xref: /freebsd/sys/fs/ext2fs/fs.h (revision 6574b8ed19b093f0af09501d2c9676c28993cb97)
1 /*-
2  *  modified for EXT2FS support in Lites 1.1
3  *
4  *  Aug 1995, Godmar Back (gback@cs.utah.edu)
5  *  University of Utah, Department of Computer Science
6  */
7 /*-
8  * Copyright (c) 1982, 1986, 1993
9  *	The Regents of the University of California.  All rights reserved.
10  *
11  * Redistribution and use in source and binary forms, with or without
12  * modification, are permitted provided that the following conditions
13  * are met:
14  * 1. Redistributions of source code must retain the above copyright
15  *    notice, this list of conditions and the following disclaimer.
16  * 2. Redistributions in binary form must reproduce the above copyright
17  *    notice, this list of conditions and the following disclaimer in the
18  *    documentation and/or other materials provided with the distribution.
19  * 4. Neither the name of the University nor the names of its contributors
20  *    may be used to endorse or promote products derived from this software
21  *    without specific prior written permission.
22  *
23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33  * SUCH DAMAGE.
34  *
35  *	@(#)fs.h	8.7 (Berkeley) 4/19/94
36  * $FreeBSD$
37  */
38 
39 #ifndef _FS_EXT2FS_FS_H_
40 #define	_FS_EXT2FS_FS_H_
41 
42 /*
43  * Each disk drive contains some number of file systems.
44  * A file system consists of a number of cylinder groups.
45  * Each cylinder group has inodes and data.
46  *
47  * A file system is described by its super-block, which in turn
48  * describes the cylinder groups.  The super-block is critical
49  * data and is replicated in each cylinder group to protect against
50  * catastrophic loss.  This is done at `newfs' time and the critical
51  * super-block data does not change, so the copies need not be
52  * referenced further unless disaster strikes.
53  *
54  * The first boot and super blocks are given in absolute disk addresses.
55  * The byte-offset forms are preferred, as they don't imply a sector size.
56  */
57 #define	SBSIZE		1024
58 #define	SBLOCK		2
59 
60 /*
61  * The path name on which the file system is mounted is maintained
62  * in fs_fsmnt. MAXMNTLEN defines the amount of space allocated in
63  * the super block for this name.
64  */
65 #define	MAXMNTLEN	512
66 
67 /*
68  * A summary of contiguous blocks of various sizes is maintained
69  * in each cylinder group. Normally this is set by the initial
70  * value of fs_maxcontig.
71  *
72  * XXX:FS_MAXCONTIG is set to 16 to conserve space. Here we set
73  * EXT2_MAXCONTIG to 32 for better performance.
74  */
75 #define	EXT2_MAXCONTIG	32
76 
77 /*
78  * Grigoriy Orlov <gluk@ptci.ru> has done some extensive work to fine
79  * tune the layout preferences for directories within a filesystem.
80  * His algorithm can be tuned by adjusting the following parameters
81  * which tell the system the average file size and the average number
82  * of files per directory. These defaults are well selected for typical
83  * filesystems, but may need to be tuned for odd cases like filesystems
84  * being used for squid caches or news spools.
85  * AVFPDIR is the expected number of files per directory. AVGDIRSIZE is
86  * obtained by multiplying AVFPDIR and AVFILESIZ which is assumed to be
87  * 16384.
88  */
89 
90 #define	AFPDIR		64
91 #define	AVGDIRSIZE	1048576
92 
93 /*
94  * Macros for access to superblock array structures
95  */
96 
97 /*
98  * Turn file system block numbers into disk block addresses.
99  * This maps file system blocks to device size blocks.
100  */
101 #define	fsbtodb(fs, b)	((daddr_t)(b) << (fs)->e2fs_fsbtodb)
102 #define	dbtofsb(fs, b)	((b) >> (fs)->e2fs_fsbtodb)
103 
104 /* get group containing inode */
105 #define	ino_to_cg(fs, x)	(((x) - 1) / (fs->e2fs_ipg))
106 
107 /* get block containing inode from its number x */
108 #define	ino_to_fsba(fs, x)                                              \
109         ((fs)->e2fs_gd[ino_to_cg((fs), (x))].ext2bgd_i_tables +         \
110         (((x) - 1) % (fs)->e2fs->e2fs_ipg) / (fs)->e2fs_ipb)
111 
112 /* get offset for inode in block */
113 #define	ino_to_fsbo(fs, x)	((x-1) % (fs->e2fs_ipb))
114 
115 /*
116  * Give cylinder group number for a file system block.
117  * Give cylinder group block number for a file system block.
118  */
119 #define	dtog(fs, d)	(((d) - fs->e2fs->e2fs_first_dblock) / \
120 			EXT2_BLOCKS_PER_GROUP(fs))
121 #define	dtogd(fs, d)	(((d) - fs->e2fs->e2fs_first_dblock) % \
122 			EXT2_BLOCKS_PER_GROUP(fs))
123 
124 /*
125  * The following macros optimize certain frequently calculated
126  * quantities by using shifts and masks in place of divisions
127  * modulos and multiplications.
128  */
129 #define	blkoff(fs, loc)		/* calculates (loc % fs->fs_bsize) */ \
130 	((loc) & (fs)->e2fs_qbmask)
131 
132 #define	lblktosize(fs, blk)	/* calculates (blk * fs->fs_bsize) */ \
133 	((blk) << (fs->e2fs_bshift))
134 
135 #define	lblkno(fs, loc)		/* calculates (loc / fs->fs_bsize) */ \
136 	((loc) >> (fs->e2fs_bshift))
137 
138 /* no fragments -> logical block number equal # of frags */
139 #define	numfrags(fs, loc)	/* calculates (loc / fs->fs_fsize) */ \
140 	((loc) >> (fs->e2fs_bshift))
141 
142 #define	fragroundup(fs, size)	/* calculates roundup(size, fs->fs_fsize) */ \
143 	roundup(size, fs->e2fs_fsize)
144 	/* was (((size) + (fs)->fs_qfmask) & (fs)->fs_fmask) */
145 
146 /*
147  * Determining the size of a file block in the file system.
148  * easy w/o fragments
149  */
150 #define	blksize(fs, ip, lbn) ((fs)->e2fs_fsize)
151 
152 /*
153  * INOPB is the number of inodes in a secondary storage block.
154  */
155 #define	INOPB(fs)	(fs->e2fs_ipb)
156 
157 /*
158  * NINDIR is the number of indirects in a file system block.
159  */
160 #define	NINDIR(fs)	(EXT2_ADDR_PER_BLOCK(fs))
161 
162 #endif /* !_FS_EXT2FS_FS_H_ */
163