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Date:   Mon, 18 Mar 2019 10:16:24 -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 5/8] nbd: 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/nbd.c | 2 +
>  1 file changed, 1 insertion(), 1 deletion(-)
> 
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index 7c9a949..9e7e828 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -747,7 +747,7 @@ static bool nbd_clear_req(struct request *req, void *data, bool reserved)
>  static void nbd_clear_que(struct nbd_device *nbd)
>  {
>         blk_mq_quiesce_queue(nbd->disk->queue);
> -       blk_mq_tagset_busy_iter(&nbd->tag_set, nbd_clear_req, NULL);
> +       blk_mq_queue_tag_busy_iter(nbd->disk->queue, nbd_clear_req, NULL, true);
>         blk_mq_unquiesce_queue(nbd->disk->queue);
>         dev_dbg(disk_to_dev(nbd->disk), "queue cleared\n");
>  }

Hi Jianchao,

The nbd driver calls nbd_clear_que() after having called sock_shutdown(). So
what makes you think that it's not safe to call blk_mq_tagset_busy_iter()
from nbd_clear_que()?

Thanks,

Bart.

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