Experimental features

User space tools (btrfs-progs)

Experimental or unstable features may be enabled by

./configure --enable-experimental

but as it says, the interface, command names, output formatting should be considered unstable and not for production use. However testing is welcome and feedback or bugs filed as issues.

In the code use it like:

if (EXPERIMENTAL) {
    ...
}

in case it does not interfere with other code or does not depend on an #if where it would break default build.

Or:

#if EXPERIMENTAL
...
#endif

for larger code blocks.

Note

Do not use #ifdef as the macro is always defined so this would not work as expected.

Each feature should be tracked in an issue with label experimental (list of active issues https://github.com/kdave/btrfs-progs/labels/experimental), with a description and a TODO list items. Individual tasks can be tracked in other issues if needed.

Kernel module

The kernel module can be configured to enable experimental features or functionality since version 6.13 by CONFIG_BTRFS_EXPERIMENTAL . The features can get added or removed in each release. At runtime the status can be seen in the system log message once the kernel module is loaded:

Btrfs loaded, experimental=on, debug=on, assert=on, ref-verify=on, zoned=yes, fsverity=yes

In some cases (standalone features) it’s exported in /sys/fs/btrfs/FSID/features.