The Lustre Filesystem Dropped from the Linux 4.18 Kernel

It’s now official: the latest RC1 pull request for the Linux 4.18 will not
host the nearly 15-year-old Lustre filesystem.

Greg Kroah-Hartman has been growing weary of the team developing its source
code not pushing cleaner and fixed code to the staging tree. The removal was
committed on June 5, 2018:
with the following notes:

The Lustre filesystem has been in the kernel tree for over 5 years now. While
it has been an endless source of enjoyment for new kernel developers learning
how to do basic coding style cleanups, as well as a semi-entertaining source
of bewilderment from the vfs developers any time they have looked into the
codebase to try to figure out how to port their latest api changes to this
filesystem, it has not really moved forward into the “this is in shape to get
out of staging” despite many half-completed attempts.

And getting code out of staging is the main goal of that portion of the
kernel tree. Code should not stagnate, and it feels like having this code in
staging is only causing the development cycle of the filesystem to take
longer than it should. There is a whole separate out-of-tree copy of this
codebase where the developers work on it, and then random changes are thrown
over the wall at staging at some later point in time. This dual-tree
development model has never worked, and the state of this codebase is proof
of that.

So, let’s just delete the whole mess. Now the lustre developers can go off
and work in their out-of-tree codebase and not have to worry about providing
valid changelog entries and breaking their patches up into logical pieces.
They can take the time they have spent doing those types of housekeeping
chores and get the codebase into a much better shape, and it can be submitted
for inclusion into the real part of the kernel tree when ready.

Honestly, I do not blame him. The staging tree is primarily intended for
unstable and less than mature code, which ideally should move to the mainline
within a short time of further development. It’s a temporary (that is,
staging) location. It’s not that I don’t appreciate the Lustre
filesystem. In fact, I once wrote about it for Linux Journal in the past.

For those who are less familiar with this filesystem: Lustre (or Linux
Cluster) is a distributed filesystem typically deployed in large-scale
cluster computing environments. Lustre is designed to be both performant and
to scale to tens of thousands of nodes and to petabytes of storage. And as
what may have just been alluded to already, a distributed filesystem allows
access to files from multiple hosts sharing a computer network.

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