On Tue, Nov 15 2016 at 7:40pm -0500, Bart Van Assche <bart.vanassche@xxxxxxxxxxx> wrote: > On 11/15/2016 04:37 PM, Mike Snitzer wrote: > >On Tue, Nov 15 2016 at 6:35pm -0500, > >Bart Van Assche <bart.vanassche@xxxxxxxxxxx> wrote: > >>If a single-queue dm device is stacked on top of multi-queue block > >>devices and map_tio_request() is called while there are no paths then > >>the request will be prepared for a single-queue path. If a path is > >>added after a request was prepared and before __multipath_map() is > >>called return DM_MAPIO_REQUEUE such that it gets unprepared and > >>reprepared as a blk-mq request. > > > >This patch makes little sense to me. There isn't a scenario that I'm > >aware of that would allow the request_queue to transition between old > >.request_fn and new blk-mq. > > > >The dm-table code should prevent this. > > Hello Mike, > > Are you aware that dm_table_determine_type() sets "all_blk_mq" to > false if there are no paths, even if the dm device is in blk-mq > mode? That shouldn't matter. Once the type is established, it is used to initialize the DM device's request_queue, the type cannot change across different table loads. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
