mm: migrate: move_pages() supports thp migration

This patch enables thp migration for move_pages(2).

Link: http://lkml.kernel.org/r/20170717193955.20207-10-zi.yan@sent.com
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Zi Yan <zi.yan@cs.rutgers.edu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David Nellans <dnellans@nvidia.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: Naoya Horiguchi

mm/migrate.c

@@ -185,8 +185,8 @@ void putback_movable_pages(struct list_head *l)
 			unlock_page(page);
 			put_page(page);
 		} else {
-			dec_node_page_state(page, NR_ISOLATED_ANON +
-					page_is_file_cache(page));
+			mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
+					page_is_file_cache(page), -hpage_nr_pages(page));
 			putback_lru_page(page);
 		}
 	}
@@ -1146,8 +1146,8 @@ static ICE_noinline int unmap_and_move(new_page_t get_new_page,
 		 * as __PageMovable
 		 */
 		if (likely(!__PageMovable(page)))
-			dec_node_page_state(page, NR_ISOLATED_ANON +
-					page_is_file_cache(page));
+			mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
+					page_is_file_cache(page), -hpage_nr_pages(page));
 	}
 
 	/*
@@ -1421,7 +1421,17 @@ static struct page *new_page_node(struct page *p, unsigned long private,
 	if (PageHuge(p))
 		return alloc_huge_page_node(page_hstate(compound_head(p)),
 					pm->node);
-	else
+	else if (thp_migration_supported() && PageTransHuge(p)) {
+		struct page *thp;
+
+		thp = alloc_pages_node(pm->node,
+			(GFP_TRANSHUGE | __GFP_THISNODE) & ~__GFP_RECLAIM,
+			HPAGE_PMD_ORDER);
+		if (!thp)
+			return NULL;
+		prep_transhuge_page(thp);
+		return thp;
+	} else
 		return __alloc_pages_node(pm->node,
 				GFP_HIGHUSER_MOVABLE | __GFP_THISNODE, 0);
 }
@@ -1448,15 +1458,19 @@ static int do_move_page_to_node_array(struct mm_struct *mm,
 	for (pp = pm; pp->node != MAX_NUMNODES; pp++) {
 		struct vm_area_struct *vma;
 		struct page *page;
+		struct page *head;
+		unsigned int follflags;
 
 		err = -EFAULT;
 		vma = find_vma(mm, pp->addr);
 		if (!vma || pp->addr < vma->vm_start || !vma_migratable(vma))
 			goto set_status;
 
 		/* FOLL_DUMP to ignore special (like zero) pages */
-		page = follow_page(vma, pp->addr,
-				FOLL_GET | FOLL_SPLIT | FOLL_DUMP);
+		follflags = FOLL_GET | FOLL_DUMP;
+		if (!thp_migration_supported())
+			follflags |= FOLL_SPLIT;
+		page = follow_page(vma, pp->addr, follflags);
 
 		err = PTR_ERR(page);
 		if (IS_ERR(page))
@@ -1466,7 +1480,6 @@ static int do_move_page_to_node_array(struct mm_struct *mm,
 		if (!page)
 			goto set_status;
 
-		pp->page = page;
 		err = page_to_nid(page);
 
 		if (err == pp->node)
@@ -1481,16 +1494,22 @@ static int do_move_page_to_node_array(struct mm_struct *mm,
 			goto put_and_set;
 
 		if (PageHuge(page)) {
-			if (PageHead(page))
+			if (PageHead(page)) {
 				isolate_huge_page(page, &pagelist);
+				err = 0;
+				pp->page = page;
+			}
 			goto put_and_set;
 		}
 
-		err = isolate_lru_page(page);
+		pp->page = compound_head(page);
+		head = compound_head(page);
+		err = isolate_lru_page(head);
 		if (!err) {
-			list_add_tail(&page->lru, &pagelist);
-			inc_node_page_state(page, NR_ISOLATED_ANON +
-					    page_is_file_cache(page));
+			list_add_tail(&head->lru, &pagelist);
+			mod_node_page_state(page_pgdat(head),
+				NR_ISOLATED_ANON + page_is_file_cache(head),
+				hpage_nr_pages(head));
 		}
 put_and_set:
 		/*