Re: [PATCH v4 22/28] cxl/region/extent: Expose region extent information in sysfs

[Jonathan Cameron]

On Mon, 07 Oct 2024 18:16:28 -0500
ira.weiny@xxxxxxxxx wrote:

> From: Navneet Singh <navneet.singh@xxxxxxxxx>
> 
> Extent information can be helpful to the user to coordinate memory usage
> with the external orchestrator and FM.
> 
> Expose the details of region extents by creating the following
> sysfs entries.
> 
>         /sys/bus/cxl/devices/dax_regionX/extentX.Y
>         /sys/bus/cxl/devices/dax_regionX/extentX.Y/offset
>         /sys/bus/cxl/devices/dax_regionX/extentX.Y/length
>         /sys/bus/cxl/devices/dax_regionX/extentX.Y/tag
> 
> Signed-off-by: Navneet Singh <navneet.singh@xxxxxxxxx>
> Co-developed-by: Ira Weiny <ira.weiny@xxxxxxxxx>
> Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>
> 
Trivial comments inline.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>

> ---
> Changes:
> [djiang: Split sysfs docs up]
> [iweiny: Adjust sysfs docs dates]
> ---
>  Documentation/ABI/testing/sysfs-bus-cxl | 32 ++++++++++++++++++
>  drivers/cxl/core/extent.c               | 58 +++++++++++++++++++++++++++++++++
>  2 files changed, 90 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl
> index b63ab622515f..64918180a3c9 100644
> --- a/Documentation/ABI/testing/sysfs-bus-cxl
> +++ b/Documentation/ABI/testing/sysfs-bus-cxl
> @@ -632,3 +632,35 @@ Description:
>  		See Documentation/ABI/stable/sysfs-devices-node. access0 provides
>  		the number to the closest initiator and access1 provides the
>  		number to the closest CPU.
> +
> +What:		/sys/bus/cxl/devices/dax_regionX/extentX.Y/offset
> +Date:		December, 2024
> +KernelVersion:	v6.13
> +Contact:	linux-cxl@xxxxxxxxxxxxxxx
> +Description:
> +		(RO) [For Dynamic Capacity regions only] Users can use the
> +		extent information to create DAX devices on specific extents.
> +		This is done by creating and destroying DAX devices in specific
> +		sequences and looking at the mappings created. 

Similar to earlier patch, maybe put this doc for the directory, then
have much less duplication?


> Extent offset
> +		within the region.
> +
> +What:		/sys/bus/cxl/devices/dax_regionX/extentX.Y/length
> +Date:		December, 2024
> +KernelVersion:	v6.13
> +Contact:	linux-cxl@xxxxxxxxxxxxxxx
> +Description:
> +		(RO) [For Dynamic Capacity regions only] Users can use the
> +		extent information to create DAX devices on specific extents.
> +		This is done by creating and destroying DAX devices in specific
> +		sequences and looking at the mappings created.  Extent length
> +		within the region.
> +
> +What:		/sys/bus/cxl/devices/dax_regionX/extentX.Y/tag
> +Date:		December, 2024
> +KernelVersion:	v6.13
> +Contact:	linux-cxl@xxxxxxxxxxxxxxx
> +Description:
> +		(RO) [For Dynamic Capacity regions only] Users can use the
> +		extent information to create DAX devices on specific extents.
> +		This is done by creating and destroying DAX devices in specific
> +		sequences and looking at the mappings created.  Extent tag.

Maybe say we are treating it as a UUID?

> diff --git a/drivers/cxl/core/extent.c b/drivers/cxl/core/extent.c
> index 69a7614ba6a9..a1eb6e8e4f1a 100644
> --- a/drivers/cxl/core/extent.c
> +++ b/drivers/cxl/core/extent.c
> @@ -6,6 +6,63 @@

> +static struct attribute *region_extent_attrs[] = {
> +	&dev_attr_offset.attr,
> +	&dev_attr_length.attr,
> +	&dev_attr_tag.attr,
> +	NULL,
No need for trailing comma (one of my 'favourite' review comments :)

> +};