Module features 

ext4 feature flags — COMPAT, INCOMPAT, RO_COMPAT.

Spec source: kernel.org/doc/html/latest/filesystems/ext4/super.html

Structs

Compat

COMPAT features — safe to ignore if unknown.

Incompat

INCOMPAT features — kernel MUST understand or refuse to mount.

RoCompat

RO_COMPAT features — must mount read-only if unknown.

Enums

FsFlavor

Filesystem dialect — derived from the on-disk feature flags at mount time. Drives runtime behaviour where ext2 / ext3 / ext4 differ:

Constants

MAINTAINED_RO_COMPAT

RO_COMPAT bits this driver maintains, as opposed to tolerates.

READ_BREAKING_RO_COMPAT

RO_COMPAT bits that change how the filesystem is read, and so cannot be ignored even by a read-only mount. None, today.

SUPPORTED_INCOMPAT

INCOMPAT bits this driver mounts. Anything else in feature_incompat means refuse-to-mount. Some of these can be read and not written: see WRITE_BREAKING_INCOMPAT.

SUPPORTED_RO_COMPAT

RO_COMPAT bits a mount accepts. Accepting one is not the same as keeping it correct through a write: see MAINTAINED_RO_COMPAT.

WRITE_BREAKING_INCOMPAT

INCOMPAT bits that are safe to READ and not safe to WRITE.

Functions

check_mountable

Check whether the filesystem can be mounted read-only. Returns Err with the unsupported bits if not.

unmaintained_ro_compat

The RO_COMPAT bits on this volume that a write here would not keep consistent: anything outside MAINTAINED_RO_COMPAT.

write_breaking_incompat

The INCOMPAT bits on this volume that a write here would not keep consistent. Zero means the volume may be mounted read-write.