Interoperability

cgroups

Cgroups are supported for the IO controller, for compressed and uncompressed data. This can be used to limit bandwidth or for accounting. The cgroups can be configured directly or e.g. via systemd directives IOAccounting, IOWeight etc.

fsverity

The fs-verity is a support layer that filesystems can hook into to support transparent integrity and authenticity protection of read-only files. This requires a separate management utility fsverity.

The ioctls supported by btrfs:

idmapped mounts

Btrfs supports mount with UID/GID mapped according to another namespace since version 5.15.

Device mapper, MD-RAID

Btrfs works on top of device mapper (DM) and linux multi-device software RAID (MD-RAID) block devices transparently without any need for additional configuration. There is no integration so device failures are not handled automatically in any way, must be resolved either in btrfs or on the DM/MD layer.

The functionality of DM/MD may duplicate the one provided by btrfs (like mirroring), it’s possible to use it that way but it’s probably wasteful and may degrade performance. Creating a filesystem on top of the multiplexed device is likely the desired way.

overlayfs

Since kernel 4.15 the btrfs filesystem can be used as lower filesystem for overlayfs (supporting the rename modes of exchange and whiteout).

SELinux

The SELinux labels can be defined via mount option context and since version 6.8 there are no limitations. Until that version some cases were not supported.

io_uring

Basic file operations are supported. Since 6.12 the Encoded IO read/write ioctls the read is supported and write since 6.13.

NFS

NFS is supported. When exporting a subvolume it is recommended to use the fsid option with a unique id in case the server needs to restart. This is recommended namely when clients use the mount option hard.

Example of server side export:

/mnt/data/subvolume1      192.168.1.2/24(fsid=12345,rw,sync)
/mnt/data/subvolume2      192.168.1.2/24(fsid=23456,rw,sync)

Samba

The Samba VFS module btrfs adds support for compression, snapshots and server-side copy (backed by reflink/clone range ioctl).