Merge branch 'bpf-range_tree-for-bpf-arena'

Alexei Starovoitov says:

====================
bpf: range_tree for bpf arena

From: Alexei Starovoitov <ast@kernel.org>

Introduce range_tree (interval tree plus rbtree) to track
unallocated ranges in bpf arena and replace maple_tree with it.
This is a step towards making bpf_arena|free_alloc_pages non-sleepable.
The previous approach to reuse drm_mm to replace maple_tree reached
dead end, since sizeof(struct drm_mm_node) = 168 and
sizeof(struct maple_node) = 256 while
sizeof(struct range_node) = 64 introduced in this patch.
Not only it's smaller, but the algorithm splits and merges
adjacent ranges. Ultimate performance doesn't matter.
The main objective of range_tree is to work in context
where kmalloc/kfree are not safe. It achieves that via bpf_mem_alloc.
====================

Link: https://patch.msgid.link/20241108025616.17625-1-alexei.starovoitov@gmail.com
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>