Driver for ext4 filesystem

[Martin Decky]

Implement a native HelenOS driver for the ext4 file system.

Details

The new driver should be realized as a standalone server process which plugs itself into the HelenOS VFS framework and implements the VFS and libfs interfaces in the ext4 specific way.

The implementation can proceed in several phases. In the first phase, read-only support for ext4 should be implemented. In the following phases, write features corresponding to specific compatibility levels (plain ext2, ext2 with large files, ext2 with hashed B-trees, ext2 with sparse superblocks, ext3 with journaling, ext4 with extends) can be incrementally added.

What Gains and Benefits will this bring?

The only persistent file system supported by HelenOS so far has been FAT16. This file system has some inconvenient limitations such as the 8.3 file names and, which is more important, does not force VFS to provide interfaces for writing back the superblock. On the other hand, ext4 is a reasonably advanced file system commonly used on the Linux platform and its implementation will lead to adding needed abstractions to the VFS protocol. This will benefit future additions of other persistent file systems.

Difficulty

medium (read-only ext4) to hard (full ext4 write support)

Required skills

A successful applicant will have good skills of programming in the C language and also the ability to program in a multi-server environment, which includes communicating using HelenOS IPC.

Documentation

• DeveloperDocs
• Implementation and design of the file system layer
• IPC for Dummies

Possible mentors

HelenOS Core Team, Jakub Jermar, Martin Decky

[Jakub Jermář]

Changing the Summary in order to be specific.

[Jakub Jermář]

In mainline,1005, read-only support for Ext2 was merged.

[Jakub Jermář]

Merged in mainline,1590.