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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 7.1 (Berkeley) 6/4/86
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: */
32: #define BBSIZE 8192
33: #define SBSIZE 8192
34: #define BBLOCK ((daddr_t)(0))
35: #define SBLOCK ((daddr_t)(BBLOCK + BBSIZE / DEV_BSIZE))
36:
37: /*
38: * Addresses stored in inodes are capable of addressing fragments
39: * of `blocks'. File system blocks of at most size MAXBSIZE can
40: * be optionally broken into 2, 4, or 8 pieces, each of which is
41: * addressible; these pieces may be DEV_BSIZE, or some multiple of
42: * a DEV_BSIZE unit.
43: *
44: * Large files consist of exclusively large data blocks. To avoid
45: * undue wasted disk space, the last data block of a small file may be
46: * allocated as only as many fragments of a large block as are
47: * necessary. The file system format retains only a single pointer
48: * to such a fragment, which is a piece of a single large block that
49: * has been divided. The size of such a fragment is determinable from
50: * information in the inode, using the ``blksize(fs, ip, lbn)'' macro.
51: *
52: * The file system records space availability at the fragment level;
53: * to determine block availability, aligned fragments are examined.
54: *
55: * The root inode is the root of the file system.
56: * Inode 0 can't be used for normal purposes and
57: * historically bad blocks were linked to inode 1,
58: * thus the root inode is 2. (inode 1 is no longer used for
59: * this purpose, however numerous dump tapes make this
60: * assumption, so we are stuck with it)
61: * The lost+found directory is given the next available
62: * inode when it is created by ``mkfs''.
63: */
64: #define ROOTINO ((ino_t)2) /* i number of all roots */
65: #define LOSTFOUNDINO (ROOTINO + 1)
66:
67: /*
68: * Cylinder group related limits.
69: *
70: * For each cylinder we keep track of the availability of blocks at different
71: * rotational positions, so that we can lay out the data to be picked
72: * up with minimum rotational latency. NRPOS is the number of rotational
73: * positions which we distinguish. With NRPOS 8 the resolution of our
74: * summary information is 2ms for a typical 3600 rpm drive.
75: */
76: #define NRPOS 8 /* number distinct rotational positions */
77:
78: /*
79: * MAXIPG bounds the number of inodes per cylinder group, and
80: * is needed only to keep the structure simpler by having the
81: * only a single variable size element (the free bit map).
82: *
83: * N.B.: MAXIPG must be a multiple of INOPB(fs).
84: */
85: #define MAXIPG 2048 /* max number inodes/cyl group */
86:
87: /*
88: * MINBSIZE is the smallest allowable block size.
89: * In order to insure that it is possible to create files of size
90: * 2^32 with only two levels of indirection, MINBSIZE is set to 4096.
91: * MINBSIZE must be big enough to hold a cylinder group block,
92: * thus changes to (struct cg) must keep its size within MINBSIZE.
93: * MAXCPG is limited only to dimension an array in (struct cg);
94: * it can be made larger as long as that structures size remains
95: * within the bounds dictated by MINBSIZE.
96: * Note that super blocks are always of size SBSIZE,
97: * and that both SBSIZE and MAXBSIZE must be >= MINBSIZE.
98: */
99: #define MINBSIZE 4096
100: #define MAXCPG 32 /* maximum fs_cpg */
101:
102: /*
103: * The path name on which the file system is mounted is maintained
104: * in fs_fsmnt. MAXMNTLEN defines the amount of space allocated in
105: * the super block for this name.
106: * The limit on the amount of summary information per file system
107: * is defined by MAXCSBUFS. It is currently parameterized for a
108: * maximum of two million cylinders.
109: */
110: #define MAXMNTLEN 512
111: #define MAXCSBUFS 32
112:
113: /*
114: * Per cylinder group information; summarized in blocks allocated
115: * from first cylinder group data blocks. These blocks have to be
116: * read in from fs_csaddr (size fs_cssize) in addition to the
117: * super block.
118: *
119: * N.B. sizeof(struct csum) must be a power of two in order for
120: * the ``fs_cs'' macro to work (see below).
121: */
122: struct csum {
123: long cs_ndir; /* number of directories */
124: long cs_nbfree; /* number of free blocks */
125: long cs_nifree; /* number of free inodes */
126: long cs_nffree; /* number of free frags */
127: };
128:
129: /*
130: * Super block for a file system.
131: */
132: #define FS_MAGIC 0x011954
133: struct fs
134: {
135: struct fs *fs_link; /* linked list of file systems */
136: struct fs *fs_rlink; /* used for incore super blocks */
137: daddr_t fs_sblkno; /* addr of super-block in filesys */
138: daddr_t fs_cblkno; /* offset of cyl-block in filesys */
139: daddr_t fs_iblkno; /* offset of inode-blocks in filesys */
140: daddr_t fs_dblkno; /* offset of first data after cg */
141: long fs_cgoffset; /* cylinder group offset in cylinder */
142: long fs_cgmask; /* used to calc mod fs_ntrak */
143: time_t fs_time; /* last time written */
144: long fs_size; /* number of blocks in fs */
145: long fs_dsize; /* number of data blocks in fs */
146: long fs_ncg; /* number of cylinder groups */
147: long fs_bsize; /* size of basic blocks in fs */
148: long fs_fsize; /* size of frag blocks in fs */
149: long fs_frag; /* number of frags in a block in fs */
150: /* these are configuration parameters */
151: long fs_minfree; /* minimum percentage of free blocks */
152: long fs_rotdelay; /* num of ms for optimal next block */
153: long fs_rps; /* disk revolutions per second */
154: /* these fields can be computed from the others */
155: long fs_bmask; /* ``blkoff'' calc of blk offsets */
156: long fs_fmask; /* ``fragoff'' calc of frag offsets */
157: long fs_bshift; /* ``lblkno'' calc of logical blkno */
158: long fs_fshift; /* ``numfrags'' calc number of frags */
159: /* these are configuration parameters */
160: long fs_maxcontig; /* max number of contiguous blks */
161: long fs_maxbpg; /* max number of blks per cyl group */
162: /* these fields can be computed from the others */
163: long fs_fragshift; /* block to frag shift */
164: long fs_fsbtodb; /* fsbtodb and dbtofsb shift constant */
165: long fs_sbsize; /* actual size of super block */
166: long fs_csmask; /* csum block offset */
167: long fs_csshift; /* csum block number */
168: long fs_nindir; /* value of NINDIR */
169: long fs_inopb; /* value of INOPB */
170: long fs_nspf; /* value of NSPF */
171: long fs_optim; /* optimization preference, see below */
172: long fs_sparecon[5]; /* reserved for future constants */
173: /* sizes determined by number of cylinder groups and their sizes */
174: daddr_t fs_csaddr; /* blk addr of cyl grp summary area */
175: long fs_cssize; /* size of cyl grp summary area */
176: long fs_cgsize; /* cylinder group size */
177: /* these fields should be derived from the hardware */
178: long fs_ntrak; /* tracks per cylinder */
179: long fs_nsect; /* sectors per track */
180: long fs_spc; /* sectors per cylinder */
181: /* this comes from the disk driver partitioning */
182: long fs_ncyl; /* cylinders in file system */
183: /* these fields can be computed from the others */
184: long fs_cpg; /* cylinders per group */
185: long fs_ipg; /* inodes per group */
186: long fs_fpg; /* blocks per group * fs_frag */
187: /* this data must be re-computed after crashes */
188: struct csum fs_cstotal; /* cylinder summary information */
189: /* these fields are cleared at mount time */
190: char fs_fmod; /* super block modified flag */
191: char fs_clean; /* file system is clean flag */
192: char fs_ronly; /* mounted read-only flag */
193: char fs_flags; /* currently unused flag */
194: char fs_fsmnt[MAXMNTLEN]; /* name mounted on */
195: /* these fields retain the current block allocation info */
196: long fs_cgrotor; /* last cg searched */
197: struct csum *fs_csp[MAXCSBUFS];/* list of fs_cs info buffers */
198: long fs_cpc; /* cyl per cycle in postbl */
199: short fs_postbl[MAXCPG][NRPOS];/* head of blocks for each rotation */
200: long fs_magic; /* magic number */
201: u_char fs_rotbl[1]; /* list of blocks for each rotation */
202: /* actually longer */
203: };
204: /*
205: * Preference for optimization.
206: */
207: #define FS_OPTTIME 0 /* minimize allocation time */
208: #define FS_OPTSPACE 1 /* minimize disk fragmentation */
209:
210: /*
211: * Convert cylinder group to base address of its global summary info.
212: *
213: * N.B. This macro assumes that sizeof(struct csum) is a power of two.
214: */
215: #define fs_cs(fs, indx) \
216: fs_csp[(indx) >> (fs)->fs_csshift][(indx) & ~(fs)->fs_csmask]
217:
218: /*
219: * MAXBPC bounds the size of the rotational layout tables and
220: * is limited by the fact that the super block is of size SBSIZE.
221: * The size of these tables is INVERSELY proportional to the block
222: * size of the file system. It is aggravated by sector sizes that
223: * are not powers of two, as this increases the number of cylinders
224: * included before the rotational pattern repeats (fs_cpc).
225: * Its size is derived from the number of bytes remaining in (struct fs)
226: */
227: #define MAXBPC (SBSIZE - sizeof (struct fs))
228:
229: /*
230: * Cylinder group block for a file system.
231: */
232: #define CG_MAGIC 0x090255
233: struct cg {
234: struct cg *cg_link; /* linked list of cyl groups */
235: struct cg *cg_rlink; /* used for incore cyl groups */
236: time_t cg_time; /* time last written */
237: long cg_cgx; /* we are the cgx'th cylinder group */
238: short cg_ncyl; /* number of cyl's this cg */
239: short cg_niblk; /* number of inode blocks this cg */
240: long cg_ndblk; /* number of data blocks this cg */
241: struct csum cg_cs; /* cylinder summary information */
242: long cg_rotor; /* position of last used block */
243: long cg_frotor; /* position of last used frag */
244: long cg_irotor; /* position of last used inode */
245: long cg_frsum[MAXFRAG]; /* counts of available frags */
246: long cg_btot[MAXCPG]; /* block totals per cylinder */
247: short cg_b[MAXCPG][NRPOS]; /* positions of free blocks */
248: char cg_iused[MAXIPG/NBBY]; /* used inode map */
249: long cg_magic; /* magic number */
250: u_char cg_free[1]; /* free block map */
251: /* actually longer */
252: };
253:
254: /*
255: * MAXBPG bounds the number of blocks of data per cylinder group,
256: * and is limited by the fact that cylinder groups are at most one block.
257: * Its size is derived from the size of blocks and the (struct cg) size,
258: * by the number of remaining bits.
259: */
260: #define MAXBPG(fs) \
261: (fragstoblks((fs), (NBBY * ((fs)->fs_bsize - (sizeof (struct cg))))))
262:
263: /*
264: * Turn file system block numbers into disk block addresses.
265: * This maps file system blocks to device size blocks.
266: */
267: #define fsbtodb(fs, b) ((b) << (fs)->fs_fsbtodb)
268: #define dbtofsb(fs, b) ((b) >> (fs)->fs_fsbtodb)
269:
270: /*
271: * Cylinder group macros to locate things in cylinder groups.
272: * They calc file system addresses of cylinder group data structures.
273: */
274: #define cgbase(fs, c) ((daddr_t)((fs)->fs_fpg * (c)))
275: #define cgstart(fs, c) \
276: (cgbase(fs, c) + (fs)->fs_cgoffset * ((c) & ~((fs)->fs_cgmask)))
277: #define cgsblock(fs, c) (cgstart(fs, c) + (fs)->fs_sblkno) /* super blk */
278: #define cgtod(fs, c) (cgstart(fs, c) + (fs)->fs_cblkno) /* cg block */
279: #define cgimin(fs, c) (cgstart(fs, c) + (fs)->fs_iblkno) /* inode blk */
280: #define cgdmin(fs, c) (cgstart(fs, c) + (fs)->fs_dblkno) /* 1st data */
281:
282: /*
283: * Macros for handling inode numbers:
284: * inode number to file system block offset.
285: * inode number to cylinder group number.
286: * inode number to file system block address.
287: */
288: #define itoo(fs, x) ((x) % INOPB(fs))
289: #define itog(fs, x) ((x) / (fs)->fs_ipg)
290: #define itod(fs, x) \
291: ((daddr_t)(cgimin(fs, itog(fs, x)) + \
292: (blkstofrags((fs), (((x) % (fs)->fs_ipg) / INOPB(fs))))))
293:
294: /*
295: * Give cylinder group number for a file system block.
296: * Give cylinder group block number for a file system block.
297: */
298: #define dtog(fs, d) ((d) / (fs)->fs_fpg)
299: #define dtogd(fs, d) ((d) % (fs)->fs_fpg)
300:
301: /*
302: * Extract the bits for a block from a map.
303: * Compute the cylinder and rotational position of a cyl block addr.
304: */
305: #define blkmap(fs, map, loc) \
306: (((map)[(loc) / NBBY] >> ((loc) % NBBY)) & (0xff >> (NBBY - (fs)->fs_frag)))
307: #define cbtocylno(fs, bno) \
308: ((bno) * NSPF(fs) / (fs)->fs_spc)
309: #define cbtorpos(fs, bno) \
310: ((bno) * NSPF(fs) % (fs)->fs_spc % (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: #define fragstoblks(fs, frags) /* calculates (frags / fs->fs_frag) */ \
330: ((frags) >> (fs)->fs_fragshift)
331: #define blkstofrags(fs, blks) /* calculates (blks * fs->fs_frag) */ \
332: ((blks) << (fs)->fs_fragshift)
333: #define fragnum(fs, fsb) /* calculates (fsb % fs->fs_frag) */ \
334: ((fsb) & ((fs)->fs_frag - 1))
335: #define blknum(fs, fsb) /* calculates rounddown(fsb, fs->fs_frag) */ \
336: ((fsb) &~ ((fs)->fs_frag - 1))
337:
338: /*
339: * Determine the number of available frags given a
340: * percentage to hold in reserve
341: */
342: #define freespace(fs, percentreserved) \
343: (blkstofrags((fs), (fs)->fs_cstotal.cs_nbfree) + \
344: (fs)->fs_cstotal.cs_nffree - ((fs)->fs_dsize * (percentreserved) / 100))
345:
346: /*
347: * Determining the size of a file block in the file system.
348: */
349: #define blksize(fs, ip, lbn) \
350: (((lbn) >= NDADDR || (ip)->i_size >= ((lbn) + 1) << (fs)->fs_bshift) \
351: ? (fs)->fs_bsize \
352: : (fragroundup(fs, blkoff(fs, (ip)->i_size))))
353: #define dblksize(fs, dip, lbn) \
354: (((lbn) >= NDADDR || (dip)->di_size >= ((lbn) + 1) << (fs)->fs_bshift) \
355: ? (fs)->fs_bsize \
356: : (fragroundup(fs, blkoff(fs, (dip)->di_size))))
357:
358: /*
359: * Number of disk sectors per block; assumes DEV_BSIZE byte sector size.
360: */
361: #define NSPB(fs) ((fs)->fs_nspf << (fs)->fs_fragshift)
362: #define NSPF(fs) ((fs)->fs_nspf)
363:
364: /*
365: * INOPB is the number of inodes in a secondary storage block.
366: */
367: #define INOPB(fs) ((fs)->fs_inopb)
368: #define INOPF(fs) ((fs)->fs_inopb >> (fs)->fs_fragshift)
369:
370: /*
371: * NINDIR is the number of indirects in a file system block.
372: */
373: #define NINDIR(fs) ((fs)->fs_nindir)
374:
375: #ifdef KERNEL
376: struct fs *getfs();
377: struct fs *mountfs();
378: #endif
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