On Tue, Jun 04, 2024 at 04:44:34AM -0700, Bart Van Assche wrote: > On 6/3/24 21:40, Christoph Hellwig wrote: >> There is no requirement to process them synchronously, there is just >> a requirement to preserve the order. Note that my suggestion a few >> arounds ago also included a copy id to match them up. If we don't >> need that I'm happy to leave it away. If need it it to make stacking >> drivers' lifes easier that suggestion still stands. > > Including an ID in REQ_OP_COPY_DST and REQ_OP_COPY_SRC operations sounds > much better to me than abusing the merge infrastructure for combining > these two operations into a single request. With the ID-based approach > stacking drivers are allowed to process copy bios asynchronously and it > is no longer necessary to activate merging for copy operations if > merging is disabled (QUEUE_FLAG_NOMERGES). Again, we can decided on QUEUE_FLAG_NOMERGES per request type. In fact I think we should not use it for discards as that just like copy is a very different kind of "merge". I'm in fact much more happy about avoiding the copy_id IFF we can. It it a fair amout of extra overhead, so we should only add it if there is a real need for it
