minix/usr.sbin/mkfs.mfs/v3/super.h
Antoine Leca e35821b207 mkfs.mfs: various programs
Split in as many programs as needed to support various variants of MFS
Manual page updated (in mandoc format)
2013-05-13 11:18:15 +02:00

74 lines
3 KiB
C

#ifndef _MKFS_MFS_SUPER_H__
#define _MKFS_MFS_SUPER_H__
/* Super block table. The entry holds information about the sizes of the bit
* maps and inodes. The s_ninodes field gives the number of inodes available
* for files and directories, including the root directory. Inode 0 is
* on the disk, but not used. Thus s_ninodes = 4 means that 5 bits will be
* used in the bit map, bit 0, which is always 1 and not used, and bits 1-4
* for files and directories. The disk layout is:
*
* Item # blocks
* boot block 1
* super block 1 (offset 1kB)
* inode map s_imap_blocks
* zone map s_zmap_blocks
* inodes (s_ninodes + 'inodes per block' - 1)/'inodes per block'
* unused whatever is needed to fill out the current zone
* data zones (s_zones - s_firstdatazone) << s_log_zone_size
*/
struct super_block {
uint32_t s_ninodes; /* # usable inodes on the minor device */
uint16_t s_nzones; /* total device size, including bit maps etc */
int16_t s_imap_blocks; /* # of blocks used by inode bit map */
int16_t s_zmap_blocks; /* # of blocks used by zone bit map */
uint16_t s_firstdatazone_old; /* number of first data zone (small) */
uint16_t s_log_zone_size; /* log2 of blocks/zone */
uint16_t s_flags; /* FS state flags */
int32_t s_max_size; /* maximum file size on this device */
uint32_t s_zones; /* number of zones (replaces s_nzones in V2) */
int16_t s_magic; /* magic number to recognize super-blocks */
/* The following items are valid on disk only for V3 and above */
int16_t s_pad2; /* try to avoid compiler-dependent padding */
/* The block size in bytes. Minimum MIN_BLOCK SIZE. SECTOR_SIZE multiple.*/
uint16_t s_block_size; /* block size in bytes. */
int8_t s_disk_version; /* filesystem format sub-version */
/* The following items are only used when the super_block is in memory.
* If this ever changes, i.e. more fields after s_disk_version has to go to
* disk, update LAST_ONDISK_FIELD in servers/mfs/super.c as that controls
* which part of the struct is copied to and from disk.
*/
/* XXX padding inserted here... */
unsigned s_inodes_per_block; /* precalculated from magic number */
uint32_t s_firstdatazone; /* number of first data zone (big) */
} superblock;
/* s_flags contents; undefined flags are guaranteed to be zero on disk
* (not counting future versions of mfs setting them!)
*/
#define MFSFLAG_CLEAN (1L << 0) /* 0: dirty; 1: FS was unmounted cleanly */
/* Future compatability (or at least, graceful failure):
* if any of these bits are on, and the MFS or fsck
* implementation doesn't understand them, do not mount/fsck
* the FS.
*/
#define MFSFLAG_MANDATORY_MASK 0xff00
/* The block size should be registered on disk, even
* multiple. If V1 or V2 filesystem, this should be
* initialised to STATIC_BLOCK_SIZE.
*/
#define MFS_SUPER_BLOCK_SIZE s_block_size
/* To keep the super block on disk clean, the MFS server only read/write up to
* and including this field:
*/
#define LAST_ONDISK_FIELD s_disk_version
#endif