'\"macro stdmacro
.if n .pH g4.fs_ufs @(#)fs_ufs	40.6 of 1/17/90
.\" Copyright 1989 AT&T
.nr X
.if \nX=0 .ds x} fs 4 "UFS" "" "\&"
.if \nX=1 .ds x} fs 4 "UFS" ""
.if \nX=2 .ds x} fs 4 "" "\&"
.if \nX=3 .ds x} fs "" "" "\&"
.TH \*(x}
.SH NAME
\f4fs\fP (ufs) \- format of \f4ufs\fP file system volume
.SH SYNOPSIS
\f4#include <sys/param.h>\fP
.br
\f4#include <sys/types.h>\fP
.br
\f4#include <sys/fs/ufs_fs.h>\fP
.SH DESCRIPTION
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.
.PP
A file system is described by its super-block, and by the information
in the cylinder group blocks.  The super-block is critical
data and is replicated before each cylinder group block to protect against
catastrophic loss.  This is done at \f4mkfs\fP time; the critical
super-block data does not change, so the copies need not
normally be referenced further.
.PP
.ps -1
.vs -1
.ft 4
.nf
.ta 2.25i
/*
 * Super block for a file system.
 */
#define FS_MAGIC    0x011954
#define FSACTIVE    0x5e72d81a	/* fs_state: mounted */
#define FSOKAY      0x7c269d38	/* fs_state: clean */
#define FSBAD       0xcb096f43	/* fs_state: bad root */

struct  fs {
        struct  fs *fs_link;	/* linked list of file systems */
        struct  fs *fs_rlink;	/* used for incore super blocks */
        daddr_t fs_sblkno;	/* addr of super-block in filesys */
        daddr_t fs_cblkno;	/* offset of cyl-block in filesys */
        daddr_t fs_iblkno;	/* offset of inode-blocks in filesys */
        daddr_t fs_dblkno;	/* offset of first data after cg */
        long    fs_cgoffset;	/* cylinder group offset in cylinder */
        long    fs_cgmask;	/* used to calc mod fs_ntrak */
        time_t  fs_time;	/* last time written */
        long    fs_size;	/* number of blocks in fs */
        long    fs_dsize;	/* number of data blocks in fs */
        long    fs_ncg;	/* number of cylinder groups */
        long    fs_bsize;	/* size of basic blocks in fs */
        long    fs_fsize;	/* size of frag blocks in fs */
        long    fs_frag;	/* number of frags in a block in fs */
/* these are configuration parameters */
        long    fs_minfree;	/* minimum percentage of free blocks */
        long    fs_rotdelay;	/* num of ms for optimal next block */
        long    fs_rps;	/* disk revolutions per second */
/* these fields can be computed from the others */
        long    fs_bmask;	/* ``blkoff'' calc of blk offsets */
        long    fs_fmask;	/* ``fragoff'' calc of frag offsets */
        long    fs_bshift;	/* ``lblkno'' calc of logical blkno */
        long    fs_fshift;	/* ``numfrags'' calc number of frags */
/* these are configuration parameters */
        long    fs_maxcontig;	/* max number of contiguous blks */
        long    fs_maxbpg;	/* max number of blks per cyl group */
.bp
/* these fields can be computed from the others */
        long    fs_fragshift;	/* block to frag shift */
        long    fs_fsbtodb;	/* fsbtodb and dbtofsb shift constant */
        long    fs_sbsize;	/* actual size of super block */
        long    fs_csmask;	/* csum block offset */
        long    fs_csshift;	/* csum block number */
        long    fs_nindir;	/* value of NINDIR */
        long    fs_inopb;	/* value of INOPB */
        long    fs_nspf;	/* value of NSPF */
        long    fs_optim;	/* optimization preference, see below */
        long    fs_state;	/* file system state */
        long    fs_sparecon[2];	/* reserved for future constants */
/* a unique id for this filesystem (currently unused and unmaintained) */
        long    fs_id[2];	/* file system id */
/* sizes determined by number of cylinder groups and their sizes */
        daddr_t fs_csaddr;	/* blk addr of cyl grp summary area */
        long    fs_cssize;	/* size of cyl grp summary area */
        long    fs_cgsize;	/* cylinder group size */
/* these fields should be derived from the hardware */
        long    fs_ntrak;	/* tracks per cylinder */
        long    fs_nsect;	/* sectors per track */
        long    fs_spc;	/* sectors per cylinder */
/* this comes from the disk driver partitioning */
        long    fs_ncyl;	/* cylinders in file system */
/* these fields can be computed from the others */
        long    fs_cpg;	/* cylinders per group */
        long    fs_ipg;	/* inodes per group */
        long    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 */
        char    fs_fmod;	/* super block modified flag */
        char    fs_clean;	/* file system is clean flag */
        char    fs_ronly;	/* mounted read-only flag */
        char    fs_flags;	/* currently unused flag */
        char    fs_fsmnt[MAXMNTLEN];	/* name mounted on */
/* these fields retain the current block allocation info */
        long    fs_cgrotor;	/* last cg searched */
        struct  csum *fs_csp[MAXCSBUFS];	/* list of fs_cs info buffers */
        long    fs_cpc;	/* cyl per cycle in postbl */
        short   fs_postbl[MAXCPG][NRPOS];	/* head of blocks for each rotation */
        long    fs_magic;	/* magic number */
        u_char  fs_rotbl[1];	/* list of blocks for each rotation */
};
.fi
.PP
.ft 4
.ps -1
.vs -1
/*
 * Cylinder group block for a file system.
 */
.PP
.ps -1
.vs -1
.ta 2.25i
.ft 4
.nf
#define CG_MAGIC      0x090255
struct  cg {
        struct  cg *cg_link;	/* linked list of cyl groups */
        struct  cg *cg_rlink;	/* used for incore cyl groups */
        time_t  cg_time;	/* time last written */
        long    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 */
        long    cg_ndblk;	/* number of data blocks this cg */
        struct  csum cg_cs;	/* cylinder summary information */
        long    cg_rotor;	/* position of last used block */
        long    cg_frotor;	/* position of last used frag */
        long    cg_irotor;	/* position of last used inode */
        long    cg_frsum[MAXFRAG];	/* counts of available frags */
        long    cg_btot[MAXCPG];	/* block totals per cylinder */
        short   cg_b[MAXCPG][NRPOS];	/* positions of free blocks */
        char    cg_iused[MAXIPG/NBBY];	/* used inode map */
        long    cg_magic;	/* magic number */
        u_char  cg_free[1];	/* free block map */
};	
.fi
.ft 1
.ps +1
.vs +1
.SH SEE ALSO
\f4ufs\fP-specific \f4inode\fP(4)
