[PATCH v2] mm: remove migration for HugePage in isolate_single_pageblock()

[Kefeng Wang <wangkefeng.wang@huawei.com>]

The gigantic page size may larger than memory block size, so memory
offline always fails in this case after commit b2c9e2fbba32 ("mm: make
alloc_contig_range work at pageblock granularity"),

offline_pages
  start_isolate_page_range
    start_isolate_page_range(isolate_before=true)
      isolate [isolate_start, isolate_start + pageblock_nr_pages)
    start_isolate_page_range(isolate_before=false)
      isolate [isolate_end - pageblock_nr_pages, isolate_end) pageblock
       	__alloc_contig_migrate_range
          isolate_migratepages_range
            isolate_migratepages_block
              isolate_or_dissolve_huge_page
                if (hstate_is_gigantic(h))
                    return -ENOMEM;

[   15.815756] memory offlining [mem 0x3c0000000-0x3c7ffffff] failed due to failure to isolate range

Gigantic PageHuge is bigger than a pageblock, but since it is freed as
order-0 pages, its pageblocks after being freed will get to the right
free list. There is no need to have special handling code for them in
start_isolate_page_range(). For both alloc_contig_range() and memory
offline cases, the migration code after start_isolate_page_range() will
be able to migrate gigantic PageHuge when possible.

Let's clean up start_isolate_page_range() and fix the aforementioned
memory offline failure issue all together.

Fixes: b2c9e2fbba32 ("mm: make alloc_contig_range work at pageblock granularity")
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
v2:
- update changelog, thanks Zi, David

 mm/page_isolation.c | 28 +++-------------------------
 1 file changed, 3 insertions(+), 25 deletions(-)

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 39fb8c07aeb7..7e04047977cf 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -403,30 +403,8 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
 			unsigned long head_pfn = page_to_pfn(head);
 			unsigned long nr_pages = compound_nr(head);
 
-			if (head_pfn + nr_pages <= boundary_pfn) {
-				pfn = head_pfn + nr_pages;
-				continue;
-			}
-
-#if defined CONFIG_COMPACTION || defined CONFIG_CMA
-			if (PageHuge(page)) {
-				int page_mt = get_pageblock_migratetype(page);
-				struct compact_control cc = {
-					.nr_migratepages = 0,
-					.order = -1,
-					.zone = page_zone(pfn_to_page(head_pfn)),
-					.mode = MIGRATE_SYNC,
-					.ignore_skip_hint = true,
-					.no_set_skip_hint = true,
-					.gfp_mask = gfp_flags,
-					.alloc_contig = true,
-				};
-				INIT_LIST_HEAD(&cc.migratepages);
-
-				ret = __alloc_contig_migrate_range(&cc, head_pfn,
-							head_pfn + nr_pages, page_mt);
-				if (ret)
-					goto failed;
+			if (head_pfn + nr_pages <= boundary_pfn ||
+			    PageHuge(page)) {
 				pfn = head_pfn + nr_pages;
 				continue;
 			}
@@ -440,7 +418,7 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
 			 */
 			VM_WARN_ON_ONCE_PAGE(PageLRU(page), page);
 			VM_WARN_ON_ONCE_PAGE(__PageMovable(page), page);
-#endif
+
 			goto failed;
 		}
 
-- 
2.27.0