On Thu, Sep 26, 2013 at 7:56 PM, Hitoshi Mitake <mitake.hitoshi@xxxxxxxxx> wrote: > At Thu, 26 Sep 2013 19:29:06 -0700, > ronnie sahlberg wrote: >> >> On Thu, Sep 26, 2013 at 6:59 PM, Dan Mick <dan.mick@xxxxxxxxxxx> wrote: >> > >> >>> Some might say this had better to be a dynamic loadable >> >>> library. Either is fine by me because it doesn't depend on any >> >>> original C header files. >> >> >> >> >> >> I'm ccing people who would be interested in modular backing >> >> stores, Ronnie Sahlberg and Andy Grover. I think the sheepdog backing >> >> store support doesn't have to be a module because it doesn't create >> >> any new dependencies. Any comments? >> > >> > >> > It seems that you've accomplished this by including structure and constant >> > definitions (and presumably protocol-marshalling routines) in the tgt source >> > file itself, which seems to me to be the wrong way to do it, but it does >> > free you from requiring headers or libraries, so >> > technically speaking, true. >> > >> > I wouldn't write the plugin this way (copying code), but that's me. >> >> >> What Dan said! >> Since you don't add any new dependencies it shouldn't matter if this >> is built-in or a module. >> >> However, you do this at the cost of having a full blown >> re-implementation (or it is a copy?) of a sheepdog client in the >> backing store file. >> I assume there are client libraries for sheepdog available? >> >> So I think from a maintenance viewpoint, it would probably be better >> if you had the backend just be a thin layer that would call out to and >> link to the sheepdog client library. >> I.e. link to a sheedog library instead of reimplementing it in the backend. >> And in that case then this should be a module. > > Thanks for your comment, Dan and Ronnie. > > Currently, sheepdog doesn't have its client library. We have a plan to > implement it. But it will take time. > > In addition, the backing store support of sheepdog isn't a simple copy > (from QEMU). We can't re-implement it by simple copy because current > sheepdog users, QEMU and tgt, have very different I/O models. e.g. > QEMU is a heavy user of coroutine. > > After implementing the library, the backing store support of sheepdog > can be a module. But for now, this patch would be optimal because it > doesn't increase the cost of tgt maintenance (the patch simply adds a > single file). > Thanks for the explanation. So if there is no sheepdog library at this stage then I guess there is no alternative to having a full reimplementation. In that case it should not matter much whether it is built in or a module. -- To unsubscribe from this list: send the line "unsubscribe stgt" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
