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Subject: Re: [PATCH 5/8] nbd: use blk_mq_queue_tag_busy_iter
From:   Bart Van Assche <bvanassche@acm.org>
To:     Jianchao Wang <jianchao.w.wang@oracle.com>, axboe@kernel.dk
Cc:     hch@lst.de, jthumshirn@suse.de, hare@suse.de, josef@toxicpanda.com,
        sagi@grimberg.me, keith.busch@intel.com, jsmart2021@gmail.com,
        linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
        linux-kernel@vger.kernel.org
Date:   Mon, 18 Mar 2019 10:16:24 -0700
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         <1552640264-26101-6-git-send-email-jianchao.w.wang@oracle.com>
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On Fri, 2019-03-15 at 16:57 +-0800, Jianchao Wang wrote:
+AD4 blk+AF8-mq+AF8-tagset+AF8-busy+AF8-iter is not safe that it could get stale request
+AD4 in tags-+AD4-rqs+AFsAXQ. Use blk+AF8-mq+AF8-queue+AF8-tag+AF8-busy+AF8-iter here.
+AD4 
+AD4 Signed-off-by: Jianchao Wang +ADw-jianchao.w.wang+AEA-oracle.com+AD4
+AD4 ---
+AD4  drivers/block/nbd.c +AHw 2 +-
+AD4  1 file changed, 1 insertion(), 1 deletion(-)
+AD4 
+AD4 diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
+AD4 index 7c9a949..9e7e828 100644
+AD4 --- a/drivers/block/nbd.c
+AD4 +-+-+- b/drivers/block/nbd.c
+AD4 +AEAAQA -747,7 +-747,7 +AEAAQA static bool nbd+AF8-clear+AF8-req(struct request +ACo-req, void +ACo-data, bool reserved)
+AD4  static void nbd+AF8-clear+AF8-que(struct nbd+AF8-device +ACo-nbd)
+AD4  +AHs
+AD4         blk+AF8-mq+AF8-quiesce+AF8-queue(nbd-+AD4-disk-+AD4-queue)+ADs
+AD4 -       blk+AF8-mq+AF8-tagset+AF8-busy+AF8-iter(+ACY-nbd-+AD4-tag+AF8-set, nbd+AF8-clear+AF8-req, NULL)+ADs
+AD4 +-       blk+AF8-mq+AF8-queue+AF8-tag+AF8-busy+AF8-iter(nbd-+AD4-disk-+AD4-queue, nbd+AF8-clear+AF8-req, NULL, true)+ADs
+AD4         blk+AF8-mq+AF8-unquiesce+AF8-queue(nbd-+AD4-disk-+AD4-queue)+ADs
+AD4         dev+AF8-dbg(disk+AF8-to+AF8-dev(nbd-+AD4-disk), +ACI-queue cleared+AFw-n+ACI)+ADs
+AD4  +AH0

Hi Jianchao,

The nbd driver calls nbd+AF8-clear+AF8-que() after having called sock+AF8-shutdown(). So
what makes you think that it's not safe to call blk+AF8-mq+AF8-tagset+AF8-busy+AF8-iter()
from nbd+AF8-clear+AF8-que()?

Thanks,

Bart.