FreeBSD/Linux Kernel Cross Reference
sys/ufs/ffs/fs.h

     /*      $OpenBSD: fs.h,v 1.44 2022/01/11 03:13:59 jsg Exp $     */
     /*      $NetBSD: fs.h,v 1.6 1995/04/12 21:21:02 mycroft Exp $   */
     
     /*
      * Copyright (c) 1982, 1986, 1993
      *      The Regents of the University of California.  All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)fs.h        8.10 (Berkeley) 10/27/94
     */
    
    /*
     * Each disk drive contains some number of file systems.
     * A file system consists of a number of cylinder groups.
     * Each cylinder group has inodes and data.
     *
     * A file system is described by its super-block, which in turn
     * describes the cylinder groups.  The super-block is critical
     * data and is replicated in each cylinder group to protect against
     * catastrophic loss.  This is done at `newfs' time and the critical
     * super-block data does not change, so the copies need not be
     * referenced further unless disaster strikes.
     *
     * For file system fs, the offsets of the various blocks of interest
     * are given in the super block as:
     *      [fs->fs_sblkno]         Super-block
     *      [fs->fs_cblkno]         Cylinder group block
     *      [fs->fs_iblkno]         Inode blocks
     *      [fs->fs_dblkno]         Data blocks
     * The beginning of cylinder group cg in fs, is given by
     * the ``cgbase(fs, cg)'' macro.
     *
     * The first boot and super blocks are given in absolute disk addresses.
     * The byte-offset forms are preferred, as they don't imply a sector size.
     */
    #define BBSIZE          8192
    #define SBSIZE          8192
    #define BBOFF           ((off_t)(0))
    #define SBOFF           ((off_t)(BBOFF + BBSIZE))
    #define BBLOCK          ((daddr_t)(0))
    #define SBLOCK          ((daddr_t)(BBLOCK + BBSIZE / DEV_BSIZE))
    #define SBLOCK_UFS1     8192
    #define SBLOCK_UFS2     65536
    #define SBLOCK_PIGGY    262144
    #define SBLOCKSIZE      8192
    #define SBLOCKSEARCH \
            { SBLOCK_UFS2, SBLOCK_UFS1, SBLOCK_PIGGY, -1 }
    
    /*
     * Addresses stored in inodes are capable of addressing fragments
     * of `blocks'. File system blocks of at most size MAXBSIZE can 
     * be optionally broken into 2, 4, or 8 pieces, each of which is
     * addressable; these pieces may be DEV_BSIZE, or some multiple of
     * a DEV_BSIZE unit.
     *
     * Large files consist of exclusively large data blocks.  To avoid
     * undue wasted disk space, the last data block of a small file may be
     * allocated as only as many fragments of a large block as are
     * necessary.  The file system format retains only a single pointer
     * to such a fragment, which is a piece of a single large block that
     * has been divided.  The size of such a fragment is determinable from
     * information in the inode, using the ``blksize(fs, ip, lbn)'' macro.
     *
     * The file system records space availability at the fragment level;
     * to determine block availability, aligned fragments are examined.
     */
    
    #define MAXFRAG         8
    
    /*
     * MINBSIZE is the smallest allowable block size.
     * In order to insure that it is possible to create files of size
     * 2^32 with only two levels of indirection, MINBSIZE is set to 4096.
     * MINBSIZE must be big enough to hold a cylinder group block,
     * thus changes to (struct cg) must keep its size within MINBSIZE.
     * Note that super blocks are always of size SBSIZE,
    * and that both SBSIZE and MAXBSIZE must be >= MINBSIZE.
    */
   #define MINBSIZE        4096
   
   /*
    * The path name on which the file system is mounted is maintained
    * in fs_fsmnt. MAXMNTLEN defines the amount of space allocated in
    * the super block for this name.
    */
   #define MAXMNTLEN       468
   
   /*
    * The volume name for this file system is kept in fs_volname.
    * MAXVOLLEN defines the length of the buffer allocated.
    */
   #define MAXVOLLEN       32
   
   /*
    * There is a 128-byte region in the superblock reserved for in-core
    * pointers to summary information. Originally this included an array
    * of pointers to blocks of struct csum; now there are just three
    * pointers and the remaining space is padded with fs_ocsp[].
    *
    * NOCSPTRS determines the size of this padding. One pointer (fs_csp)
    * is taken away to point to a contiguous array of struct csum for
    * all cylinder groups; a second (fs_maxcluster) points to an array
    * of cluster sizes that is computed as cylinder groups are inspected,
    * and the third points to an array that tracks the creation of new
    * directories.
    */
   #define NOCSPTRS        ((128 / sizeof(void *)) - 4)
   
   /*
    * A summary of contiguous blocks of various sizes is maintained
    * in each cylinder group. Normally this is set by the initial
    * value of fs_maxcontig. To conserve space, a maximum summary size
    * is set by FS_MAXCONTIG.
    */
   #define FS_MAXCONTIG    16
   
   /*
    * MINFREE gives the minimum acceptable percentage of file system
    * blocks which may be free. If the freelist drops below this level
    * only the superuser may continue to allocate blocks. This may
    * be set to 0 if no reserve of free blocks is deemed necessary,
    * however throughput drops by fifty percent if the file system
    * is run at between 95% and 100% full; thus the minimum default
    * value of fs_minfree is 5%. However, to get good clustering
    * performance, 10% is a better choice. With 5% free space,
    * fragmentation is not a problem, so we choose to optimize for time.
    */
   #define MINFREE         5
   #define DEFAULTOPT      FS_OPTTIME
   
   /*
    * The directory preference algorithm(dirpref) can be tuned by adjusting
    * the following parameters which tell the system the average file size
    * and the average number of files per directory. These defaults are well
    * selected for typical filesystems, but may need to be tuned for odd
    * cases like filesystems being used for squid caches or news spools.
    */
   #define AVFILESIZ       16384   /* expected average file size */
   #define AFPDIR          64      /* expected number of files per directory */
   
   /*
    * Size of superblock space reserved for snapshots.
    */
   #define FSMAXSNAP       20
   
   /*
    * Per cylinder group information; summarized in blocks allocated
    * from first cylinder group data blocks.  These blocks have to be
    * read in from fs_csaddr (size fs_cssize) in addition to the
    * super block.
    */
   struct csum {
           int32_t cs_ndir;                /* number of directories */
           int32_t cs_nbfree;              /* number of free blocks */
           int32_t cs_nifree;              /* number of free inodes */
           int32_t cs_nffree;              /* number of free frags */
   };
   
   struct csum_total {
           int64_t cs_ndir;                /* number of directories */
           int64_t cs_nbfree;              /* number of free blocks */
           int64_t cs_nifree;              /* number of free inodes */
           int64_t cs_nffree;              /* number of free frags */
           int64_t cs_spare[4];            /* future expansion */
   };
   
   /*
    * Super block for an FFS file system.
    */
   struct fs {
           int32_t  fs_firstfield;         /* historic file system linked list, */
           int32_t  fs_unused_1;           /*     used for incore super blocks */
           int32_t  fs_sblkno;             /* addr of super-block / frags */
           int32_t  fs_cblkno;             /* offset of cyl-block / frags */
           int32_t  fs_iblkno;             /* offset of inode-blocks / frags */
           int32_t  fs_dblkno;             /* offset of first data / frags */
           int32_t  fs_cgoffset;           /* cylinder group offset in cylinder */
           int32_t  fs_cgmask;             /* used to calc mod fs_ntrak */
           int32_t  fs_ffs1_time;          /* last time written */
           int32_t  fs_ffs1_size;          /* # of blocks in fs / frags */
           int32_t  fs_ffs1_dsize;         /* # of data blocks in fs */
           u_int32_t fs_ncg;               /* # of cylinder groups */
           int32_t  fs_bsize;              /* size of basic blocks / bytes */
           int32_t  fs_fsize;              /* size of frag blocks / bytes */
           int32_t  fs_frag;               /* # of frags in a block in fs */
   /* these are configuration parameters */
           int32_t  fs_minfree;            /* minimum percentage of free blocks */
           int32_t  fs_rotdelay;           /* # of ms for optimal next block */
           int32_t  fs_rps;                /* disk revolutions per second */
   /* these fields can be computed from the others */
           int32_t  fs_bmask;              /* ``blkoff'' calc of blk offsets */
           int32_t  fs_fmask;              /* ``fragoff'' calc of frag offsets */
           int32_t  fs_bshift;             /* ``lblkno'' calc of logical blkno */
           int32_t  fs_fshift;             /* ``numfrags'' calc # of frags */
   /* these are configuration parameters */
           int32_t  fs_maxcontig;          /* max # of contiguous blks */
           int32_t  fs_maxbpg;             /* max # of blks per cyl group */
   /* these fields can be computed from the others */
           int32_t  fs_fragshift;          /* block to frag shift */
           int32_t  fs_fsbtodb;            /* fsbtodb and dbtofsb shift constant */
           int32_t  fs_sbsize;             /* actual size of super block */
           int32_t  fs_csmask;             /* csum block offset (now unused) */
           int32_t  fs_csshift;            /* csum block number (now unused) */
           int32_t  fs_nindir;             /* value of NINDIR */
           u_int32_t fs_inopb;             /* inodes per file system block */
           int32_t  fs_nspf;               /* DEV_BSIZE sectors per frag */
   /* yet another configuration parameter */
           int32_t  fs_optim;              /* optimization preference, see below */
   /* these fields are derived from the hardware */
           int32_t  fs_npsect;             /* DEV_BSIZE sectors/track + spares */
           int32_t  fs_interleave;         /* DEV_BSIZE sector interleave */
           int32_t  fs_trackskew;          /* sector 0 skew, per track */
   /* fs_id takes the space of the unused fs_headswitch and fs_trkseek fields */
           int32_t  fs_id[2];              /* unique filesystem id */
   /* sizes determined by number of cylinder groups and their sizes */
           int32_t  fs_ffs1_csaddr;        /* blk addr of cyl grp summary area */
           int32_t  fs_cssize;             /* cyl grp summary area size / bytes */
           int32_t  fs_cgsize;             /* cyl grp block size / bytes */
   /* these fields are derived from the hardware */
           int32_t  fs_ntrak;              /* tracks per cylinder */
           int32_t  fs_nsect;              /* DEV_BSIZE sectors per track */
           int32_t  fs_spc;                /* DEV_BSIZE sectors per cylinder */
   /* this comes from the disk driver partitioning */
           int32_t  fs_ncyl;               /* cylinders in file system */
   /* these fields can be computed from the others */
           int32_t  fs_cpg;                /* cylinders per group */
           u_int32_t fs_ipg;               /* inodes per group */
           int32_t  fs_fpg;                /* blocks per group * fs_frag */
   /* this data must be re-computed after crashes */
           struct  csum fs_ffs1_cstotal;   /* cylinder summary information */
   /* these fields are cleared at mount time */
           int8_t   fs_fmod;               /* super block modified flag */
           int8_t   fs_clean;              /* file system is clean flag */
           int8_t   fs_ronly;              /* mounted read-only flag */
           int8_t   fs_ffs1_flags;         /* see FS_ below */
           u_char   fs_fsmnt[MAXMNTLEN];   /* name mounted on */
           u_char   fs_volname[MAXVOLLEN]; /* volume name */
           u_int64_t fs_swuid;             /* system-wide uid */
           int32_t  fs_pad;                /* due to alignment of fs_swuid */
   /* these fields retain the current block allocation info */
           int32_t  fs_cgrotor;            /* last cg searched */
           void    *fs_ocsp[NOCSPTRS];     /* padding; was list of fs_cs buffers */
           u_int8_t *fs_contigdirs;        /* # of contiguously allocated dirs */
           struct csum *fs_csp;            /* cg summary info buffer for fs_cs */
           int32_t *fs_maxcluster;         /* max cluster in each cyl group */
           u_char  *fs_active;             /* reserved for snapshots */
           int32_t  fs_cpc;                /* cyl per cycle in postbl */
   /* this area is only allocated if fs_ffs1_flags & FS_FLAGS_UPDATED */
           int32_t  fs_maxbsize;           /* maximum blocking factor permitted */
           int64_t  fs_spareconf64[17];    /* old rotation block list head */
           int64_t  fs_sblockloc;          /* offset of standard super block */
           struct  csum_total fs_cstotal;  /* cylinder summary information */
           int64_t  fs_time;               /* time last written */
           int64_t  fs_size;               /* number of blocks in fs */
           int64_t  fs_dsize;              /* number of data blocks in fs */
           int64_t  fs_csaddr;             /* blk addr of cyl grp summary area */
           int64_t  fs_pendingblocks;      /* blocks in process of being freed */
           u_int32_t fs_pendinginodes;     /* inodes in process of being freed */
           u_int32_t fs_snapinum[FSMAXSNAP];/* space reserved for snapshots */
   /* back to stuff that has been around a while */
           u_int32_t fs_avgfilesize;       /* expected average file size */
           u_int32_t fs_avgfpdir;          /* expected # of files per directory */
           int32_t  fs_sparecon[26];       /* reserved for future constants */
           u_int32_t fs_flags;             /* see FS_ flags below */
           int32_t  fs_fscktime;           /* last time fsck(8)ed */
           int32_t  fs_contigsumsize;      /* size of cluster summary array */ 
           int32_t  fs_maxsymlinklen;      /* max length of an internal symlink */
           int32_t  fs_inodefmt;           /* format of on-disk inodes */
           u_int64_t fs_maxfilesize;       /* maximum representable file size */
           int64_t  fs_qbmask;             /* ~fs_bmask - for use with quad size */
           int64_t  fs_qfmask;             /* ~fs_fmask - for use with quad size */
           int32_t  fs_state;              /* validate fs_clean field */
           int32_t  fs_postblformat;       /* format of positional layout tables */
           int32_t  fs_nrpos;              /* number of rotational positions */
           int32_t  fs_postbloff;          /* (u_int16) rotation block list head */
           int32_t  fs_rotbloff;           /* (u_int8) blocks for each rotation */
           int32_t  fs_magic;              /* magic number */
           u_int8_t fs_space[1];           /* list of blocks for each rotation */
   /* actually longer */
   };
   
   /*
    * Filesystem identification
    */
   #define FS_MAGIC        0x011954        /* the fast filesystem magic number */
   #define FS_UFS1_MAGIC   0x011954        /* the fast filesystem magic number */
   #define FS_UFS2_MAGIC   0x19540119      /* UFS fast filesystem magic number */
   #define FS_OKAY         0x7c269d38      /* superblock checksum */
   #define FS_42INODEFMT   -1              /* 4.2BSD inode format */
   #define FS_44INODEFMT   2               /* 4.4BSD inode format */
   
   /*
    * Filesystem clean flags
    */
   #define FS_ISCLEAN      0x01
   #define FS_WASCLEAN     0x02
   
   /*
    * Preference for optimization.
    */
   #define FS_OPTTIME      0       /* minimize allocation time */
   #define FS_OPTSPACE     1       /* minimize disk fragmentation */
   
   /* 
    * Filesystem flags.
    */
   #define FS_UNCLEAN      0x01    /* filesystem not clean at mount */
   #define FS_DOSOFTDEP    0x02    /* filesystem using soft dependencies */
   /*
    * The following flag is used to detect a FFS1 file system that had its flags
    * moved to the new (FFS2) location for compatibility.
    */
   #define FS_FLAGS_UPDATED        0x80    /* file system has FFS2-like flags */
   
   /*
    * Rotational layout table format types
    */
   #define FS_42POSTBLFMT          -1      /* 4.2BSD rotational table format */
   #define FS_DYNAMICPOSTBLFMT     1       /* dynamic rotational table format */
   /*
    * Macros for access to superblock array structures
    */
   #define fs_rotbl(fs) \
       (((fs)->fs_postblformat == FS_42POSTBLFMT) \
       ? ((fs)->fs_space) \
       : ((u_int8_t *)((u_int8_t *)(fs) + (fs)->fs_rotbloff)))
   
   /*
    * The size of a cylinder group is calculated by CGSIZE. The maximum size
    * is limited by the fact that cylinder groups are at most one block.
    * Its size is derived from the size of the maps maintained in the
    * cylinder group and the (struct cg) size.
    */
   #define CGSIZE(fs) \
       /* base cg */       (sizeof(struct cg) + sizeof(int32_t) + \
       /* blktot size */   (fs)->fs_cpg * sizeof(int32_t) + \
       /* blks size */     (fs)->fs_cpg * (fs)->fs_nrpos * sizeof(int16_t) + \
       /* inode map */     howmany((fs)->fs_ipg, NBBY) + \
       /* block map */     howmany((fs)->fs_fpg, NBBY) + \
       /* if present */    ((fs)->fs_contigsumsize <= 0 ? 0 : \
       /* cluster sum */   (fs)->fs_contigsumsize * sizeof(int32_t) + \
       /* cluster map */   howmany(fragstoblks(fs, (fs)->fs_fpg), NBBY)))
   
   /*
    * Convert cylinder group to base address of its global summary info.
    */
   #define fs_cs(fs, indx) fs_csp[indx]
   
   /*
    * Cylinder group block for a file system.
    */
   #define CG_MAGIC        0x090255
   struct cg {
           int32_t  cg_firstfield;         /* historic cyl groups linked list */
           int32_t  cg_magic;              /* magic number */
           int32_t  cg_time;               /* time last written */
           u_int32_t cg_cgx;               /* we are the cgx'th cylinder group */
           int16_t  cg_ncyl;               /* number of cyl's this cg */
           int16_t  cg_niblk;              /* number of inode blocks this cg */
           u_int32_t cg_ndblk;             /* number of data blocks this cg */
           struct  csum cg_cs;             /* cylinder summary information */
           u_int32_t cg_rotor;             /* position of last used block */
           u_int32_t cg_frotor;            /* position of last used frag */
           u_int32_t cg_irotor;            /* position of last used inode */
           u_int32_t cg_frsum[MAXFRAG];    /* counts of available frags */
           int32_t  cg_btotoff;            /* (int32) block totals per cylinder */
           int32_t  cg_boff;               /* (u_int16) free block positions */
           u_int32_t cg_iusedoff;          /* (u_int8) used inode map */
           u_int32_t cg_freeoff;           /* (u_int8) free block map */
           u_int32_t cg_nextfreeoff;       /* (u_int8) next available space */
           u_int32_t cg_clustersumoff;     /* (u_int32) counts of avail clusters */
           u_int32_t cg_clusteroff;        /* (u_int8) free cluster map */
           u_int32_t cg_nclusterblks;      /* number of clusters this cg */
           u_int32_t cg_ffs2_niblk;        /* number of inode blocks this cg */
           u_int32_t cg_initediblk;        /* last initialized inode */
           int32_t  cg_sparecon32[3];      /* reserved for future use */
           int64_t  cg_ffs2_time;          /* time last written */
           int64_t  cg_sparecon64[3];      /* reserved for future use */
   /* actually longer */
   };
   
   /*
    * Macros for access to cylinder group array structures
    */
   #define cg_blktot(cgp) \
       (((cgp)->cg_magic != CG_MAGIC) \
       ? (((struct ocg *)(cgp))->cg_btot) \
       : ((int32_t *)((u_int8_t *)(cgp) + (cgp)->cg_btotoff)))
   #define cg_blks(fs, cgp, cylno) \
       (((cgp)->cg_magic != CG_MAGIC) \
       ? (((struct ocg *)(cgp))->cg_b[cylno]) \
       : ((int16_t *)((u_int8_t *)(cgp) + \
           (cgp)->cg_boff) + (cylno) * (fs)->fs_nrpos))
   #define cg_inosused(cgp) \
       (((cgp)->cg_magic != CG_MAGIC) \
       ? (((struct ocg *)(cgp))->cg_iused) \
       : ((u_int8_t *)((u_int8_t *)(cgp) + (cgp)->cg_iusedoff)))
   #define cg_blksfree(cgp) \
       (((cgp)->cg_magic != CG_MAGIC) \
       ? (((struct ocg *)(cgp))->cg_free) \
       : ((u_int8_t *)((u_int8_t *)(cgp) + (cgp)->cg_freeoff)))
   #define cg_chkmagic(cgp) \
       ((cgp)->cg_magic == CG_MAGIC || ((struct ocg *)(cgp))->cg_magic == CG_MAGIC)
   #define cg_clustersfree(cgp) \
       ((u_int8_t *)((u_int8_t *)(cgp) + (cgp)->cg_clusteroff))
   #define cg_clustersum(cgp) \
       ((int32_t *)((u_int8_t *)(cgp) + (cgp)->cg_clustersumoff))
   
   /*
    * The following structure is defined
    * for compatibility with old file systems.
    */
   struct ocg {
           int32_t  cg_firstfield;         /* historic linked list of cyl groups */
           int32_t  cg_unused_1;           /*     used for incore cyl groups */
           int32_t  cg_time;               /* time last written */
           int32_t  cg_cgx;                /* we are the cgx'th cylinder group */
           int16_t  cg_ncyl;               /* number of cyl's this cg */
           int16_t  cg_niblk;              /* number of inode blocks this cg */
           int32_t  cg_ndblk;              /* number of data blocks this cg */
           struct  csum cg_cs;             /* cylinder summary information */
           int32_t  cg_rotor;              /* position of last used block */
           int32_t  cg_frotor;             /* position of last used frag */
           int32_t  cg_irotor;             /* position of last used inode */
           int32_t  cg_frsum[8];           /* counts of available frags */
           int32_t  cg_btot[32];           /* block totals per cylinder */
           int16_t  cg_b[32][8];           /* positions of free blocks */
           u_int8_t cg_iused[256];         /* used inode map */
           int32_t  cg_magic;              /* magic number */
           u_int8_t cg_free[1];            /* free block map */
   /* actually longer */
   };
   
   /*
    * Turn file system block numbers into disk block addresses.
    * This maps file system blocks to DEV_BSIZE (a.k.a. 512-byte) size disk
    * blocks.
    */
   #define fsbtodb(fs, b)  ((b) << (fs)->fs_fsbtodb)
   #define dbtofsb(fs, b)  ((b) >> (fs)->fs_fsbtodb)
   
   /*
    * Cylinder group macros to locate things in cylinder groups.
    * They calc file system addresses of cylinder group data structures.
    */
   #define cgbase(fs, c)   ((daddr_t)(fs)->fs_fpg * (c))
   #define cgdata(fs, c)   (cgdmin(fs, c) + (fs)->fs_minfree)      /* data zone */
   #define cgmeta(fs, c)   (cgdmin(fs, c))                         /* meta data */
   #define cgdmin(fs, c)   (cgstart(fs, c) + (fs)->fs_dblkno)      /* 1st data */
   #define cgimin(fs, c)   (cgstart(fs, c) + (fs)->fs_iblkno)      /* inode blk */
   #define cgsblock(fs, c) (cgstart(fs, c) + (fs)->fs_sblkno)      /* super blk */
   #define cgtod(fs, c)    (cgstart(fs, c) + (fs)->fs_cblkno)      /* cg block */
   #define cgstart(fs, c)                                                  \
           (cgbase(fs, c) + (fs)->fs_cgoffset * ((c) & ~((fs)->fs_cgmask)))
   
   /*
    * Macros for handling inode numbers:
    *     inode number to file system block offset.
    *     inode number to cylinder group number.
    *     inode number to file system block address.
    */
   #define ino_to_cg(fs, x)        ((x) / (fs)->fs_ipg)
   #define ino_to_fsba(fs, x)                                              \
           ((daddr_t)(cgimin(fs, ino_to_cg(fs, x)) +                       \
               (blkstofrags((fs), (((x) % (fs)->fs_ipg) / INOPB(fs))))))
   #define ino_to_fsbo(fs, x)      ((x) % INOPB(fs))
   
   /*
    * Give cylinder group number for a file system block.
    * Give frag block number in cylinder group for a file system block.
    */
   #define dtog(fs, d)     ((d) / (fs)->fs_fpg)
   #define dtogd(fs, d)    ((d) % (fs)->fs_fpg)
   
   /*
    * Extract the bits for a block from a map.
    * Compute the cylinder and rotational position of a cyl block addr.
    */
   #define blkmap(fs, map, loc) \
       (((map)[(loc) / NBBY] >> ((loc) % NBBY)) & (0xff >> (NBBY - (fs)->fs_frag)))
   #define cbtocylno(fs, bno) \
       (fsbtodb(fs, bno) / (fs)->fs_spc)
   #define cbtorpos(fs, bno) \
       ((fs)->fs_nrpos <= 1 ? 0 : \
        (fsbtodb(fs, bno) % (fs)->fs_spc / (fs)->fs_nsect * (fs)->fs_trackskew + \
        fsbtodb(fs, bno) % (fs)->fs_spc % (fs)->fs_nsect * (fs)->fs_interleave) % \
        (fs)->fs_nsect * (fs)->fs_nrpos / (fs)->fs_npsect)
   
   /*
    * The following macros optimize certain frequently calculated
    * quantities by using shifts and masks in place of divisions
    * modulos and multiplications.
    */
   #define blkoff(fs, loc)         /* calculates (loc % fs->fs_bsize) */ \
           ((loc) & (fs)->fs_qbmask)
   #define fragoff(fs, loc)        /* calculates (loc % fs->fs_fsize) */ \
           ((loc) & (fs)->fs_qfmask)
   #define lblktosize(fs, blk)     /* calculates ((off_t)blk * fs->fs_bsize) */ \
           ((off_t)(blk) << (fs)->fs_bshift)
   #define lblkno(fs, loc)         /* calculates (loc / fs->fs_bsize) */ \
           ((loc) >> (fs)->fs_bshift)
   #define numfrags(fs, loc)       /* calculates (loc / fs->fs_fsize) */ \
           ((loc) >> (fs)->fs_fshift)
   #define blkroundup(fs, size)    /* calculates roundup(size, fs->fs_bsize) */ \
           (((size) + (fs)->fs_qbmask) & (fs)->fs_bmask)
   #define fragroundup(fs, size)   /* calculates roundup(size, fs->fs_fsize) */ \
           (((size) + (fs)->fs_qfmask) & (fs)->fs_fmask)
   #define fragstoblks(fs, frags)  /* calculates (frags / fs->fs_frag) */ \
           ((frags) >> (fs)->fs_fragshift)
   #define blkstofrags(fs, blks)   /* calculates (blks * fs->fs_frag) */ \
           ((blks) << (fs)->fs_fragshift)
   #define fragnum(fs, fsb)        /* calculates (fsb % fs->fs_frag) */ \
           ((fsb) & ((fs)->fs_frag - 1))
   #define blknum(fs, fsb)         /* calculates rounddown(fsb, fs->fs_frag) */ \
           ((fsb) &~ ((fs)->fs_frag - 1))
   
   /*
    * Determine the number of available frags given a
    * percentage to hold in reserve.
    */
   #define freespace(fs, percentreserved) \
           (blkstofrags((fs), (fs)->fs_cstotal.cs_nbfree) + \
           (fs)->fs_cstotal.cs_nffree - ((fs)->fs_dsize * (percentreserved) / 100))
   
   /*
    * Determining the size of a file block in the file system.
    */
   #define blksize(fs, ip, lbn) \
           (((lbn) >= NDADDR || DIP((ip), size) >= ((lbn) + 1) << (fs)->fs_bshift) \
               ? (u_int64_t)(fs)->fs_bsize \
               : (fragroundup(fs, blkoff(fs, DIP((ip), size)))))
   #define dblksize(fs, dip, lbn) \
           (((lbn) >= NDADDR || (dip)->di_size >= ((lbn) + 1) << (fs)->fs_bshift) \
               ? (u_int64_t)(fs)->fs_bsize \
               : (fragroundup(fs, blkoff(fs, (dip)->di_size))))
   
   #define sblksize(fs, size, lbn) \
           (((lbn) >= NDADDR || (size) >= ((lbn) + 1) << (fs)->fs_bshift) \
               ? (u_int64_t)(fs)->fs_bsize \
               : (fragroundup(fs, blkoff(fs, (size)))))
   
   
   /*
    * Number of disk sectors per block/fragment; assumes DEV_BSIZE byte
    * sector size.
    */
   #define NSPB(fs)        ((fs)->fs_nspf << (fs)->fs_fragshift)
   #define NSPF(fs)        ((fs)->fs_nspf)
   
   /* Number of inodes per file system block (fs->fs_bsize) */
   #define INOPB(fs)       ((fs)->fs_inopb)
   /* Number of inodes per file system fragment (fs->fs_fsize) */
   #define INOPF(fs)       ((fs)->fs_inopb >> (fs)->fs_fragshift)
   
   /*
    * Number of indirects in a file system block.
    */
   #define NINDIR(fs)      ((fs)->fs_nindir)
   
   /* Maximum file size the kernel allows.
    * Even though ffs can handle files up to 16TB, we do limit the max file
    * to 2^31 pages to prevent overflow of a 32-bit unsigned int.  The buffer
    * cache has its own checks but a little added paranoia never hurts.
    */
   #define FS_KERNMAXFILESIZE(pgsiz, fs)   ((u_int64_t)0x80000000 * \
       MIN((pgsiz), (fs)->fs_bsize) - 1)
   
   extern const int inside[], around[];
   extern const u_char *fragtbl[];

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