NAME

fs (ufs) - format of ufs file system volume

SYNOPSIS

#include <sys/param.h>
#include <sys/types.h>
#include <sys/fs/ufs_fs.h>

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.

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 mkfs time; the critical super-block data does not change, so the copies need not normally be referenced further.

/*
 * 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 */

/* 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 */
};

/*
 * Cylinder group block for a file system.
 */

#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 */
};

SEE ALSO

ufs-specific inode(4)