61 lines
2.9 KiB
C
61 lines
2.9 KiB
C
/* 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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ino_t s_ninodes; /* # usable inodes on the minor device */
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zone1_t s_nzones; /* total device size, including bit maps etc */
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short s_imap_blocks; /* # of blocks used by inode bit map */
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short s_zmap_blocks; /* # of blocks used by zone bit map */
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zone1_t s_firstdatazone; /* number of first data zone */
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short s_log_zone_size; /* log2 of blocks/zone */
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short s_pad; /* try to avoid compiler-dependent padding */
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off_t s_max_size; /* maximum file size on this device */
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zone_t s_zones; /* number of zones (replaces s_nzones in V2) */
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short 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. Maximum MAX_BLOCK_SIZE.
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*/
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short s_pad2; /* try to avoid compiler-dependent padding */
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unsigned short s_block_size; /* block size in bytes. */
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char 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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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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dev_t s_dev; /* whose super block is this? */
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int s_rd_only; /* set to 1 iff file sys mounted read only */
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int s_native; /* set to 1 iff not byte swapped file system */
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int s_version; /* file system version, zero means bad magic */
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int s_ndzones; /* # direct zones in an inode */
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int s_nindirs; /* # indirect zones per indirect block */
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bit_t s_isearch; /* inodes below this bit number are in use */
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bit_t s_zsearch; /* all zones below this bit number are in use*/
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} super_block[NR_SUPERS];
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#define NIL_SUPER (struct super_block *) 0
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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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