Commits
Mike Snitzer committed b7f874eedc9
dm round robin: revert "use percpu 'repeat_count' and 'current_path'" commit 37a098e9d10db6e2efc05fe61e3a6ff2e9802c53 upstream. The sloppy nature of lockless access to percpu pointers (s->current_path) in rr_select_path(), from multiple threads, is causing some paths to used more than others -- which results in less IO performance being observed. Revert these upstream commits to restore truly symmetric round-robin IO submission in DM multipath: b0b477c dm round robin: use percpu 'repeat_count' and 'current_path' 802934b dm round robin: do not use this_cpu_ptr() without having preemption disabled There is no benefit to all this complexity if repeat_count = 1 (which is the recommended default). Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>