The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/fs/ext2fs/fs.h

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    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: releng/9.0/sys/fs/ext2fs/fs.h 202283 2010-01-14 14:30:54Z lulf $
   37  */
   38 
   39 /*
   40  * Each disk drive contains some number of file systems.
   41  * A file system consists of a number of cylinder groups.
   42  * Each cylinder group has inodes and data.
   43  *
   44  * A file system is described by its super-block, which in turn
   45  * describes the cylinder groups.  The super-block is critical
   46  * data and is replicated in each cylinder group to protect against
   47  * catastrophic loss.  This is done at `newfs' time and the critical
   48  * super-block data does not change, so the copies need not be
   49  * referenced further unless disaster strikes.
   50  *
   51  * The first boot and super blocks are given in absolute disk addresses.
   52  * The byte-offset forms are preferred, as they don't imply a sector size.
   53  */
   54 #define SBSIZE          1024
   55 #define SBLOCK          2
   56 
   57 /*
   58  * The path name on which the file system is mounted is maintained
   59  * in fs_fsmnt. MAXMNTLEN defines the amount of space allocated in 
   60  * the super block for this name. 
   61  */
   62 #define MAXMNTLEN       512
   63 
   64 /*
   65  * Grigoriy Orlov <gluk@ptci.ru> has done some extensive work to fine
   66  * tune the layout preferences for directories within a filesystem.
   67  * His algorithm can be tuned by adjusting the following parameters
   68  * which tell the system the average file size and the average number
   69  * of files per directory. These defaults are well selected for typical
   70  * filesystems, but may need to be tuned for odd cases like filesystems
   71  * being used for squid caches or news spools.
   72  * AVFPDIR is the expected number of files per directory. AVGDIRSIZE is 
   73  * obtained by multiplying AVFPDIR and AVFILESIZ which is assumed to be 
   74  * 16384.
   75  */
   76 
   77 #define AFPDIR          64
   78 #define AVGDIRSIZE      1048576
   79 
   80 /*
   81  * Macros for access to superblock array structures
   82  */
   83 
   84 /*
   85  * Turn file system block numbers into disk block addresses.
   86  * This maps file system blocks to device size blocks.
   87  */
   88 #define fsbtodb(fs, b)  ((b) << ((fs)->e2fs_fsbtodb))
   89 #define dbtofsb(fs, b)  ((b) >> ((fs)->e2fs_fsbtodb))
   90 
   91 /* get group containing inode */
   92 #define ino_to_cg(fs, x)        (((x) - 1) / (fs->e2fs_ipg))
   93 
   94 /* get block containing inode from its number x */
   95 #define ino_to_fsba(fs, x)                                              \
   96         ((fs)->e2fs_gd[ino_to_cg((fs), (x))].ext2bgd_i_tables +         \
   97         (((x) - 1) % (fs)->e2fs->e2fs_ipg) / (fs)->e2fs_ipb)
   98 
   99 /* get offset for inode in block */
  100 #define ino_to_fsbo(fs, x)      ((x-1) % (fs->e2fs_ipb))
  101 
  102 /*
  103  * Give cylinder group number for a file system block.
  104  * Give cylinder group block number for a file system block.
  105  */
  106 #define dtog(fs, d)     (((d) - fs->e2fs->e2fs_first_dblock) / \
  107                         EXT2_BLOCKS_PER_GROUP(fs))
  108 #define dtogd(fs, d)    (((d) - fs->e2fs->e2fs_first_dblock) % \
  109                         EXT2_BLOCKS_PER_GROUP(fs))
  110 
  111 /*
  112  * The following macros optimize certain frequently calculated
  113  * quantities by using shifts and masks in place of divisions
  114  * modulos and multiplications.
  115  */
  116 #define blkoff(fs, loc)         /* calculates (loc % fs->fs_bsize) */ \
  117         ((loc) & (fs)->e2fs_qbmask)
  118 
  119 #define lblktosize(fs, blk)     /* calculates (blk * fs->fs_bsize) */ \
  120         ((blk) << (fs->e2fs_bshift))
  121 
  122 #define lblkno(fs, loc)         /* calculates (loc / fs->fs_bsize) */ \
  123         ((loc) >> (fs->e2fs_bshift))
  124 
  125 /* no fragments -> logical block number equal # of frags */
  126 #define numfrags(fs, loc)       /* calculates (loc / fs->fs_fsize) */ \
  127         ((loc) >> (fs->e2fs_bshift))
  128 
  129 #define fragroundup(fs, size)   /* calculates roundup(size, fs->fs_fsize) */ \
  130         roundup(size, fs->e2fs_fsize)
  131         /* was (((size) + (fs)->fs_qfmask) & (fs)->fs_fmask) */
  132 
  133 /*
  134  * Determining the size of a file block in the file system.
  135  * easy w/o fragments
  136  */
  137 #define blksize(fs, ip, lbn) ((fs)->e2fs_fsize)
  138 
  139 /*
  140  * INOPB is the number of inodes in a secondary storage block.
  141  */
  142 #define INOPB(fs)       (fs->e2fs_ipb)
  143 
  144 /*
  145  * NINDIR is the number of indirects in a file system block.
  146  */
  147 #define NINDIR(fs)      (EXT2_ADDR_PER_BLOCK(fs))
  148 
  149 extern int inside[], around[];
  150 extern u_char *fragtbl[];
  151 
  152 

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