On Thu, Mar 14, 2019 at 7:16 AM Javier González <javier@xxxxxxxxxxx> wrote: > > > On 14 Mar 2019, at 06.49, Igor Konopko <igor.j.konopko@xxxxxxxxx> wrote: > > > > While reading this patch, idea came to my mind - maybe it would be simply better to get rid of partial read handling from pblk in current form at all and use bio_split() & bio_chain() combination instead? > > > > This would definitely reduce a number of this 'kind of complicated' code inside pblk and let block layer help us with that. Even that the performance of such a requests could be a little worse (few smaller IOs instead of single vector IO), I believe that partial read is more a corner case, then a typical use case, so maybe this would be a path to go. > > > > Let me know what you think about such an approach - I can make a patch with that if you want. I like this idea as it will clean up a lot of code and get rid of the read_bitmap. Note that a single request can be turned into up to 32 requests if cached and non-cached sectors alternate, each one probably requiring an l2p lookup. I still think it's worth doing though. When you split, note that you have to release all line_refs which were acquired during l2p lookup. > > I agree with Igor. > > As I mentioned offline, we should fix this in a way that survives > further changes in struct bio; either making pblk handling visible to > the outside or rethinking the whole thing. > > Igor: If you can send a patch you mention, it would be great. I have > been trying the helper approach for some time, but it is too specific, > as fixing holes in the bvec breaks the bio advance-only semantics. Your > approach seems much better. > > Thanks, > Javier
