Linux 2.6.30 is currently in development. The last prepatch version is -rc2, released the 15th April.
This page is, obviously, a work in progress.
1. Prominent features (the cool stuff)
1.1. NILFS2, a log-structured filesystem
NILFS2 is a new filesystem, contributed by [http://en.wikipedia.org/wiki/Nippon_Telegraph_and_Telephone_Corporation NTT] (Nippon Telegraph and Telephone Corporation) Labs. It uses a [http://en.wikipedia.org/wiki/Log-structured_file_system log-structured] design. What makes log-structured filesystems different is that they treat the whole disk as a consecutive list of blocks (called log). All the operations append data at the end of the log, they never rewrite blocks (except when there's no space left - in that case, new blocks are reclaimed from the tail of the log). The advantage of this approach is that writes are always sequential. Crashes can't corrupt the filesystem. On mount, the filesystem detects the real end of the log, and continues working from that point.
Another advantage of this approach is that the log offers a coherent historical view of all the operations done in the disk in the past. This is called "continuous snapshotting" - snapshots of modifications done in all the filesystem at any time are created automatically due to the log-structure design, with no requeriment of intervention from an admin, and with the filesystem size as the only limit. NILFS2 allows to access those snapshots and even mount them (on read-only mode).
NILFS2 is [http://www.nilfs.org/en/current_status.html under development]. Code: [http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=tree;f=fs/nilfs2;hb=HEAD fs/nilfs2/]. Filesystem web page: [http://www.nilfs.org www.nilfs.org]
1.2. Support for Object-Based Storage Device
Object-Based Storage Device (OSD) are basically "smart" disks, which do not store the data as blocks, but more elaborated objects. 2.6.30 adds support to these devices in the SCSI layer, as well as the addition of a filesystem (exofs, Extended Object File System) able to use them.
([http://lwn.net/Articles/305740/ LWN's Article], where exofs is still known by its old name, osdfs)
1.3. FS-Cache, a caching filesystem
Recommended LWN article: [http://lwn.net/Articles/100321/ A general caching filesystem]
FS-Cache is the Linux implementation of a cache layer for networking filesystems, similar to the [http://en.wikipedia.org/wiki/CacheFS CacheFS] of other Unixes.
With this system, data from the networked filesystems can be cached on the disk, speeding up operations. This version adds support for NFS and AFS, but it's a generic layer that could be used by other networking filesystems or even non-networking (such as ISO9660)
Code: Slow-work related changes: [http://git.kernel.org/linus/07fe7cb7c7c179f473fd9c823348fd3eb5dad369 (commit 1], [http://git.kernel.org/linus/109d9272c423f46604d45fedfe87e21ee0b25180 2], [http://git.kernel.org/linus/12e22c5e4bc08ab4b05ac079fe40d9891c5e81a0 3], [http://git.kernel.org/linus/8f0aa2f25b31ba27db84259141e52ee6ec0d2820 4)], FS-cache [http://git.kernel.org/linus/03fb3d2af96c2783c3a5bc03f3d984cf422f0e69 (commit 1], [http://git.kernel.org/linus/266cf658efcf6ac33541a46740f74f50c79d2b6b 2], [http://git.kernel.org/linus/2d6fff637037395cc946ef910a880b5fa67b5370 3], [http://git.kernel.org/linus/0dfc41d1efcc4180abfd32f68f0ade540e636ff6 4], [http://git.kernel.org/linus/06b3db1b9bccdc8c2c743122a89745279e5ecc46 5], [http://git.kernel.org/linus/7394daa8c61dfda4baa687f133748fa0b599b017 6], [http://git.kernel.org/linus/a6891645cf2ddd4778096848a864580e7258faba 7], [http://git.kernel.org/linus/0e04d4cefcf4d8fbbdb2c50e93ad541582933fd2 8], [http://git.kernel.org/linus/4c515dd47ab41be3f89e757d441661795470b376 9], [http://git.kernel.org/linus/955d00917f0c094e0f2fb88df967e980ab66b8ca 10], [http://git.kernel.org/linus/726dd7ff10c217dd74329c94643dc8ebea27334b 11], [http://git.kernel.org/linus/2868cbea72dc89ae0eb17693596b1dedaafff1c5 12], [http://git.kernel.org/linus/36c9559022850f919269564a74bf17fdabf4bb30 13], [http://git.kernel.org/linus/ccc4fc3d11e91477036d1f82bfa2d442f6ce77f0 14], [http://git.kernel.org/linus/952efe7b7840e1c726ae88222245e4efe6bd88f3 15] [http://git.kernel.org/linus/b510882281d56873e1194021643b7c325336f84f 16], [http://git.kernel.org/linus/385e1ca5f21c4680ad6a46a3aa2ea8af99e99c92 17] [http://git.kernel.org/linus/800a964787faef3509d194fa33268628c3d1daa9 18], [http://git.kernel.org/linus/9ae326a69004dea8af2dae4fde58de27db700a8d 19)]; AFS and NFS changes: [http://git.kernel.org/linus/9b3f26c9110dcea62716aca9b8c68ceb482227ef (commit 1], [http://git.kernel.org/linus/6b9b3514aa188183e74049853be43380ad49314f 2], [http://git.kernel.org/linus/c6a6f19e22da0a3d74214ee010224c9a30a794c1 3], [http://git.kernel.org/linus/3b9ce977b2f31b6c396b6fb620df9881a30fac9d 4], [http://git.kernel.org/linus/8ec442ae4c6577ed181682e534d4eef524e30b3c 5], [http://git.kernel.org/linus/147272813e043fb44bd112527951da70c1e663de 6], [http://git.kernel.org/linus/08734048b380103f0412f58b84c2f76a2c8b599f 7], [http://git.kernel.org/linus/10329a5d48f5abc14a37d30b706e330f8598297a 8], [http://git.kernel.org/linus/ef79c097bbe9724e13937271b3457df560e00370 9], [http://git.kernel.org/linus/d599064a1bca7bcbaabe54b94fa73ea86952cae3 10], [http://git.kernel.org/linus/6a51091d0775cdc4a923f2172c61925ad416aa32 11], [http://git.kernel.org/linus/545db45f0fc0d4203b045047798ce156972a3056 12], [http://git.kernel.org/linus/1fcdf534885b65e6d39780a5a89e9dfc5431cf68 13], [http://git.kernel.org/linus/f42b293d6d5259043a8944b556eeab427c695d57 14], [http://git.kernel.org/linus/9a9fc1c03315f1606596e55b4096d39e2079a041 15] [http://git.kernel.org/linus/7f8e05f60c87646e12c761fef61dd71a7e67112e 16], [http://git.kernel.org/linus/5d1acff159730770cbab68b19443518c92ab1000 17] [http://git.kernel.org/linus/b797cac7487dee6bfddeb161631c1bbc54fa3cdb 18)], Documentation: [http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=Documentation/filesystems/caching/fscache.txt Documentation/filesystems/caching/fscache.txt].
1.4. Filesystems performance improvement
Shortly after the 2.6.29 release, lots of discussions occurred on LKML about disk I/O (summary available [http://lwn.net/Articles/326471/ at LWN]), and how (and why) they can stall processes for minutes. Some measure have been taken to limit this, like setting the default mount-option to relatime, with 24 hours refresh time ([http://valhenson.livejournal.com/36519.html Detailed article in Valerie Aurora's blog]), and imporving fsync() for ext3.
1.5. Microblaze CPU architecture
This release adds support for the MMU-less [http://en.wikipedia.org/wiki/MicroBlaze Microblaze] FDT CPU architecture.
Code: [http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=tree;f=arch/microblaze;hb=HEAD arch/microblaze/]
1.6. Integrity Management Architecture
This is an infrastructure which use the Trusted Platform Module (TPM) to check that the OS has not been tampered with. ([LWN's article http://lwn.net/Articles/227937/]
2. Various core changes
- Memory management
- Integrity Management Architecture has been merged.
- Lots of clean-ups.
- fsync() improvements.
- Now makes use of the FSCache infrastructure.
- Now makes use of the FSCache infrastructure.
- Stack usage improvements.
- The filesystem has been merged for this release. (see above)
- The filesystem has been merged for this release.(see above)
11. Architecture-specific changes
- Add OSD support. (see above)
13. Other sources about 2.6.30 kernel
- Heise Online's Kernel Log :
[http://www.h-online.com/open/Kernel-Log-Linux-2-6-30-is-taking-shape--/news/113036 Linux 2.6.30 is taking shape]
- Linux Weekly news :
[http://lwn.net/Articles/325921/ 2.6.30 merge window, part I]