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Date:   Tue, 23 Mar 2021 17:17:02 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Chao Leng <lengchao@huawei.com>
Cc:     Sagi Grimberg <sagi@grimberg.me>, Christoph Hellwig <hch@lst.de>,
        Keith Busch <kbusch@kernel.org>, Jens Axboe <axboe@kernel.dk>,
        linux-block@vger.kernel.org, linux-nvme@lists.infradead.org
Subject: Re: [PATCH 2/2] nvme-multipath: don't block on blk_queue_enter of
 the underlying device
Message-ID: <20210323161702.GB13402@lst.de>
References: <20210322073726.788347-1-hch@lst.de> <20210322073726.788347-3-hch@lst.de> <34e574dc-5e80-4afe-b858-71e6ff5014d6@grimberg.me> <33ec8b12-0b2b-e934-acb1-aae8d0259e2e@grimberg.me> <31e7f7f4-55fa-6b0c-426d-7f7e7638ab4b@huawei.com> <5d28226d-4619-74b6-1c73-c13ed57aa7ea@grimberg.me> <87a0ede6-b696-d34d-e74d-56429fe32ae7@huawei.com>
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On Tue, Mar 23, 2021 at 04:13:09PM +0800, Chao Leng wrote:
>> The above reproduces with the patch applied on upstream nvme code.The new patch(blk_mq_submit_bio_direct) will cause the bug again.
> Because it revert add the bio to current->bio_list.
> Just try the upstream nvme code, and do not apply the new patch(blk_mq_submit_bio_direct).

Indeed, the patch removes the deferred submission, so the original
deadlock should not happen.