On Thu, Mar 08, 2018@11:36:23AM -0700, Jason Gunthorpe wrote:

On Thu, Mar 08, 2018@07:56:37PM +0200, Sagi Grimberg wrote:

quoted

If the SQE and DB update have been reordered,

But that can't happen, the SQE is written before
nvme_dbbuf_update_and_check_event(), and that function does wmb.

I believe Sagi is talking about the typical controller that doesn't
have shadow db registers (no real nvme device has those), which doesn't
currently go through a path calling wmb().