linux-kernel - Re: [PATCH 2/2] blk-mq: sync the update nr_hw_queues with part_in

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Message-ID: <CACVXFVO+g2ACx9XYx4XtwRkpSC9bCYeSFEj07Z==6r7nT-HxkQ@mail.gmail.com>
Date:   Thu, 16 Aug 2018 12:50:31 +0800
From:   Ming Lei <tom.leiming@...il.com>
To:     Jianchao Wang <jianchao.w.wang@...cle.com>
Cc:     Jens Axboe <axboe@...nel.dk>,
        Bart Van Assche <bart.vanassche@....com>,
        Keith Busch <keith.busch@...ux.intel.com>,
        linux-block <linux-block@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] blk-mq: sync the update nr_hw_queues with part_in_flight

On Wed, Aug 15, 2018 at 3:25 PM, Jianchao Wang
<jianchao.w.wang@...cle.com> wrote:
> For blk-mq, part_in_flight/rw will invoke blk_mq_in_flight/rw to
> account the inflight requests. It will access the queue_hw_ctx and
> nr_hw_queues w/o any protection. When updating nr_hw_queues and
> blk_mq_in_flight/rw occur concurrently, panic comes up.

When updating nr_hw_queues, all queues are frozen, and there shouldn't
be any inflight requests, so there shouldn't be such issue.


Thanks,
Ming Lei