servers/vfs/super.h

   1 /* Super block table.  The root file system and every mounted file system
   2  * has an entry here.  The entry holds information about the sizes of the bit
   3  * maps and inodes.  The s_ninodes field gives the number of inodes available
   4  * for files and directories, including the root directory.  Inode 0 is
   5  * on the disk, but not used.  Thus s_ninodes = 4 means that 5 bits will be
   6  * used in the bit map, bit 0, which is always 1 and not used, and bits 1-4
   7  * for files and directories.  The disk layout is:
   8  *
   9  *    Item        # blocks
  10  *    boot block      1
  11  *    super block     1    (offset 1kB)
  12  *    inode map     s_imap_blocks
  13  *    zone map      s_zmap_blocks
  14  *    inodes        (s_ninodes + 'inodes per block' - 1)/'inodes per block'
  15  *    unused        whatever is needed to fill out the current zone
  16  *    data zones    (s_zones - s_firstdatazone) << s_log_zone_size
  17  *
  18  * A super_block slot is free if s_dev == NO_DEV.
  19  */
  20
  21 EXTERN struct super_block {
  22   ino_t s_ninodes;              /* # usable inodes on the minor device */
  23   zone1_t  s_nzones;            /* total device size, including bit maps etc */
  24   short s_imap_blocks;          /* # of blocks used by inode bit map */
  25   short s_zmap_blocks;          /* # of blocks used by zone bit map */
  26   zone1_t s_firstdatazone;      /* number of first data zone */
  27   short s_log_zone_size;        /* log2 of blocks/zone */
  28   short s_pad;                  /* try to avoid compiler-dependent padding */
  29   off_t s_max_size;             /* maximum file size on this device */
  30   zone_t s_zones;               /* number of zones (replaces s_nzones in V2) */
  31   short s_magic;                /* magic number to recognize super-blocks */
  32
  33   /* The following items are valid on disk only for V3 and above */
  34
  35   /* The block size in bytes. Minimum MIN_BLOCK SIZE. SECTOR_SIZE
  36    * multiple. If V1 or V2 filesystem, this should be
  37    * initialised to STATIC_BLOCK_SIZE. Maximum MAX_BLOCK_SIZE.
  38    */
  39   short s_pad2;                 /* try to avoid compiler-dependent padding */
  40   unsigned short s_block_size;  /* block size in bytes. */
  41   char s_disk_version;          /* filesystem format sub-version */
  42
  43   /* The following items are only used when the super_block is in memory. */
  44   struct inode *s_isup;         /* inode for root dir of mounted file sys */
  45   struct inode *s_imount;       /* inode mounted on */
  46   unsigned s_inodes_per_block;  /* precalculated from magic number */
  47   dev_t s_dev;                  /* whose super block is this? */
  48   int s_rd_only;                /* set to 1 iff file sys mounted read only */
  49   int s_native;                 /* set to 1 iff not byte swapped file system */
  50   int s_version;                /* file system version, zero means bad magic */
  51   int s_ndzones;                /* # direct zones in an inode */
  52   int s_nindirs;                /* # indirect zones per indirect block */
  53   bit_t s_isearch;              /* inodes below this bit number are in use */
  54   bit_t s_zsearch;              /* all zones below this bit number are in use*/
  55 } super_block[NR_SUPERS];
  56
  57 #define NIL_SUPER (struct super_block *) 0
  58 #define IMAP            0       /* operating on the inode bit map */
  59 #define ZMAP            1       /* operating on the zone bit map */