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

Damien Le Moal
2023-03-29T08:40:27Z

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