dbtofsb
#define dbtofsb(fs, b) ((b) >> (fs)->fs_fsbtodb)
#define dbtofsb(blkno) ((blkno) / (fsbsize / DEV_BSIZE))
#define dbtofsb(fs, b) ((b) >> (fs)->fs_fsbtodb)
#define dbtofsb(fs, b) ((b) >> (fs)->fs_fsbtodb)
#define dbtofsb(fs, b) ((b) >> (fs)->fs_fsbtodb)