>> Finally got to this patch. I think, find it adding too many edge cases >> and it isn't integrated consistently into what we have now. I would love >> to hear your vision, but I'd try to implement them in such a way, that it >> doesn't need to modify the framework, at least for some particular case. >> In other words, as opcodes could have been added from the outside with a >> function table. > > I agree, it could do with a bit of cleanup. Incrementals would be > appreciated! > >> Also, it's not so consistent with the userspace API as well. >> >> 1. If we specified drain for the timeout, should its start be delayed >> until then? I would prefer so. >> >> E.g. send_msg + drained linked_timeout, which would set a timeout from the >> start of the send. > > What cases would that apply to, what would the timeout even do in this > case? The point of the linked timeout is to abort the previous command. > Maybe I'm not following what you mean here. > Hmm, got it a bit wrong with defer. io_queue_link_head() can defer it without setting timeout. However, it seems that io_wq_submit_work() won't set a timer, as it uses __io_submit_sqe(), but not __io_queue_sqe(), which handles all this with linked timeouts. Indeed, maybe it be, that you wanted to place it in __io_submit_sqe? >> 2. Why it could be only the second one in a link? May we want to cancel >> from a certain point? >> e.g. "op1 -> op2 -> timeout -> op3" cancels op2 and op3 > > Logically it need not be the second, it just has to follow another > request. Is there a bug there? > __io_queue_sqe looks only for the second one in a link. Other linked timeouts will be ignored, if I get the code right. Also linking may (or __may not__) be an issue. As you remember, the head is linked through link_list, and all following with list. i.e. req_head.link_list <-> req.list <-> req.list <-> req.list free_req() (last time I saw it), expects that timeout's previous request is linked with link_list. If a timeout can fire in the middle of a link (during execution), this could be not the case. But it depends on when we set an timeout. BTW, personally I'd link them all through link_list. E.g. may get rid of splicing in free_req(). I'll try to make it later. >> 3. It's a bit strange, that the timeout affects a request from the left, >> and after as an consequence cancels everything on the right (i.e. chain). >> Could we place it in the head? So it would affect all requests on the right >> from it. > > But that's how links work, though. If you keep linking, then everything > that depends on X will fail, if X itself isn't succesful. > Right. That's about what userspace API would be saner. To place timeout on the left of a request, or on the right, with the same resulting effect. Let put this question away until the others are clear. >> 4. I'd prefer to handle it as a new generic command and setting a timer >> in __io_submit_sqe(). >> >> I believe we can do it more gracefully, and at the same moment giving >> more freedom to the user. What do you think? > > I just think we need to make sure the ground rules are sane. I'm going > to write a few test cases to make sure we do the right thing. > -- Pavel Begunkov
