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

Sorry, ignore this, I missed the first patch. I'll write a longer reply 
to that one.

Matt

On 7/23/26 12:18 PM, Matthew Sakai wrote:
> 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
>