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
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.
60 #define SBLOCKSIZE 1024
61 #define SBLOCKOFFSET 1024
62 #define SBLOCKBLKSIZE 4096
65 * The path name on which the file system is mounted is maintained
66 * in fs_fsmnt. MAXMNTLEN defines the amount of space allocated in
67 * the super block for this name.
72 * A summary of contiguous blocks of various sizes is maintained
73 * in each cylinder group. Normally this is set by the initial
74 * value of fs_maxcontig.
76 * XXX:FS_MAXCONTIG is set to 16 to conserve space. Here we set
77 * EXT2_MAXCONTIG to 32 for better performance.
79 #define EXT2_MAXCONTIG 32
82 * Grigoriy Orlov <gluk@ptci.ru> has done some extensive work to fine
83 * tune the layout preferences for directories within a filesystem.
84 * His algorithm can be tuned by adjusting the following parameters
85 * which tell the system the average file size and the average number
86 * of files per directory. These defaults are well selected for typical
87 * filesystems, but may need to be tuned for odd cases like filesystems
88 * being used for squid caches or news spools.
89 * AVFPDIR is the expected number of files per directory. AVGDIRSIZE is
90 * obtained by multiplying AVFPDIR and AVFILESIZ which is assumed to be
95 #define AVGDIRSIZE 1048576
98 * Macros for access to superblock array structures
102 * Turn file system block numbers into disk block addresses.
103 * This maps file system blocks to device size blocks.
105 #define fsbtodb(fs, b) ((daddr_t)(b) << (fs)->e2fs_fsbtodb)
106 #define dbtofsb(fs, b) ((b) >> (fs)->e2fs_fsbtodb)
108 /* get group containing inode */
109 #define ino_to_cg(fs, x) (((x) - 1) / (fs->e2fs_ipg))
111 /* get block containing inode from its number x */
112 #define ino_to_fsba(fs, x) \
113 (e2fs_gd_get_i_tables(&(fs)->e2fs_gd[ino_to_cg((fs), (x))]) + \
114 (((x) - 1) % (fs)->e2fs_ipg) / (fs)->e2fs_ipb)
116 /* get offset for inode in block */
117 #define ino_to_fsbo(fs, x) ((x-1) % (fs->e2fs_ipb))
120 * Give cylinder group number for a file system block.
121 * Give cylinder group block number for a file system block.
123 #define dtog(fs, d) (((d) - le32toh(fs->e2fs->e2fs_first_dblock)) / \
124 EXT2_BLOCKS_PER_GROUP(fs))
125 #define dtogd(fs, d) (((d) - le32toh(fs->e2fs->e2fs_first_dblock)) % \
126 EXT2_BLOCKS_PER_GROUP(fs))
129 * The following macros optimize certain frequently calculated
130 * quantities by using shifts and masks in place of divisions
131 * modulos and multiplications.
133 #define blkoff(fs, loc) /* calculates (loc % fs->fs_bsize) */ \
134 ((loc) & (fs)->e2fs_qbmask)
136 #define lblktosize(fs, blk) /* calculates (blk * fs->fs_bsize) */ \
137 ((blk) << (fs->e2fs_bshift))
139 #define lblkno(fs, loc) /* calculates (loc / fs->fs_bsize) */ \
140 ((loc) >> (fs->e2fs_bshift))
142 /* no fragments -> logical block number equal # of frags */
143 #define numfrags(fs, loc) /* calculates (loc / fs->fs_fsize) */ \
144 ((loc) >> (fs->e2fs_bshift))
146 #define fragroundup(fs, size) /* calculates roundup(size, fs->fs_fsize) */ \
147 roundup(size, fs->e2fs_fsize)
148 /* was (((size) + (fs)->fs_qfmask) & (fs)->fs_fmask) */
151 * Determining the size of a file block in the file system.
154 #define blksize(fs, ip, lbn) ((fs)->e2fs_fsize)
157 * INOPB is the number of inodes in a secondary storage block.
159 #define INOPB(fs) (fs->e2fs_ipb)
162 * NINDIR is the number of indirects in a file system block.
164 #define NINDIR(fs) (EXT2_ADDR_PER_BLOCK(fs))
167 * Use if additional debug logging is required.
169 /* #define EXT2FS_PRINT_EXTENTS */
171 #endif /* !_FS_EXT2FS_FS_H_ */