */
static inline xfs_dir2_db_t
xfs_dir2_dataptr_to_db(struct xfs_mount *mp, xfs_dir2_dataptr_t dp)
{
	return xfs_dir2_byte_to_db(mp, xfs_dir2_dataptr_to_byte(mp, dp));
}

/*
 * Convert byte in space to offset in a block
 */
static inline xfs_dir2_data_aoff_t
xfs_dir2_byte_to_off(struct xfs_mount *mp, xfs_dir2_off_t by)
{
	return (xfs_dir2_data_aoff_t)(by &
		((1 << (mp->m_sb.sb_blocklog + mp->m_sb.sb_dirblklog)) - 1));
}

/*
 * Convert dataptr to a byte offset in a block
 */
static inline xfs_dir2_data_aoff_t
xfs_dir2_dataptr_to_off(struct xfs_mount *mp, xfs_dir2_dataptr_t dp)
{
	return xfs_dir2_byte_to_off(mp, xfs_dir2_dataptr_to_byte(mp, dp));
}

/*
 * Convert block and offset to byte in space
 */
static inline xfs_dir2_off_t
xfs_dir2_db_off_to_byte(struct xfs_mount *mp, xfs_dir2_db_t db,
			xfs_dir2_data_aoff_t o)
{
	return ((xfs_dir2_off_t)db <<
		(mp->m_sb.sb_blocklog + mp->m_sb.sb_dirblklog)) + o;
}

/*
 * Convert block (DB) to block (dablk)
 */
static inline xfs_dablk_t
xfs_dir2_db_to_da(struct xfs_mount *mp, xfs_dir2_db_t db)
{
	return (xfs_dablk_t)(db << mp->m_sb.sb_dirblklog);
}

/*
 * Convert byte in space to (DA) block
 */
static inline xfs_dablk_t
xfs_dir2_byte_to_da(struct xfs_mount *mp, xfs_dir2_off_t by)
{
	return xfs_dir2_db_to_da(mp, xfs_dir2_byte_to_db(mp, by));
}

/*
 * Convert block and offset to dataptr
 */
static inline xfs_dir2_dataptr_t
xfs_dir2_db_off_to_dataptr(struct xfs_mount *mp, xfs_dir2_db_t db,
			   xfs_dir2_data_aoff_t o)
{
	return xfs_dir2_byte_to_dataptr(mp, xfs_dir2_db_off_to_byte(mp, db, o));
}

/*
 * Convert block (dablk) to block (DB)
 */
static inline xfs_dir2_db_t
xfs_dir2_da_to_db(struct xfs_mount *mp, xfs_dablk_t da)
{
	return (xfs_dir2_db_t)(da >> mp->m_sb.sb_dirblklog);
}

/*
 * Convert block (dablk) to byte offset in space
 */
static inline xfs_dir2_off_t
xfs_dir2_da_to_byte(struct xfs_mount *mp, xfs_dablk_t da)
{
	return xfs_dir2_db_off_to_byte(mp, xfs_dir2_da_to_db(mp, da), 0);
}

/*
 * Free space block defintions for the node format.
 */

/*
 * Offset of the freespace index.
 */
#define	XFS_DIR2_FREE_SPACE	2
#define	XFS_DIR2_FREE_OFFSET	(XFS_DIR2_FREE_SPACE * XFS_DIR2_SPACE_SIZE)
#define	XFS_DIR2_FREE_FIRSTDB(mp)	\
	xfs_dir2_byte_to_db(mp, XFS_DIR2_FREE_OFFSET)

typedef	struct xfs_dir2_free_hdr {
	__be32			magic;		/* XFS_DIR2_FREE_MAGIC */
	__be32			firstdb;	/* db of first entry */
	__be32			nvalid;		/* count of valid entries */
	__be32			nused;		/* count of used entries */
} xfs_dir2_free_hdr_t;

typedef struct xfs_dir2_free {
	xfs_dir2_free_hdr_t	hdr;		/* block header */
	__be16			bests[];	/* best free counts */
						/* unused entries are -1 */
} xfs_dir2_free_t;

struct xfs_dir3_free_hdr {
	struct xfs_dir3_blk_hdr	hdr;
	__be32			firstdb;	/* db of first entry */
	__be32			nvalid;		/* count of valid entries */
	__be32			nused;		/* count of used entries */
	__be32			pad;		/* 64 bit alignment */
};

struct xfs_dir3_free {
	struct xfs_dir3_free_hdr hdr;
	__be16			bests[];	/* best free counts */
						/* unused entries are -1 */
};

#define XFS_DIR3_FREE_CRC_OFF  offsetof(struct xfs_dir3_free, hdr.hdr.crc)

/*
 * In core version of the free block header, abstracted away from on-disk format
 * differences. Use this in the code, and convert to/from the disk version using
 * xfs_dir3_free_hdr_from_disk/xfs_dir3_free_hdr_to_disk.
 */
struct xfs_dir3_icfree_hdr {
	__uint32_t	magic;
	__uint32_t	firstdb;
	__uint32_t	nvalid;
	__uint32_t	nused;

};

void xfs_dir3_free_hdr_from_disk(struct xfs_dir3_icfree_hdr *to,
				 struct xfs_dir2_free *from);

static inline int
xfs_dir3_free_hdr_size(struct xfs_mount *mp)
{
	if (xfs_sb_version_hascrc(&mp->m_sb))
		return sizeof(struct xfs_dir3_free_hdr);
	return sizeof(struct xfs_dir2_free_hdr);
}

static inline int
xfs_dir3_free_max_bests(struct xfs_mount *mp)
{
	return (mp->m_dirblksize - xfs_dir3_free_hdr_size(mp)) /
		sizeof(xfs_dir2_data_off_t);
}

static inline __be16 *
xfs_dir3_free_bests_p(struct xfs_mount *mp, struct xfs_dir2_free *free)
{
	return (__be16 *)((char *)free + xfs_dir3_free_hdr_size(mp));
}

/*
 * Convert data space db to the corresponding free db.
 */
static inline xfs_dir2_db_t
xfs_dir2_db_to_fdb(struct xfs_mount *mp, xfs_dir2_db_t db)
{
	return XFS_DIR2_FREE_FIRSTDB(mp) + db / xfs_dir3_free_max_bests(mp);
}

/*
 * Convert data space db to the corresponding index in a free db.
 */
static inline int
xfs_dir2_db_to_fdindex(struct xfs_mount *mp, xfs_dir2_db_t db)
{
	return db % xfs_dir3_free_max_bests(mp);
}

/*
 * Single block format.
 *
 * The single block format looks like the following drawing on disk:
 *
 *    +-------------------------------------------------+
 *    | xfs_dir2_data_hdr_t                             |
 *    +-------------------------------------------------+
 *    | xfs_dir2_data_entry_t OR xfs_dir2_data_unused_t |
 *    | xfs_dir2_data_entry_t OR xfs_dir2_data_unused_t |
 *    | xfs_dir2_data_entry_t OR xfs_dir2_data_unused_t :
 *    | ...                                             |
 *    +-------------------------------------------------+
 *    | unused space                                    |
 *    +-------------------------------------------------+
 *    | ...                                             |
 *    | xfs_dir2_leaf_entry_t                           |
 *    | xfs_dir2_leaf_entry_t                           |
 *    +-------------------------------------------------+
 *    | xfs_dir2_block_tail_t                           |
 *    +-------------------------------------------------+
 *
 * As all the entries are variable size structures the accessors below should
 * be used to iterate over them.
 */

typedef struct xfs_dir2_block_tail {
	__be32		count;			/* count of leaf entries */
	__be32		stale;			/* count of stale lf entries */
} xfs_dir2_block_tail_t;

/*
 * Pointer to the leaf header embedded in a data block (1-block format)
 */
static inline struct xfs_dir2_block_tail *
xfs_dir2_block_tail_p(struct xfs_mount *mp, struct xfs_dir2_data_hdr *hdr)
{
	return ((struct xfs_dir2_block_tail *)
		((char *)hdr + mp->m_dirblksize)) - 1;
}

/*
 * Pointer to the leaf entries embedded in a data block (1-block format)
 */
static inline struct xfs_dir2_leaf_entry *
xfs_dir2_block_leaf_p(struct xfs_dir2_block_tail *btp)
{
	return ((struct xfs_dir2_leaf_entry *)btp) - be32_to_cpu(btp->count);
}


/*
 * Attribute storage layout
 *
 * Attribute lists are structured around Btrees where all the data
 * elements are in the leaf nodes.  Attribute names are hashed into an int,
 * then that int is used as the index into the Btree.  Since the hashval
 * of an attribute name may not be unique, we may have duplicate keys.  The
 * internal links in the Btree are logical block offsets into the file.
 *
 *========================================================================
 * Attribute structure when equal to XFS_LBSIZE(mp) bytes.
 *========================================================================
 *
 * Struct leaf_entry's are packed from the top.  Name/values grow from the
 * bottom but are not packed.  The freemap contains run-length-encoded entries
 * for the free bytes after the leaf_entry's, but only the N largest such,
 * smaller runs are dropped.  When the freemap doesn't show enough space
 * for an allocation, we compact the name/value area and try again.  If we
 * still don't have enough space, then we have to split the block.  The
 * name/value structs (both local and remote versions) must be 32bit aligned.
 *
 * Since we have duplicate hash keys, for each key that matches, compare
 * the actual name string.  The root and intermediate node search always
 * takes the first-in-the-block key match found, so we should only have
 * to work "forw"ard.  If none matches, continue with the "forw"ard leaf
 * nodes until the hash key changes or the attribute name is found.
 *
 * We store the fact that an attribute is a ROOT/USER/SECURE attribute in
 * the leaf_entry.  The namespaces are independent only because we also look
 * at the namespace bit when we are looking for a matching attribute name.
 *
 * We also store an "incomplete" bit in the leaf_entry.  It shows that an
 * attribute is in the middle of being created and should not be shown to
 * the user if we crash during the time that the bit is set.  We clear the
 * bit when we have finished setting up the attribute.  We do this because
 * we cannot create some large attributes inside a single transaction, and we
 * need some indication that we weren't finished if we crash in the middle.
 */
#define XFS_ATTR_LEAF_MAPSIZE	3	/* how many freespace slots */

typedef struct xfs_attr_leaf_map {	/* RLE map of free bytes */
	__be16	base;			  /* base of free region */
	__be16	size;			  /* length of free region */
} xfs_attr_leaf_map_t;

typedef struct xfs_attr_leaf_hdr {	/* constant-structure header block */
	xfs_da_blkinfo_t info;		/* block type, links, etc. */
	__be16	count;			/* count of active leaf_entry's */
	__be16	usedbytes;		/* num bytes of names/values stored */
	__be16	firstused;		/* first used byte in name area */
	__u8	holes;			/* != 0 if blk needs compaction */
	__u8	pad1;
	xfs_attr_leaf_map_t freemap[XFS_ATTR_LEAF_MAPSIZE];
					/* N largest free regions */
} xfs_attr_leaf_hdr_t;

typedef struct xfs_attr_leaf_entry {	/* sorted on key, not name */
	__be32	hashval;		/* hash value of name */
	__be16	nameidx;		/* index into buffer of name/value */
	__u8	flags;			/* LOCAL/ROOT/SECURE/INCOMPLETE flag */
	__u8	pad2;			/* unused pad byte */
} xfs_attr_leaf_entry_t;

typedef struct xfs_attr_leaf_name_local {
	__be16	valuelen;		/* number of bytes in value */
	__u8	namelen;		/* length of name bytes */
	__u8	nameval[1];		/* name/value bytes */
} xfs_attr_leaf_name_local_t;

typedef struct xfs_attr_leaf_name_remote {
	__be32	valueblk;		/* block number of value bytes */
	__be32	valuelen;		/* number of bytes in value */
	__u8	namelen;		/* length of name bytes */
	__u8	name[1];		/* name bytes */
} xfs_attr_leaf_name_remote_t;

typedef struct xfs_attr_leafblock {
	xfs_attr_leaf_hdr_t	hdr;	/* constant-structure header block */
	xfs_attr_leaf_entry_t	entries[1];	/* sorted on key, not name */
	xfs_attr_leaf_name_local_t namelist;	/* grows from bottom of buf */
	xfs_attr_leaf_name_remote_t valuelist;	/* grows from bottom of buf */
} xfs_attr_leafblock_t;

/*
 * CRC enabled leaf structures. Called "version 3" structures to match the
 * version number of the directory and dablk structures for this feature, and
 * attr2 is already taken by the variable inode attribute fork size feature.
 */
struct xfs_attr3_leaf_hdr {
	struct xfs_da3_blkinfo	info;
	__be16			count;
	__be16			usedbytes;
	__be16			firstused;
	__u8			holes;
	__u8			pad1;
	struct xfs_attr_leaf_map freemap[XFS_ATTR_LEAF_MAPSIZE];
	__be32			pad2;		/* 64 bit alignment */
};

#define XFS_ATTR3_LEAF_CRC_OFF	(offsetof(struct xfs_attr3_leaf_hdr, info.crc))

struct xfs_attr3_leafblock {
	struct xfs_attr3_leaf_hdr	hdr;
	struct xfs_attr_leaf_entry	entries[1];

	/*
	 * The rest of the block contains the following structures after the
	 * leaf entries, growing from the bottom up. The variables are never
	 * referenced, the locations accessed purely from helper functions.
	 *
	 * struct xfs_attr_leaf_name_local
	 * struct xfs_attr_leaf_name_remote
	 */
};

/*
 * incore, neutral version of the attribute leaf header
 */
struct xfs_attr3_icleaf_hdr {
	__uint32_t	forw;
	__uint32_t	back;
	__uint16_t	magic;
	__uint16_t	count;
	__uint16_t	usedbytes;
	__uint16_t	firstused;
	__u8		holes;
	struct {
		__uint16_t	base;
		__uint16_t	size;
	} freemap[XFS_ATTR_LEAF_MAPSIZE];
};

/*
 * Flags used in the leaf_entry[i].flags field.
 * NOTE: the INCOMPLETE bit must not collide with the flags bits specified
 * on the system call, they are "or"ed together for various operations.
 */
#define	XFS_ATTR_LOCAL_BIT	0	/* attr is stored locally */
#define	XFS_ATTR_ROOT_BIT	1	/* limit access to trusted attrs */
#define	XFS_ATTR_SECURE_BIT	2	/* limit access to secure attrs */
#define	XFS_ATTR_INCOMPLETE_BIT	7	/* attr in middle of create/delete */
#define XFS_ATTR_LOCAL		(1 << XFS_ATTR_LOCAL_BIT)
#define XFS_ATTR_ROOT		(1 << XFS_ATTR_ROOT_BIT)
#define XFS_ATTR_SECURE		(1 << XFS_ATTR_SECURE_BIT)
#define XFS_ATTR_INCOMPLETE	(1 << XFS_ATTR_INCOMPLETE_BIT)

/*
 * Conversion macros for converting namespace bits from argument flags
 * to ondisk flags.
 */
#define XFS_ATTR_NSP_ARGS_MASK		(ATTR_ROOT | ATTR_SECURE)
#define XFS_ATTR_NSP_ONDISK_MASK	(XFS_ATTR_ROOT | XFS_ATTR_SECURE)
#define XFS_ATTR_NSP_ONDISK(flags)	((flags) & XFS_ATTR_NSP_ONDISK_MASK)
#define XFS_ATTR_NSP_ARGS(flags)	((flags) & XFS_ATTR_NSP_ARGS_MASK)
#define XFS_ATTR_NSP_ARGS_TO_ONDISK(x)	(((x) & ATTR_ROOT ? XFS_ATTR_ROOT : 0) |\
					 ((x) & ATTR_SECURE ? XFS_ATTR_SECURE : 0))
#define XFS_ATTR_NSP_ONDISK_TO_ARGS(x)	(((x) & XFS_ATTR_ROOT ? ATTR_ROOT : 0) |\
					 ((x) & XFS_ATTR_SECURE ? ATTR_SECURE : 0))

/*
 * Alignment for namelist and valuelist entries (since they are mixed
 * there can be only one alignment value)
 */
#define	XFS_ATTR_LEAF_NAME_ALIGN	((uint)sizeof(xfs_dablk_t))

static inline int
xfs_attr3_leaf_hdr_size(struct xfs_attr_leafblock *leafp)
{
	if (leafp->hdr.info.magic == cpu_to_be16(XFS_ATTR3_LEAF_MAGIC))
		return sizeof(struct xfs_attr3_leaf_hdr);
	return sizeof(struct xfs_attr_leaf_hdr);
}

static inline struct xfs_attr_leaf_entry *
xfs_attr3_leaf_entryp(xfs_attr_leafblock_t *leafp)
{
	if (leafp->hdr.info.magic == cpu_to_be16(XFS_ATTR3_LEAF_MAGIC))
		return &((struct xfs_attr3_leafblock *)leafp)->entries[0];
	return &leafp->entries[0];
}

/*
 * Cast typed pointers for "local" and "remote" name/value structs.
 */
static inline char *
xfs_attr3_leaf_name(xfs_attr_leafblock_t *leafp, int idx)
{
	struct xfs_attr_leaf_entry *entries = xfs_attr3_leaf_entryp(leafp);

	return &((char *)leafp)[be16_to_cpu(entries[idx].nameidx)];
}

static inline xfs_attr_leaf_name_remote_t *
xfs_attr3_leaf_name_remote(xfs_attr_leafblock_t *leafp, int idx)
{
	return (xfs_attr_leaf_name_remote_t *)xfs_attr3_leaf_name(leafp, idx);
}

static inline xfs_attr_leaf_name_local_t *
xfs_attr3_leaf_name_local(xfs_attr_leafblock_t *leafp, int idx)
{
	return (xfs_attr_leaf_name_local_t *)xfs_attr3_leaf_name(leafp, idx);
}

/*
 * Calculate total bytes used (including trailing pad for alignment) for
 * a "local" name/value structure, a "remote" name/value structure, and
 * a pointer which might be either.
 */
static inline int xfs_attr_leaf_entsize_remote(int nlen)
{
	return ((uint)sizeof(xfs_attr_leaf_name_remote_t) - 1 + (nlen) + \
		XFS_ATTR_LEAF_NAME_ALIGN - 1) & ~(XFS_ATTR_LEAF_NAME_ALIGN - 1);
}

static inline int xfs_attr_leaf_entsize_local(int nlen, int vlen)
{
	return ((uint)sizeof(xfs_attr_leaf_name_local_t) - 1 + (nlen) + (vlen) +
		XFS_ATTR_LEAF_NAME_ALIGN - 1) & ~(XFS_ATTR_LEAF_NAME_ALIGN - 1);
}

static inline int xfs_attr_leaf_entsize_local_max(int bsize)
{
	return (((bsize) >> 1) + ((bsize) >> 2));
}



/*
 * Remote attribute block format definition
 *
 * There is one of these headers per filesystem block in a remote attribute.
 * This is done to ensure there is a 1:1 mapping between the attribute value
 * length and the number of blocks needed to store the attribute. This makes the
 * verification of a buffer a little more complex, but greatly simplifies the
 * allocation, reading and writing of these attributes as we don't have to guess
 * the number of blocks needed to store the attribute data.
 */
#define XFS_ATTR3_RMT_MAGIC	0x5841524d	/* XARM */

struct xfs_attr3_rmt_hdr {
	__be32	rm_magic;
	__be32	rm_offset;
	__be32	rm_bytes;
	__be32	rm_crc;
	uuid_t	rm_uuid;
	__be64	rm_owner;
	__be64	rm_blkno;
	__be64	rm_lsn;
};

#define XFS_ATTR3_RMT_CRC_OFF	offsetof(struct xfs_attr3_rmt_hdr, rm_crc)

#define XFS_ATTR3_RMT_BUF_SPACE(mp, bufsize)	\
	((bufsize) - (xfs_sb_version_hascrc(&(mp)->m_sb) ? \
			sizeof(struct xfs_attr3_rmt_hdr) : 0))

#endif /* __XFS_DA_FORMAT_H__ */