On Fri, Oct 19, 2018 at 4:42 AM, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote: > > On Wed, Oct 17, 2018 at 4:59 PM Bryan Gurney <bgurney@xxxxxxxxxx> wrote: > > > I feel strongly about the prevention of users running into errors > > because of an incorrect scheduler default, because I encountered that > > situation three times in my testing with zoned block devices. The > > switch to SCSI_MQ would resolve that, since mq-deadline is the > > default, but in my case, I was using Fedora 28, which disables > > CONFIG_SCSI_MQ_DEFAULT (which is enabled in the 4.18 kernel), so my > > default scheduler was cfq. > > I think we should make a patch to the kernel that makes it > impossible (even from sysfs) to choose a non-zone aware > scheduler for these devices. > > It's another topic than $SUBJECT patch though. I take this > into account in this version. > I like this idea. I don't have enough experience to write this patch myself, but I imagine something like adding "bool is_zoned_aware" to "struct elevator_type", and setting that true only for the schedulers that are currently zoned-device aware (which is currently deadline on single queue, mq-deadline on blk-mq). Thanks, Bryan
