[RFC PATCH 1/2] mm,page_alloc: Make alloc_contig_range handle in-use hugetlb pages

[Oscar Salvador <osalvador@suse.de>]

alloc_contig_range is not prepared to handle hugetlb pages and will
fail if it ever sees one, but since they can be migrated as any other
page (LRU and Movable), it makes sense to also handle them.

For now, do it only when coming from alloc_contig_range.

Signed-off-by: Oscar Salvador <osalvador@suse.de>
---
 mm/compaction.c | 17 +++++++++++++++++
 mm/vmscan.c     |  5 +++--
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index e5acb9714436..89cd2e60da29 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -940,6 +940,22 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
 			goto isolate_fail;
 		}
 
+		/*
+		 * Handle hugetlb pages only when coming from alloc_contig
+		 */
+		if (PageHuge(page) && cc->alloc_contig) {
+			if (page_count(page)) {
+				/*
+				 * Hugetlb page in-use. Isolate and migrate.
+				 */
+				if (isolate_huge_page(page, &cc->migratepages)) {
+					low_pfn += compound_nr(page) - 1;
+					goto isolate_success_no_list;
+				}
+			}
+			goto isolate_fail;
+		}
+
 		/*
 		 * Check may be lockless but that's ok as we recheck later.
 		 * It's possible to migrate LRU and non-lru movable pages.
@@ -1041,6 +1057,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
 
 isolate_success:
 		list_add(&page->lru, &cc->migratepages);
+isolate_success_no_list:
 		cc->nr_migratepages += compound_nr(page);
 		nr_isolated += compound_nr(page);
 
diff --git a/mm/vmscan.c b/mm/vmscan.c
index b1b574ad199d..0803adca4469 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1506,8 +1506,9 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone,
 	LIST_HEAD(clean_pages);
 
 	list_for_each_entry_safe(page, next, page_list, lru) {
-		if (page_is_file_lru(page) && !PageDirty(page) &&
-		    !__PageMovable(page) && !PageUnevictable(page)) {
+		if (!PageHuge(page) && page_is_file_lru(page) &&
+		    !PageDirty(page) && !__PageMovable(page) &&
+		    !PageUnevictable(page)) {
 			ClearPageActive(page);
 			list_move(&page->lru, &clean_pages);
 		}
-- 
2.16.3