From: Naoya Horiguchi <redacted>

This patch enables thp migration for memory hotremove.

Signed-off-by: Naoya Horiguchi <redacted>
---
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 257166ebdff0..ecae0852994f 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c

@@ -1574,6 +1574,7 @@ 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,

@@ -1584,6 +1585,11 @@ 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)

@@ -1591,12 +1597,15 @@ 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);
+