fs.h

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    long fs_state;		/* validate fs_clean field */
    int fs_postblformat;	/* format of positional layout tables */
    int fs_nrpos;		/* number of rotaional positions */
    int fs_postbloff;		/* (short) rotation block list head */
    int fs_rotbloff;		/* (u_char) blocks for each rotation */
    int fs_magic;		/* magic number */
    u_char fs_space[1];		/* list of blocks for each rotation */
/* actually longer */
  };
/*
 * Preference for optimization.
 */
#define FS_OPTTIME	0	/* minimize allocation time */
#define FS_OPTSPACE	1	/* minimize disk fragmentation */

/*
 * 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_postbl(fs, cylno) \
    (((fs)->fs_postblformat == FS_42POSTBLFMT) \
    ? ((fs)->fs_opostbl[cylno]) \
    : ((short *)((char *)(fs) + (fs)->fs_postbloff) + (cylno) * (fs)->fs_nrpos))
#define fs_rotbl(fs) \
    (((fs)->fs_postblformat == FS_42POSTBLFMT) \
    ? ((fs)->fs_space) \
    : ((u_char *)((char *)(fs) + (fs)->fs_rotbloff)))

/*
 * Convert cylinder group to base address of its global summary info.
 *
 * N.B. This macro assumes that sizeof(struct csum) is a power of two.
 */
#define fs_cs(fs, indx) \
	fs_csp[(indx) >> (fs)->fs_csshift][(indx) & ~(fs)->fs_csmask]

/*
 * Cylinder group block for a file system.
 */
#define	CG_MAGIC	0x090255
struct cg
  {
    int xxx1;			/* struct       cg *cg_link; */
    int cg_magic;		/* magic number */
    mach_time_t cg_time;		/* time last written */
    int cg_cgx;			/* we are the cgx'th cylinder group */
    short cg_ncyl;		/* number of cyl's this cg */
    short cg_niblk;		/* number of inode blocks this cg */
    int cg_ndblk;		/* number of data blocks this cg */
    struct csum cg_cs;		/* cylinder summary information */
    int cg_rotor;		/* position of last used block */
    int cg_frotor;		/* position of last used frag */
    int cg_irotor;		/* position of last used inode */
    int cg_frsum[MAXFRAG];	/* counts of available frags */
    int cg_btotoff;		/* (long) block totals per cylinder */
    int cg_boff;		/* (short) free block positions */
    int cg_iusedoff;		/* (char) used inode map */
    int cg_freeoff;		/* (u_char) free block map */
    int cg_nextfreeoff;		/* (u_char) next available space */
    int cg_sparecon[16];	/* reserved for future use */
    u_char cg_space[1];		/* space for cylinder group maps */
/* actually longer */
  };
/*
 * Macros for access to cylinder group array structures
 */
#define cg_blktot(cgp) \
    (((cgp)->cg_magic != CG_MAGIC) \
    ? (((struct ocg *)(cgp))->cg_btot) \
    : ((int *)((char *)(cgp) + (cgp)->cg_btotoff)))
#define cg_blks(fs, cgp, cylno) \
    (((cgp)->cg_magic != CG_MAGIC) \
    ? (((struct ocg *)(cgp))->cg_b[cylno]) \
    : ((short *)((char *)(cgp) + (cgp)->cg_boff) + (cylno) * (fs)->fs_nrpos))
#define cg_inosused(cgp) \
    (((cgp)->cg_magic != CG_MAGIC) \
    ? (((struct ocg *)(cgp))->cg_iused) \
    : ((char *)((char *)(cgp) + (cgp)->cg_iusedoff)))
#define cg_blksfree(cgp) \
    (((cgp)->cg_magic != CG_MAGIC) \
    ? (((struct ocg *)(cgp))->cg_free) \
    : ((u_char *)((char *)(cgp) + (cgp)->cg_freeoff)))
#define cg_chkmagic(cgp) \
    ((cgp)->cg_magic == CG_MAGIC || ((struct ocg *)(cgp))->cg_magic == CG_MAGIC)

/*
 * The following structure is defined
 * for compatibility with old file systems.
 */
struct ocg
  {
    int xxx1;			/* struct       ocg *cg_link; */
    int xxx2;			/* struct       ocg *cg_rlink; */
    mach_time_t cg_time;	/* time last written */
    int cg_cgx;			/* we are the cgx'th cylinder group */
    short cg_ncyl;		/* number of cyl's this cg */
    short cg_niblk;		/* number of inode blocks this cg */
    int cg_ndblk;		/* number of data blocks this cg */
    struct csum cg_cs;		/* cylinder summary information */
    int cg_rotor;		/* position of last used block */
    int cg_frotor;		/* position of last used frag */
    int cg_irotor;		/* position of last used inode */
    int cg_frsum[8];		/* counts of available frags */
    int cg_btot[32];		/* block totals per cylinder */
    short cg_b[32][8];		/* positions of free blocks */
    char cg_iused[256];		/* used inode map */
    int cg_magic;		/* magic number */
    u_char cg_free[1];		/* free block map */
/* actually longer */
  };

/*
 * Turn file system block numbers into disk block addresses.
 * This maps file system blocks to device size 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)	((mach_daddr_t)((fs)->fs_fpg * (c)))
#define cgstart(fs, c) \
	(cgbase(fs, c) + (fs)->fs_cgoffset * ((c) & ~((fs)->fs_cgmask)))
#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	cgimin(fs, c)	(cgstart(fs, c) + (fs)->fs_iblkno)	/* inode blk */
#define	cgdmin(fs, c)	(cgstart(fs, c) + (fs)->fs_dblkno)	/* 1st data */

/*
 * 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	itoo(fs, x)	((x) % INOPB(fs))
#define	itog(fs, x)	((x) / (fs)->fs_ipg)
#define	itod(fs, x) \
	((mach_daddr_t)(cgimin(fs, itog(fs, x)) + \
	(blkstofrags((fs), (((x) % (fs)->fs_ipg) / INOPB(fs))))))

/*
 * Give cylinder group number for a file system block.
 * Give cylinder group block number 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) \
    ((bno) * NSPF(fs) / (fs)->fs_spc)
#define cbtorpos(fs, bno) \
    (((bno) * NSPF(fs) % (fs)->fs_spc / (fs)->fs_nsect * (fs)->fs_trackskew + \
     (bno) * NSPF(fs) % (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_bmask)
#define fragoff(fs, loc)	/* calculates (loc % fs->fs_fsize) */ \
	((loc) & ~(fs)->fs_fmask)
#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_bsize - 1) & (fs)->fs_bmask)
#define fragroundup(fs, size)	/* calculates roundup(size, fs->fs_fsize) */ \
	(((size) + (fs)->fs_fsize - 1) & (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 || (ip)->i_size >= ((lbn) + 1) << (fs)->fs_bshift) \
	    ? (fs)->fs_bsize \
	    : (fragroundup(fs, blkoff(fs, (ip)->i_size))))
#define dblksize(fs, dip, lbn) \
	(((lbn) >= NDADDR || (dip)->di_size >= ((lbn) + 1) << (fs)->fs_bshift) \
	    ? (fs)->fs_bsize \
	    : (fragroundup(fs, blkoff(fs, (dip)->di_size))))

/*
 * Number of disk sectors per block; assumes DEV_BSIZE byte sector size.
 */
#define	NSPB(fs)	((fs)->fs_nspf << (fs)->fs_fragshift)
#define	NSPF(fs)	((fs)->fs_nspf)

/*
 * INOPB is the number of inodes in a secondary storage block.
 */
#define	INOPB(fs)	((fs)->fs_inopb)
#define	INOPF(fs)	((fs)->fs_inopb >> (fs)->fs_fragshift)

/*
 * NINDIR is the number of indirects in a file system block.
 */
#define	NINDIR(fs)	((fs)->fs_nindir)