Re: [PATCH 2/2] Documentation: device-mapper: document VDO zstd

This is attempting to document a feature that does not exist in dm-vdo.
We cannot accept this.

Matt

On 7/23/26 12:13 PM, Rhajune Park wrote:
> document zstd compression with dm-vdo
> 
> Assisted-by: opencode:gpt-5.6-sol
> Signed-off-by: Rhajune Park <[email protected]>
> ---
>   .../admin-guide/device-mapper/vdo.rst         | 21 ++++++++++++++++++-
>   1 file changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/admin-guide/device-mapper/vdo.rst b/Documentation/admin-guide/device-mapper/vdo.rst
> index 8a67b320a97b..24a6b26bb990 100644
> --- a/Documentation/admin-guide/device-mapper/vdo.rst
> +++ b/Documentation/admin-guide/device-mapper/vdo.rst
> @@ -171,6 +171,20 @@ Miscellaneous parameters:
>   		Whether compression is enabled. The default is 'off'; the
>   		acceptable values are 'on' and 'off'.
>   
> +	compressionAlgorithm:
> +		The algorithm used to compress data. The acceptable values are
> +		'lz4' and 'zstd'; the default for a new volume is 'lz4'. The
> +		algorithm is recorded when the volume is formatted and cannot be
> +		changed afterward. If specified when loading an existing volume,
> +		it must match the recorded algorithm.
> +
> +	compressionLevel:
> +		The Zstd compression level. The default is 1; negative levels are
> +		accepted when supported by the kernel Zstd implementation. This
> +		option is invalid with LZ4. The level may be changed after fully
> +		deactivating the volume, but not by reloading an active VDO table.
> +		It does not affect the readability of data written at another level.
> +
>   Device modification
>   -------------------
>   
> @@ -178,6 +192,8 @@ A modified table may be loaded into a running, non-suspended vdo volume.
>   The modifications will take effect when the device is next resumed. The
>   modifiable parameters are <logical device size>, <physical device size>,
>   <maxDiscard>, <compression>, and <deduplication>.
> +The <compressionAlgorithm> parameter is a format-time property and is not
> +modifiable.
>   
>   If the logical device size or physical device size are changed, upon
>   successful resume vdo will store the new values and require them on future
> @@ -255,7 +271,10 @@ The messages are:
>   	config:
>   		Outputs useful vdo configuration information. Mostly used
>   		by users who want to recreate a similar VDO volume and
> -		want to know the creation configuration used.
> +		want to know the creation configuration used. Output version
> +		3 contains physicalSize, logicalSize, slabSize,
> +		compressionAlgorithm, the Zstd compressionLevel when applicable,
> +		and index configuration fields.
>   
>   	dump:
>   		Dumps many internal structures to the system log. This is