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1.1 root 1: /* fs.h 6.1 83/07/29 */
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: *
15: * For file system fs, the offsets of the various blocks of interest
16: * are given in the super block as:
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
22: * the ``cgbase(fs, cg)'' macro.
23: *
24: * The first boot and super blocks are given in absolute disk addresses.
25: */
26: #define BBSIZE 8192
27: #define SBSIZE 8192
28: #define BBLOCK ((daddr_t)(0))
29: #define SBLOCK ((daddr_t)(BBLOCK + BBSIZE / DEV_BSIZE))
30:
31: /*
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.
37: *
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.
45: *
46: * The file system records space availability at the fragment level;
47: * to determine block availability, aligned fragments are examined.
48: *
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:
61: /*
62: * Cylinder group related limits.
63: *
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: */
70: #define NRPOS 8 /* number distinct rotational positions */
71:
72: /*
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).
78: */
79: #define MAXIPG 2048 /* max number inodes/cyl group */
80:
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
94: #define MAXCPG 32 /* maximum fs_cpg */
95:
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.
100: * The limit on the amount of summary information per file system
101: * is defined by MAXCSBUFS. It is currently parameterized for a
102: * maximum of two million cylinders.
103: */
104: #define MAXMNTLEN 512
105: #define MAXCSBUFS 32
106:
107: /*
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.
112: *
113: * N.B. sizeof(struct csum) must be a power of two in order for
114: * the ``fs_cs'' macro to work (see below).
115: */
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: };
122:
123: /*
124: * Super block for a file system.
125: */
126: #define FS_MAGIC 0x011954
127: struct fs
128: {
129: struct fs *fs_link; /* linked list of file systems */
130: struct fs *fs_rlink; /* used for incore super blocks */
131: daddr_t fs_sblkno; /* addr of super-block in filesys */
132: daddr_t fs_cblkno; /* offset of cyl-block in filesys */
133: daddr_t fs_iblkno; /* offset of inode-blocks in filesys */
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 */
137: time_t fs_time; /* last time written */
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 */
141: long fs_bsize; /* size of basic blocks in fs */
142: long fs_fsize; /* size of frag blocks in fs */
143: long fs_frag; /* number of frags in a block in fs */
144: /* these are configuration parameters */
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 */
148: /* these fields can be computed from the others */
149: long fs_bmask; /* ``blkoff'' calc of blk offsets */
150: long fs_fmask; /* ``fragoff'' calc of frag offsets */
151: long fs_bshift; /* ``lblkno'' calc of logical blkno */
152: long fs_fshift; /* ``numfrags'' calc number of frags */
153: /* these are configuration parameters */
154: long fs_maxcontig; /* max number of contiguous blks */
155: long fs_maxbpg; /* max number of blks per cyl group */
156: /* these fields can be computed from the others */
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 */
166: /* sizes determined by number of cylinder groups and their sizes */
167: daddr_t fs_csaddr; /* blk addr of cyl grp summary area */
168: long fs_cssize; /* size of cyl grp summary area */
169: long fs_cgsize; /* cylinder group size */
170: /* these fields should be derived from the hardware */
171: long fs_ntrak; /* tracks per cylinder */
172: long fs_nsect; /* sectors per track */
173: long fs_spc; /* sectors per cylinder */
174: /* this comes from the disk driver partitioning */
175: long fs_ncyl; /* cylinders in file system */
176: /* these fields can be computed from the others */
177: long fs_cpg; /* cylinders per group */
178: long fs_ipg; /* inodes per group */
179: long fs_fpg; /* blocks per group * fs_frag */
180: /* this data must be re-computed after crashes */
181: struct csum fs_cstotal; /* cylinder summary information */
182: /* these fields are cleared at mount time */
183: char fs_fmod; /* super block modified flag */
184: char fs_clean; /* file system is clean flag */
185: char fs_ronly; /* mounted read-only flag */
186: char fs_flags; /* currently unused flag */
187: char fs_fsmnt[MAXMNTLEN]; /* name mounted on */
188: /* these fields retain the current block allocation info */
189: long fs_cgrotor; /* last cg searched */
190: struct csum *fs_csp[MAXCSBUFS];/* list of fs_cs info buffers */
191: long fs_cpc; /* cyl per cycle in postbl */
192: short fs_postbl[MAXCPG][NRPOS];/* head of blocks for each rotation */
193: long fs_magic; /* magic number */
194: u_char fs_rotbl[1]; /* list of blocks for each rotation */
195: /* actually longer */
196: };
197:
198: /*
199: * Convert cylinder group to base address of its global summary info.
200: *
201: * N.B. This macro assumes that sizeof(struct csum) is a power of two.
202: */
203: #define fs_cs(fs, indx) \
204: fs_csp[(indx) >> (fs)->fs_csshift][(indx) & ~(fs)->fs_csmask]
205:
206: /*
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)
214: */
215: #define MAXBPC (SBSIZE - sizeof (struct fs))
216:
217: /*
218: * Cylinder group block for a file system.
219: */
220: #define CG_MAGIC 0x090255
221: struct cg {
222: struct cg *cg_link; /* linked list of cyl groups */
223: struct cg *cg_rlink; /* used for incore cyl groups */
224: time_t cg_time; /* time last written */
225: long cg_cgx; /* we are the cgx'th cylinder group */
226: short cg_ncyl; /* number of cyl's this cg */
227: short cg_niblk; /* number of inode blocks this cg */
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 */
233: long cg_frsum[MAXFRAG]; /* counts of available frags */
234: long cg_btot[MAXCPG]; /* block totals per cylinder */
235: short cg_b[MAXCPG][NRPOS]; /* positions of free blocks */
236: char cg_iused[MAXIPG/NBBY]; /* used inode map */
237: long cg_magic; /* magic number */
238: u_char cg_free[1]; /* free block map */
239: /* actually longer */
240: };
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) \
249: (fragstoblks((fs), (NBBY * ((fs)->fs_bsize - (sizeof (struct cg))))))
250:
251: /*
252: * Turn file system block numbers into disk block addresses.
253: * This maps file system blocks to device size blocks.
254: */
255: #define fsbtodb(fs, b) ((b) << (fs)->fs_fsbtodb)
256: #define dbtofsb(fs, b) ((b) >> (fs)->fs_fsbtodb)
257:
258: /*
259: * Cylinder group macros to locate things in cylinder groups.
260: * They calc file system addresses of cylinder group data structures.
261: */
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 */
269:
270: /*
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.
275: */
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)) + \
280: (blkstofrags((fs), (((x) % (fs)->fs_ipg) / INOPB(fs))))))
281:
282: /*
283: * Give cylinder group number for a file system block.
284: * Give cylinder group block number for a file system block.
285: */
286: #define dtog(fs, d) ((d) / (fs)->fs_fpg)
287: #define dtogd(fs, d) ((d) % (fs)->fs_fpg)
288:
289: /*
290: * Extract the bits for a block from a map.
291: * Compute the cylinder and rotational position of a cyl block addr.
292: */
293: #define blkmap(fs, map, loc) \
294: (((map)[loc / NBBY] >> (loc % NBBY)) & (0xff >> (NBBY - (fs)->fs_frag)))
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:
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: #define fragstoblks(fs, frags) /* calculates (frags / fs->fs_frag) */ \
318: ((frags) >> (fs)->fs_fragshift)
319: #define blkstofrags(fs, blks) /* calculates (blks * fs->fs_frag) */ \
320: ((blks) << (fs)->fs_fragshift)
321:
322: /*
323: * Determine the number of available frags given a
324: * percentage to hold in reserve
325: */
326: #define freespace(fs, percentreserved) \
327: (blkstofrags((fs), (fs)->fs_cstotal.cs_nbfree) + \
328: (fs)->fs_cstotal.cs_nffree - ((fs)->fs_dsize * (percentreserved) / 100))
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_bshift) \
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_bshift) \
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_nspf << (fs)->fs_fragshift)
346: #define NSPF(fs) ((fs)->fs_nspf)
347:
348: /*
349: * INOPB is the number of inodes in a secondary storage block.
350: */
351: #define INOPB(fs) ((fs)->fs_inopb)
352: #define INOPF(fs) ((fs)->fs_inopb >> (fs)->fs_fragshift)
353:
354: /*
355: * NINDIR is the number of indirects in a file system block.
356: */
357: #define NINDIR(fs) ((fs)->fs_nindir)
358:
359: #ifdef KERNEL
360: struct fs *getfs();
361: struct fs *mountfs();
362: #endif
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