On Fri, Sep 08 2017 at 1:07pm -0400, Mike Snitzer <snitzer@xxxxxxxxxx> wrote: > On Fri, Sep 08 2017 at 12:48pm -0400, > Jens Axboe <axboe@xxxxxxxxx> wrote: > > > > Please see the following untested patch. All > > > testing/review/comments/acks appreciated. > > > > > > I elected to use elevator_change() rather than fiddle with adding a new > > > blk-mq elevator hook (e.g. ->request_prepared) to verify that each > > > blk-mq elevator enabled request did in fact get prepared. > > > > > > Bart, please test this patch and reply with your review/feedback. > > > > > > Jens, if you're OK with this solution please reply with your Ack and > > > I'll send it to Linus along with the rest of the handful of DM changes I > > > have for 4.14. > > > > I am not - we used to have this elevator change functionality from > > inside the kernel, and finally got rid of it when certain drivers killed > > it. I don't want to be bringing it back. > > Fine. BTW, while I conceded "Fine": I think your justification for not reintroducing elevator_change() lacks substance. What is inherently problematic about elevator_change()? Having an elevator attached to a DM multipath device's underlying path's request_queue just asks for trouble (especially given the blk-mq elevator interface). Please own this issue as a regression and help me arrive at a timely way forward. Thanks, Mike
