84 lines
3.6 KiB
C
84 lines
3.6 KiB
C
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#ifndef __MFS_SUPER_H__
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#define __MFS_SUPER_H__
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/* Super block table. The root file system and every mounted file system
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* has an entry here. The entry holds information about the sizes of the bit
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* maps and inodes. The s_ninodes field gives the number of inodes available
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* for files and directories, including the root directory. Inode 0 is
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* on the disk, but not used. Thus s_ninodes = 4 means that 5 bits will be
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* used in the bit map, bit 0, which is always 1 and not used, and bits 1-4
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* for files and directories. The disk layout is:
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*
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* Item # blocks
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* boot block 1
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* super block 1 (offset 1kB)
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* inode map s_imap_blocks
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* zone map s_zmap_blocks
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* inodes (s_ninodes + 'inodes per block' - 1)/'inodes per block'
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* unused whatever is needed to fill out the current zone
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* data zones (s_zones - s_firstdatazone) << s_log_zone_size
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*
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* A super_block slot is free if s_dev == NO_DEV.
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*/
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EXTERN struct super_block {
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uint32_t s_ninodes; /* # usable inodes on the minor device */
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uint16_t s_nzones; /* total device size, including bit maps etc */
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int16_t s_imap_blocks; /* # of blocks used by inode bit map */
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int16_t s_zmap_blocks; /* # of blocks used by zone bit map */
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uint16_t s_firstdatazone_old; /* number of first data zone (small) */
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uint16_t s_log_zone_size; /* log2 of blocks/zone */
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uint16_t s_flags; /* FS state flags */
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int32_t s_max_size; /* maximum file size on this device */
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uint32_t s_zones; /* number of zones (replaces s_nzones in V2) */
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int16_t s_magic; /* magic number to recognize super-blocks */
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/* The following items are valid on disk only for V3 and above */
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/* The block size in bytes. Minimum MIN_BLOCK SIZE. SECTOR_SIZE
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* multiple. If V1 or V2 filesystem, this should be
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* initialised to STATIC_BLOCK_SIZE.
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*/
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int16_t s_pad2; /* try to avoid compiler-dependent padding */
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uint16_t s_block_size; /* block size in bytes. */
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int8_t s_disk_version; /* filesystem format sub-version */
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/* The following items are only used when the super_block is in memory.
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* If this ever changes, i.e. more fields after s_disk_version has to go to
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* disk, update LAST_ONDISK_FIELD in super.c as that controls which part of the
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* struct is copied to and from disk.
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*/
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/*struct inode *s_isup;*/ /* inode for root dir of mounted file sys */
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/*struct inode *s_imount;*/ /* inode mounted on */
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unsigned s_inodes_per_block; /* precalculated from magic number */
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uint32_t s_firstdatazone; /* number of first data zone (big) */
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dev_t s_dev; /* whose super block is this? */
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int32_t s_rd_only; /* set to 1 iff file sys mounted read only */
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int32_t s_native; /* set to 1 iff not byte swapped file system */
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int32_t s_version; /* file system version, zero means bad magic */
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int32_t s_ndzones; /* # direct zones in an inode */
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int32_t s_nindirs; /* # indirect zones per indirect block */
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uint32_t s_isearch; /* inodes below this bit number are in use */
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uint32_t s_zsearch; /* all zones below this bit number are in use*/
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int8_t s_is_root;
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} superblock;
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#define IMAP 0 /* operating on the inode bit map */
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#define ZMAP 1 /* operating on the zone bit map */
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/* s_flags contents; undefined flags are guaranteed to be zero on disk
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* (not counting future versions of mfs setting them!)
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*/
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#define MFSFLAG_CLEAN (1L << 0) /* 0: dirty; 1: FS was unmounted cleanly */
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/* Future compatability (or at least, graceful failure):
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* if any of these bits are on, and the MFS or fsck
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* implementation doesn't understand them, do not mount/fsck
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* the FS.
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*/
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#define MFSFLAG_MANDATORY_MASK 0xff00
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#endif
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