isblock
if (isblock(&sblock, cg_blksfree(&acg), d / sblock.fs_frag))
static int isblock(struct fs *fs, unsigned char *cp, int h);
if (isblock(fs, blksfree, (daddr_t)fragstoblks(fs, bpref))) {
if (isblock(fs, blksfree, (daddr_t)(bno + i))) {
if (isblock(fs, blksfree, cgbno)) {
if (!isblock(fs, blksfree, cgbno))
if (isblock(fs, blksfree, blkno)) {
extern int isblock(struct fs *, uchar_t *, daddr_t);