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