[PATCH 2/2] mm: Make alloc_contig_range handle in-use hugetlb pages

[Oscar Salvador]

In-use hugetlb pages can be migrated as any other page (LRU
and Movable), so let alloc_contig_range handle them.

All we need is to succesfully isolate such page.

Signed-off-by: Oscar Salvador <osalvador@xxxxxxx>
---
 include/linux/hugetlb.h |  5 +++--
 mm/compaction.c         | 11 ++++++++++-
 mm/hugetlb.c            |  6 ++++--
 mm/vmscan.c             |  5 +++--
 4 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 72352d718829..8c17d0dbc87c 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -505,7 +505,7 @@ struct huge_bootmem_page {
 	struct hstate *hstate;
 };
 
-bool isolate_or_dissolve_huge_page(struct page *page);
+bool isolate_or_dissolve_huge_page(struct page *page, struct list_head *list);
 struct page *alloc_huge_page(struct vm_area_struct *vma,
 				unsigned long addr, int avoid_reserve);
 struct page *alloc_huge_page_nodemask(struct hstate *h, int preferred_nid,
@@ -776,7 +776,8 @@ void set_page_huge_active(struct page *page);
 #else	/* CONFIG_HUGETLB_PAGE */
 struct hstate {};
 
-static inline bool isolate_or_dissolve_huge_page(struct page *page)
+static inline bool isolate_or_dissolve_huge_page(struct page *page,
+						 struct list_head *list)
 {
 	return false;
 }
diff --git a/mm/compaction.c b/mm/compaction.c
index d52506ed9db7..55a41a9228a9 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -906,9 +906,17 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
 		}
 
 		if (PageHuge(page) && cc->alloc_contig) {
-			if (!isolate_or_dissolve_huge_page(page))
+			if (!isolate_or_dissolve_huge_page(page, &cc->migratepages))
 				goto isolate_fail;
 
+			if (PageHuge(page)) {
+				/*
+				 * Hugepage was succesfully isolated.
+				 */
+				low_pfn += compound_nr(page) - 1;
+				goto isolate_success_no_list;
+			}
+
 			/*
 			 * Ok, the hugepage was dissolved. Now these pages are
 			 * Buddy and cannot be re-allocated because they are
@@ -1053,6 +1061,7 @@ 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/hugetlb.c b/mm/hugetlb.c
index b78926bca60a..9fa678d13c68 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2351,7 +2351,7 @@ static bool alloc_and_dissolve_huge_page(struct hstate *h, struct page *page)
 	return ret;
 }
 
-bool isolate_or_dissolve_huge_page(struct page *page)
+bool isolate_or_dissolve_huge_page(struct page *page, struct list_head *list)
 {
 	struct hstate *h = NULL;
 	struct page *head;
@@ -2379,7 +2379,9 @@ bool isolate_or_dissolve_huge_page(struct page *page)
 		 */
 		return ret;
 
-	if(!page_count(head) && alloc_and_dissolve_huge_page(h, head))
+	if (page_count(head) && isolate_huge_page(head, list))
+		ret = true;
+	else if(!page_count(head) && alloc_and_dissolve_huge_page(h, head))
 		ret = true;
 
 	return ret;
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