[ Upstream commit 028288df635f5a9addd48ac4677b720192747944 ]

In raid1_sync_request func, rdev should be checked before reference.
Signed-off-by: NZhiqiang Liu <liuzhiqiang26@huawei.com>
Signed-off-by: NSong Liu <songliubraving@fb.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>