Fix coverity defects: CID 147452, 147447, 147446

coverity scan CID:147452, Type:Unchecked return value from library
coverity scan CID:147447, Type:Unchecked return value from library
coverity scan CID:147446, Type:Unchecked return value from library

Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: cao.xuewen <cao.xuewen@zte.com.cn>
Closes #5264