Re: [PATCH] bfq: backport: update internal depth state when queue depth changes

From: Sasha Levin
Date: Mon May 13 2019 - 09:10:52 EST

On Mon, May 13, 2019 at 09:03:37AM +0200, Greg KH wrote:
On Fri, May 10, 2019 at 04:18:55PM -0400, Sasha Levin wrote:
On Fri, May 10, 2019 at 10:56:32AM -0700, Eric Wheeler wrote:
> From: Jens Axboe <axboe@xxxxxxxxx>
> commit 77f1e0a52d26242b6c2dba019f6ebebfb9ff701e upstream
> A previous commit moved the shallow depth and BFQ depth map calculations
> to be done at init time, moving it outside of the hotter IO path. This
> potentially causes hangs if the users changes the depth of the scheduler
> map, by writing to the 'nr_requests' sysfs file for that device.
> Add a blk-mq-sched hook that allows blk-mq to inform the scheduler if
> the depth changes, so that the scheduler can update its internal state.
> Signed-off-by: Eric Wheeler <bfq@xxxxxxxxxxxxxxxxxx>
> Tested-by: Kai Krakow <kai@xxxxxxxxxxx>
> Reported-by: Paolo Valente <paolo.valente@xxxxxxxxxx>
> Fixes: f0635b8a416e ("bfq: calculate shallow depths at init time")
> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx

I wasn't clear on what was backported here, so I've queued the upstream
version on 4.19 and 4.14, it doesn't seem to be relevant to older

I only see this added to the 5.0 and 4.19 queues, did you forget to push
the 4.14 update?

Sorry, I meant to say that I applied it to 5.0 and 4.19. The patch it
fixes, f0635b8a416e ("bfq: calculate shallow depths at init time"),
isn't in 4.14 nor was it backported there by us.