lklhaikufs: features galore

The LKL-based Haiku driver has progressed well in the last few weeks.

The set of features already implemented:

• mounting and unmounting ext3, ext4 disk images*, both read-only and read-write
• listing file system attributes (read-only/read-write, file system size, number of files created, number of files remaining to be created, etc.)
• browsing the contents of any folder on the file system
• listing file permissions, owner, group, type (directory, symlink, regular file, etc.)
• opening/closing existing files, and creating new files
• reading and writing data into files
• creating new directories

What still needs to be done:

Anatomy of an elf

Porting LKL to Haiku's kernel API may not have been very hard, but convincing Haiku to load a properly built LKL-based add-on has presented some interesting and challenging problems.

Booting LKL inside Haiku

The first milestone in this GSoC journey to building a generic file system driver based on Linux kernel code is booting LKL (Linux Kernel Library) inside Haiku.

For the short attention span: it works :)

...
KERN: KDiskDeviceManager::_AddDiskSystem() done: No error
KERN: file system: file_systems/iso9660/v1
KERN: KDiskDeviceManager::_AddDiskSystem(file_systems/iso9660/v1)
KERN: KDiskDeviceManager::_AddDiskSystem() done: No error
KERN: lklhaikufs: unhandled pheader type 0x4
KERN: file system: file_systems/lklhaikufs/v1
KERN: KDiskDeviceManager::_AddDiskSystem(file_systems/lklhaikufs/v1)
KERN: khaiku_env_timer:: LKL_TIMER_INIT
KERN: [lkl-console] Linux version 2.6.29 (gringo@lethe) (gcc version 4.4.4 (GCC) ) #10 Fri Jun 18 14:45:38 EEST 2010
KERN: [lkl-console] Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 16256
KERN: [lkl-console] Kernel command line: 
KERN: [lkl-console] lkl: IRQs initialized
KERN: [lkl-console] PID hash table entries: 256 (order: 8, 1024 bytes)
KERN: [lkl-console] lkl: timer initialized
KERN: [lkl-console] Dentry cache hash table entries: 8192 (order: 3, 32768 bytes)
KERN: [lkl-console] Inode-cache hash table entries: 4096 (order: 2, 16384 bytes)
KERN: [lkl-console] Memory available: 64900k/65536k RAM, (862k kernel code, 270k data)
KERN: [lkl-console] Mount-cache hash table entries: 512
KERN: [lkl-console] bio: create slab  at 0
KERN: [lkl-console] io scheduler noop registered (default)
KERN: [lkl-console] lkl: syscall interface initialized
KERN: [lkl-console] console [lkl_console0] enabled
KERN: [lkl-console] Warning: unable to open an initial console.
KERN: [lkl-console] Switched to NOHz mode on CPU #0
KERN: [lkl-console] System halted.
KERN: khaiku_env_timer:: LKL_TIMER_SHUTDOWN
KERN: [lkl-console] lkl: IRQs freed
KERN: lkl: halt user callback called
KERN: KDiskDeviceManager::_AddDiskSystem() done: No error
KERN: file system: file_systems/nfs/v1
KERN: KDiskDeviceManager::_AddDiskSystem(file_systems/nfs/v1)
...

Haiku file system drivers for any Linux supported file system

Haiku has great support for its own file system, but most others are only available read-only or not accessible. Providing reliable read-write support to one such file system is a complex task, and needs to be repeated for each type of file system.

Linux contains state of the art, full featured implementations for a large number of file systems.

lkl-haiku-fsd is a generic driver based on the Linux kernel library (LKL), reusing Linux' optimized and debugged file system implementations.