2 * Copyright (c) 2003,2004 Cluster File Systems, Inc, info@clusterfs.com
3 * Written by Alex Tomas <alex@clusterfs.com>
6 * This file may be redistributed under the terms of the GNU Library
7 * General Public License, version 2.
11 #ifndef _LINUX_EXT3_EXTENTS
12 #define _LINUX_EXT3_EXTENTS
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
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.
28 struct ext3_extent_tail {
29 __le32 et_checksum; /* crc32c(uuid+inum+extent_block) */
33 * this is extent on-disk structure
34 * it's used at the bottom of the tree
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 */
44 * this is index on-disk structure
45 * it's used at all the levels, but the bottom
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 */
56 * each block (leaves and indexes), even inode-stored has header
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 */
66 #define EXT3_EXT_MAGIC 0xf30a
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
73 struct ext3_ext_path {
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;
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.
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).
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)
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)
126 #endif /* _LINUX_EXT3_EXTENTS */