On Tue, Jun 19, 2018 at 11:11 AM, John Hubbard <jhubbard@xxxxxxxxxx> wrote: > On 06/19/2018 03:41 AM, Jan Kara wrote: >> On Tue 19-06-18 02:02:55, Matthew Wilcox wrote: >>> On Tue, Jun 19, 2018 at 10:29:49AM +0200, Jan Kara wrote: [..] >> And then there's the aspect that both these approaches are a bit too >> heavyweight for some get_user_pages_fast() users (e.g. direct IO) - Al Viro >> had an idea to use page lock for that path but e.g. fs/direct-io.c would have >> problems due to lock ordering constraints (filesystem ->get_block would >> suddently get called with the page lock held). But we can probably leave >> performance optimizations for phase two. > > > So I assume that phase one would be to apply this approach only to > get_user_pages_longterm. (Please let me know if that's wrong.) I think that's wrong, because get_user_pages_longterm() is only a filesystem-dax avoidance mechanism, it's not trying to address all the problems that Jan is talking about. I don't see any viable half-step solutions.
