JFS布局:日志文件系统如何处理磁盘布局(12)

/*
 *  dmap summary tree
 *
 * dmaptree_t must be consistent with dmapctl_t.
 */
typedef struct {
    int32   nleafs;             /* 4: number of tree leafs     */
    int32   l2nleafs;           /* 4: l2 number of tree leafs      */
    int32   leafidx;            /* 4: index of first tree leaf     */
    int32   height;             /* 4: height of the tree       */
    int8    budmin;             /* 1: min l2 tree leaf value to combine*/
    int8    stree[TREESIZE];        /* TREESIZE: tree          */
    uint8   pad[2];             /* 2: pad to word boundary     */
} dmaptree_t;                   /* - 360 -             */


/*
 *  dmap page per 8K blocks bitmap
 */
typedef struct {
    int32       nblocks;      /* 4: num blks covered by this dmap */
    int32       nfree;        /* 4: num of free blks in this dmap */
    int64       start;        /* 8: starting blkno for this dmap  */
    dmaptree_t  tree;         /* 360: dmap tree                   */
    uint8       pad[1672];    /* 1672: pad to 2048 bytes          */
    uint32      wmap[LPERDMAP];   /* 1024: bits of the working map    */
    uint32      pmap[LPERDMAP];   /* 1024: bits of the persistent map */
} dmap_t;                 /* - 4096 -                         */