FreeBSD/Linux Kernel Cross Reference
2 * modified for EXT2FS support in Lites 1.1
4 * Aug 1995, Godmar Back (firstname.lastname@example.org)
5 * University of Utah, Department of Computer Science
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35 * @(#)fs.h 8.7 (Berkeley) 4/19/94
36 * $FreeBSD: releng/10.3/sys/fs/ext2fs/fs.h 262723 2014-03-04 03:10:31Z pfg $
39 #ifndef _FS_EXT2FS_FS_H_
40 #define _FS_EXT2FS_FS_H_
43 * Each disk drive contains some number of file systems.
44 * A file system consists of a number of cylinder groups.
45 * Each cylinder group has inodes and data.
47 * A file system is described by its super-block, which in turn
48 * describes the cylinder groups. The super-block is critical
49 * data and is replicated in each cylinder group to protect against
50 * catastrophic loss. This is done at `newfs' time and the critical
51 * super-block data does not change, so the copies need not be
52 * referenced further unless disaster strikes.
54 * The first boot and super blocks are given in absolute disk addresses.
55 * The byte-offset forms are preferred, as they don't imply a sector size.
57 #define SBSIZE 1024
58 #define SBLOCK 2
61 * The path name on which the file system is mounted is maintained
62 * in fs_fsmnt. MAXMNTLEN defines the amount of space allocated in
63 * the super block for this name.
65 #define MAXMNTLEN 512
68 * A summary of contiguous blocks of various sizes is maintained
69 * in each cylinder group. Normally this is set by the initial
70 * value of fs_maxcontig.
72 * XXX:FS_MAXCONTIG is set to 16 to conserve space. Here we set
73 * EXT2_MAXCONTIG to 32 for better performance.
75 #define EXT2_MAXCONTIG 32
78 * Grigoriy Orlov <email@example.com> has done some extensive work to fine
79 * tune the layout preferences for directories within a filesystem.
80 * His algorithm can be tuned by adjusting the following parameters
81 * which tell the system the average file size and the average number
82 * of files per directory. These defaults are well selected for typical
83 * filesystems, but may need to be tuned for odd cases like filesystems
84 * being used for squid caches or news spools.
85 * AVFPDIR is the expected number of files per directory. AVGDIRSIZE is
86 * obtained by multiplying AVFPDIR and AVFILESIZ which is assumed to be
87 * 16384.
90 #define AFPDIR 64
91 #define AVGDIRSIZE 1048576
94 * Macros for access to superblock array structures
98 * Turn file system block numbers into disk block addresses.
99 * This maps file system blocks to device size blocks.
101 #define fsbtodb(fs, b) ((daddr_t)(b) << (fs)->e2fs_fsbtodb)
102 #define dbtofsb(fs, b) ((b) >> (fs)->e2fs_fsbtodb)
104 /* get group containing inode */
105 #define ino_to_cg(fs, x) (((x) - 1) / (fs->e2fs_ipg))
107 /* get block containing inode from its number x */
108 #define ino_to_fsba(fs, x) \
109 ((fs)->e2fs_gd[ino_to_cg((fs), (x))].ext2bgd_i_tables + \
110 (((x) - 1) % (fs)->e2fs->e2fs_ipg) / (fs)->e2fs_ipb)
112 /* get offset for inode in block */
113 #define ino_to_fsbo(fs, x) ((x-1) % (fs->e2fs_ipb))
116 * Give cylinder group number for a file system block.
117 * Give cylinder group block number for a file system block.
119 #define dtog(fs, d) (((d) - fs->e2fs->e2fs_first_dblock) / \
121 #define dtogd(fs, d) (((d) - fs->e2fs->e2fs_first_dblock) % \
125 * The following macros optimize certain frequently calculated
126 * quantities by using shifts and masks in place of divisions
127 * modulos and multiplications.
129 #define blkoff(fs, loc) /* calculates (loc % fs->fs_bsize) */ \
130 ((loc) & (fs)->e2fs_qbmask)
132 #define lblktosize(fs, blk) /* calculates (blk * fs->fs_bsize) */ \
133 ((blk) << (fs->e2fs_bshift))
135 #define lblkno(fs, loc) /* calculates (loc / fs->fs_bsize) */ \
136 ((loc) >> (fs->e2fs_bshift))
138 /* no fragments -> logical block number equal # of frags */
139 #define numfrags(fs, loc) /* calculates (loc / fs->fs_fsize) */ \
140 ((loc) >> (fs->e2fs_bshift))
142 #define fragroundup(fs, size) /* calculates roundup(size, fs->fs_fsize) */ \
143 roundup(size, fs->e2fs_fsize)
144 /* was (((size) + (fs)->fs_qfmask) & (fs)->fs_fmask) */
147 * Determining the size of a file block in the file system.
148 * easy w/o fragments
150 #define blksize(fs, ip, lbn) ((fs)->e2fs_fsize)
153 * INOPB is the number of inodes in a secondary storage block.
155 #define INOPB(fs) (fs->e2fs_ipb)
158 * NINDIR is the number of indirects in a file system block.
160 #define NINDIR(fs) (EXT2_ADDR_PER_BLOCK(fs))
162 #endif /* !_FS_EXT2FS_FS_H_ */
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