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

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Message-ID: <20190513130916.GB11972@sasha-vm>
Date:   Mon, 13 May 2019 09:09:16 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Greg KH <greg@...ah.com>
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 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@...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?

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.

--
Thanks,
Sasha