minix/fs/mfs/super.h

   1 #ifndef __MFS_SUPER_H__
   2 #define __MFS_SUPER_H__
   3
   4 /* Super block table.  The root file system and every mounted file system
   5  * has an entry here.  The entry holds information about the sizes of the bit
   6  * maps and inodes.  The s_ninodes field gives the number of inodes available
   7  * for files and directories, including the root directory.  Inode 0 is
   8  * on the disk, but not used.  Thus s_ninodes = 4 means that 5 bits will be
   9  * used in the bit map, bit 0, which is always 1 and not used, and bits 1-4
  10  * for files and directories.  The disk layout is:
  11  *
  12  *    Item        # blocks
  13  *    boot block      1
  14  *    super block     1    (offset 1kB)
  15  *    inode map     s_imap_blocks
  16  *    zone map      s_zmap_blocks
  17  *    inodes        (s_ninodes + 'inodes per block' - 1)/'inodes per block'
  18  *    unused        whatever is needed to fill out the current zone
  19  *    data zones    (s_zones - s_firstdatazone) << s_log_zone_size
  20  *
  21  * A super_block slot is free if s_dev == NO_DEV.
  22  */
  23
  24 EXTERN struct super_block {
  25   u32_t s_ninodes;              /* # usable inodes on the minor device */
  26   zone1_t  s_nzones;            /* total device size, including bit maps etc */
  27   short s_imap_blocks;          /* # of blocks used by inode bit map */
  28   short s_zmap_blocks;          /* # of blocks used by zone bit map */
  29   zone1_t s_firstdatazone_old;  /* number of first data zone (small) */
  30   short s_log_zone_size;        /* log2 of blocks/zone */
  31   unsigned short s_flags;       /* FS state flags */
  32   i32_t s_max_size;             /* maximum file size on this device */
  33   zone_t s_zones;               /* number of zones (replaces s_nzones in V2) */
  34   short s_magic;                /* magic number to recognize super-blocks */
  35
  36   /* The following items are valid on disk only for V3 and above */
  37
  38   short s_pad2;                 /* try to avoid compiler-dependent padding */
  39   unsigned short s_block_size;  /* block size in bytes. */
  40   char s_disk_version;          /* filesystem format sub-version */
  41
  42   /* The following items are only used when the super_block is in memory.
  43    * If this ever changes, i.e. more fields after s_disk_version has to go to
  44    * disk, update LAST_ONDISK_FIELD in super.c as that controls which part of the
  45    * struct is copied to and from disk.
  46    */
  47
  48   /*struct inode *s_isup;*/     /* inode for root dir of mounted file sys */
  49   /*struct inode *s_imount;*/   /* inode mounted on */
  50   unsigned s_inodes_per_block;  /* precalculated from magic number */
  51   zone_t s_firstdatazone;       /* number of first data zone (big) */
  52   dev_t s_dev;                  /* whose super block is this? */
  53   int s_rd_only;                /* set to 1 iff file sys mounted read only */
  54   int s_native;                 /* set to 1 iff not byte swapped file system */
  55   int s_version;                /* file system version, zero means bad magic */
  56   int s_ndzones;                /* # direct zones in an inode */
  57   int s_nindirs;                /* # indirect zones per indirect block */
  58   bit_t s_isearch;              /* inodes below this bit number are in use */
  59   bit_t s_zsearch;              /* all zones below this bit number are in use*/
  60 } superblock;
  61
  62 #define IMAP            0       /* operating on the inode bit map */
  63 #define ZMAP            1       /* operating on the zone bit map */
  64
  65 /* s_flags contents; undefined flags are guaranteed to be zero on disk
  66  * (not counting future versions of mfs setting them!)
  67  */
  68 #define MFSFLAG_CLEAN   (1L << 0) /* 0: dirty; 1: FS was unmounted cleanly */
  69
  70 /* Future compatability (or at least, graceful failure):
  71  * if any of these bits are on, and the MFS or fsck
  72  * implementation doesn't understand them, do not mount/fsck
  73  * the FS.
  74  */
  75 #define MFSFLAG_MANDATORY_MASK 0xff00
  76
  77 #endif
  78