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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 tail on-disk structure.
23  * All other extent structures are 12 bytes long.  It turns out that
24  * block_size % 12 >= 4 for at least all powers of 2 greater than 512, which
25  * covers all valid ext4 block sizes.  Therefore, this tail structure can be
26  * crammed into the end of the block without having to rebalance the tree.
27  */
28 struct ext3_extent_tail {
29 	__le32	et_checksum;	/* crc32c(uuid+inum+extent_block) */
30 };
31 
32 /*
33  * this is extent on-disk structure
34  * it's used at the bottom of the tree
35  */
36 struct ext3_extent {
37 	__le32	ee_block;	/* first logical block extent covers */
38 	__le16	ee_len;		/* number of blocks covered by extent */
39 	__le16	ee_start_hi;	/* high 16 bits of physical block */
40 	__le32	ee_start;	/* low 32 bigs of physical block */
41 };
42 
43 /*
44  * this is index on-disk structure
45  * it's used at all the levels, but the bottom
46  */
47 struct ext3_extent_idx {
48 	__le32	ei_block;	/* index covers logical blocks from 'block' */
49 	__le32	ei_leaf;	/* pointer to the physical block of the next *
50 				 * level. leaf or next index could bet here */
51 	__le16	ei_leaf_hi;	/* high 16 bits of physical block */
52 	__le16	ei_unused;
53 };
54 
55 /*
56  * each block (leaves and indexes), even inode-stored has header
57  */
58 struct ext3_extent_header {
59 	__le16	eh_magic;	/* probably will support different formats */
60 	__le16	eh_entries;	/* number of valid entries */
61 	__le16	eh_max;		/* capacity of store in entries */
62 	__le16	eh_depth;	/* has tree real underlying blocks? */
63 	__le32	eh_generation;	/* generation of the tree */
64 };
65 
66 #define EXT3_EXT_MAGIC		0xf30a
67 
68 /*
69  * array of ext3_ext_path contains path to some extent
70  * creation/lookup routines use it for traversal/splitting/etc
71  * truncate uses it to simulate recursive walking
72  */
73 struct ext3_ext_path {
74 	__u32				p_block;
75 	__u16				p_depth;
76 	struct ext3_extent		*p_ext;
77 	struct ext3_extent_idx		*p_idx;
78 	struct ext3_extent_header	*p_hdr;
79 	struct buffer_head		*p_bh;
80 };
81 
82 /*
83  * EXT_INIT_MAX_LEN is the maximum number of blocks we can have in an
84  * initialized extent. This is 2^15 and not (2^16 - 1), since we use the
85  * MSB of ee_len field in the extent datastructure to signify if this
86  * particular extent is an initialized extent or an uninitialized (i.e.
87  * preallocated).
88  * EXT_UNINIT_MAX_LEN is the maximum number of blocks we can have in an
89  * uninitialized extent.
90  * If ee_len is <= 0x8000, it is an initialized extent. Otherwise, it is an
91  * uninitialized one. In other words, if MSB of ee_len is set, it is an
92  * uninitialized extent with only one special scenario when ee_len = 0x8000.
93  * In this case we can not have an uninitialized extent of zero length and
94  * thus we make it as a special case of initialized extent with 0x8000 length.
95  * This way we get better extent-to-group alignment for initialized extents.
96  * Hence, the maximum number of blocks we can have in an *initialized*
97  * extent is 2^15 (32768) and in an *uninitialized* extent is 2^15-1 (32767).
98  */
99 #define EXT_INIT_MAX_LEN	(1UL << 15)
100 #define EXT_UNINIT_MAX_LEN	(EXT_INIT_MAX_LEN - 1)
101 #define EXT_MAX_EXTENT_LBLK	(((__u64) 1 << 32) - 1)
102 #define EXT_MAX_EXTENT_PBLK	(((__u64) 1 << 48) - 1)
103 
104 #define EXT_FIRST_EXTENT(__hdr__) \
105 	((struct ext3_extent *) (((char *) (__hdr__)) +		\
106 				 sizeof(struct ext3_extent_header)))
107 #define EXT_FIRST_INDEX(__hdr__) \
108 	((struct ext3_extent_idx *) (((char *) (__hdr__)) +	\
109 				     sizeof(struct ext3_extent_header)))
110 #define EXT_HAS_FREE_INDEX(__path__) \
111 	(ext2fs_le16_to_cpu((__path__)->p_hdr->eh_entries) < \
112 	 ext2fs_le16_to_cpu((__path__)->p_hdr->eh_max))
113 #define EXT_LAST_EXTENT(__hdr__) \
114 	(EXT_FIRST_EXTENT((__hdr__)) + \
115 	ext2fs_le16_to_cpu((__hdr__)->eh_entries) - 1)
116 #define EXT_LAST_INDEX(__hdr__) \
117 	(EXT_FIRST_INDEX((__hdr__)) + \
118 	ext2fs_le16_to_cpu((__hdr__)->eh_entries) - 1)
119 #define EXT_MAX_EXTENT(__hdr__) \
120 	(EXT_FIRST_EXTENT((__hdr__)) + \
121 	ext2fs_le16_to_cpu((__hdr__)->eh_max) - 1)
122 #define EXT_MAX_INDEX(__hdr__) \
123 	(EXT_FIRST_INDEX((__hdr__)) + \
124 	ext2fs_le16_to_cpu((__hdr__)->eh_max) - 1)
125 
126 #endif /* _LINUX_EXT3_EXTENTS */
127 
128