** start xfs mount testing ...
FORMAT:
TEST: "" "pass" "allocsize" "false"
-TEST: "-o allocsize=4k" "pass" "allocsize=4k" "true"
+TEST: "-o allocsize=PAGESIZE" "pass" "allocsize=PAGESIZE" "true"
TEST: "-o allocsize=1048576k" "pass" "allocsize=1048576k" "true"
TEST: "-o allocsize=2048" "fail"
TEST: "-o allocsize=2g" "fail"