Simplify the code by using the PTR_ERR_OR_ZERO, instead of the
open code. It is better.
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>