On Mon, Oct 10, 2016 at 6:25 AM, Mike Snitzer <snitzer@xxxxxxxxxx> wrote: > I have to believe this was born out of code inspection rather than > actual need (due to crash, etc)? This got originated from several crashes I have seen with 4.3 kernel. The crashes were caused by null dereferencing of io_barrier->per_cpu_ref. The issue may no longer be relevant after commit c91852ff0815 ("dm: optimize dm_request_fn()") because conditions for accessing io_barrier may not longer exist. But fix should be considered for forked stable trees. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel