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

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Date:   Mon, 13 May 2019 09:03:37 +0200
From:   Greg KH <greg@...ah.com>
To:     Sasha Levin <sashal@...nel.org>
Cc:     Eric Wheeler <stable@...ts.ewheeler.net>,
        Paolo Valente <paolo.valente@...aro.org>,
        Jens Axboe <axboe@...nel.dk>,
        "open list:BFQ I/O SCHEDULER" <linux-block@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Eric Wheeler <bfq@...ux.ewheeler.net>, stable@...r.kernel.org
Subject: Re: [PATCH] bfq: backport: update internal depth state when queue
 depth changes

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@...nel.dk>
> > 
> > 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@...ux.ewheeler.net>
> > Tested-by: Kai Krakow <kai@...shome.de>
> > Reported-by: Paolo Valente <paolo.valente@...aro.org>
> > Fixes: f0635b8a416e ("bfq: calculate shallow depths at init time")
> > Signed-off-by: Jens Axboe <axboe@...nel.dk>
> > Cc: stable@...r.kernel.org
> 
> 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
> branches.

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

thanks,

greg k-h