Although handling a mapping request with no permissions is a
trivial no-op, defer the early return until after the size/range
checks so that we are consistent with other mapping requests.
Signed-off-by: NKeqian Zhu <zhukeqian1@huawei.com>
Link: https://lore.kernel.org/r/20201207115758.9400-1-zhukeqian1@huawei.comSigned-off-by: NWill Deacon <will@kernel.org>