dbAllocBottomUp
extern int dbAllocBottomUp(struct inode *ip, s64 blkno, s64 nblocks);
if ((rc = dbAllocBottomUp(ip, xaddr, (s64) nblocks)) == 0) {
if ((rc = dbAllocBottomUp(ip, xaddr, (s64) xlen)))
if ((rc = dbAllocBottomUp(ip, xaddr, (s64) xlen)))