New ext4 features

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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

First Class Quota Support

Big Allocation Blocks

Metadata Checksumming

  • Primary developer: Darrick J. Wong
  • Status: In progress
  • Design document: Design for Metadata Checksums
  • e2fsprogs changes: Yes, needed.
  • 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

Done

Multiblock Allocation

  • Primary developer: Alex Tomas
  • Status: Done
  • Changes on-disk format: No
  • Target Date: ?
  • e2fsprogs changes: No
  • outstanding issues: None

Delayed Allocation

  • Primary developer: Alex Tomas
  • Status: Done
  • Changes on-disk format: No
  • Target Date: (in patch queue)
  • e2fsprogs changes: No
  • outstanding issues: Done

Break 32000 subdirectory limit

  • Primary developer: Andreas
  • Status: Done
  • Changes on-disk format: Yes
  • Target Date: (in patch queue)
  • e2fsprogs changes: done
  • outstanding issues: None

directory Inodes reservation

  • Primary developer: Coly
  • Status: Patch available
  • Changes on-disk format: No
  • Target Date: Nov, 2007
  • e2fsprogs changes: Needed
  • outstanding issues:

nsec timestamps

  • Primary developer: Andreas
  • Status: Done
  • Change on-disk format: Yes
  • Target Date: (in patch queue)
  • e2fsprogs changes: Done
  • outstanding issues:

inode version on disk

  • Primary developer: Jean-Noel Cordenner, Kalpak Shah
  • Status: Done
  • Change on-disk format: Yes
  • Target Date: (in patch queue)
  • e2fsprogs changes: None
  • outstanding issues: None

uninitialized groups

  • Primary developer: Andreas Dilger
  • Status: Done
  • Change on-disk format: Yes
  • Target Date: (in patch queue)
  • e2fsprogs changes: Done
  • outstanding issues: lazy zeroing of unused inode table blocks after filesystem is first mounted

journal checksumming

  • Primary developer: Andreas
  • Status: Prototype available
  • Change on-disk format: Yes
  • Target Date: (in patch queue)
  • e2fsprogs changes: Needed
  • outstanding issues:

persistent preallocation

  • Primary developer: Amit Arora, Suparna
  • Status: Done
  • Change on-disk format: Yes
  • Target Date: (in patch queue)
  • e2fsprogs changes: complete
  • outstanding issues:

Online Defragmentation

  • Primary developer: Takashi Sato
  • Status:
 latest patch: v0.2 posted on Jan 10th.
 Previous tries:
 http://marc.theaimsgroup.com/?l=linux-ext4&m=116678507906760&w=2
 http://marc.theaimsgroup.com/?l=linux-ext4&m=116307062907075&w=2
  • 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
  • Target Date:
  • e2fsprogs changes: No
  • outstanding issues:

Undelete Feature for Ext4

  • Primary Developer:
  • status: Idea was proposed on the mailing list, still need more thought on the feature.
  • Change on-disk format:
  • Target Date:
  • e2fsprogs changes:
  • outstanding issues: Should the kernel be involved with undelete

Large file support

  • Primary Developer: Takashi Sato
  • status: Done
  • Change on-disk format:
  • Target Date: (in patch queue)
  • e2fsprogs Changes: Done
  • outstanding issues:
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