> Non-inlining in the loop module doesn't seem like a big trouble. OTOH, > other callers may be more sensitive and would need to rely on inlining. Yes, this is my concern as well. > I can't currently think of a nice way to have both the exported and the > exlicitly inlined variant at once. It seems it's either API or perf > craft in the end but both are uncertain, so I guess the current approach > is fine in the end. > > > Yes it is intentional. All requests (not just aio) go through the loop > > worker which grabs the blkcg reference in loop_queue_work() on > > construction. So I believe grabbing a reference per request is > > unnecessary. > > Isn't there a window without the reference between loop_queue_rq and > loop_queue_work? Hmm, perhaps I'm not understanding how the reference counting works, but my understanding is that we enter loop_queue_rq with presumably some code earlier holding a reference to the blkcg, we only need to acquire a reference sometime before returning from loop_queue_rq. The "window" between loop_queue_rq and loop_queue_work is all straight-line code so there's no possibility for the earlier code to get control back and drop the reference. > I don't know, you seem to know better, so I'd suggest > dropping a comment line into the code explaining this. I wouldn't be so sure that I know any better here :D - I'm fairly inexperienced in this domain. Where would you suggest putting such a comment? The change in question removed a particular case where we explicitly grab a reference to the blkcg because now we do it uniformly in one place. Would you like a comment explaining why we acquire a reference for all loop workers or one explaining specifically why we don't need to acquire one for aio?
