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Date:   Wed, 29 Jun 2022 08:10:33 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Bart Van Assche <bvanassche@acm.org>
Cc:     Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
        linux-block@vger.kernel.org, Jaegeuk Kim <jaegeuk@kernel.org>,
        Keith Busch <kbusch@kernel.org>,
        Sagi Grimberg <sagi@grimberg.me>,
        Chaitanya Kulkarni <kch@nvidia.com>
Subject: Re: [PATCH v3 8/8] nvme: Enable pipelining of zoned writes
Message-ID: <20220629061033.GA16858@lst.de>
References: <20220627234335.1714393-1-bvanassche@acm.org> <20220627234335.1714393-9-bvanassche@acm.org> <20220628044939.GA22504@lst.de> <858f5f5c-720a-d054-a409-b41c3cfb9717@acm.org>
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[look like my previously reply accidentally lost the first half,
 so here is is]

On Tue, Jun 28, 2022 at 09:30:09AM -0700, Bart Van Assche wrote:
> Agreed that the NVMe specification allows to reorder outstanding commands. 
> Are there any NVMe controllers that do this if multiple zoned write 
> commands are outstanding for a single zone? I do not expect that an NVMe 
> controller would reorder write commands in such a way that an I/O error is 
> introduced.

NVMe not only allows reordering, but actually requires it due to the
round robin command arbitrary. Moreoever once you are on IP based
transports there is plenty of reordering that can and will go on before
even reaching the controller.