lib/ext2fs/jfs_dat.h

   1 /*
   2  * jfs_dat.h --- stripped down header file which only contains the JFS
   3  *      on-disk data structures
   4  */
   5
   6 #define JFS_MAGIC_NUMBER 0xc03b3998U /* The first 4 bytes of /dev/random! */
   7
   8 /*
   9  * On-disk structures
  10  */
  11
  12 /*
  13  * Descriptor block types:
  14  */
  15
  16 #define JFS_DESCRIPTOR_BLOCK    1
  17 #define JFS_COMMIT_BLOCK        2
  18 #define JFS_SUPERBLOCK          3
  19
  20 /*
  21  * Standard header for all descriptor blocks:
  22  */
  23 typedef struct journal_header_s
  24 {
  25         __u32           h_magic;
  26         __u32           h_blocktype;
  27         __u32           h_sequence;
  28 } journal_header_t;
  29
  30
  31 /*
  32  * The block tag: used to describe a single buffer in the journal
  33  */
  34 typedef struct journal_block_tag_s
  35 {
  36         __u32           t_blocknr;      /* The on-disk block number */
  37         __u32           t_flags;        /* See below */
  38 } journal_block_tag_t;
  39
  40 /* Definitions for the journal tag flags word: */
  41 #define JFS_FLAG_ESCAPE         1       /* on-disk block is escaped */
  42 #define JFS_FLAG_SAME_UUID      2       /* block has same uuid as previous */
  43 #define JFS_FLAG_DELETED        4       /* block deleted by this transaction */
  44 #define JFS_FLAG_LAST_TAG       8       /* last tag in this descriptor block */
  45
  46
  47 /*
  48  * The journal superblock
  49  */
  50 typedef struct journal_superblock_s
  51 {
  52         journal_header_t s_header;
  53
  54         /* Static information describing the journal */
  55         __u32           s_blocksize;    /* journal device blocksize */
  56         __u32           s_maxlen;       /* total blocks in journal file */
  57         __u32           s_first;        /* first block of log information */
  58
  59         /* Dynamic information describing the current state of the log */
  60         __u32           s_sequence;     /* first commit ID expected in log */
  61         __u32           s_start;        /* blocknr of start of log */
  62
  63 } journal_superblock_t;
  64