fs(4SFS) (SFS) fs(4SFS)
NAME
fs (sfs) - format of sfs file system volume
SYNOPSIS
#include <sys/param.h>
#include <sys/types.h>
#include <sys/fs/sfs_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 SFS_MAGIC 0xbd101155
#define UFS_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;/* min. percent of free blocks;
Copyright 1994 Novell, Inc. Page 1
fs(4SFS) (SFS) fs(4SFS)
an optimization value */
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 */
Copyright 1994 Novell, Inc. Page 2
fs(4SFS) (SFS) fs(4SFS)
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 */
};
REFERENCES
ufs-specific inode(4UFS)
Copyright 1994 Novell, Inc. Page 3