/* Copyright (c) 1981 Regents of the University of California */
* 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, which in turn
* describes the cylinder groups. The super-block is critical
* data and is replicated in each cylinder group to protect against
* catastrophic loss. This is done at mkfs time and the critical
* super-block data does not change, so the copies need not be
* referenced further unless disaster strikes.
* For file system fs and a cylinder group number cg:
* [BBLOCK] Boot sector and bad block information
* [CBLOCK] Cylinder group block
* [IBLOCK..IBLOCK+fs.fs_ipg/INOPB)
* [IBLOCK+fs.fs_ipg/INOPB..fs.fs_fpg/FRAG)
* The beginning of data blocks for cg in fs is also given by cgdmin(cg,fs).
#define BBLOCK ((daddr_t)(0*FRAG))
#define SBLOCK ((daddr_t)(1*FRAG))
#define CBLOCK ((daddr_t)(2*FRAG))
#define IBLOCK ((daddr_t)(3*FRAG))
* Addresses stored in inodes are capable of addressing fragments of `blocks.'
* File system blocks of size BSIZE can be broken into FRAG pieces,
* each of which is addressible; these pieces may be sectors, or some
* multiple of a sector size (e.g. 1k byte units).
* Large files consist of exclusively large (BSIZE) data blocks. To avoid
* undue fragmentation, the last data block of a small file may be
* allocated as only as many pieces
* of a large block as are necessary. The file system format retains
* only a single pointer to such a fragment, which is a piece of a single
* BSIZE block which has been divided. The size of such a fragment is
* determinable from information in the inode.
* The file system records space availability at the fragment level;
* to determine block availability, aligned fragments are examined.
* For each cylinder we keep track of the availability of blocks at different
* rotational positions, so that we can lay out the data to be picked
* up with minimum rotational latency. NRPOS is the number of rotational
* positions which we distinguish. With NRPOS 8 the resolution of our
* summary information is 2ms for a typical 3600 rpm drive.
#define NRPOS 8 /* number distinct rotational positions */
* Information per cylinder group summarized in blocks allocated
* from first cylinder group data blocks. These blocks have to be
* specially noticed in mkfs, icheck and fsck.
long cs_ndir
; /* number of directories */
long cs_nbfree
; /* number of free blocks */
long cs_nifree
; /* number of free inodes */
long cs_nffree
; /* number of free frags */
#define cssize(fs) ((fs)->fs_ncg*sizeof(struct csum))
#define csaddr(fs) (cgdmin(0, fs))
* Each file system has a number of inodes statically allocated.
* We allocate one inode slot per NBPI data bytes, expecting this
* to be far more than we will ever need.
#define DESCPG 16 /* desired fs_cpg */
#define MAXCPG 32 /* maximum fs_cpg */
/* MAXCPG is limited only to dimension an array in (struct cg); */
/* it can be made larger as long as that structures size remains sane. */
* Super block for a file system.
* The super block is nominally located at disk block 1 although
* this is naive due to bad blocks. Inode 0 can't be used for normal
* purposes, historically bad blocks were linked to inode 1,
* thus the root inode is 2. (inode 1 is no longer used for
* this purpose, however numerous dump tapes make this
* assumption, so we are stuck with it)
#define ROOTINO ((ino_t)2) /* i number of all roots */
#define FS_MAGIC 0x110854
long fs_magic
; /* magic number */
daddr_t fs_sblkno
; /* offset of super-block in filesys */ 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 */
/* sizes determined by number of cylinder groups and their sizes */
long fs_cssize
; /* size of cyl grp summary area */
long fs_cgsize
; /* cylinder group size */
/* these fields should be derived from the hardware */
short fs_ntrak
; /* tracks per cylinder */
short 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 */
short fs_cpg
; /* cylinders per group */
short fs_ipg
; /* inodes per group */
long fs_fpg
; /* blocks per group*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_ronly
; /* mounted read-only flag */
char fs_fsmnt
[34]; /* name mounted on */
/* these fields retain the current block allocation info */
long fs_cgrotor
; /* last cg searched */
struct csum
*fs_csp
[NBUF
]; /* list of fs_cs info buffers */
short fs_postbl
[NRPOS
]; /* head of blocks for each rotation */
short fs_rotbl
[1]; /* list of blocks for each rotation */
#define fs_cs(indx) fs_csp[(indx) / (BSIZE / sizeof(struct csum))] \
[(indx) % (BSIZE / sizeof(struct csum))]
* Cylinder group macros to locate things in cylinder groups.
/* cylinder group to disk block at very beginning */
#define cgbase(c,fs) ((daddr_t)((fs)->fs_fpg*(c)))
/* cylinder group to spare super block address */
/* convert cylinder group to index of its cg block */
/* give address of first inode block in cylinder group */
/* give address of first data block in cylinder group */
#define cgdmin(c,fs) (cgimin(c,fs) + (fs)->fs_ipg / INOPF)
/* turn inode number into cylinder group number */
#define itog(x,fs) ((x)/(fs)->fs_ipg)
/* turn inode number into disk block address */
#define itod(x,fs) ((daddr_t)(cgimin(itog(x,fs),fs)+FRAG*((x)%(fs)->fs_ipg/INOPB)))
/* turn inode number into disk block offset */
#define itoo(x) ((x)%INOPB)
/* give cylinder group number for a disk block */
#define dtog(d,fs) ((d)/(fs)->fs_fpg)
/* give cylinder group block number for a disk block */
#define dtogd(d,fs) ((d)%(fs)->fs_fpg)
* Cylinder group related limits.
* MAXIPG bounds the number of inodes per cylinder group, and
* is needed only to keep the structure simpler by having the
* only a single variable size element (the free bit map).
* N.B.: MAXIPG must be a multiple of INOPB.
#define MAXIPG 2048 /* max number inodes/cyl group */
* MAXBPG bounds the number of blocks of data per cylinder group,
* and is limited by the fact that cylinder groups are at most one block.
* Its size is derived from the size of blocks and the (struct cg) size,
* by the number of remaining bits.
#define MAXBPG (NBBY*(BSIZE-(sizeof (struct cg)))/FRAG)
#define CG_MAGIC 0x092752
long cg_magic
; /* magic number */
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
[FRAG
]; /* counts of available frags */
short cg_b
[MAXCPG
][NRPOS
]; /* positions of free blocks */
char cg_iused
[MAXIPG
/NBBY
]; /* used inode map */
char cg_free
[1]; /* free block map */
#define cgsize(fp) (sizeof (struct cg) + ((fp)->fs_fpg+NBBY-1)/NBBY)
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