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 slicing ∗/
        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)

  —  UFS