/* 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, the offsets of the various blocks of interest
* are given in the super block as:
* [fs->fs_sblkno] Super-block
* [fs->fs_cblkno] Cylinder group block
* [fs->fs_iblkno] Inode blocks
* [fs->fs_dblkno] Data blocks
* The beginning of cylinder group cg in fs, is given by
* the ``cgbase(fs, cg)'' macro.
* The first boot and super blocks are given in absolute disk addresses.
#define BBLOCK ((daddr_t)(0))
#define SBLOCK ((daddr_t)(BBLOCK + BBSIZE / DEV_BSIZE))
* Addresses stored in inodes are capable of addressing fragments
* of `blocks'. File system blocks of at most size MAXBSIZE can
* be optionally broken into 2, 4, or 8 pieces, each of which is
* addressible; these pieces may be DEV_BSIZE, or some multiple of
* Large files consist of exclusively large data blocks. To avoid
* undue wasted disk space, the last data block of a small file may be
* allocated as only as many fragments 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 large block that
* has been divided. The size of such a fragment is determinable from
* information in the inode, using the ``blksize(fs, ip, lbn)'' macro.
* The file system records space availability at the fragment level;
* to determine block availability, aligned fragments are examined.
* The root inode is the root of the file system.
* Inode 0 can't be used for normal purposes and
* 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)
* The lost+found directory is given the next available
* inode when it is created by ``mkfs''.
#define ROOTINO ((ino_t)2) /* i number of all roots */
#define LOSTFOUNDINO (ROOTINO + 1)
* MINFREE gives the minimum acceptable percentage of file system
* blocks which may be free. If the freelist drops below this level
* only the superuser may continue to allocate blocks. This may
* be set to 0 if no reserve of free blocks is deemed necessary,
* however severe performance degredations will be observed if the
* file system is run at greater than 90% full; thus the default
* value of fs_minfree is 10%.
* Empirically the best trade-off between block fragmentation and
* overall disk utilization at a loading of 90% comes with a
* fragmentation of 4, thus the default fragment size is a fourth
* Under current technology, most 300MB disks have 32 sectors and
* 16 tracks, thus these are the defaults used for fs_nsect and
* Cylinder group related limits.
* 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.
* ROTDELAY gives the minimum number of milliseconds to initiate
* another disk transfer on the same cylinder. It is used in
* determining the rotationally optimal layout for disk blocks
* within a file; the default of fs_rotdelay is 2ms.
#define NRPOS 8 /* number distinct rotational positions */
* Each file system has a number of inodes statically allocated.
* We allocate one inode slot per NBPI bytes, expecting this
* to be far more than we will ever need.
* 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(fs).
#define MAXIPG 2048 /* max number inodes/cyl group */
* MINBSIZE is the smallest allowable block size.
* In order to insure that it is possible to create files of size
* 2^32 with only two levels of indirection, MINBSIZE is set to 4096.
* MINBSIZE must be big enough to hold a cylinder group block,
* thus changes to (struct cg) must keep its size within MINBSIZE.
* MAXCPG is limited only to dimension an array in (struct cg);
* it can be made larger as long as that structures size remains
* within the bounds dictated by MINBSIZE.
* Note that super blocks are always of size MAXBSIZE,
* and that MAXBSIZE must be >= MINBSIZE.
#define DESCPG 16 /* desired fs_cpg */
#define MAXCPG 32 /* maximum fs_cpg */
* The path name on which the file system is mounted is maintained
* in fs_fsmnt. MAXMNTLEN defines the amount of space allocated in
* the super block for this name.
* The limit on the amount of summary information per file system
* is defined by MAXCSBUFS. It is currently parameterized for a
* maximum of two million cylinders.
* Per cylinder group information; summarized in blocks allocated
* from first cylinder group data blocks. These blocks have to be
* read in from fs_csaddr (size fs_cssize) in addition to the
* N.B. sizeof(struct csum) must be a power of two in order for
* the ``fs_cs'' macro to work (see below).
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 */
* Super block for a file system.
#define FS_MAGIC 0x110854
long fs_magic
; /* magic number */
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 */
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 */
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 */
long fs_sparecon
[16]; /* reserved for future constants */
/* 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 */
u_char fs_rotbl
[1]; /* list of blocks for each rotation */ * Convert cylinder group to base address of its global summary info.
* N.B. This macro assumes that sizeof(struct csum) is a power of two.
#define fs_cs(fs, indx) \
fs_csp[(indx) / ((fs)->fs_bsize / sizeof(struct csum))] \
[(indx) % ((fs)->fs_bsize / sizeof(struct csum))]
* MAXBPC bounds the size of the rotational layout tables and
* is limited by the fact that the super block is of size SBSIZE.
* The size of these tables is INVERSELY proportional to the block
* size of the file system. It is aggravated by sector sizes that
* are not powers of two, as this increases the number of cylinders
* included before the rotational pattern repeats (fs_cpc).
* Its size is derived from the number of bytes remaining in (struct fs)
#define MAXBPC (SBSIZE - sizeof (struct fs))
* Cylinder group block for a file system.
#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
[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 */
char cg_free
[1]; /* free block map */
* 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.
(NBBY * ((fs)->fs_bsize - (sizeof (struct cg))) / (fs)->fs_frag)
* Turn file system block numbers into disk block addresses.
* This maps file system blocks to device size blocks.
#define fsbtodb(fs, b) ((b) * ((fs)->fs_fsize / DEV_BSIZE))
#define dbtofsb(fs, b) ((b) / ((fs)->fs_fsize / DEV_BSIZE))
* Cylinder group macros to locate things in cylinder groups.
* They calc file system addresses of cylinder group data structures.
#define cgbase(fs, c) ((daddr_t)((fs)->fs_fpg * (c)))
(cgbase(fs, c) + (fs)->fs_cgoffset * ((c) & ~((fs)->fs_cgmask)))
#define cgsblock(fs, c) (cgstart(fs, c) + (fs)->fs_sblkno) /* super blk */
#define cgtod(fs, c) (cgstart(fs, c) + (fs)->fs_cblkno) /* cg block */
#define cgimin(fs, c) (cgstart(fs, c) + (fs)->fs_iblkno) /* inode blk */
#define cgdmin(fs, c) (cgstart(fs, c) + (fs)->fs_dblkno) /* 1st data */
* Macros for handling inode numbers:
* inode number to file system block offset.
* inode number to cylinder group number.
* inode number to file system block address.
#define itoo(fs, x) ((x) % INOPB(fs))
#define itog(fs, x) ((x) / (fs)->fs_ipg)
((daddr_t)(cgimin(fs, itog(fs, x)) + \
(x) % (fs)->fs_ipg / INOPB(fs) * (fs)->fs_frag))
* Give cylinder group number for a file system block.
* Give cylinder group block number for a file system block.
#define dtog(fs, d) ((d) / (fs)->fs_fpg)
#define dtogd(fs, d) ((d) % (fs)->fs_fpg)
* Extract the bits for a block from a map.
* Compute the cylinder and rotational position of a cyl block addr.
#define blkmap(fs, map, loc) \
(((map)[loc / NBBY] >> (loc % NBBY)) & (0xff >> (NBBY - (fs)->fs_frag)))
#define cbtocylno(fs, bno) \
((bno) * NSPF(fs) / (fs)->fs_spc)
#define cbtorpos(fs, bno) \
((bno) * NSPF(fs) % (fs)->fs_nsect * NRPOS / (fs)->fs_nsect)
* The following macros optimize certain frequently calculated
* quantities by using shifts and masks in place of divisions
* modulos and multiplications.
#define blkoff(fs, loc) /* calculates (loc % fs->fs_bsize) */ \
((loc) & ~(fs)->fs_bmask)
#define fragoff(fs, loc) /* calculates (loc % fs->fs_fsize) */ \
((loc) & ~(fs)->fs_fmask)
#define lblkno(fs, loc) /* calculates (loc / fs->fs_bsize) */ \
((loc) >> (fs)->fs_bshift)
#define numfrags(fs, loc) /* calculates (loc / fs->fs_fsize) */ \
((loc) >> (fs)->fs_fshift)
#define blkroundup(fs, size) /* calculates roundup(size, fs->fs_bsize) */ \
(((size) + (fs)->fs_bsize - 1) & (fs)->fs_bmask)
#define fragroundup(fs, size) /* calculates roundup(size, fs->fs_fsize) */ \
(((size) + (fs)->fs_fsize - 1) & (fs)->fs_fmask)
* Determining the size of a file block in the file system.
#define blksize(fs, ip, lbn) \
(((lbn) >= NDADDR || (ip)->i_size >= ((lbn) + 1) * (fs)->fs_bsize) \
: (fragroundup(fs, blkoff(fs, (ip)->i_size))))
#define dblksize(fs, dip, lbn) \
(((lbn) >= NDADDR || (dip)->di_size >= ((lbn) + 1) * (fs)->fs_bsize) \
: (fragroundup(fs, blkoff(fs, (dip)->di_size))))
* Number of disk sectors per block; assumes DEV_BSIZE byte sector size.
#define NSPB(fs) ((fs)->fs_bsize / DEV_BSIZE)
#define NSPF(fs) ((fs)->fs_fsize / DEV_BSIZE)
* INOPB is the number of inodes in a secondary storage block.
#define INOPB(fs) ((fs)->fs_bsize / sizeof (struct dinode))
#define INOPF(fs) ((fs)->fs_fsize / sizeof (struct dinode))
* NINDIR is the number of indirects in a file system block.
#define NINDIR(fs) ((fs)->fs_bsize / sizeof (daddr_t))
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