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Date:   Thu, 20 Jul 2023 10:00:26 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Nitesh Shetty <nj.shetty@samsung.com>
Cc:     Jens Axboe <axboe@kernel.dk>, Jonathan Corbet <corbet@lwn.net>,
        Alasdair Kergon <agk@redhat.com>,
        Mike Snitzer <snitzer@kernel.org>, dm-devel@redhat.com,
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        Christoph Hellwig <hch@lst.de>,
        Sagi Grimberg <sagi@grimberg.me>,
        Chaitanya Kulkarni <kch@nvidia.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
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        Kanchan Joshi <joshi.k@samsung.com>,
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        linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v13 5/9] nvme: add copy offload support
Message-ID: <20230720080026.GB6246@lst.de>
References: <20230627183629.26571-1-nj.shetty@samsung.com> <CGME20230627184039epcas5p2decb92731d3e7dfdf9f2c05309a90bd7@epcas5p2.samsung.com> <20230627183629.26571-6-nj.shetty@samsung.com>
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> +	if (blk_rq_nr_phys_segments(req) != 2)
> +		return BLK_STS_IOERR;

The magic number of segments adding up source and dest really need
constants and helpers to make the code understandable.

> +	/* +1 shift as dst+src length is added in request merging, we send copy
> +	 * for half the length.
> +	 */
> +	n_lba = blk_rq_bytes(req) >> (ns->lba_shift + 1);

I do not understand the logic and comment here.

> +	if (WARN_ON(!n_lba))

WARN_ON_ONCE

> +		return BLK_STS_NOTSUPP;

and BLK_STS_NOTSUPP seems like the wrong error here, this is an
invalid argument.