FreeBSD/Linux Kernel Cross Reference
2 * modified for EXT2FS support in Lites 1.1
4 * Aug 1995, Godmar Back (email@example.com)
5 * University of Utah, Department of Computer Science
8 * SPDX-License-Identifier: BSD-3-Clause
10 * Copyright (c) 1982, 1986, 1993
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37 * @(#)fs.h 8.7 (Berkeley) 4/19/94
38 * $FreeBSD$
41 #ifndef _FS_EXT2FS_FS_H_
42 #define _FS_EXT2FS_FS_H_
45 * Each disk drive contains some number of file systems.
46 * A file system consists of a number of cylinder groups.
47 * Each cylinder group has inodes and data.
49 * A file system is described by its super-block, which in turn
50 * describes the cylinder groups. The super-block is critical
51 * data and is replicated in each cylinder group to protect against
52 * catastrophic loss. This is done at `newfs' time and the critical
53 * super-block data does not change, so the copies need not be
54 * referenced further unless disaster strikes.
56 * The first boot and super blocks are given in absolute disk addresses.
57 * The byte-offset forms are preferred, as they don't imply a sector size.
59 #define SBSIZE 1024
60 #define SBLOCK 2
63 * The path name on which the file system is mounted is maintained
64 * in fs_fsmnt. MAXMNTLEN defines the amount of space allocated in
65 * the super block for this name.
67 #define MAXMNTLEN 512
70 * A summary of contiguous blocks of various sizes is maintained
71 * in each cylinder group. Normally this is set by the initial
72 * value of fs_maxcontig.
74 * XXX:FS_MAXCONTIG is set to 16 to conserve space. Here we set
75 * EXT2_MAXCONTIG to 32 for better performance.
77 #define EXT2_MAXCONTIG 32
80 * Grigoriy Orlov <firstname.lastname@example.org> has done some extensive work to fine
81 * tune the layout preferences for directories within a filesystem.
82 * His algorithm can be tuned by adjusting the following parameters
83 * which tell the system the average file size and the average number
84 * of files per directory. These defaults are well selected for typical
85 * filesystems, but may need to be tuned for odd cases like filesystems
86 * being used for squid caches or news spools.
87 * AVFPDIR is the expected number of files per directory. AVGDIRSIZE is
88 * obtained by multiplying AVFPDIR and AVFILESIZ which is assumed to be
89 * 16384.
92 #define AFPDIR 64
93 #define AVGDIRSIZE 1048576
96 * Macros for access to superblock array structures
100 * Turn file system block numbers into disk block addresses.
101 * This maps file system blocks to device size blocks.
103 #define fsbtodb(fs, b) ((daddr_t)(b) << (fs)->e2fs_fsbtodb)
104 #define dbtofsb(fs, b) ((b) >> (fs)->e2fs_fsbtodb)
106 /* get group containing inode */
107 #define ino_to_cg(fs, x) (((x) - 1) / (fs->e2fs_ipg))
109 /* get block containing inode from its number x */
110 #define ino_to_fsba(fs, x) \
111 (e2fs_gd_get_i_tables(&(fs)->e2fs_gd[ino_to_cg((fs), (x))]) + \
112 (((x) - 1) % (fs)->e2fs_ipg) / (fs)->e2fs_ipb)
114 /* get offset for inode in block */
115 #define ino_to_fsbo(fs, x) ((x-1) % (fs->e2fs_ipb))
118 * Give cylinder group number for a file system block.
119 * Give cylinder group block number for a file system block.
121 #define dtog(fs, d) (((d) - le32toh(fs->e2fs->e2fs_first_dblock)) / \
123 #define dtogd(fs, d) (((d) - le32toh(fs->e2fs->e2fs_first_dblock)) % \
127 * The following macros optimize certain frequently calculated
128 * quantities by using shifts and masks in place of divisions
129 * modulos and multiplications.
131 #define blkoff(fs, loc) /* calculates (loc % fs->fs_bsize) */ \
132 ((loc) & (fs)->e2fs_qbmask)
134 #define lblktosize(fs, blk) /* calculates (blk * fs->fs_bsize) */ \
135 ((blk) << (fs->e2fs_bshift))
137 #define lblkno(fs, loc) /* calculates (loc / fs->fs_bsize) */ \
138 ((loc) >> (fs->e2fs_bshift))
140 /* no fragments -> logical block number equal # of frags */
141 #define numfrags(fs, loc) /* calculates (loc / fs->fs_fsize) */ \
142 ((loc) >> (fs->e2fs_bshift))
144 #define fragroundup(fs, size) /* calculates roundup(size, fs->fs_fsize) */ \
145 roundup(size, fs->e2fs_fsize)
146 /* was (((size) + (fs)->fs_qfmask) & (fs)->fs_fmask) */
149 * Determining the size of a file block in the file system.
150 * easy w/o fragments
152 #define blksize(fs, ip, lbn) ((fs)->e2fs_fsize)
155 * INOPB is the number of inodes in a secondary storage block.
157 #define INOPB(fs) (fs->e2fs_ipb)
160 * NINDIR is the number of indirects in a file system block.
162 #define NINDIR(fs) (EXT2_ADDR_PER_BLOCK(fs))
165 * Use if additional debug logging is required.
167 /* #define EXT2FS_PRINT_EXTENTS */
169 #endif /* !_FS_EXT2FS_FS_H_ */
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