New ext4 features
From Ext4
Introduction
This page contains information about new ext4 features which are currently under development.
For a description of Ext4 features as they appeared in the original 2.6.28 kernel when ext4 was first released, please see the Ext4 Kernelnewbies article.
Currently being worked on
Online Directory Shrink
- Primary developer: Harshad Shirwadkar
- Status: In progress
- Latest patches: https://lore.kernel.org/linux-ext4/20190824023110.GB19348@mit.edu/T/#t
- e2fsprogs changes: Should not be needed with large directory support
- Outstanding issues: only shrinks if last block in directory is empty, needs to handle arbitrary empty blocks
Done
Multiblock Allocation
- Primary developer: Alex Tomas
- Status: Done
- Changes on-disk format: No
- e2fsprogs changes: No
- Outstanding issues: None
Delayed Allocation
- Primary developer: Alex Tomas
- Status: Done
- Changes on-disk format: No
- e2fsprogs changes: No
- Outstanding issues: None
Exceed 32000 subdirectory limit
- Primary developer: Andreas Dilger
- Status: Done
- Changes on-disk format: Yes
- e2fsprogs changes: done
- Outstanding issues: None
directory Inodes reservation
- Primary developer: Coly
- Status: Patch available
- Changes on-disk format: No
- e2fsprogs changes: Needed
- Outstanding issues:
nsec timestamps
- Primary developer: Andreas Dilger
- Status: Done
- Change on-disk format: Yes
- e2fsprogs changes: Done
- Outstanding issues:
inode version on disk
- Primary developer: Jean-Noel Cordenner, Kalpak Shah
- Status: Done
- Change on-disk format: Yes
- e2fsprogs changes: None
- Outstanding issues: None
uninitialized block groups
- Primary developer: Andreas Dilger
- Status: Done
- Change on-disk format: Yes
- e2fsprogs changes: Done
- Outstanding issues: None
journal checksumming
- Primary developer: Darrick Wong
- Status: Prototype available
- Change on-disk format: Yes
- e2fsprogs changes: Done
- Outstanding issues: None
persistent preallocation (fallocate)
- Primary developer: Amit Arora, Suparna
- Status: Done
- Change on-disk format: Yes
- e2fsprogs changes: complete
- Outstanding issues:
Online Defragmentation
- Primary developer: Takashi Sato
- Status: Done
- Related discussions
ext3 online defrag: http://marc.theaimsgroup.com/?l=linux-fsdevel&m=116160640814410&w=2
- Dependencies: Multiple block allocation from Alex Thomas
- Change on-disk format: No
- e2fsprogs changes: No
- Outstanding issues:
First Class Quota Support
- Primary developer: Aditya Kali
- Status: Done
- Design document: Design For 1st Class Quota in Ext4
- e2fsprogs changes: Done
- Outstanding issues: None
Big Allocation Blocks
- Primary developer: Theodore Ts'o
- Status: Done
- Design document: Design for Big Allocation Blocks
- e2fsprogs changes: Done
- Outstanding issues: None
Metadata Checksums
- Primary developer: Darrick J. Wong
- Status: Done
- Design document: Design for Metadata Checksums
- e2fsprogs changes: Done
- Disk format change needed: Minor tweaks to existing structures. Old code will still be able to mount read-only. tune2fs/e2fsck generally can make the changes without problems.
- Outstanding issues: None
Large file support
- Primary Developer: Takashi Sato
- status: Done
- Change on-disk format:
- e2fsprogs Changes: Done
- Outstanding issues:
Large directory support
- Primary Developer: Liang Zhen, Artem Blagodarenko
- status: Done
- Change on-disk format: increase maximum htree level to 3, allow directories over 2GB
- e2fsprogs Changes: Done
- Outstanding issues: None