mm: hugetlb: optimize replace_free_hugepage_folios()

mm: hugetlb: optimize replace_free_hugepage_folios()

If no free hugepage folios are available, there is no need to perform any
replacement operations.  Additionally, gigantic folios should not be
replaced under any circumstances.  Therefore, we only check for the
presence of non-gigantic folios, also adding the gigantic folio check to
avoid accidental replacement.

To optimize performance, we skip unnecessary iterations over pfn for
compound pages and high-order buddy pages to save processing time.

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: 0m0.602s
After:  0m0.431s

[wangkefeng.wang@huawei.com: v2]
Link: https://lkml.kernel.org/r/20260114135512.2159799-1-wangkefeng.wang@huawei.com
[akpm@linux-foundation.org: use single-return-point style, tweak comment]
Link: https://lkml.kernel.org/r/20260112150954.1802953-4-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.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: Oscar Salvador <osalvador@suse.de>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>