Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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1 /*- 2 * modified for EXT2FS support in Lites 1.1 3 * 4 * Aug 1995, Godmar Back (email@example.com) 5 * University of Utah, Department of Computer Science 6 */ 7 /*- 8 * Copyright (c) 1982, 1986, 1993 9 * The Regents of the University of California. All rights reserved. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 4. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 * 35 * @(#)fs.h 8.7 (Berkeley) 4/19/94 36 * $FreeBSD: releng/10.4/sys/fs/ext2fs/fs.h 311232 2017-01-04 02:43:33Z pfg $ 37 */ 38 39 #ifndef _FS_EXT2FS_FS_H_ 40 #define _FS_EXT2FS_FS_H_ 41 42 /* 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. 46 * 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. 53 * 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. 56 */ 57 #define SBSIZE 1024 58 #define SBLOCK 2 59 60 /* 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. 64 */ 65 #define MAXMNTLEN 512 66 67 /* 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. 71 * 72 * XXX:FS_MAXCONTIG is set to 16 to conserve space. Here we set 73 * EXT2_MAXCONTIG to 32 for better performance. 74 */ 75 #define EXT2_MAXCONTIG 32 76 77 /* 78 * Grigoriy Orlov <firstname.lastname@example.org> 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. 88 */ 89 90 #define AFPDIR 64 91 #define AVGDIRSIZE 1048576 92 93 /* 94 * Macros for access to superblock array structures 95 */ 96 97 /* 98 * Turn file system block numbers into disk block addresses. 99 * This maps file system blocks to device size blocks. 100 */ 101 #define fsbtodb(fs, b) ((daddr_t)(b) << (fs)->e2fs_fsbtodb) 102 #define dbtofsb(fs, b) ((b) >> (fs)->e2fs_fsbtodb) 103 104 /* get group containing inode */ 105 #define ino_to_cg(fs, x) (((x) - 1) / (fs->e2fs_ipg)) 106 107 /* 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) 111 112 /* get offset for inode in block */ 113 #define ino_to_fsbo(fs, x) ((x-1) % (fs->e2fs_ipb)) 114 115 /* 116 * Give cylinder group number for a file system block. 117 * Give cylinder group block number for a file system block. 118 */ 119 #define dtog(fs, d) (((d) - fs->e2fs->e2fs_first_dblock) / \ 120 EXT2_BLOCKS_PER_GROUP(fs)) 121 #define dtogd(fs, d) (((d) - fs->e2fs->e2fs_first_dblock) % \ 122 EXT2_BLOCKS_PER_GROUP(fs)) 123 124 /* 125 * The following macros optimize certain frequently calculated 126 * quantities by using shifts and masks in place of divisions 127 * modulos and multiplications. 128 */ 129 #define blkoff(fs, loc) /* calculates (loc % fs->fs_bsize) */ \ 130 ((loc) & (fs)->e2fs_qbmask) 131 132 #define lblktosize(fs, blk) /* calculates (blk * fs->fs_bsize) */ \ 133 ((blk) << (fs->e2fs_bshift)) 134 135 #define lblkno(fs, loc) /* calculates (loc / fs->fs_bsize) */ \ 136 ((loc) >> (fs->e2fs_bshift)) 137 138 /* no fragments -> logical block number equal # of frags */ 139 #define numfrags(fs, loc) /* calculates (loc / fs->fs_fsize) */ \ 140 ((loc) >> (fs->e2fs_bshift)) 141 142 #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) */ 145 146 /* 147 * Determining the size of a file block in the file system. 148 * easy w/o fragments 149 */ 150 #define blksize(fs, ip, lbn) ((fs)->e2fs_fsize) 151 152 /* 153 * INOPB is the number of inodes in a secondary storage block. 154 */ 155 #define INOPB(fs) (fs->e2fs_ipb) 156 157 /* 158 * NINDIR is the number of indirects in a file system block. 159 */ 160 #define NINDIR(fs) (EXT2_ADDR_PER_BLOCK(fs)) 161 162 #endif /* !_FS_EXT2FS_FS_H_ */
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