简化DAX vmemmap优化 · v3

vmemmap_populate_compound_pages() is no longer used outside radix_pgtable.c. Make it static and drop the unused dev_pagemap argument from its only remaining caller to simplify the code. Signed-off-b

Whether the optimized mapping can be used is now decided in the architecture-specific vmemmap_populate() path. When PowerPC has to fall back, such as on Hash MMU, it can disable optimization for the p

LoongArch selects ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP but not ARCH_WANT_OPTIMIZE_DAX_VMEMMAP. Its vmemmap_free() implementation is also empty, so it cannot tear down optimized Device DAX mappings. A l

section_vmemmap_optimizable() can already decide whether a section uses vmemmap optimization based on the section compound order. The DAX-specific vmemmap_can_optimize() helper duplicates that policy,

The vmemmap population and memory hotplug paths no longer need @pgmap to decide whether a mapping can be optimized. That state is now carried in mem_section, and the architecture-specific population c