[PATCH v4 11/11] mm: memory_hotplug: memory hotremove supports thp migration

[Zi Yan <zi.yan@sent.com>]

From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>

This patch enables thp migration for memory hotremove.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
---
ChangeLog v1->v2:
- base code switched from alloc_migrate_target to new_node_page()
---
 include/linux/huge_mm.h |  8 ++++++++
 mm/memory_hotplug.c     | 17 ++++++++++++++---
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 6f44a2352597..92c2161704c3 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -189,6 +189,13 @@ static inline int hpage_nr_pages(struct page *page)
 	return 1;
 }
 
+static inline int hpage_order(struct page *page)
+{
+	if (unlikely(PageTransHuge(page)))
+		return HPAGE_PMD_ORDER;
+	return 0;
+}
+
 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
 		pmd_t *pmd, int flags);
 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
@@ -233,6 +240,7 @@ static inline bool thp_migration_supported(void)
 #define HPAGE_PUD_SIZE ({ BUILD_BUG(); 0; })
 
 #define hpage_nr_pages(x) 1
+#define hpage_order(x) 0
 
 #define transparent_hugepage_enabled(__vma) 0
 
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 6fb6bd2df787..2b014017a217 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1566,6 +1566,7 @@ static struct page *new_node_page(struct page *page, unsigned long private,
 	int nid = page_to_nid(page);
 	nodemask_t nmask = node_states[N_MEMORY];
 	struct page *new_page = NULL;
+	unsigned int order = 0;
 
 	/*
 	 * TODO: allocate a destination hugepage from a nearest neighbor node,
@@ -1576,6 +1577,11 @@ static struct page *new_node_page(struct page *page, unsigned long private,
 		return alloc_huge_page_node(page_hstate(compound_head(page)),
 					next_node_in(nid, nmask));
 
+	if (thp_migration_supported() && PageTransHuge(page)) {
+		order = hpage_order(page);
+		gfp_mask |= GFP_TRANSHUGE;
+	}
+
 	node_clear(nid, nmask);
 
 	if (PageHighMem(page)
@@ -1583,12 +1589,15 @@ static struct page *new_node_page(struct page *page, unsigned long private,
 		gfp_mask |= __GFP_HIGHMEM;
 
 	if (!nodes_empty(nmask))
-		new_page = __alloc_pages_nodemask(gfp_mask, 0,
+		new_page = __alloc_pages_nodemask(gfp_mask, order,
 					node_zonelist(nid, gfp_mask), &nmask);
 	if (!new_page)
-		new_page = __alloc_pages(gfp_mask, 0,
+		new_page = __alloc_pages(gfp_mask, order,
 					node_zonelist(nid, gfp_mask));
 
+	if (new_page && order == hpage_order(page))
+		prep_transhuge_page(new_page);
+
 	return new_page;
 }
 
@@ -1618,7 +1627,9 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 			if (isolate_huge_page(page, &source))
 				move_pages -= 1 << compound_order(head);
 			continue;
-		}
+		} else if (thp_migration_supported() && PageTransHuge(page))
+			pfn = page_to_pfn(compound_head(page))
+				+ hpage_nr_pages(page) - 1;
 
 		if (!get_page_unless_zero(page))
 			continue;
-- 
2.11.0