1/*
2 * Copyright (c) 2003,2004 Cluster File Systems, Inc, info@clusterfs.com
3 * Written by Alex Tomas <alex@clusterfs.com>
4 *
5 * %Begin-Header%
6 * This file may be redistributed under the terms of the GNU Library
7 * General Public License, version 2.
8 * %End-Header%
9 */
10
11#ifndef _LINUX_EXT3_EXTENTS
12#define _LINUX_EXT3_EXTENTS
13
14/*
15 * ext3_inode has i_block array (total 60 bytes)
16 * first 4 bytes are used to store:
17 *  - tree depth (0 mean there is no tree yet. all extents in the inode)
18 *  - number of alive extents in the inode
19 */
20
21/*
22 * this is extent on-disk structure
23 * it's used at the bottom of the tree
24 */
25struct ext3_extent {
26	__u32	ee_block;	/* first logical block extent covers */
27	__u16	ee_len;		/* number of blocks covered by extent */
28	__u16	ee_start_hi;	/* high 16 bits of physical block */
29	__u32	ee_start;	/* low 32 bigs of physical block */
30};
31
32/*
33 * this is index on-disk structure
34 * it's used at all the levels, but the bottom
35 */
36struct ext3_extent_idx {
37	__u32	ei_block;	/* index covers logical blocks from 'block' */
38	__u32	ei_leaf;	/* pointer to the physical block of the next *
39				 * level. leaf or next index could bet here */
40	__u16	ei_leaf_hi;	/* high 16 bits of physical block */
41	__u16	ei_unused;
42};
43
44/*
45 * each block (leaves and indexes), even inode-stored has header
46 */
47struct ext3_extent_header {
48	__u16	eh_magic;	/* probably will support different formats */
49	__u16	eh_entries;	/* number of valid entries */
50	__u16	eh_max;		/* capacity of store in entries */
51	__u16	eh_depth;	/* has tree real underlaying blocks? */
52	__u32	eh_generation;	/* generation of the tree */
53};
54
55#define EXT3_EXT_MAGIC		0xf30a
56
57/*
58 * array of ext3_ext_path contains path to some extent
59 * creation/lookup routines use it for traversal/splitting/etc
60 * truncate uses it to simulate recursive walking
61 */
62struct ext3_ext_path {
63	__u32				p_block;
64	__u16				p_depth;
65	struct ext3_extent		*p_ext;
66	struct ext3_extent_idx		*p_idx;
67	struct ext3_extent_header	*p_hdr;
68	struct buffer_head		*p_bh;
69};
70
71/*
72 * EXT_INIT_MAX_LEN is the maximum number of blocks we can have in an
73 * initialized extent. This is 2^15 and not (2^16 - 1), since we use the
74 * MSB of ee_len field in the extent datastructure to signify if this
75 * particular extent is an initialized extent or an uninitialized (i.e.
76 * preallocated).
77 * EXT_UNINIT_MAX_LEN is the maximum number of blocks we can have in an
78 * uninitialized extent.
79 * If ee_len is <= 0x8000, it is an initialized extent. Otherwise, it is an
80 * uninitialized one. In other words, if MSB of ee_len is set, it is an
81 * uninitialized extent with only one special scenario when ee_len = 0x8000.
82 * In this case we can not have an uninitialized extent of zero length and
83 * thus we make it as a special case of initialized extent with 0x8000 length.
84 * This way we get better extent-to-group alignment for initialized extents.
85 * Hence, the maximum number of blocks we can have in an *initialized*
86 * extent is 2^15 (32768) and in an *uninitialized* extent is 2^15-1 (32767).
87 */
88#define EXT_INIT_MAX_LEN	(1UL << 15)
89#define EXT_UNINIT_MAX_LEN	(EXT_INIT_MAX_LEN - 1)
90
91#define EXT_FIRST_EXTENT(__hdr__) \
92	((struct ext3_extent *) (((char *) (__hdr__)) +		\
93				 sizeof(struct ext3_extent_header)))
94#define EXT_FIRST_INDEX(__hdr__) \
95	((struct ext3_extent_idx *) (((char *) (__hdr__)) +	\
96				     sizeof(struct ext3_extent_header)))
97#define EXT_HAS_FREE_INDEX(__path__) \
98	((__path__)->p_hdr->eh_entries < (__path__)->p_hdr->eh_max)
99#define EXT_LAST_EXTENT(__hdr__) \
100	(EXT_FIRST_EXTENT((__hdr__)) + (__hdr__)->eh_entries - 1)
101#define EXT_LAST_INDEX(__hdr__) \
102	(EXT_FIRST_INDEX((__hdr__)) + (__hdr__)->eh_entries - 1)
103#define EXT_MAX_EXTENT(__hdr__) \
104	(EXT_FIRST_EXTENT((__hdr__)) + (__hdr__)->eh_max - 1)
105#define EXT_MAX_INDEX(__hdr__) \
106	(EXT_FIRST_INDEX((__hdr__)) + (__hdr__)->eh_max - 1)
107
108#endif /* _LINUX_EXT3_EXTENTS */
109
110