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fs_ufs(4)


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 */ };

References

inode_ufs(4)
© 2004 The SCO Group, Inc. All rights reserved.
UnixWare 7 Release 7.1.4 - 25 April 2004