Adrian Bunk posted a list of known regressions in the latest 2.6.20-rc4 Linux kernel compared to the previous 2.6.19 stable release [story]. In two emails, he listed six regressions that don't have fixes yet, and six regressions with fixes that haven't been merged yet.
In another email thread, Linux creator Linus Torvalds noted that his goal for 2.6.20 is to focus primarily on stability. He also noted that he intends to release the stable kernel at some point after linux.conf.au which is happening this year in Sydney, Australia between January 15th and 20th. He explains, "hopefully 'final -rc' before LCA, but I'll do the actual 2.6.20 release afterwards. I don't want to have a merge window during LCA, as I and many others will all be out anyway. So it's much better to have LCA happen during the end of the stabilization phase when there's hopefully not a lot going on. (Of course, often at the end of the stabilization phase there is all the 'ok, what about regression XyZ?' panic)"
Linus Torvalds announced the release of the 2.6.19 Linux kernel, following the previous stable kernel release by two months [story]. "It's one of those rare 'perfect' kernels," Linus joked, "so if it doesn't happen to compile with your config (or it does compile, but then does unspeakable acts of perversion with your pet dachshund), you can rest easy knowing that it's all your own d*mn fault, and you should just fix your evil ways." He went on to add, "you could send me and the kernel mailing list a note about it anyway, of course. (And perhaps pictures, if your dachshund is involved. Not that we'd be interested, of course. No. Just so that we'd know to avoid it next time)."
The latest kernel source can be downloaded from your nearest Linux Kernel archive mirror [story]. You can browse through all the changes using the gitweb interface. Kernel Newbiews also maintains a useful summary of all the changes that went into this new version of the Linux kernel, including the inclusion of three new filesystems, GFS2, ext4 [story], and eCryptfs.
With the release of the 2.6.19-rc1-mm1 kernel, the ext4 filesystem [story] was merged into Andrew Morton [interview]'s -mm tree for further testing. In the announcement Andrew notes that the new filesystem is compatible with ext3 until you add a file that has extents. He also notes, "when comparing performance with other filesystems, remember that ext3/4 by default offers higher data integrity guarantees than most. So when comparing with a metadata-only journalling filesystem, use `mount -o data=writeback'. (Although this doesn't seem to make much difference with ext3)" The goal is to stabilize the new filesystem within the next six to nine months, and ultimately to replace the ext3 filesystem.
Andrew Morton [interview] posted his patch queue with numerous comments about merge plans into the mainline kernel. Among his comments he noted that he would not yet be merging the Reiser4 filesystem [story], "reiser4. I was planning on merging this, but the batch_write/writev problemight wreck things, and I don't think the patches arising from my recent partial review have come through yet. So it's looking more like 2.6.20."
A large discussion followed Andrew's posting that focused on the current kernel development process [story]. Andrew expressed his concerns on what's currently happening, "people seem to treat the stabilisation period as a wonderful quiet time in which to run off and develop new features, rather than participating in the stabilisation. This has the following effects: 1: release cycles get longer 2: the kernel has more bugs 3: we put new features into the kernel faster than we otherwise would (see 2:, above)." Alan Cox [interview] proposed an idea, "a suggestion from the department of evil ideas: Call even cycles development odd ones stabilizing. Nothing gets into an odd one without a review and linux-kernel signoff/ack?" Linus Torvalds replied favorably, going on to note that he was surprised at how well the decision to only accept big merges in the two weeks following a major release has been accepted, "I actually expected people to dislike arbitrary rules more than they do, but I've come to believe that people _like_ having rules that they have to obey, as long as it's not a big pain for them. In other words, arbitrary rules are not actually disliked at all, people actually _like_ them, because suddenly there's less need for making unnecessary judgement decisions." Linus went on to spell out the idea further, "2.6.<odd> is 'the big initial merges with all the obvious fixes to make it all work' (ie roughly the current -rc2 or perhaps -rc3). 2.6.<even> is 'no big merges, just careful fixes' (ie the current 'real release')". He went on to caution:
"That said, I think Andrew was of the opinion that it doesn't really _fix_ anything, and he may well be right. What's the point of the odd release, if the weekly snapshots after that are supposed to be strictly better than it anyway? So I think I may like it just because it _seems_ to combine the good features of both the old naming scheme and the current one, but I suspect Andrew may be right in that it doesn't _really_ change anything, deep down."