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7e2a7a5c | 1 | /* fs.h 4.7 83/01/09 */ |
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2 | |
3 | /* | |
4 | * Each disk drive contains some number of file systems. | |
5 | * A file system consists of a number of cylinder groups. | |
6 | * Each cylinder group has inodes and data. | |
7 | * | |
8 | * A file system is described by its super-block, which in turn | |
9 | * describes the cylinder groups. The super-block is critical | |
10 | * data and is replicated in each cylinder group to protect against | |
11 | * catastrophic loss. This is done at mkfs time and the critical | |
12 | * super-block data does not change, so the copies need not be | |
13 | * referenced further unless disaster strikes. | |
14 | * | |
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15 | * For file system fs, the offsets of the various blocks of interest |
16 | * are given in the super block as: | |
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17 | * [fs->fs_sblkno] Super-block |
18 | * [fs->fs_cblkno] Cylinder group block | |
19 | * [fs->fs_iblkno] Inode blocks | |
20 | * [fs->fs_dblkno] Data blocks | |
21 | * The beginning of cylinder group cg in fs, is given by | |
6994bf5d | 22 | * the ``cgbase(fs, cg)'' macro. |
b6407c9d | 23 | * |
aca50d72 | 24 | * The first boot and super blocks are given in absolute disk addresses. |
b6407c9d | 25 | */ |
1df1dbcd | 26 | #define BBSIZE 8192 |
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27 | #define SBSIZE 8192 |
28 | #define BBLOCK ((daddr_t)(0)) | |
29 | #define SBLOCK ((daddr_t)(BBLOCK + BBSIZE / DEV_BSIZE)) | |
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30 | |
31 | /* | |
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32 | * Addresses stored in inodes are capable of addressing fragments |
33 | * of `blocks'. File system blocks of at most size MAXBSIZE can | |
34 | * be optionally broken into 2, 4, or 8 pieces, each of which is | |
35 | * addressible; these pieces may be DEV_BSIZE, or some multiple of | |
36 | * a DEV_BSIZE unit. | |
1ef63481 | 37 | * |
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38 | * Large files consist of exclusively large data blocks. To avoid |
39 | * undue wasted disk space, the last data block of a small file may be | |
40 | * allocated as only as many fragments of a large block as are | |
41 | * necessary. The file system format retains only a single pointer | |
42 | * to such a fragment, which is a piece of a single large block that | |
43 | * has been divided. The size of such a fragment is determinable from | |
44 | * information in the inode, using the ``blksize(fs, ip, lbn)'' macro. | |
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45 | * |
46 | * The file system records space availability at the fragment level; | |
47 | * to determine block availability, aligned fragments are examined. | |
743f1ef7 | 48 | * |
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49 | * The root inode is the root of the file system. |
50 | * Inode 0 can't be used for normal purposes and | |
51 | * historically bad blocks were linked to inode 1, | |
52 | * thus the root inode is 2. (inode 1 is no longer used for | |
53 | * this purpose, however numerous dump tapes make this | |
54 | * assumption, so we are stuck with it) | |
55 | * The lost+found directory is given the next available | |
56 | * inode when it is created by ``mkfs''. | |
57 | */ | |
58 | #define ROOTINO ((ino_t)2) /* i number of all roots */ | |
59 | #define LOSTFOUNDINO (ROOTINO + 1) | |
60 | ||
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61 | /* |
62 | * Cylinder group related limits. | |
63 | * | |
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64 | * For each cylinder we keep track of the availability of blocks at different |
65 | * rotational positions, so that we can lay out the data to be picked | |
66 | * up with minimum rotational latency. NRPOS is the number of rotational | |
67 | * positions which we distinguish. With NRPOS 8 the resolution of our | |
68 | * summary information is 2ms for a typical 3600 rpm drive. | |
69 | */ | |
80cc8328 | 70 | #define NRPOS 8 /* number distinct rotational positions */ |
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71 | |
72 | /* | |
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73 | * MAXIPG bounds the number of inodes per cylinder group, and |
74 | * is needed only to keep the structure simpler by having the | |
75 | * only a single variable size element (the free bit map). | |
76 | * | |
77 | * N.B.: MAXIPG must be a multiple of INOPB(fs). | |
1ef63481 | 78 | */ |
80cc8328 | 79 | #define MAXIPG 2048 /* max number inodes/cyl group */ |
1ef63481 | 80 | |
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81 | /* |
82 | * MINBSIZE is the smallest allowable block size. | |
83 | * In order to insure that it is possible to create files of size | |
84 | * 2^32 with only two levels of indirection, MINBSIZE is set to 4096. | |
85 | * MINBSIZE must be big enough to hold a cylinder group block, | |
86 | * thus changes to (struct cg) must keep its size within MINBSIZE. | |
87 | * MAXCPG is limited only to dimension an array in (struct cg); | |
88 | * it can be made larger as long as that structures size remains | |
89 | * within the bounds dictated by MINBSIZE. | |
90 | * Note that super blocks are always of size MAXBSIZE, | |
91 | * and that MAXBSIZE must be >= MINBSIZE. | |
92 | */ | |
93 | #define MINBSIZE 4096 | |
b6407c9d | 94 | #define MAXCPG 32 /* maximum fs_cpg */ |
80cc8328 | 95 | |
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96 | /* |
97 | * The path name on which the file system is mounted is maintained | |
98 | * in fs_fsmnt. MAXMNTLEN defines the amount of space allocated in | |
99 | * the super block for this name. | |
1b807fc9 | 100 | * The limit on the amount of summary information per file system |
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101 | * is defined by MAXCSBUFS. It is currently parameterized for a |
102 | * maximum of two million cylinders. | |
2c9afb08 | 103 | */ |
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104 | #define MAXMNTLEN 512 |
105 | #define MAXCSBUFS 32 | |
2c9afb08 | 106 | |
1ef63481 | 107 | /* |
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108 | * Per cylinder group information; summarized in blocks allocated |
109 | * from first cylinder group data blocks. These blocks have to be | |
110 | * read in from fs_csaddr (size fs_cssize) in addition to the | |
111 | * super block. | |
1ef63481 | 112 | * |
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113 | * N.B. sizeof(struct csum) must be a power of two in order for |
114 | * the ``fs_cs'' macro to work (see below). | |
1ef63481 | 115 | */ |
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116 | struct csum { |
117 | long cs_ndir; /* number of directories */ | |
118 | long cs_nbfree; /* number of free blocks */ | |
119 | long cs_nifree; /* number of free inodes */ | |
120 | long cs_nffree; /* number of free frags */ | |
121 | }; | |
1ef63481 | 122 | |
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123 | /* |
124 | * Super block for a file system. | |
125 | */ | |
b9b166c6 | 126 | #define FS_MAGIC 0x011954 |
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127 | struct fs |
128 | { | |
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129 | struct fs *fs_link; /* linked list of file systems */ |
130 | struct fs *fs_rlink; /* used for incore super blocks */ | |
26169eda | 131 | daddr_t fs_sblkno; /* addr of super-block in filesys */ |
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132 | daddr_t fs_cblkno; /* offset of cyl-block in filesys */ |
133 | daddr_t fs_iblkno; /* offset of inode-blocks in filesys */ | |
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134 | daddr_t fs_dblkno; /* offset of first data after cg */ |
135 | long fs_cgoffset; /* cylinder group offset in cylinder */ | |
136 | long fs_cgmask; /* used to calc mod fs_ntrak */ | |
1ef63481 | 137 | time_t fs_time; /* last time written */ |
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138 | long fs_size; /* number of blocks in fs */ |
139 | long fs_dsize; /* number of data blocks in fs */ | |
140 | long fs_ncg; /* number of cylinder groups */ | |
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141 | long fs_bsize; /* size of basic blocks in fs */ |
142 | long fs_fsize; /* size of frag blocks in fs */ | |
26169eda | 143 | long fs_frag; /* number of frags in a block in fs */ |
7e2a7a5c | 144 | /* these are configuration parameters */ |
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145 | long fs_minfree; /* minimum percentage of free blocks */ |
146 | long fs_rotdelay; /* num of ms for optimal next block */ | |
147 | long fs_rps; /* disk revolutions per second */ | |
7e2a7a5c | 148 | /* these fields can be computed from the others */ |
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149 | long fs_bmask; /* ``blkoff'' calc of blk offsets */ |
150 | long fs_fmask; /* ``fragoff'' calc of frag offsets */ | |
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151 | long fs_bshift; /* ``lblkno'' calc of logical blkno */ |
152 | long fs_fshift; /* ``numfrags'' calc number of frags */ | |
7e2a7a5c | 153 | /* these are configuration parameters */ |
af0b24db SL |
154 | long fs_maxcontig; /* max number of contiguous blks */ |
155 | long fs_maxbpg; /* max number of blks per cyl group */ | |
7e2a7a5c | 156 | /* these fields can be computed from the others */ |
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157 | long fs_fragshift; /* block to frag shift */ |
158 | long fs_fsbtodb; /* fsbtodb and dbtofsb shift constant */ | |
159 | long fs_sbsize; /* actual size of super block */ | |
160 | long fs_csmask; /* csum block offset */ | |
161 | long fs_csshift; /* csum block number */ | |
162 | long fs_nindir; /* value of NINDIR */ | |
163 | long fs_inopb; /* value of INOPB */ | |
164 | long fs_nspf; /* value of NSPF */ | |
165 | long fs_sparecon[6]; /* reserved for future constants */ | |
1ef63481 | 166 | /* sizes determined by number of cylinder groups and their sizes */ |
b6407c9d | 167 | daddr_t fs_csaddr; /* blk addr of cyl grp summary area */ |
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168 | long fs_cssize; /* size of cyl grp summary area */ |
169 | long fs_cgsize; /* cylinder group size */ | |
1ef63481 | 170 | /* these fields should be derived from the hardware */ |
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171 | long fs_ntrak; /* tracks per cylinder */ |
172 | long fs_nsect; /* sectors per track */ | |
003319d1 | 173 | long fs_spc; /* sectors per cylinder */ |
1ef63481 | 174 | /* this comes from the disk driver partitioning */ |
003319d1 | 175 | long fs_ncyl; /* cylinders in file system */ |
1ef63481 | 176 | /* these fields can be computed from the others */ |
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177 | long fs_cpg; /* cylinders per group */ |
178 | long fs_ipg; /* inodes per group */ | |
b6407c9d | 179 | long fs_fpg; /* blocks per group * fs_frag */ |
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180 | /* this data must be re-computed after crashes */ |
181 | struct csum fs_cstotal; /* cylinder summary information */ | |
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182 | /* these fields are cleared at mount time */ |
183 | char fs_fmod; /* super block modified flag */ | |
26169eda | 184 | char fs_clean; /* file system is clean flag */ |
1ef63481 | 185 | char fs_ronly; /* mounted read-only flag */ |
26169eda | 186 | char fs_flags; /* currently unused flag */ |
2c9afb08 | 187 | char fs_fsmnt[MAXMNTLEN]; /* name mounted on */ |
743f1ef7 | 188 | /* these fields retain the current block allocation info */ |
003319d1 | 189 | long fs_cgrotor; /* last cg searched */ |
1b807fc9 | 190 | struct csum *fs_csp[MAXCSBUFS];/* list of fs_cs info buffers */ |
26169eda | 191 | long fs_cpc; /* cyl per cycle in postbl */ |
aca50d72 | 192 | short fs_postbl[MAXCPG][NRPOS];/* head of blocks for each rotation */ |
b9b166c6 | 193 | long fs_magic; /* magic number */ |
aca50d72 | 194 | u_char fs_rotbl[1]; /* list of blocks for each rotation */ |
743f1ef7 | 195 | /* actually longer */ |
1ef63481 | 196 | }; |
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197 | |
198 | /* | |
2c9afb08 | 199 | * Convert cylinder group to base address of its global summary info. |
80cc8328 | 200 | * |
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201 | * N.B. This macro assumes that sizeof(struct csum) is a power of two. |
202 | */ | |
203 | #define fs_cs(fs, indx) \ | |
7e2a7a5c | 204 | fs_csp[(indx) >> (fs)->fs_csshift][(indx) & ~(fs)->fs_csmask] |
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205 | |
206 | /* | |
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207 | * MAXBPC bounds the size of the rotational layout tables and |
208 | * is limited by the fact that the super block is of size SBSIZE. | |
209 | * The size of these tables is INVERSELY proportional to the block | |
210 | * size of the file system. It is aggravated by sector sizes that | |
211 | * are not powers of two, as this increases the number of cylinders | |
212 | * included before the rotational pattern repeats (fs_cpc). | |
213 | * Its size is derived from the number of bytes remaining in (struct fs) | |
1ef63481 | 214 | */ |
aca50d72 | 215 | #define MAXBPC (SBSIZE - sizeof (struct fs)) |
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216 | |
217 | /* | |
80cc8328 | 218 | * Cylinder group block for a file system. |
1ef63481 | 219 | */ |
b9b166c6 | 220 | #define CG_MAGIC 0x090255 |
1ef63481 | 221 | struct cg { |
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222 | struct cg *cg_link; /* linked list of cyl groups */ |
223 | struct cg *cg_rlink; /* used for incore cyl groups */ | |
1ef63481 | 224 | time_t cg_time; /* time last written */ |
003319d1 | 225 | long cg_cgx; /* we are the cgx'th cylinder group */ |
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226 | short cg_ncyl; /* number of cyl's this cg */ |
227 | short cg_niblk; /* number of inode blocks this cg */ | |
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228 | long cg_ndblk; /* number of data blocks this cg */ |
229 | struct csum cg_cs; /* cylinder summary information */ | |
230 | long cg_rotor; /* position of last used block */ | |
231 | long cg_frotor; /* position of last used frag */ | |
232 | long cg_irotor; /* position of last used inode */ | |
b6407c9d | 233 | long cg_frsum[MAXFRAG]; /* counts of available frags */ |
d37938c8 | 234 | long cg_btot[MAXCPG]; /* block totals per cylinder */ |
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235 | short cg_b[MAXCPG][NRPOS]; /* positions of free blocks */ |
236 | char cg_iused[MAXIPG/NBBY]; /* used inode map */ | |
b9b166c6 | 237 | long cg_magic; /* magic number */ |
110d7a57 | 238 | u_char cg_free[1]; /* free block map */ |
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239 | /* actually longer */ |
240 | }; | |
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241 | |
242 | /* | |
243 | * MAXBPG bounds the number of blocks of data per cylinder group, | |
244 | * and is limited by the fact that cylinder groups are at most one block. | |
245 | * Its size is derived from the size of blocks and the (struct cg) size, | |
246 | * by the number of remaining bits. | |
247 | */ | |
248 | #define MAXBPG(fs) \ | |
7e2a7a5c | 249 | (NBBY * ((fs)->fs_bsize - (sizeof (struct cg))) >> (fs)->fs_fragshift) |
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250 | |
251 | /* | |
252 | * Turn file system block numbers into disk block addresses. | |
253 | * This maps file system blocks to device size blocks. | |
254 | */ | |
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255 | #define fsbtodb(fs, b) ((b) << (fs)->fs_fsbtodb) |
256 | #define dbtofsb(fs, b) ((b) >> (fs)->fs_fsbtodb) | |
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257 | |
258 | /* | |
259 | * Cylinder group macros to locate things in cylinder groups. | |
26169eda | 260 | * They calc file system addresses of cylinder group data structures. |
80cc8328 | 261 | */ |
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262 | #define cgbase(fs, c) ((daddr_t)((fs)->fs_fpg * (c))) |
263 | #define cgstart(fs, c) \ | |
264 | (cgbase(fs, c) + (fs)->fs_cgoffset * ((c) & ~((fs)->fs_cgmask))) | |
265 | #define cgsblock(fs, c) (cgstart(fs, c) + (fs)->fs_sblkno) /* super blk */ | |
266 | #define cgtod(fs, c) (cgstart(fs, c) + (fs)->fs_cblkno) /* cg block */ | |
267 | #define cgimin(fs, c) (cgstart(fs, c) + (fs)->fs_iblkno) /* inode blk */ | |
268 | #define cgdmin(fs, c) (cgstart(fs, c) + (fs)->fs_dblkno) /* 1st data */ | |
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269 | |
270 | /* | |
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271 | * Macros for handling inode numbers: |
272 | * inode number to file system block offset. | |
273 | * inode number to cylinder group number. | |
274 | * inode number to file system block address. | |
80cc8328 | 275 | */ |
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276 | #define itoo(fs, x) ((x) % INOPB(fs)) |
277 | #define itog(fs, x) ((x) / (fs)->fs_ipg) | |
278 | #define itod(fs, x) \ | |
279 | ((daddr_t)(cgimin(fs, itog(fs, x)) + \ | |
7e2a7a5c | 280 | ((((x) % (fs)->fs_ipg) / INOPB(fs)) << (fs)->fs_fragshift))) |
80cc8328 | 281 | |
80cc8328 | 282 | /* |
2c9afb08 KM |
283 | * Give cylinder group number for a file system block. |
284 | * Give cylinder group block number for a file system block. | |
80cc8328 | 285 | */ |
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286 | #define dtog(fs, d) ((d) / (fs)->fs_fpg) |
287 | #define dtogd(fs, d) ((d) % (fs)->fs_fpg) | |
80cc8328 | 288 | |
aca50d72 | 289 | /* |
2c9afb08 KM |
290 | * Extract the bits for a block from a map. |
291 | * Compute the cylinder and rotational position of a cyl block addr. | |
aca50d72 | 292 | */ |
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293 | #define blkmap(fs, map, loc) \ |
294 | (((map)[loc / NBBY] >> (loc % NBBY)) & (0xff >> (NBBY - (fs)->fs_frag))) | |
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295 | #define cbtocylno(fs, bno) \ |
296 | ((bno) * NSPF(fs) / (fs)->fs_spc) | |
297 | #define cbtorpos(fs, bno) \ | |
298 | ((bno) * NSPF(fs) % (fs)->fs_nsect * NRPOS / (fs)->fs_nsect) | |
299 | ||
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300 | /* |
301 | * The following macros optimize certain frequently calculated | |
302 | * quantities by using shifts and masks in place of divisions | |
303 | * modulos and multiplications. | |
304 | */ | |
305 | #define blkoff(fs, loc) /* calculates (loc % fs->fs_bsize) */ \ | |
306 | ((loc) & ~(fs)->fs_bmask) | |
307 | #define fragoff(fs, loc) /* calculates (loc % fs->fs_fsize) */ \ | |
308 | ((loc) & ~(fs)->fs_fmask) | |
309 | #define lblkno(fs, loc) /* calculates (loc / fs->fs_bsize) */ \ | |
310 | ((loc) >> (fs)->fs_bshift) | |
311 | #define numfrags(fs, loc) /* calculates (loc / fs->fs_fsize) */ \ | |
312 | ((loc) >> (fs)->fs_fshift) | |
313 | #define blkroundup(fs, size) /* calculates roundup(size, fs->fs_bsize) */ \ | |
314 | (((size) + (fs)->fs_bsize - 1) & (fs)->fs_bmask) | |
315 | #define fragroundup(fs, size) /* calculates roundup(size, fs->fs_fsize) */ \ | |
316 | (((size) + (fs)->fs_fsize - 1) & (fs)->fs_fmask) | |
317 | ||
80cc8328 | 318 | /* |
2c9afb08 | 319 | * Determining the size of a file block in the file system. |
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320 | */ |
321 | #define blksize(fs, ip, lbn) \ | |
7e2a7a5c | 322 | (((lbn) >= NDADDR || (ip)->i_size >= ((lbn) + 1) << (fs)->fs_bshift) \ |
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323 | ? (fs)->fs_bsize \ |
324 | : (fragroundup(fs, blkoff(fs, (ip)->i_size)))) | |
80cc8328 | 325 | #define dblksize(fs, dip, lbn) \ |
7e2a7a5c | 326 | (((lbn) >= NDADDR || (dip)->di_size >= ((lbn) + 1) << (fs)->fs_bshift) \ |
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327 | ? (fs)->fs_bsize \ |
328 | : (fragroundup(fs, blkoff(fs, (dip)->di_size)))) | |
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329 | |
330 | /* | |
2c9afb08 | 331 | * Number of disk sectors per block; assumes DEV_BSIZE byte sector size. |
80cc8328 | 332 | */ |
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333 | #define NSPB(fs) ((fs)->fs_nspf << (fs)->fs_fragshift) |
334 | #define NSPF(fs) ((fs)->fs_nspf) | |
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335 | |
336 | /* | |
2c9afb08 | 337 | * INOPB is the number of inodes in a secondary storage block. |
80cc8328 | 338 | */ |
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339 | #define INOPB(fs) ((fs)->fs_inopb) |
340 | #define INOPF(fs) ((fs)->fs_inopb >> (fs)->fs_fragshift) | |
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341 | |
342 | /* | |
2c9afb08 | 343 | * NINDIR is the number of indirects in a file system block. |
80cc8328 | 344 | */ |
7e2a7a5c | 345 | #define NINDIR(fs) ((fs)->fs_nindir) |
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346 | |
347 | #ifdef KERNEL | |
348 | struct fs *getfs(); | |
1bbbd864 | 349 | struct fs *mountfs(); |
1ef63481 | 350 | #endif |