Revert "vfs: make AIO use the proper rw_verify_area() area helpers"

This reverts commit 77d284259922be4bb9941fee3e003fa16c1fbb19.
Revert "CPU hotplug, writeback: Don't call writeback_set_ratelimit() too often during hotplug"

This reverts commit 083d8babfb99b6c8305b186ce1f0facfedd359e9.
Revert " tmpfs: fix mempolicy object leaks"

This reverts commit 0e470a9580c3bb5f5452855eab3cdc99ba00bcba.
Revert "tmpfs: fix use-after-free of mempolicy object"

This reverts commit 6ba1670cc4205b292b5fa3723c9a471738d4cd87.