linux-kernel - Re: [PATCH 6/8] skd: use blk_mq_queue_tag_busy

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Message-ID: <1552929635.152266.30.camel@acm.org>
Date:   Mon, 18 Mar 2019 10:20:35 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Jianchao Wang <jianchao.w.wang@...cle.com>, axboe@...nel.dk
Cc:     hch@....de, jthumshirn@...e.de, hare@...e.de, josef@...icpanda.com,
        sagi@...mberg.me, keith.busch@...el.com, jsmart2021@...il.com,
        linux-block@...r.kernel.org, linux-nvme@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/8] skd: use blk_mq_queue_tag_busy_iter

On Fri, 2019-03-15 at 16:57 +0800, Jianchao Wang wrote:
> blk_mq_tagset_busy_iter is not safe that it could get stale request
> in tags->rqs[]. Use blk_mq_queue_tag_busy_iter here.
> 
> Signed-off-by: Jianchao Wang <jianchao.w.wang@...cle.com>
> ---
>  drivers/block/skd_main.c | 4 ﭗ橸ṷ梧뇪觬(), 2 deletions(-)
> 
> diff --git a/drivers/block/skd_main.c b/drivers/block/skd_main.c
> index ab893a7..60c34ff 100644
> --- a/drivers/block/skd_main.c
> diff --git a/drivers/block/skd_main.c b/drivers/block/skd_main.c
> index ab893a7..60c34ff 100644
> --- a/drivers/block/skd_main.c
> +++ b/drivers/block/skd_main.c
> @@ -395,7 +395,7 @@ static int skd_in_flight(struct skd_device *skdev)
>  {
>         int count = 0;
>  
> -       blk_mq_tagset_busy_iter(&skdev->tag_set, skd_inc_in_flight, &count);
> +       blk_mq_queue_tag_busy_iter(skdev->queue, skd_inc_in_flight, &count, true);
>  
>         return count;
>  }

Hi Jianchao,

If you have a look at the skd_in_flight() callers you will see that the above
change is not necessary.

> @@ -1916,7 +1916,7 @@ static bool skd_recover_request(struct request *req, void *data, bool reserved)
>  
>  static void skd_recover_requests(struct skd_device *skdev)
>  {
> -	blk_mq_tagset_busy_iter(&skdev->tag_set, skd_recover_request, skdev);
> +	blk_mq_queue_tag_busy_iter(skdev->queue, skd_recover_request, skdev, true);
>  }

Same comment here. If you have a look at the callers of this function you will
see that this change is not necessary.

Thanks,

Bart.