Re: [PATCH v8 1/9] block: Introduce queue limits for copy-offload support

From: Damien Le Moal <damien.lemoal@opensource.wdc.com>
To: Anuj Gupta <anuj20.g@samsung.com>, Jens Axboe <axboe@kernel.dk>,
	Alasdair Kergon <agk@redhat.com>,
	Mike Snitzer <snitzer@kernel.org>,
	dm-devel@redhat.com, Keith Busch <kbusch@kernel.org>,
	Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>,
	James Smart <james.smart@broadcom.com>,
	Chaitanya Kulkarni <kch@nvidia.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Christian Brauner <brauner@kernel.org>
Cc: bvanassche@acm.org, hare@suse.de, ming.lei@redhat.com,
	joshi.k@samsung.com, nitheshshetty@gmail.com,
	gost.dev@samsung.com, Nitesh Shetty <nj.shetty@samsung.com>,
	linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v8 1/9] block: Introduce queue limits for copy-offload support
Date: Wed, 29 Mar 2023 17:40:09 +0900	[thread overview]
Message-ID: <e725768d-19f5-a78a-2b05-c0b189624fea@opensource.wdc.com> (raw)
In-Reply-To: <20230327084103.21601-2-anuj20.g@samsung.com>

On 3/27/23 17:40, Anuj Gupta wrote:
> From: Nitesh Shetty <nj.shetty@samsung.com>
> 
> Add device limits as sysfs entries,
>         - copy_offload (RW)
>         - copy_max_bytes (RW)
>         - copy_max_bytes_hw (RO)
> 
> Above limits help to split the copy payload in block layer.
> copy_offload: used for setting copy offload(1) or emulation(0).
> copy_max_bytes: maximum total length of copy in single payload.
> copy_max_bytes_hw: Reflects the device supported maximum limit.
> 
> Reviewed-by: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
> Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
> Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
> ---
>  Documentation/ABI/stable/sysfs-block | 36 ++++++++++++++++
>  block/blk-settings.c                 | 24 +++++++++++
>  block/blk-sysfs.c                    | 64 ++++++++++++++++++++++++++++
>  include/linux/blkdev.h               | 12 ++++++
>  include/uapi/linux/fs.h              |  3 ++
>  5 files changed, 139 insertions(+)
> 
> diff --git a/Documentation/ABI/stable/sysfs-block b/Documentation/ABI/stable/sysfs-block
> index c57e5b7cb532..f5c56ad91ad6 100644
> --- a/Documentation/ABI/stable/sysfs-block
> +++ b/Documentation/ABI/stable/sysfs-block
> @@ -155,6 +155,42 @@ Description:
>  		last zone of the device which may be smaller.
>  
>  
> +What:		/sys/block/<disk>/queue/copy_offload
> +Date:		November 2022
> +Contact:	linux-block@vger.kernel.org
> +Description:
> +		[RW] When read, this file shows whether offloading copy to
> +		device is enabled (1) or disabled (0). Writing '0' to this

...to a device...

> +		file will disable offloading copies for this device.
> +		Writing any '1' value will enable this feature. If device

If the device does...

> +		does not support offloading, then writing 1, will result in
> +		error.
> +
> +
> +What:		/sys/block/<disk>/queue/copy_max_bytes
> +Date:		November 2022
> +Contact:	linux-block@vger.kernel.org
> +Description:
> +		[RW] While 'copy_max_bytes_hw' is the hardware limit for the
> +		device, 'copy_max_bytes' setting is the software limit.
> +		Setting this value lower will make Linux issue smaller size
> +		copies from block layer.

		This is the maximum number of bytes that the block
                layer will allow for a copy request. Must be smaller than
                or equal to the maximum size allowed by the hardware indicated
		by copy_max_bytes_hw. Write 0 to use the default kernel
		settings.

> +
> +
> +What:		/sys/block/<disk>/queue/copy_max_bytes_hw
> +Date:		November 2022
> +Contact:	linux-block@vger.kernel.org
> +Description:
> +		[RO] Devices that support offloading copy functionality may have
> +		internal limits on the number of bytes that can be offloaded
> +		in a single operation. The `copy_max_bytes_hw`
> +		parameter is set by the device driver to the maximum number of
> +		bytes that can be copied in a single operation. Copy
> +		requests issued to the device must not exceed this limit.
> +		A value of 0 means that the device does not
> +		support copy offload.

		[RO] This is the maximum number of kilobytes supported in a
                single data copy offload operation. A value of 0 means that the
		device does not support copy offload.

> +
> +
>  What:		/sys/block/<disk>/queue/crypto/
>  Date:		February 2022
>  Contact:	linux-block@vger.kernel.org
> diff --git a/block/blk-settings.c b/block/blk-settings.c
> index 896b4654ab00..350f3584f691 100644
> --- a/block/blk-settings.c
> +++ b/block/blk-settings.c
> @@ -59,6 +59,8 @@ void blk_set_default_limits(struct queue_limits *lim)
>  	lim->zoned = BLK_ZONED_NONE;
>  	lim->zone_write_granularity = 0;
>  	lim->dma_alignment = 511;
> +	lim->max_copy_sectors_hw = 0;
> +	lim->max_copy_sectors = 0;
>  }
>  
>  /**
> @@ -82,6 +84,8 @@ void blk_set_stacking_limits(struct queue_limits *lim)
>  	lim->max_dev_sectors = UINT_MAX;
>  	lim->max_write_zeroes_sectors = UINT_MAX;
>  	lim->max_zone_append_sectors = UINT_MAX;
> +	lim->max_copy_sectors_hw = ULONG_MAX;
> +	lim->max_copy_sectors = ULONG_MAX;
>  }
>  EXPORT_SYMBOL(blk_set_stacking_limits);
>  
> @@ -183,6 +187,22 @@ void blk_queue_max_discard_sectors(struct request_queue *q,
>  }
>  EXPORT_SYMBOL(blk_queue_max_discard_sectors);
>  
> +/**
> + * blk_queue_max_copy_sectors_hw - set max sectors for a single copy payload
> + * @q:  the request queue for the device
> + * @max_copy_sectors: maximum number of sectors to copy
> + **/
> +void blk_queue_max_copy_sectors_hw(struct request_queue *q,
> +		unsigned int max_copy_sectors)
> +{
> +	if (max_copy_sectors >= MAX_COPY_TOTAL_LENGTH)

Confusing name as LENGTH may be interpreted as bytes. MAX_COPY_SECTORS would be
better.

> +		max_copy_sectors = MAX_COPY_TOTAL_LENGTH;
> +
> +	q->limits.max_copy_sectors_hw = max_copy_sectors;
> +	q->limits.max_copy_sectors = max_copy_sectors;
> +}
> +EXPORT_SYMBOL_GPL(blk_queue_max_copy_sectors_hw);

-- 
Damien Le Moal
Western Digital Research