New ext4 features

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OBSOLETE CONTENT

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For latest ext4 documentation, see Kernel Docs.

Contents

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

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

Big Allocation Blocks

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
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