mm: page_alloc: optimize pfn_range_valid_contig()

mm: page_alloc: optimize pfn_range_valid_contig()

The alloc_contig_pages() spends a significant amount of time within
pfn_range_valid_contig().

- set_max_huge_pages
   - 99.98% alloc_pool_huge_folio
        only_alloc_fresh_hugetlb_folio.isra.0
      - alloc_contig_frozen_pages_noprof
         - 87.00% pfn_range_valid_contig
              pfn_to_online_page
         - 12.91% alloc_contig_frozen_range_noprof
              4.51% replace_free_hugepage_folios
            - 4.02% prep_new_page
                 prep_compound_page
            - 2.98% undo_isolate_page_range
               - 2.79% unset_migratetype_isolate
                  - 2.75% __move_freepages_block_isolate
                       2.71% __move_freepages_block
            - 0.98% start_isolate_page_range
                 0.66% set_migratetype_isolate

To optimize this process, use the new helper page_is_unmovable() to avoid
more unnecessary iterations for compound pages, such as THP not on LRU,
and high-order buddy pages, which significantly improving the efficiency
of contiguous memory allocation.

A simple test on machine with 114G free memory, allocate 120 * 1G
HugeTLB folios(104 successfully returned),

  time echo 120 > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages

Before: 0m3.605s
After:  0m0.602s

Link: https://lkml.kernel.org/r/20260112150954.1802953-3-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>