linux-kernel - Re: [PATCH v20 07/12] nvme: add copy offload support

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Message-ID: <20240603114340.5rvx3o57h2zojfjs@nj.shetty@samsung.com>
Date: Mon, 3 Jun 2024 11:43:40 +0000
From: Nitesh Shetty <nj.shetty@...sung.com>
To: Christoph Hellwig <hch@....de>
Cc: Jens Axboe <axboe@...nel.dk>, Jonathan Corbet <corbet@....net>, Alasdair
	Kergon <agk@...hat.com>, Mike Snitzer <snitzer@...nel.org>, Mikulas Patocka
	<mpatocka@...hat.com>, Keith Busch <kbusch@...nel.org>, Sagi Grimberg
	<sagi@...mberg.me>, Chaitanya Kulkarni <kch@...dia.com>, Alexander Viro
	<viro@...iv.linux.org.uk>, Christian Brauner <brauner@...nel.org>, Jan Kara
	<jack@...e.cz>, martin.petersen@...cle.com, bvanassche@....org,
	david@...morbit.com, hare@...e.de, damien.lemoal@...nsource.wdc.com,
	anuj20.g@...sung.com, joshi.k@...sung.com, nitheshshetty@...il.com,
	gost.dev@...sung.com, Javier Gonz??lez <javier.gonz@...sung.com>,
	linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org, dm-devel@...ts.linux.dev,
	linux-nvme@...ts.infradead.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v20 07/12] nvme: add copy offload support

On 01/06/24 08:22AM, Christoph Hellwig wrote:
>On Mon, May 20, 2024 at 03:50:20PM +0530, Nitesh Shetty wrote:
>> +	if (blk_rq_nr_phys_segments(req) != BLK_COPY_MAX_SEGMENTS)
>> +		return BLK_STS_IOERR;
>
>This sounds like BLK_COPY_MAX_SEGMENTS is misnamed.  Right now this is
>not a max segments, but the exact number of segments required.
>
We will move this check to block layer, with name
BLK_COPY_TOTAL_SEGMENTS.

>>  /*
>>   * Recommended frequency for KATO commands per NVMe 1.4 section 7.12.1:
>> - *
>> + *
>
>Please submit this whitespace fix separately.
>
>> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
>> index 8b1edb46880a..1c5974bb23d5 100644
>> --- a/include/linux/blkdev.h
>> +++ b/include/linux/blkdev.h
>> @@ -1287,6 +1287,7 @@ static inline unsigned int bdev_discard_granularity(struct block_device *bdev)
>>
>>  /* maximum copy offload length, this is set to 128MB based on current testing */
>>  #define BLK_COPY_MAX_BYTES		(1 << 27)
>> +#define BLK_COPY_MAX_SEGMENTS		2
>
>... and this doesn't belong into a NVMe patch.  I'd also expect that
>the block layer would verify this before sending of the request to the driver.
>
Acked

>> diff --git a/include/linux/nvme.h b/include/linux/nvme.h
>> index 425573202295..5275a0962a02 100644
>> --- a/include/linux/nvme.h
>> +++ b/include/linux/nvme.h
>
>Note that we've usually kept adding new protocol bits to nvme.h separate
>from the implementation in the host or target code.
>
Acked, will move it to a separate patch.

Thank you,
Nitesh Shetty