dm writecache: fix writing beyond end of underlying device when shrinking

stable inclusion
from linux-4.19.199
commit 797b950e8aaec3fc30312bb9a44d702c6cc9d25e

--------------------------------

commit 4134455f upstream.

Do not attempt to write any data beyond the end of the underlying data
device while shrinking it.

The DM writecache device must be suspended when the underlying data
device is shrunk.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>