On 5/25/18 4:18 PM, Jeff Moyer wrote: > Hi, Jens, > > Jens Axboe <axboe@xxxxxxxxx> writes: > >> On 5/25/18 3:14 PM, Jeff Moyer wrote: >>> Bryan Gurney reported I/O errors when using dm-zoned with a host-managed >>> SMR device. It turns out he was using CFQ, which is the default. >>> Unfortunately, as of v4.16, only the deadline schedulers work well with >>> host-managed SMR devices. This series aatempts to switch the elevator >>> to deadline for those devices. >>> >>> NOTE: I'm not super happy with setting up one iosched and then >>> immediately tearing it down. I'm open to suggestions on better ways >>> to accomplish this goal. >> >> Let's please not do this, a few years ago I finally managed to kill >> drivers changing the scheduler manually. Why can't this go into a >> udev (or similar) rule? That's where it belongs, imho. > > We could do that. The downside is that distros will have to pick up > udev rules, which they haven't done yet, and the udev rules will have to > be kernel version dependent. And then later, when this restriction is > lifted, we'll have to update the udev rules. That also sounds awful to > me. They only have to be feature dependent, which isn't that hard. And if I had to pick between a kernel upgrade and a udev rule package update, the choice is pretty clear. > I understand why you don't like this patch set, but I happen to think > the alternative is worse. FYI, in Bryan's case, his system actually got > bricked (likely due to buggy firmware). I disagree, I think the rule approach is much easier. If the wrong write location bricked the drive, then I think that user has much larger issues... That seems like a trivial issue that should have been caught in basic testing, I would not trust that drive with any data if it bricks that easily. -- Jens Axboe
