EXT4 On Linux 4.13 Can Now Support Around 2 Billion Directory Entries

[phoronix]

Phoronix: EXT4 On Linux 4.13 Can Now Support Around 2 Billion Directory Entries

EXT4 on Linux 4.13 is supporting its new "large directory" feature...

http://www.phoronix.com/scan.php?page=news_item&px=EXT4-Largedir-Linux-4.13

[boxie]

Good news, upper limits are supposed to be ridiculous things anyway!

[AsuMagic]

[tildearrow]

Typo:

EXT4 in Linux 4.13 also has xattr-in-inode support, parallell discards,

[starshipeleven]

Server owners are pleased. More server features for the server god!

[sarfarazahmad]

I, sire, have a noob question for you.

what does it mean that a filesystem gets new features ? Will the on-disk format change ? If I now move to this newer kernel and then for some reason have to revert back ? Will the filesystem not be usable ? How do the filesystem-utils fit into this ?

[starshipeleven]

I, sire, have a noob question for you.

what does it mean that a filesystem gets new features ?

I haz a look at the sauce https://git.kernel.org/pub/scm/linux...d988caedac731b

This feature is called "LARGEDIR" and searching for that it shows that it sets its feature code in the "incompatible features" variable in the on-disk format. (it's a variable used to set various features that break retrocompatibility, there is already a bunch)

According to comments in the sauce https://git.kernel.org/pub/scm/linux...edac731b#n1249 the kernel will refuse to mount the filesystem if it sees a number it does not recognize in this variable on disk. And userspace tools will also refuse to touch it.
So if this feature is used, older kernels will refuse mounting and e2fsck will also refuse to touch it.

It seems this feature is enabled with e2fstune. I really doubt it is on by default (just like many other special usecase features). It seems to be called "large_dir" https://ext4.wiki.kernel.org/index.php/Features

[caligula]

Don't forget real time audio support. Pulseaudio is nice, but not for studio work - yet?

[starshipeleven]

Don't forget real time audio support. Pulseaudio is nice, but not for studio work - yet?

Jack.

[caligula]

Jack.

The problem is, for some people it means switching to another distro. Setting up Jack with all rt patches is a PITA in some cases.