Btrfs For Linux 4.15 Picks Up Compression Improvements, Continued Optimizations

[phoronix]

Phoronix: Btrfs For Linux 4.15 Picks Up Compression Improvements, Continued Optimizations

David Sterba of Facebook has submitted the Btrfs file-system feature changes queued for the Linux 4.15 kernel...

http://www.phoronix.com/scan.php?page=news_item&px=Btrfs-Updates-Linux-4.15

[starshipeleven]

Michael David Sterba is a SUSE emplyee.

[ResponseWriter]

Hopefully it's going to be more resilient and clearer about metadata space...

Linux 4.15 will now popular the compression heuristics logic

Should that be 'populate'?

[Jabberwocky]

enable indexing of Btrfs as a lower file-system in OverlayFS

Does lower imply that overlayfs running on top of btrfs, if so I wonder where this index will be stored and if it is enabled by default.

I have not been following aufs, unionfs, or overlayfs.

[starshipeleven]

There is a bunch of cleanup and preparations for the "dead drive ejection" code which is still floating around in patches in the mailing list.
(logic that detects and removes from the array the dead drives automatically) mostly from Anand Jain (Omnomnomracle)

Does lower imply that overlayfs running on top of btrfs

yes. OverlayFS merges 2 filesystems, one is the "lower" and the other is the "upper". The "lower" is read-only, any change goes into the "upper" filesystem.

overlayFS is interesting for btrfs because btrfs can make in-place read-only snapshots, you can then use as lower layer with some upper rw layer.

if so I wonder where this index will be stored and if it is enabled by default.

It's this patch https://www.mail-archive.com/linux-b.../msg66452.html
It seems the index is a OverlayFS feature, which was not enabled on btrfs because it was not exposing its uuid or something simple like that. The patch is tiny.

in the docs it is called "inode index", and appears to be some way to avoid people from remounting the same upper filesystem over a different lower filesystem (likely causing breakage).
https://git.kernel.org/pub/scm/linux.../overlayfs.txt

[Jabberwocky]

Thanks for the info starshipeleven Reminds me of sandboxie when I did multiseat gaming system on Windows in 2011.

OverlayFS sounds really useful for my gaming needs, I should be able to run my Linux Stream-Lib on top of my Windows Steam-Lib which can save a few 100 gigabytes. What breaks my brain is that Steam (and or independent game devs) does not share platform-independent data...