text: /*	$NetBSD: fs.h,v 1.11 1998/07/28 17:30:01 drochner 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. All advertising materials mentioning features or use of this software
   *    must display the following acknowledgement:
   *	This product includes software developed by the University of
   *	California, Berkeley and its contributors.
   * 4. 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	8.13 (Berkeley) 3/21/95
   */
  
  /*
   * 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		((ufs_daddr_t)(0))
  #define	SBLOCK		((ufs_daddr_t)(BBLOCK + BBSIZE / DEV_BSIZE))
  
  /*
   * 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
   * addressible; 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.
   */
  
  /*
   * 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	512
  
  /*
   * The limit on the amount of summary information per file system
   * is defined by MAXCSBUFS. It is currently parameterized for a
   * size of 128 bytes (2 million cylinder groups on machines with
   * 32-bit pointers, and 1 million on 64-bit machines). One pointer
   * is taken away to point to an array of cluster sizes that is
   * computed as cylinder groups are inspected.
   */
  #define	MAXCSBUFS	((128 / sizeof(void *)) - 1)
  
  /*
   * 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. hence we use 10% as our
   * default value. With 10% free space, fragmentation is not a
   * problem, so we choose to optimize for time.
   */
  #define MINFREE		5
  #define DEFAULTOPT	FS_OPTTIME
  
  /*
   * 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.
   *
   * N.B. sizeof(struct csum) must be a power of two in order for
   * the ``fs_cs'' macro to work (see below).
   */
  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 */
  };
  
  /*
   * Super block for an FFS file system in memory.
   */
  struct fs {
  	int32_t	 fs_firstfield;		/* historic file system linked list, */
  	int32_t	 fs_unused_1;		/*     used for incore super blocks */
  	ufs_daddr_t fs_sblkno;		/* addr of super-block in filesys */
  	ufs_daddr_t fs_cblkno;		/* offset of cyl-block in filesys */
  	ufs_daddr_t fs_iblkno;		/* offset of inode-blocks in filesys */
  	ufs_daddr_t fs_dblkno;		/* offset of first data after cg */
  	int32_t	 fs_cgoffset;		/* cylinder group offset in cylinder */
  	int32_t	 fs_cgmask;		/* used to calc mod fs_ntrak */
  	time_t 	 fs_time;		/* last time written */
  	int32_t	 fs_size;		/* number of blocks in fs */
  	int32_t	 fs_dsize;		/* number of data blocks in fs */
  	int32_t	 fs_ncg;		/* number of cylinder groups */
  	int32_t	 fs_bsize;		/* size of basic blocks in fs */
  	int32_t	 fs_fsize;		/* size of frag blocks in fs */
  	int32_t	 fs_frag;		/* number of frags in a block in fs */
  /* these are configuration parameters */
  	int32_t	 fs_minfree;		/* minimum percentage of free blocks */
  	int32_t	 fs_rotdelay;		/* num 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 number of frags */
  /* these are configuration parameters */
  	int32_t	 fs_maxcontig;		/* max number of contiguous blks */
  	int32_t	 fs_maxbpg;		/* max number 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 */
  	int32_t	 fs_csshift;		/* csum block number */
  	int32_t	 fs_nindir;		/* value of NINDIR */
  	int32_t	 fs_inopb;		/* value of INOPB */
  	int32_t	 fs_nspf;		/* value of NSPF */
  /* yet another configuration parameter */
  	int32_t	 fs_optim;		/* optimization preference, see below */
  /* these fields are derived from the hardware */
  	int32_t	 fs_npsect;		/* # sectors/track including spares */
  	int32_t	 fs_interleave;		/* hardware sector interleave */
  	int32_t	 fs_trackskew;		/* sector 0 skew, per track */
  	int32_t	 fs_headswitch;		/* head switch time, usec */
  	int32_t	 fs_trkseek;		/* track-to-track seek, usec */
  /* sizes determined by number of cylinder groups and their sizes */
  	ufs_daddr_t  fs_csaddr;		/* blk addr of cyl grp summary area */
  	int32_t	 fs_cssize;		/* size of cyl grp summary area */
  	int32_t	 fs_cgsize;		/* cylinder group size */
  /* these fields are derived from the hardware */
  	int32_t	 fs_ntrak;		/* tracks per cylinder */
  	int32_t	 fs_nsect;		/* sectors per track */
  	int32_t	 fs_spc;		/* 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 */
  	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_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_flags;		/* currently unused flag */
  	u_char	 fs_fsmnt[MAXMNTLEN];	/* name mounted on */
  /* these fields retain the current block allocation info */
  	int32_t	 fs_cgrotor;		/* last cg searched */
  	struct	csum *fs_csp[MAXCSBUFS];/* list of fs_cs info buffers */
  	int32_t	 *fs_maxcluster;	/* max cluster in each cyl group */
  	int32_t	 fs_cpc;		/* cyl per cycle in postbl */
  	int16_t	 fs_opostbl[16][8];	/* old rotation block list head */
  	int32_t	 fs_sparecon[49];	/* reserved for future constants */
  	time_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_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 */
  
  /*
   * 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]) \
      : ((int16_t *)((u_int8_t *)(fs) + \
  	(fs)->fs_postbloff) + (cylno) * (fs)->fs_nrpos))
  #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_cpg * (fs)->fs_spc / NSPF(fs), NBBY) +\
      /* if present */	((fs)->fs_contigsumsize <= 0 ? 0 : \
      /* cluster sum */	(fs)->fs_contigsumsize * sizeof(int32_t) + \
      /* cluster map */	howmany((fs)->fs_cpg * (fs)->fs_spc / NSPB(fs), NBBY)))
  
  /*
   * 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 {
  	int32_t	 cg_firstfield;		/* historic cyl groups linked list */
  	int32_t	 cg_magic;		/* magic number */
  	time_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[MAXFRAG];	/* counts of available frags */
  	int32_t	 cg_btotoff;		/* (int32) block totals per cylinder */
  	int32_t	 cg_boff;		/* (u_int16) free block positions */
  	int32_t	 cg_iusedoff;		/* (u_int8) used inode map */
  	int32_t	 cg_freeoff;		/* (u_int8) free block map */
  	int32_t	 cg_nextfreeoff;	/* (u_int8) next available space */
  	int32_t	 cg_clustersumoff;	/* (u_int32) counts of avail clusters */
  	int32_t	 cg_clusteroff;		/* (u_int8) free cluster map */
  	int32_t	 cg_nclusterblks;	/* number of clusters this cg */
  	int32_t	 cg_sparecon[13];	/* reserved for future use */
  	u_int8_t cg_space[1];		/* space for cylinder group maps */
  /* actually longer */
  };
  
  /*
   * Macros for access to cylinder group array structures
   */
  #define cg_blktot(cgp, ns) \
      ((ufs_rw32((cgp)->cg_magic, (ns)) != CG_MAGIC) \
      ? (((struct ocg *)(cgp))->cg_btot) \
      : ((int32_t *)((u_int8_t *)(cgp) + \
  	ufs_rw32((cgp)->cg_btotoff, (ns)))))
  #define cg_blks(fs, cgp, cylno, ns) \
      ((ufs_rw32((cgp)->cg_magic, ns) != CG_MAGIC) \
      ? (((struct ocg *)(cgp))->cg_b[cylno]) \
      : ((int16_t *)((u_int8_t *)(cgp) + \
  	ufs_rw32((cgp)->cg_boff, (ns))) + \
  	(cylno) * (fs)->fs_nrpos))
  #define cg_inosused(cgp, ns) \
      ((ufs_rw32((cgp)->cg_magic, (ns)) != CG_MAGIC) \
      ? (((struct ocg *)(cgp))->cg_iused) \
      : ((u_int8_t *)((u_int8_t *)(cgp) + \
  	ufs_rw32((cgp)->cg_iusedoff, (ns)))))
  #define cg_blksfree(cgp, ns) \
      ((ufs_rw32((cgp)->cg_magic, (ns)) != CG_MAGIC) \
      ? (((struct ocg *)(cgp))->cg_free) \
      : ((u_int8_t *)((u_int8_t *)(cgp) + \
  	ufs_rw32((cgp)->cg_freeoff, (ns)))))
  #define cg_chkmagic(cgp, ns) \
      (ufs_rw32((cgp)->cg_magic, (ns)) == CG_MAGIC || \
  	ufs_rw32(((struct ocg *)(cgp))->cg_magic, (ns)) == \
  	CG_MAGIC)
  #define cg_clustersfree(cgp, ns) \
      ((u_int8_t *)((u_int8_t *)(cgp) + \
  	ufs_rw32((cgp)->cg_clusteroff, (ns))))
  #define cg_clustersum(cgp, ns) \
      ((int32_t *)((u_int8_t *)(cgp) + \
  	ufs_rw32((cgp)->cg_clustersumoff, (ns))))
  
  /*
   * 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 */
  	time_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 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)	((ufs_daddr_t)((fs)->fs_fpg * (c)))
  #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)						\
  	((ufs_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 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_qbmask)
  #define fragoff(fs, loc)	/* calculates (loc % fs->fs_fsize) */ \
  	((loc) & (fs)->fs_qfmask)
  #define lblktosize(fs, blk)	/* calculates (blk * fs->fs_bsize) */ \
  	((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 || (ip)->i_ffs_size >= ((lbn) + 1) << (fs)->fs_bshift) \
  	    ? (fs)->fs_bsize \
  	    : (fragroundup(fs, blkoff(fs, (ip)->i_ffs_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/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 in a secondary storage block/fragment.
   */
  #define	INOPB(fs)	((fs)->fs_inopb)
  #define	INOPF(fs)	((fs)->fs_inopb >> (fs)->fs_fragshift)
  
  /*
   * Number of indirects in a file system block.
   */
  #define	NINDIR(fs)	((fs)->fs_nindir)
  