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 65