For now just wrap the main logic, but this driver is a prime candidate for
someone wanting to eliminate the lock entirely

[lizf@cn.fujitsu.com: fix build failure]
Signed-off-by: NAlan Cox <alan@redhat.com>
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>