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1.1 root 1: /*
2: * Copyright (c) 1982, 1986 Regents of the University of California.
3: * All rights reserved. The Berkeley software License Agreement
4: * specifies the terms and conditions for redistribution.
5: *
6: * @(#)fs.h 7.3 (Berkeley) 4/2/87
7: */
8:
9: /*
10: * Each disk drive contains some number of file systems.
11: * A file system consists of a number of cylinder groups.
12: * Each cylinder group has inodes and data.
13: *
14: * A file system is described by its super-block, which in turn
15: * describes the cylinder groups. The super-block is critical
16: * data and is replicated in each cylinder group to protect against
17: * catastrophic loss. This is done at mkfs time and the critical
18: * super-block data does not change, so the copies need not be
19: * referenced further unless disaster strikes.
20: *
21: * For file system fs, the offsets of the various blocks of interest
22: * are given in the super block as:
23: * [fs->fs_sblkno] Super-block
24: * [fs->fs_cblkno] Cylinder group block
25: * [fs->fs_iblkno] Inode blocks
26: * [fs->fs_dblkno] Data blocks
27: * The beginning of cylinder group cg in fs, is given by
28: * the ``cgbase(fs, cg)'' macro.
29: *
30: * The first boot and super blocks are given in absolute disk addresses.
31: * The byte-offset forms are preferred, as they don't imply a sector size.
32: */
33: #define BBSIZE 8192
34: #define SBSIZE 8192
35: #define BBOFF ((off_t)(0))
36: #define SBOFF ((off_t)(BBOFF + BBSIZE))
37: #define BBLOCK ((daddr_t)(0))
38: #define SBLOCK ((daddr_t)(BBLOCK + BBSIZE / DEV_BSIZE))
39:
40: /*
41: * Addresses stored in inodes are capable of addressing fragments
42: * of `blocks'. File system blocks of at most size MAXBSIZE can
43: * be optionally broken into 2, 4, or 8 pieces, each of which is
44: * addressible; these pieces may be DEV_BSIZE, or some multiple of
45: * a DEV_BSIZE unit.
46: *
47: * Large files consist of exclusively large data blocks. To avoid
48: * undue wasted disk space, the last data block of a small file may be
49: * allocated as only as many fragments of a large block as are
50: * necessary. The file system format retains only a single pointer
51: * to such a fragment, which is a piece of a single large block that
52: * has been divided. The size of such a fragment is determinable from
53: * information in the inode, using the ``blksize(fs, ip, lbn)'' macro.
54: *
55: * The file system records space availability at the fragment level;
56: * to determine block availability, aligned fragments are examined.
57: *
58: * The root inode is the root of the file system.
59: * Inode 0 can't be used for normal purposes and
60: * historically bad blocks were linked to inode 1,
61: * thus the root inode is 2. (inode 1 is no longer used for
62: * this purpose, however numerous dump tapes make this
63: * assumption, so we are stuck with it)
64: * The lost+found directory is given the next available
65: * inode when it is created by ``mkfs''.
66: */
67: #define ROOTINO ((ino_t)2) /* i number of all roots */
68: #define LOSTFOUNDINO (ROOTINO + 1)
69:
70: /*
71: * Cylinder group related limits.
72: *
73: * For each cylinder we keep track of the availability of blocks at different
74: * rotational positions, so that we can lay out the data to be picked
75: * up with minimum rotational latency. NRPOS is the number of rotational
76: * positions which we distinguish. With NRPOS 8 the resolution of our
77: * summary information is 2ms for a typical 3600 rpm drive.
78: */
79: #define NRPOS 8 /* number distinct rotational positions */
80:
81: /*
82: * MAXIPG bounds the number of inodes per cylinder group, and
83: * is needed only to keep the structure simpler by having the
84: * only a single variable size element (the free bit map).
85: *
86: * N.B.: MAXIPG must be a multiple of INOPB(fs).
87: */
88: #define MAXIPG 2048 /* max number inodes/cyl group */
89:
90: /*
91: * MINBSIZE is the smallest allowable block size.
92: * In order to insure that it is possible to create files of size
93: * 2^32 with only two levels of indirection, MINBSIZE is set to 4096.
94: * MINBSIZE must be big enough to hold a cylinder group block,
95: * thus changes to (struct cg) must keep its size within MINBSIZE.
96: * MAXCPG is limited only to dimension an array in (struct cg);
97: * it can be made larger as long as that structures size remains
98: * within the bounds dictated by MINBSIZE.
99: * Note that super blocks are always of size SBSIZE,
100: * and that both SBSIZE and MAXBSIZE must be >= MINBSIZE.
101: */
102: #define MINBSIZE 4096
103: #define MAXCPG 32 /* maximum fs_cpg */
104:
105: /*
106: * The path name on which the file system is mounted is maintained
107: * in fs_fsmnt. MAXMNTLEN defines the amount of space allocated in
108: * the super block for this name.
109: * The limit on the amount of summary information per file system
110: * is defined by MAXCSBUFS. It is currently parameterized for a
111: * maximum of two million cylinders.
112: */
113: #define MAXMNTLEN 384
114: #define MAXCSBUFS 32
115:
116: /*
117: * Per cylinder group information; summarized in blocks allocated
118: * from first cylinder group data blocks. These blocks have to be
119: * read in from fs_csaddr (size fs_cssize) in addition to the
120: * super block.
121: *
122: * N.B. sizeof(struct csum) must be a power of two in order for
123: * the ``fs_cs'' macro to work (see below).
124: */
125: struct csum {
126: long cs_ndir; /* number of directories */
127: long cs_nbfree; /* number of free blocks */
128: long cs_nifree; /* number of free inodes */
129: long cs_nffree; /* number of free frags */
130: };
131:
132: /*
133: * Super block for a file system.
134: */
135: #define FS_MAGIC 0x011954
136: struct fs
137: {
138: struct fs *fs_link; /* linked list of file systems */
139: struct fs *fs_rlink; /* used for incore super blocks */
140: daddr_t fs_sblkno; /* addr of super-block in filesys */
141: daddr_t fs_cblkno; /* offset of cyl-block in filesys */
142: daddr_t fs_iblkno; /* offset of inode-blocks in filesys */
143: daddr_t fs_dblkno; /* offset of first data after cg */
144: long fs_cgoffset; /* cylinder group offset in cylinder */
145: long fs_cgmask; /* used to calc mod fs_ntrak */
146: time_t fs_time; /* last time written */
147: long fs_size; /* number of blocks in fs */
148: long fs_dsize; /* number of data blocks in fs */
149: long fs_ncg; /* number of cylinder groups */
150: long fs_bsize; /* size of basic blocks in fs */
151: long fs_fsize; /* size of frag blocks in fs */
152: long fs_frag; /* number of frags in a block in fs */
153: /* these are configuration parameters */
154: long fs_minfree; /* minimum percentage of free blocks */
155: long fs_rotdelay; /* num of ms for optimal next block */
156: long fs_rps; /* disk revolutions per second */
157: /* these fields can be computed from the others */
158: long fs_bmask; /* ``blkoff'' calc of blk offsets */
159: long fs_fmask; /* ``fragoff'' calc of frag offsets */
160: long fs_bshift; /* ``lblkno'' calc of logical blkno */
161: long fs_fshift; /* ``numfrags'' calc number of frags */
162: /* these are configuration parameters */
163: long fs_maxcontig; /* max number of contiguous blks */
164: long fs_maxbpg; /* max number of blks per cyl group */
165: /* these fields can be computed from the others */
166: long fs_fragshift; /* block to frag shift */
167: long fs_fsbtodb; /* fsbtodb and dbtofsb shift constant */
168: long fs_sbsize; /* actual size of super block */
169: long fs_csmask; /* csum block offset */
170: long fs_csshift; /* csum block number */
171: long fs_nindir; /* value of NINDIR */
172: long fs_inopb; /* value of INOPB */
173: long fs_nspf; /* value of NSPF */
174: /* yet another configuration parameter */
175: long fs_optim; /* optimization preference, see below */
176: /* these fields are derived from the hardware */
177: long fs_npsect; /* # sectors/track including spares */
178: long fs_interleave; /* hardware sector interleave */
179: long fs_trackskew; /* sector 0 skew, per track */
180: long fs_headswitch; /* head switch time, usec */
181: long fs_trkseek; /* track-to-track seek, usec */
182: /* sizes determined by number of cylinder groups and their sizes */
183: daddr_t fs_csaddr; /* blk addr of cyl grp summary area */
184: long fs_cssize; /* size of cyl grp summary area */
185: long fs_cgsize; /* cylinder group size */
186: /* these fields are derived from the hardware */
187: long fs_ntrak; /* tracks per cylinder */
188: long fs_nsect; /* sectors per track */
189: long fs_spc; /* sectors per cylinder */
190: /* this comes from the disk driver partitioning */
191: long fs_ncyl; /* cylinders in file system */
192: /* these fields can be computed from the others */
193: long fs_cpg; /* cylinders per group */
194: long fs_ipg; /* inodes per group */
195: long fs_fpg; /* blocks per group * fs_frag */
196: /* this data must be re-computed after crashes */
197: struct csum fs_cstotal; /* cylinder summary information */
198: /* these fields are cleared at mount time */
199: char fs_fmod; /* super block modified flag */
200: char fs_clean; /* file system is clean flag */
201: char fs_ronly; /* mounted read-only flag */
202: char fs_flags; /* currently unused flag */
203: char fs_fsmnt[MAXMNTLEN]; /* name mounted on */
204: long fs_dbsize; /* hardware sector size */
205: long fs_sparecon[31]; /* reserved for future constants */
206: /* these fields retain the current block allocation info */
207: long fs_cgrotor; /* last cg searched */
208: struct csum *fs_csp[MAXCSBUFS];/* list of fs_cs info buffers */
209: long fs_cpc; /* cyl per cycle in postbl */
210: short fs_postbl[MAXCPG][NRPOS];/* head of blocks for each rotation */
211: long fs_magic; /* magic number */
212: u_char fs_rotbl[1]; /* list of blocks for each rotation */
213: /* actually longer */
214: };
215: /*
216: * Preference for optimization.
217: */
218: #define FS_OPTTIME 0 /* minimize allocation time */
219: #define FS_OPTSPACE 1 /* minimize disk fragmentation */
220:
221: /*
222: * Convert cylinder group to base address of its global summary info.
223: *
224: * N.B. This macro assumes that sizeof(struct csum) is a power of two.
225: */
226: #define fs_cs(fs, indx) \
227: fs_csp[(indx) >> (fs)->fs_csshift][(indx) & ~(fs)->fs_csmask]
228:
229: /*
230: * MAXBPC bounds the size of the rotational layout tables and
231: * is limited by the fact that the super block is of size SBSIZE.
232: * The size of these tables is INVERSELY proportional to the block
233: * size of the file system. It is aggravated by sector sizes that
234: * are not powers of two, as this increases the number of cylinders
235: * included before the rotational pattern repeats (fs_cpc).
236: * Its size is derived from the number of bytes remaining in (struct fs)
237: */
238: #define MAXBPC (SBSIZE - sizeof (struct fs))
239:
240: /*
241: * Cylinder group block for a file system.
242: */
243: #define CG_MAGIC 0x090255
244: struct cg {
245: struct cg *cg_link; /* linked list of cyl groups */
246: struct cg *cg_rlink; /* used for incore cyl groups */
247: time_t cg_time; /* time last written */
248: long cg_cgx; /* we are the cgx'th cylinder group */
249: short cg_ncyl; /* number of cyl's this cg */
250: short cg_niblk; /* number of inode blocks this cg */
251: long cg_ndblk; /* number of data blocks this cg */
252: struct csum cg_cs; /* cylinder summary information */
253: long cg_rotor; /* position of last used block */
254: long cg_frotor; /* position of last used frag */
255: long cg_irotor; /* position of last used inode */
256: long cg_frsum[MAXFRAG]; /* counts of available frags */
257: long cg_btot[MAXCPG]; /* block totals per cylinder */
258: short cg_b[MAXCPG][NRPOS]; /* positions of free blocks */
259: char cg_iused[MAXIPG/NBBY]; /* used inode map */
260: long cg_magic; /* magic number */
261: u_char cg_free[1]; /* free block map */
262: /* actually longer */
263: };
264:
265: /*
266: * MAXBPG bounds the number of blocks of data per cylinder group,
267: * and is limited by the fact that cylinder groups are at most one block.
268: * Its size is derived from the size of blocks and the (struct cg) size,
269: * by the number of remaining bits.
270: */
271: #define MAXBPG(fs) \
272: (fragstoblks((fs), (NBBY * ((fs)->fs_bsize - (sizeof (struct cg))))))
273:
274: /*
275: * Turn file system block numbers into disk block addresses.
276: * This maps file system blocks to device size blocks.
277: */
278: #define fsbtodb(fs, b) ((b) << (fs)->fs_fsbtodb)
279: #define dbtofsb(fs, b) ((b) >> (fs)->fs_fsbtodb)
280:
281: /*
282: * Cylinder group macros to locate things in cylinder groups.
283: * They calc file system addresses of cylinder group data structures.
284: */
285: #define cgbase(fs, c) ((daddr_t)((fs)->fs_fpg * (c)))
286: #define cgstart(fs, c) \
287: (cgbase(fs, c) + (fs)->fs_cgoffset * ((c) & ~((fs)->fs_cgmask)))
288: #define cgsblock(fs, c) (cgstart(fs, c) + (fs)->fs_sblkno) /* super blk */
289: #define cgtod(fs, c) (cgstart(fs, c) + (fs)->fs_cblkno) /* cg block */
290: #define cgimin(fs, c) (cgstart(fs, c) + (fs)->fs_iblkno) /* inode blk */
291: #define cgdmin(fs, c) (cgstart(fs, c) + (fs)->fs_dblkno) /* 1st data */
292:
293: /*
294: * Macros for handling inode numbers:
295: * inode number to file system block offset.
296: * inode number to cylinder group number.
297: * inode number to file system block address.
298: */
299: #define itoo(fs, x) ((x) % INOPB(fs))
300: #define itog(fs, x) ((x) / (fs)->fs_ipg)
301: #define itod(fs, x) \
302: ((daddr_t)(cgimin(fs, itog(fs, x)) + \
303: (blkstofrags((fs), (((x) % (fs)->fs_ipg) / INOPB(fs))))))
304:
305: /*
306: * Give cylinder group number for a file system block.
307: * Give cylinder group block number for a file system block.
308: */
309: #define dtog(fs, d) ((d) / (fs)->fs_fpg)
310: #define dtogd(fs, d) ((d) % (fs)->fs_fpg)
311:
312: /*
313: * Extract the bits for a block from a map.
314: * Compute the cylinder and rotational position of a cyl block addr.
315: */
316: #define blkmap(fs, map, loc) \
317: (((map)[(loc) / NBBY] >> ((loc) % NBBY)) & (0xff >> (NBBY - (fs)->fs_frag)))
318: #define cbtocylno(fs, bno) \
319: ((bno) * NSPF(fs) / (fs)->fs_spc)
320: #define cbtorpos(fs, bno) \
321: (((bno) * NSPF(fs) % (fs)->fs_spc / (fs)->fs_nsect * (fs)->fs_trackskew + \
322: (bno) * NSPF(fs) % (fs)->fs_spc % (fs)->fs_nsect * (fs)->fs_interleave) % \
323: (fs)->fs_nsect * NRPOS / (fs)->fs_npsect)
324:
325: /*
326: * The following macros optimize certain frequently calculated
327: * quantities by using shifts and masks in place of divisions
328: * modulos and multiplications.
329: */
330: #define blkoff(fs, loc) /* calculates (loc % fs->fs_bsize) */ \
331: ((loc) & ~(fs)->fs_bmask)
332: #define fragoff(fs, loc) /* calculates (loc % fs->fs_fsize) */ \
333: ((loc) & ~(fs)->fs_fmask)
334: #define lblkno(fs, loc) /* calculates (loc / fs->fs_bsize) */ \
335: ((loc) >> (fs)->fs_bshift)
336: #define numfrags(fs, loc) /* calculates (loc / fs->fs_fsize) */ \
337: ((loc) >> (fs)->fs_fshift)
338: #define blkroundup(fs, size) /* calculates roundup(size, fs->fs_bsize) */ \
339: (((size) + (fs)->fs_bsize - 1) & (fs)->fs_bmask)
340: #define fragroundup(fs, size) /* calculates roundup(size, fs->fs_fsize) */ \
341: (((size) + (fs)->fs_fsize - 1) & (fs)->fs_fmask)
342: #define fragstoblks(fs, frags) /* calculates (frags / fs->fs_frag) */ \
343: ((frags) >> (fs)->fs_fragshift)
344: #define blkstofrags(fs, blks) /* calculates (blks * fs->fs_frag) */ \
345: ((blks) << (fs)->fs_fragshift)
346: #define fragnum(fs, fsb) /* calculates (fsb % fs->fs_frag) */ \
347: ((fsb) & ((fs)->fs_frag - 1))
348: #define blknum(fs, fsb) /* calculates rounddown(fsb, fs->fs_frag) */ \
349: ((fsb) &~ ((fs)->fs_frag - 1))
350:
351: /*
352: * Determine the number of available frags given a
353: * percentage to hold in reserve
354: */
355: #define freespace(fs, percentreserved) \
356: (blkstofrags((fs), (fs)->fs_cstotal.cs_nbfree) + \
357: (fs)->fs_cstotal.cs_nffree - ((fs)->fs_dsize * (percentreserved) / 100))
358:
359: /*
360: * Determining the size of a file block in the file system.
361: */
362: #define blksize(fs, ip, lbn) \
363: (((lbn) >= NDADDR || (ip)->i_size >= ((lbn) + 1) << (fs)->fs_bshift) \
364: ? (fs)->fs_bsize \
365: : (fragroundup(fs, blkoff(fs, (ip)->i_size))))
366: #define dblksize(fs, dip, lbn) \
367: (((lbn) >= NDADDR || (dip)->di_size >= ((lbn) + 1) << (fs)->fs_bshift) \
368: ? (fs)->fs_bsize \
369: : (fragroundup(fs, blkoff(fs, (dip)->di_size))))
370:
371: /*
372: * Number of disk sectors per block; assumes DEV_BSIZE byte sector size.
373: */
374: #define NSPB(fs) ((fs)->fs_nspf << (fs)->fs_fragshift)
375: #define NSPF(fs) ((fs)->fs_nspf)
376:
377: /*
378: * INOPB is the number of inodes in a secondary storage block.
379: */
380: #define INOPB(fs) ((fs)->fs_inopb)
381: #define INOPF(fs) ((fs)->fs_inopb >> (fs)->fs_fragshift)
382:
383: /*
384: * NINDIR is the number of indirects in a file system block.
385: */
386: #define NINDIR(fs) ((fs)->fs_nindir)
387:
388: #ifdef KERNEL
389: struct fs *getfs();
390: struct fs *mountfs();
391: #endif
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