[ Upstream commit 38b7c2a3ffb1fce8358ddc6006cfe5c038ff9963 ] While digging through the recent mmiowb preemption issue it came up that we aren't actually preventing IO from crossing a scheduling boundary. While it's a bit ugly to overload smp_mb__after_spinlock() with this behavior, it's what PowerPC is doing so there's some precedent. Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com> Signed-off-by: Sasha Levin <sashal@kernel.org>