From: Dan Smith <danms@xxxxxxxxxx> Subject: Re: Latest dm-userspace kernel code Date: Fri, 29 Sep 2006 19:39:46 -0700 > FT> - What is the purpose of dmu_request->deps? I guess that it is for > FT> preventing I/O being reordered. if so, again, you don't need to do > FT> that. > > Well, the problem is that a block copy would overwrite other requests. > I think that while a copy is happening, you have to be careful to not > write into that block so that your writes are not lost. > > Am I over-thinking it? Oh, I see. I think that you are right. That should not happen. > FT> - How does the current kernel/user interface support multiple > FT> destination feature? > > I'm not sure what you mean here. Can you elaborate? I thought that dm-userpsace supports a feature to map a single request to multiple devices for kinda raid. For that, I guess that struct dmu_msg_map_response includes several sets of dst_maj and dst_min. Or you might use 'linked' dmu_msg_map_response, which enables a user-space daemon to send multiple dmu_msg_map_responses for one dmu_msg_map_request (if a dmu_msg_map_response is marked 'linked', dm-userspace module clones the bio and does not free struct the dmu_request). -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
