New Filesystem Development Under Process: Ext4 Evolution Explained

It’s great to hear about exciting progress in Linux filesystem development! Theodore Ts’o, a leading Linux kernel developer, recently shared an insightful overview of the upcoming changes to the ext3 filesystem and the path toward ext4.

Community Involvement in Filesystem Development

Theodore Ts’o emphasized that many developers have a strong interest in the future of the ext2 and ext3 filesystems. As two of the most widely used filesystems, especially within the Linux kernel community, they carry significant importance. Because of this, discussions about their evolution attract broad attention and strong opinions.

Key Challenges in Ext3 Development

Theodore highlighted three major challenges that the development team faces:

1. Maintaining Stability – Ensuring that the filesystem remains reliable for all users.

2. Avoiding Compatibility Confusion – Keeping ext2, ext3, and future ext4 interactions clear and predictable.

3. Reducing Code Complexity – Simplifying the filesystem structure to enable smoother updates and maintenance.

He noted that earlier discussions often mixed these issues together, which made it harder for developers to make meaningful progress. Linus Torvalds primarily focused on stability, while others raised concerns about compatibility and complexity.

Proposed Roadmap for Ext4 Filesystem

To tackle these issues, Theodore and the ext2/3 development team outlined a four-step plan to move forward with ext4 development.

1. Introduce the ext4 Filesystem as ext3dev

The team plans to create a new filesystem named ext4, which will initially appear in the kernel as ext3dev. Developers will register it as a CONFIG_EXPERIMENTAL feature. This approach allows developers to test new features in a separate branch while maintaining the stability of the existing ext3 filesystem.

Additionally, the fs/jbd (Journaling Block Device) system will also split to support 64-bit journaling, used by both ext4 and future versions of OCFS2.

2. Add New Features to ext3dev

All new features and improvements will go into the ext3dev tree. Meanwhile, the stable ext3 branch will receive only bug fixes. This separation ensures that development continues without compromising the reliability of production systems.

3. Maintain Compatibility with ext3

Theodore stressed that ext4 must mount existing ext3 filesystems seamlessly. This backward compatibility ensures users can upgrade smoothly from ext3 to ext4 without losing data or reformatting their drives.

4. Transition to Full ext4 Integration

Once the team finalizes and tests all features—expected within 6 to 9 months—they plan to officially register fs/ext4 as the ext4 filesystem in the kernel. After confirming its stability and performance, ext4 will eventually replace ext3 entirely in the Linux source tree.

The Future of Linux Filesystems

The proposed ext4 filesystem represents a major step forward in Linux storage technology. With better scalability, 64-bit journaling, and cleaner code, ext4 aims to improve performance and reliability while maintaining compatibility with existing systems.

This development marks an important milestone for Linux users and developers who rely on robust, efficient, and forward-compatible filesystems.

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New File System