1 /* Copyright (c) 1981 Regents of the University of California */ 2 3 /* fs.h 1.14 02/25/82 */ 4 5 /* 6 * Each disk drive contains some number of file systems. 7 * A file system consists of a number of cylinder groups. 8 * Each cylinder group has inodes and data. 9 * 10 * A file system is described by its super-block, which in turn 11 * describes the cylinder groups. The super-block is critical 12 * data and is replicated in each cylinder group to protect against 13 * catastrophic loss. This is done at mkfs time and the critical 14 * super-block data does not change, so the copies need not be 15 * referenced further unless disaster strikes. 16 * 17 * For file system fs, the offsets of the various blocks of interest 18 * are given in the super block as: 19 * [fs->fs_bblkno] Boot sector 20 * [fs->fs_sblkno] Super-block 21 * [fs->fs_cblkno] Cylinder group block 22 * [fs->fs_iblkno] Inode blocks 23 * [fs->fs_dblkno] Data blocks 24 * The beginning of cylinder group cg in fs, is given by 25 * the ``cgbase(fs, cg)'' macro. 26 * 27 * The first boot and super blocks are given in absolute disk addresses. 28 */ 29 #define BBSIZE 1024 30 #define SBSIZE 8192 31 #define BBLOCK ((daddr_t)(0)) 32 #define SBLOCK ((daddr_t)(BBLOCK + BBSIZE / DEV_BSIZE)) 33 34 /* 35 * Addresses stored in inodes are capable of addressing fragments 36 * of `blocks'. File system blocks of at most size MAXBSIZE can 37 * be optionally broken into 2, 4, or 8 pieces, each of which is 38 * addressible; these pieces may be DEV_BSIZE, or some multiple of 39 * a DEV_BSIZE unit. 40 * 41 * Large files consist of exclusively large data blocks. To avoid 42 * undue wasted disk space, the last data block of a small file may be 43 * allocated as only as many fragments of a large block as are 44 * necessary. The file system format retains only a single pointer 45 * to such a fragment, which is a piece of a single large block that 46 * has been divided. The size of such a fragment is determinable from 47 * information in the inode, using the ``blksize(fs, ip, lbn)'' macro. 48 * 49 * The file system records space availability at the fragment level; 50 * to determine block availability, aligned fragments are examined. 51 * 52 * The root inode is the root of the file system. 53 * Inode 0 can't be used for normal purposes and 54 * historically bad blocks were linked to inode 1, 55 * thus the root inode is 2. (inode 1 is no longer used for 56 * this purpose, however numerous dump tapes make this 57 * assumption, so we are stuck with it) 58 * The lost+found directory is given the next available 59 * inode when it is created by ``mkfs''. 60 */ 61 #define ROOTINO ((ino_t)2) /* i number of all roots */ 62 #define LOSTFOUNDINO (ROOTINO + 1) 63 64 /* 65 * MINFREE gives the minimum acceptable percentage of file system 66 * blocks which may be free. If the freelist drops below this level 67 * only the superuser may continue to allocate blocks. This may 68 * be set to 0 if no reserve of free blocks is deemed necessary, 69 * however severe performance degredations will be observed if the 70 * file system is run at greater than 90% full; thus the default 71 * value of fs_minfree is 10%. 72 * 73 * Empirically the best trade-off between block fragmentation and 74 * overall disk utilization at a loading of 90% comes with a 75 * fragmentation of 4, thus the default fragment size is a fourth 76 * of the block size. 77 */ 78 #define MINFREE 10 79 #define DESFRAG 4 80 81 /* 82 * Under current technology, most 300MB disks have 32 sectors and 83 * 19 tracks, thus these are the defaults used for fs_nsect and 84 * fs_ntrak respectively. 85 */ 86 #define DFLNSECT 32 87 #define DFLNTRAK 19 88 89 /* 90 * Cylinder group related limits. 91 * 92 * For each cylinder we keep track of the availability of blocks at different 93 * rotational positions, so that we can lay out the data to be picked 94 * up with minimum rotational latency. NRPOS is the number of rotational 95 * positions which we distinguish. With NRPOS 8 the resolution of our 96 * summary information is 2ms for a typical 3600 rpm drive. 97 * 98 * ROTDELAY gives the minimum number of milliseconds to initiate 99 * another disk transfer on the same cylinder. It is used in 100 * determining the rotationally optimal layout for disk blocks 101 * within a file; the default of fs_rotdelay is 2ms. 102 */ 103 #define NRPOS 8 /* number distinct rotational positions */ 104 #define ROTDELAY 2 105 106 /* 107 * Each file system has a number of inodes statically allocated. 108 * We allocate one inode slot per NBPI bytes, expecting this 109 * to be far more than we will ever need. 110 * 111 * MAXIPG bounds the number of inodes per cylinder group, and 112 * is needed only to keep the structure simpler by having the 113 * only a single variable size element (the free bit map). 114 * 115 * N.B.: MAXIPG must be a multiple of INOPB(fs). 116 */ 117 #define NBPI 2048 118 #define MAXIPG 2048 /* max number inodes/cyl group */ 119 120 /* 121 * MINBSIZE is the smallest allowable block size. 122 * In order to insure that it is possible to create files of size 123 * 2^32 with only two levels of indirection, MINBSIZE is set to 4096. 124 * MINBSIZE must be big enough to hold a cylinder group block, 125 * thus changes to (struct cg) must keep its size within MINBSIZE. 126 * MAXCPG is limited only to dimension an array in (struct cg); 127 * it can be made larger as long as that structures size remains 128 * within the bounds dictated by MINBSIZE. 129 * Note that super blocks are always of size MAXBSIZE, 130 * and that MAXBSIZE must be >= MINBSIZE. 131 */ 132 #define MINBSIZE 4096 133 #define DESCPG 16 /* desired fs_cpg */ 134 #define MAXCPG 32 /* maximum fs_cpg */ 135 136 /* 137 * Per cylinder group information; summarized in blocks allocated 138 * from first cylinder group data blocks. These blocks have to be 139 * read in from fs_csaddr (size fs_cssize) in addition to the 140 * super block. 141 * 142 * N.B. sizeof(struct csum) must be a power of two in order for 143 * the ``fs_cs'' macro to work (see below). 144 */ 145 struct csum { 146 long cs_ndir; /* number of directories */ 147 long cs_nbfree; /* number of free blocks */ 148 long cs_nifree; /* number of free inodes */ 149 long cs_nffree; /* number of free frags */ 150 }; 151 152 /* 153 * Super block for a file system. 154 */ 155 #define FS_MAGIC 0x110854 156 struct fs 157 { 158 long fs_magic; /* magic number */ 159 daddr_t fs_bblkno; /* abs addr of boot-block in filesys */ 160 daddr_t fs_sblkno; /* abs addr of super-block in filesys */ 161 daddr_t fs_cblkno; /* offset of cyl-block in filesys */ 162 daddr_t fs_iblkno; /* offset of inode-blocks in filesys */ 163 daddr_t fs_dblkno; /* offset of data-blocks in filesys */ 164 time_t fs_time; /* last time written */ 165 long fs_size; /* number of blocks in fs */ 166 long fs_dsize; /* number of data blocks in fs */ 167 long fs_ncg; /* number of cylinder groups */ 168 long fs_bsize; /* size of basic blocks in fs */ 169 long fs_fsize; /* size of frag blocks in fs */ 170 short fs_frag; /* number of frags in a block in fs */ 171 short fs_minfree; /* minimum percentage of free blocks */ 172 short fs_rotdelay; /* num of ms for optimal next block */ 173 short fs_rps; /* disk revolutions per second */ 174 long fs_bmask; /* ``blkoff'' calc of blk offsets */ 175 long fs_fmask; /* ``fragoff'' calc of frag offsets */ 176 short fs_bshift; /* ``lblkno'' calc of logical blkno */ 177 short fs_fshift; /* ``numfrags'' calc number of frags */ 178 /* sizes determined by number of cylinder groups and their sizes */ 179 daddr_t fs_csaddr; /* blk addr of cyl grp summary area */ 180 long fs_cssize; /* size of cyl grp summary area */ 181 long fs_cgsize; /* cylinder group size */ 182 /* these fields should be derived from the hardware */ 183 short fs_ntrak; /* tracks per cylinder */ 184 short fs_nsect; /* sectors per track */ 185 long fs_spc; /* sectors per cylinder */ 186 /* this comes from the disk driver partitioning */ 187 long fs_ncyl; /* cylinders in file system */ 188 /* these fields can be computed from the others */ 189 short fs_cpg; /* cylinders per group */ 190 short fs_ipg; /* inodes per group */ 191 long fs_fpg; /* blocks per group * fs_frag */ 192 /* this data must be re-computed after crashes */ 193 struct csum fs_cstotal; /* cylinder summary information */ 194 /* these fields are cleared at mount time */ 195 char fs_fmod; /* super block modified flag */ 196 char fs_ronly; /* mounted read-only flag */ 197 char fs_fsmnt[34]; /* name mounted on */ 198 /* these fields retain the current block allocation info */ 199 long fs_cgrotor; /* last cg searched */ 200 struct csum *fs_csp[NBUF]; /* list of fs_cs info buffers */ 201 short fs_cpc; /* cyl per cycle in postbl */ 202 short fs_postbl[MAXCPG][NRPOS];/* head of blocks for each rotation */ 203 u_char fs_rotbl[1]; /* list of blocks for each rotation */ 204 /* actually longer */ 205 }; 206 207 /* 208 * convert cylinder group to base address of its global summary info. 209 * 210 * N.B. This macro assumes that sizeof(struct csum) is a power of two. 211 */ 212 #define fs_cs(fs, indx) \ 213 fs_csp[(indx) / ((fs)->fs_bsize / sizeof(struct csum))] \ 214 [(indx) % ((fs)->fs_bsize / sizeof(struct csum))] 215 216 /* 217 * MAXBPC bounds the size of the rotational layout tables and 218 * is limited by the fact that the super block is of size SBSIZE. 219 * The size of these tables is INVERSELY proportional to the block 220 * size of the file system. It is aggravated by sector sizes that 221 * are not powers of two, as this increases the number of cylinders 222 * included before the rotational pattern repeats (fs_cpc). 223 * Its size is derived from the number of bytes remaining in (struct fs) 224 */ 225 #define MAXBPC (SBSIZE - sizeof (struct fs)) 226 227 /* 228 * Cylinder group block for a file system. 229 */ 230 #define CG_MAGIC 0x092752 231 struct cg { 232 long cg_magic; /* magic number */ 233 time_t cg_time; /* time last written */ 234 long cg_cgx; /* we are the cgx'th cylinder group */ 235 short cg_ncyl; /* number of cyl's this cg */ 236 short cg_niblk; /* number of inode blocks this cg */ 237 long cg_ndblk; /* number of data blocks this cg */ 238 struct csum cg_cs; /* cylinder summary information */ 239 long cg_rotor; /* position of last used block */ 240 long cg_frotor; /* position of last used frag */ 241 long cg_irotor; /* position of last used inode */ 242 long cg_frsum[MAXFRAG]; /* counts of available frags */ 243 long cg_btot[MAXCPG]; /* block totals per cylinder */ 244 short cg_b[MAXCPG][NRPOS]; /* positions of free blocks */ 245 char cg_iused[MAXIPG/NBBY]; /* used inode map */ 246 char cg_free[1]; /* free block map */ 247 /* actually longer */ 248 }; 249 250 /* 251 * MAXBPG bounds the number of blocks of data per cylinder group, 252 * and is limited by the fact that cylinder groups are at most one block. 253 * Its size is derived from the size of blocks and the (struct cg) size, 254 * by the number of remaining bits. 255 */ 256 #define MAXBPG(fs) \ 257 (NBBY * ((fs)->fs_bsize - (sizeof (struct cg))) / (fs)->fs_frag) 258 259 /* 260 * Turn file system block numbers into disk block addresses. 261 * This maps file system blocks to device size blocks. 262 */ 263 #define fsbtodb(fs, b) ((b) * ((fs)->fs_fsize / DEV_BSIZE)) 264 #define dbtofsb(fs, b) ((b) / ((fs)->fs_fsize / DEV_BSIZE)) 265 266 /* 267 * Cylinder group macros to locate things in cylinder groups. 268 * 269 * cylinder group to disk block address of spare boot block 270 * and super block 271 * Note that these are in absolute addresses, and can NOT 272 * in general be expressable in terms of file system addresses. 273 */ 274 #define cgbblock(fs, c) (fsbtodb(fs, cgbase(fs, c)) + (fs)->fs_bblkno) 275 #define cgsblock(fs, c) (fsbtodb(fs, cgbase(fs, c)) + (fs)->fs_sblkno) 276 277 /* 278 * file system addresses of cylinder group data structures 279 */ 280 #define cgbase(fs, c) ((daddr_t)((fs)->fs_fpg * (c))) /* base addr */ 281 #define cgtod(fs, c) (cgbase(fs, c) + (fs)->fs_cblkno) /* cg block */ 282 #define cgimin(fs, c) (cgbase(fs, c) + (fs)->fs_iblkno) /* inode blk */ 283 #define cgdmin(fs, c) (cgbase(fs, c) + (fs)->fs_dblkno) /* 1st data */ 284 285 /* 286 * macros for handling inode numbers 287 * inode number to file system block offset 288 * inode number to cylinder group number 289 * inode number to file system block address 290 */ 291 #define itoo(fs, x) ((x) % INOPB(fs)) 292 #define itog(fs, x) ((x) / (fs)->fs_ipg) 293 #define itod(fs, x) \ 294 ((daddr_t)(cgimin(fs, itog(fs, x)) + \ 295 (x) % (fs)->fs_ipg / INOPB(fs) * (fs)->fs_frag)) 296 297 /* 298 * give cylinder group number for a file system block 299 * give cylinder group block number for a file system block 300 */ 301 #define dtog(fs, d) ((d) / (fs)->fs_fpg) 302 #define dtogd(fs, d) ((d) % (fs)->fs_fpg) 303 304 /* 305 * compute the cylinder and rotational position of a cyl block addr 306 */ 307 #define cbtocylno(fs, bno) \ 308 ((bno) * NSPF(fs) / (fs)->fs_spc) 309 #define cbtorpos(fs, bno) \ 310 ((bno) * NSPF(fs) % (fs)->fs_nsect * NRPOS / (fs)->fs_nsect) 311 312 /* 313 * The following macros optimize certain frequently calculated 314 * quantities by using shifts and masks in place of divisions 315 * modulos and multiplications. 316 */ 317 #define blkoff(fs, loc) /* calculates (loc % fs->fs_bsize) */ \ 318 ((loc) & ~(fs)->fs_bmask) 319 #define fragoff(fs, loc) /* calculates (loc % fs->fs_fsize) */ \ 320 ((loc) & ~(fs)->fs_fmask) 321 #define lblkno(fs, loc) /* calculates (loc / fs->fs_bsize) */ \ 322 ((loc) >> (fs)->fs_bshift) 323 #define numfrags(fs, loc) /* calculates (loc / fs->fs_fsize) */ \ 324 ((loc) >> (fs)->fs_fshift) 325 #define blkroundup(fs, size) /* calculates roundup(size, fs->fs_bsize) */ \ 326 (((size) + (fs)->fs_bsize - 1) & (fs)->fs_bmask) 327 #define fragroundup(fs, size) /* calculates roundup(size, fs->fs_fsize) */ \ 328 (((size) + (fs)->fs_fsize - 1) & (fs)->fs_fmask) 329 330 /* 331 * determining the size of a file block in the file system 332 */ 333 #define blksize(fs, ip, lbn) \ 334 (((lbn) >= NDADDR || (ip)->i_size >= ((lbn) + 1) * (fs)->fs_bsize) \ 335 ? (fs)->fs_bsize \ 336 : (fragroundup(fs, blkoff(fs, (ip)->i_size)))) 337 #define dblksize(fs, dip, lbn) \ 338 (((lbn) >= NDADDR || (dip)->di_size >= ((lbn) + 1) * (fs)->fs_bsize) \ 339 ? (fs)->fs_bsize \ 340 : (fragroundup(fs, blkoff(fs, (dip)->di_size)))) 341 342 /* 343 * number of disk sectors per block; assumes DEV_BSIZE byte sector size 344 */ 345 #define NSPB(fs) ((fs)->fs_bsize / DEV_BSIZE) 346 #define NSPF(fs) ((fs)->fs_fsize / DEV_BSIZE) 347 348 /* 349 * INOPB is the number of inodes in a secondary storage block 350 */ 351 #define INOPB(fs) ((fs)->fs_bsize / sizeof (struct dinode)) 352 #define INOPF(fs) ((fs)->fs_fsize / sizeof (struct dinode)) 353 354 /* 355 * NINDIR is the number of indirects in a file system block 356 */ 357 #define NINDIR(fs) ((fs)->fs_bsize / sizeof (daddr_t)) 358 359 #ifdef KERNEL 360 struct fs *getfs(); 361 #endif 362