bcachefs: Refactor bch2_btree_node_mem_alloc()

This is prep work for the next patch, which is going to fix our usage of
the percpu mode of six locks by never switching struct btree between the
two modes - which means we need separate freed lists.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
This commit is contained in:
Kent Overstreet 2022-03-04 19:50:28 -05:00 • committed by Kent Overstreet
commit 5b3f780540