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Date:   Mon, 31 Jul 2023 16:09:10 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Chengming Zhou <chengming.zhou@linux.dev>
Cc:     Christoph Hellwig <hch@lst.de>, hare@suse.de, axboe@kernel.dk,
        ming.lei@redhat.com, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org, zhouchengming@bytedance.com
Subject: Re: [PATCH v2 1/4] blk-flush: flush_rq should inherit first_rq's
 cmd_flags
Message-ID: <20230731140910.GA6835@lst.de>
References: <20230725130102.3030032-1-chengming.zhou@linux.dev> <20230725130102.3030032-2-chengming.zhou@linux.dev> <20230731060957.GA30409@lst.de> <0ee17228-4938-6ab7-3fc4-f83a81cbed8f@linux.dev>
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On Mon, Jul 31, 2023 at 10:02:39PM +0800, Chengming Zhou wrote:
> The commit 84fca1b0c461 ("block: pass failfast and driver-specific flags to
> flush requests") says:
> If flush requests are being sent to the device we need to inherit the
> failfast and driver-specific flags, too, otherwise I/O will fail.
> 
> 1) REQ_FAILFAST_MASK: agree, shouldn't set to the flush_rq I think?
> 2) REQ_DRV: I don't get why this flag not set would cause I/O fail?

I don't think it would fail I/O by it's own, but it will cause the
nvme driver to not do the correct handling of an error when a flush
is set to multipath setups.