minix/usr.sbin/mkfs.mfs/v3/super.h

   1 #ifndef _MKFS_MFS_SUPER_H__
   2 #define _MKFS_MFS_SUPER_H__
   3
   4 /* Super block table.  The entry holds information about the sizes of the bit
   5  * maps and inodes.  The s_ninodes field gives the number of inodes available
   6  * for files and directories, including the root directory.  Inode 0 is
   7  * on the disk, but not used.  Thus s_ninodes = 4 means that 5 bits will be
   8  * used in the bit map, bit 0, which is always 1 and not used, and bits 1-4
   9  * for files and directories.  The disk layout is:
  10  *
  11  *    Item        # blocks
  12  *    boot block      1
  13  *    super block     1    (offset 1kB)
  14  *    inode map     s_imap_blocks
  15  *    zone map      s_zmap_blocks
  16  *    inodes        (s_ninodes + 'inodes per block' - 1)/'inodes per block'
  17  *    unused        whatever is needed to fill out the current zone
  18  *    data zones    (s_zones - s_firstdatazone) << s_log_zone_size
  19  */
  20
  21 struct super_block {
  22   uint32_t s_ninodes;           /* # usable inodes on the minor device */
  23   uint16_t  s_nzones;           /* total device size, including bit maps etc */
  24   int16_t s_imap_blocks;        /* # of blocks used by inode bit map */
  25   int16_t s_zmap_blocks;        /* # of blocks used by zone bit map */
  26   uint16_t s_firstdatazone_old; /* number of first data zone (small) */
  27   uint16_t s_log_zone_size;     /* log2 of blocks/zone */
  28   uint16_t s_flags;             /* FS state flags */
  29   int32_t s_max_size;           /* maximum file size on this device */
  30   uint32_t s_zones;             /* number of zones (replaces s_nzones in V2) */
  31   int16_t s_magic;              /* magic number to recognize super-blocks */
  32
  33   /* The following items are valid on disk only for V3 and above */
  34
  35   int16_t s_pad2;               /* try to avoid compiler-dependent padding */
  36   /* The block size in bytes. Minimum MIN_BLOCK SIZE. SECTOR_SIZE multiple.*/
  37   uint16_t s_block_size;        /* block size in bytes. */
  38   int8_t s_disk_version;        /* filesystem format sub-version */
  39
  40   /* The following items are only used when the super_block is in memory.
  41    * If this ever changes, i.e. more fields after s_disk_version has to go to
  42    * disk, update LAST_ONDISK_FIELD in servers/mfs/super.c as that controls
  43    * which part of the struct is copied to and from disk.
  44    */
  45 /* XXX padding inserted here... */
  46
  47   unsigned s_inodes_per_block;  /* precalculated from magic number */
  48   uint32_t s_firstdatazone;     /* number of first data zone (big) */
  49 } superblock;
  50
  51 /* s_flags contents; undefined flags are guaranteed to be zero on disk
  52  * (not counting future versions of mfs setting them!)
  53  */
  54 #define MFSFLAG_CLEAN   (1L << 0) /* 0: dirty; 1: FS was unmounted cleanly */
  55
  56 /* Future compatability (or at least, graceful failure):
  57  * if any of these bits are on, and the MFS or fsck
  58  * implementation doesn't understand them, do not mount/fsck
  59  * the FS.
  60  */
  61 #define MFSFLAG_MANDATORY_MASK 0xff00
  62
  63 /* The block size should be registered on disk, even
  64  * multiple. If V1 or V2 filesystem, this should be
  65  * initialised to STATIC_BLOCK_SIZE.
  66  */
  67 #define MFS_SUPER_BLOCK_SIZE    s_block_size
  68
  69 /* To keep the super block on disk clean, the MFS server only read/write up to
  70  * and including this field:
  71  */
  72 #define LAST_ONDISK_FIELD       s_disk_version
  73
  74 #endif