2 * modified for EXT2FS support in Lites 1.1
4 * Aug 1995, Godmar Back (gback@cs.utah.edu)
5 * University of Utah, Department of Computer Science
8 * SPDX-License-Identifier: BSD-3-Clause
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37 * @(#)fs.h 8.7 (Berkeley) 4/19/94
40 #ifndef _FS_EXT2FS_FS_H_
41 #define _FS_EXT2FS_FS_H_
44 * Each disk drive contains some number of file systems.
45 * A file system consists of a number of cylinder groups.
46 * Each cylinder group has inodes and data.
48 * A file system is described by its super-block, which in turn
49 * describes the cylinder groups. The super-block is critical
50 * data and is replicated in each cylinder group to protect against
51 * catastrophic loss. This is done at `newfs' time and the critical
52 * super-block data does not change, so the copies need not be
53 * referenced further unless disaster strikes.
55 * The first boot and super blocks are given in absolute disk addresses.
56 * The byte-offset forms are preferred, as they don't imply a sector size.
59 #define SBLOCKSIZE 1024
60 #define SBLOCKOFFSET 1024
61 #define SBLOCKBLKSIZE 4096
64 * The path name on which the file system is mounted is maintained
65 * in fs_fsmnt. MAXMNTLEN defines the amount of space allocated in
66 * the super block for this name.
71 * A summary of contiguous blocks of various sizes is maintained
72 * in each cylinder group. Normally this is set by the initial
73 * value of fs_maxcontig.
75 * XXX:FS_MAXCONTIG is set to 16 to conserve space. Here we set
76 * EXT2_MAXCONTIG to 32 for better performance.
78 #define EXT2_MAXCONTIG 32
81 * Grigoriy Orlov <gluk@ptci.ru> has done some extensive work to fine
82 * tune the layout preferences for directories within a filesystem.
83 * His algorithm can be tuned by adjusting the following parameters
84 * which tell the system the average file size and the average number
85 * of files per directory. These defaults are well selected for typical
86 * filesystems, but may need to be tuned for odd cases like filesystems
87 * being used for squid caches or news spools.
88 * AVFPDIR is the expected number of files per directory. AVGDIRSIZE is
89 * obtained by multiplying AVFPDIR and AVFILESIZ which is assumed to be
94 #define AVGDIRSIZE 1048576
97 * Macros for access to superblock array structures
101 * Turn file system block numbers into disk block addresses.
102 * This maps file system blocks to device size blocks.
104 #define fsbtodb(fs, b) ((daddr_t)(b) << (fs)->e2fs_fsbtodb)
105 #define dbtofsb(fs, b) ((b) >> (fs)->e2fs_fsbtodb)
107 /* get group containing inode */
108 #define ino_to_cg(fs, x) (((x) - 1) / (fs->e2fs_ipg))
110 /* get block containing inode from its number x */
111 #define ino_to_fsba(fs, x) \
112 (e2fs_gd_get_i_tables(&(fs)->e2fs_gd[ino_to_cg((fs), (x))]) + \
113 (((x) - 1) % (fs)->e2fs_ipg) / (fs)->e2fs_ipb)
115 /* get offset for inode in block */
116 #define ino_to_fsbo(fs, x) ((x-1) % (fs->e2fs_ipb))
119 * Give cylinder group number for a file system block.
120 * Give cylinder group block number for a file system block.
122 #define dtog(fs, d) (((d) - le32toh(fs->e2fs->e2fs_first_dblock)) / \
123 EXT2_BLOCKS_PER_GROUP(fs))
124 #define dtogd(fs, d) (((d) - le32toh(fs->e2fs->e2fs_first_dblock)) % \
125 EXT2_BLOCKS_PER_GROUP(fs))
128 * The following macros optimize certain frequently calculated
129 * quantities by using shifts and masks in place of divisions
130 * modulos and multiplications.
132 #define blkoff(fs, loc) /* calculates (loc % fs->fs_bsize) */ \
133 ((loc) & (fs)->e2fs_qbmask)
135 #define lblktosize(fs, blk) /* calculates (blk * fs->fs_bsize) */ \
136 ((blk) << (fs->e2fs_bshift))
138 #define lblkno(fs, loc) /* calculates (loc / fs->fs_bsize) */ \
139 ((loc) >> (fs->e2fs_bshift))
141 /* no fragments -> logical block number equal # of frags */
142 #define numfrags(fs, loc) /* calculates (loc / fs->fs_fsize) */ \
143 ((loc) >> (fs->e2fs_bshift))
145 #define fragroundup(fs, size) /* calculates roundup(size, fs->fs_fsize) */ \
146 roundup(size, fs->e2fs_fsize)
147 /* was (((size) + (fs)->fs_qfmask) & (fs)->fs_fmask) */
150 * Determining the size of a file block in the file system.
153 #define blksize(fs, ip, lbn) ((fs)->e2fs_fsize)
156 * INOPB is the number of inodes in a secondary storage block.
158 #define INOPB(fs) (fs->e2fs_ipb)
161 * NINDIR is the number of indirects in a file system block.
163 #define NINDIR(fs) (EXT2_ADDR_PER_BLOCK(fs))
166 * Use if additional debug logging is required.
168 /* #define EXT2FS_PRINT_EXTENTS */
170 #endif /* !_FS_EXT2FS_FS_H_ */