ext2fs.h revision 1.1
1 /* $NetBSD: ext2fs.h,v 1.1 1997/06/11 09:33:37 bouyer Exp $ */ 2 3 /* 4 * Copyright (c) 1997 Manuel Bouyer. 5 * Copyright (c) 1982, 1986, 1993 6 * The Regents of the University of California. All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 * 36 * @(#)fs.h 8.10 (Berkeley) 10/27/94 37 * Modified for ext2fs by Manuel Bouyer. 38 */ 39 40 /* 41 * Each disk drive contains some number of file systems. 42 * A file system consists of a number of cylinder groups. 43 * Each cylinder group has inodes and data. 44 * 45 * A file system is described by its super-block, which in turn 46 * describes the cylinder groups. The super-block is critical 47 * data and is replicated in each cylinder group to protect against 48 * catastrophic loss. This is done at `newfs' time and the critical 49 * super-block data does not change, so the copies need not be 50 * referenced further unless disaster strikes. 51 * 52 * The first boot and super blocks are given in absolute disk addresses. 53 * The byte-offset forms are preferred, as they don't imply a sector size. 54 */ 55 #define BBSIZE 1024 56 #define SBSIZE 1024 57 #define BBOFF ((off_t)(0)) 58 #define SBOFF ((off_t)(BBOFF + BBSIZE)) 59 #define BBLOCK ((daddr_t)(0)) 60 #define SBLOCK ((daddr_t)(BBLOCK + BBSIZE / DEV_BSIZE)) 61 62 /* 63 * Addresses stored in inodes are capable of addressing blocks 64 * XXX 65 */ 66 67 /* 68 * MINBSIZE is the smallest allowable block size. 69 * MINBSIZE must be big enough to hold a cylinder group block, 70 * thus changes to (struct cg) must keep its size within MINBSIZE. 71 * Note that super blocks are always of size SBSIZE, 72 * and that both SBSIZE and MAXBSIZE must be >= MINBSIZE. 73 */ 74 #define LOG_MINBSIZE 10 75 #define MINBSIZE (1 << LOG_MINBSIZE) 76 77 /* 78 * The path name on which the file system is mounted is maintained 79 * in fs_fsmnt. MAXMNTLEN defines the amount of space allocated in 80 * the super block for this name. 81 */ 82 #define MAXMNTLEN 512 83 84 /* 85 * MINFREE gives the minimum acceptable percentage of file system 86 * blocks which may be free. If the freelist drops below this level 87 * only the superuser may continue to allocate blocks. This may 88 * be set to 0 if no reserve of free blocks is deemed necessary, 89 * however throughput drops by fifty percent if the file system 90 * is run at between 95% and 100% full; thus the minimum default 91 * value of fs_minfree is 5%. However, to get good clustering 92 * performance, 10% is a better choice. hence we use 10% as our 93 * default value. With 10% free space, fragmentation is not a 94 * problem, so we choose to optimize for time. 95 */ 96 #define MINFREE 5 97 98 /* 99 * Super block for an ext2fs file system. 100 */ 101 struct ext2fs { 102 u_int32_t e2fs_icount; /* Inode count */ 103 u_int32_t e2fs_bcount; /* blocks count */ 104 u_int32_t e2fs_rbcount; /* reserved blocks count */ 105 u_int32_t e2fs_fbcount; /* free blocks count */ 106 u_int32_t e2fs_ficount; /* free inodes count */ 107 u_int32_t e2fs_first_dblock; /* first data block */ 108 u_int32_t e2fs_log_bsize; /* block size = 1024*(2^e2fs_log_bsize) */ 109 u_int32_t e2fs_fsize; /* fragment size */ 110 u_int32_t e2fs_bpg; /* blocks per group */ 111 u_int32_t e2fs_fpg; /* frags per group */ 112 u_int32_t e2fs_ipg; /* inodes per group */ 113 u_int32_t e2fs_mtime; /* mount time */ 114 u_int32_t e2fs_wtime; /* write time */ 115 u_int16_t e2fs_mnt_count; /* mount count */ 116 u_int16_t e2fs_max_mnt_count; /* max mount count */ 117 u_int16_t e2fs_magic; /* magic number */ 118 u_int16_t e2fs_state; /* file system state */ 119 u_int16_t e2fs_beh; /* behavior on errors */ 120 u_int16_t reserved; 121 u_int32_t e2fs_lastfsck; /* time of last fsck */ 122 u_int32_t e2fs_fsckintv; /* max time between fscks */ 123 u_int32_t e2fs_creator; /* creator OS */ 124 u_int32_t e2fs_rev; /* revision level */ 125 u_int16_t e2fs_ruid; /* default uid for reserved blocks */ 126 u_int16_t e2fs_rgid; /* default gid for reserved blocks */ 127 u_int32_t reserved2[235]; 128 }; 129 130 131 /* in-memory data for ext2fs */ 132 struct m_ext2fs { 133 struct ext2fs e2fs; 134 u_char e2fs_fsmnt[MAXMNTLEN]; /* name mounted on */ 135 int8_t e2fs_ronly; /* mounted read-only flag */ 136 int8_t e2fs_fmod; /* super block modified flag */ 137 int32_t e2fs_bsize; /* block size */ 138 int32_t e2fs_bshift; /* ``lblkno'' calc of logical blkno */ 139 int32_t e2fs_bmask; /* ``blkoff'' calc of blk offsets */ 140 int64_t e2fs_qbmask; /* ~fs_bmask - for use with quad size */ 141 int32_t e2fs_fsbtodb; /* fsbtodb and dbtofsb shift constant */ 142 int32_t e2fs_ncg; /* number of cylinder groups */ 143 int32_t e2fs_ngdb; /* number of group descriptor block */ 144 int32_t e2fs_ipb; /* number of inodes per block */ 145 int32_t e2fs_itpg; /* number of inode table per group */ 146 struct ext2_gd *e2fs_gd; /* group descripors */ 147 }; 148 149 150 151 /* 152 * Filesystem identification 153 */ 154 #define E2FS_MAGIC 0xef53 /* the ext2fs magic number */ 155 #define E2FS_REV 0 /* revision level */ 156 157 /* 158 * OS identification 159 */ 160 #define E2FS_OS_LINUX 0 161 #define E2FS_OS_HURD 1 162 #define E2FS_OS_MASIX 2 163 164 /* 165 * Filesystem clean flags 166 */ 167 #define E2FS_ISCLEAN 0x01 168 #define E2FS_ERRORS 0x02 169 170 /* ext2 file system block group descriptor */ 171 172 struct ext2_gd { 173 u_int32_t ext2bgd_b_bitmap; /* blocks bitmap block */ 174 u_int32_t ext2bgd_i_bitmap; /* inodes bitmap block */ 175 u_int32_t ext2bgd_i_tables; /* inodes table block */ 176 u_int16_t ext2bgd_nbfree; /* number of free blocks */ 177 u_int16_t ext2bgd_nifree; /* number of free inodes */ 178 u_int16_t ext2bgd_ndirs; /* number of directories */ 179 u_int16_t reserved; 180 u_int32_t reserved2[3]; 181 182 }; 183 184 /* 185 * Turn file system block numbers into disk block addresses. 186 * This maps file system blocks to device size blocks. 187 */ 188 #define fsbtodb(fs, b) ((b) << (fs)->e2fs_fsbtodb) 189 #define dbtofsb(fs, b) ((b) >> (fs)->e2fs_fsbtodb) 190 191 /* 192 * Macros for handling inode numbers: 193 * inode number to file system block offset. 194 * inode number to cylinder group number. 195 * inode number to file system block address. 196 */ 197 #define ino_to_cg(fs, x) (((x) - 1) / (fs)->e2fs.e2fs_ipg) 198 #define ino_to_fsba(fs, x) \ 199 ((fs)->e2fs_gd[ino_to_cg(fs, x)].ext2bgd_i_tables + \ 200 (((x)-1) % (fs)->e2fs.e2fs_ipg)/(fs)->e2fs_ipb) 201 #define ino_to_fsbo(fs, x) (((x)-1) % (fs)->e2fs_ipb) 202 203 /* 204 * Give cylinder group number for a file system block. 205 * Give cylinder group block number for a file system block. 206 */ 207 #define dtog(fs, d) (((d) - (fs)->e2fs.e2fs_first_dblock) / (fs)->e2fs.e2fs_fpg) 208 #define dtogd(fs, d) \ 209 (((d) - (fs)->e2fs.e2fs_first_dblock) % (fs)->e2fs.e2fs_fpg) 210 211 /* 212 * The following macros optimize certain frequently calculated 213 * quantities by using shifts and masks in place of divisions 214 * modulos and multiplications. 215 */ 216 #define blkoff(fs, loc) /* calculates (loc % fs->e2fs_bsize) */ \ 217 ((loc) & (fs)->e2fs_qbmask) 218 #define lblktosize(fs, blk) /* calculates (blk * fs->e2fs_bsize) */ \ 219 ((blk) << (fs)->e2fs_bshift) 220 #define lblkno(fs, loc) /* calculates (loc / fs->e2fs_bsize) */ \ 221 ((loc) >> (fs)->e2fs_bshift) 222 #define blkroundup(fs, size) /* calculates roundup(size, fs->e2fs_bsize) */ \ 223 (((size) + (fs)->e2fs_qbmask) & (fs)->e2fs_bmask) 224 #define fragroundup(fs, size) /* calculates roundup(size, fs->e2fs_bsize) */ \ 225 (((size) + (fs)->e2fs_qbmask) & (fs)->e2fs_bmask) 226 /* 227 * Determine the number of available frags given a 228 * percentage to hold in reserve. 229 */ 230 #define freespace(fs) \ 231 ((fs)->e2fs.e2fs_fbcount - (fs)->e2fs.e2fs_rbcount) 232 233 /* 234 * Number of indirects in a file system block. 235 */ 236 #define NINDIR(fs) ((fs)->e2fs_bsize / sizeof(u_int32_t)) 237
Indexes created Sun Oct 19 02:09:48 GMT 2025