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
