[PATCH v2 03/12] mm: thp: introduce separate TTU flag for thp freezing

[Naoya Horiguchi]

TTU_MIGRATION is used to convert pte into migration entry until thp split
completes. This behavior conflicts with thp migration added later patches,
so let's introduce a new TTU flag specifically for freezing.

Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
---
 include/linux/rmap.h | 1 +
 mm/huge_memory.c     | 2 +-
 mm/rmap.c            | 8 +++++---
 3 files changed, 7 insertions(+), 4 deletions(-)

diff --git v4.9-rc2-mmotm-2016-10-27-18-27/include/linux/rmap.h v4.9-rc2-mmotm-2016-10-27-18-27_patched/include/linux/rmap.h
index b46bb56..a2fa425 100644
--- v4.9-rc2-mmotm-2016-10-27-18-27/include/linux/rmap.h
+++ v4.9-rc2-mmotm-2016-10-27-18-27_patched/include/linux/rmap.h
@@ -87,6 +87,7 @@ enum ttu_flags {
 	TTU_MUNLOCK = 4,		/* munlock mode */
 	TTU_LZFREE = 8,			/* lazy free mode */
 	TTU_SPLIT_HUGE_PMD = 16,	/* split huge PMD if any */
+	TTU_SPLIT_FREEZE = 32,		/* freeze pte under splitting thp */
 
 	TTU_IGNORE_MLOCK = (1 << 8),	/* ignore mlock */
 	TTU_IGNORE_ACCESS = (1 << 9),	/* don't age */
diff --git v4.9-rc2-mmotm-2016-10-27-18-27/mm/huge_memory.c v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/huge_memory.c
index 2d1d6bb..0509d17 100644
--- v4.9-rc2-mmotm-2016-10-27-18-27/mm/huge_memory.c
+++ v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/huge_memory.c
@@ -1794,7 +1794,7 @@ static void freeze_page(struct page *page)
 	VM_BUG_ON_PAGE(!PageHead(page), page);
 
 	if (PageAnon(page))
-		ttu_flags |= TTU_MIGRATION;
+		ttu_flags |= TTU_SPLIT_FREEZE;
 
 	/* We only need TTU_SPLIT_HUGE_PMD once */
 	ret = try_to_unmap(page, ttu_flags | TTU_SPLIT_HUGE_PMD);
diff --git v4.9-rc2-mmotm-2016-10-27-18-27/mm/rmap.c v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/rmap.c
index 1ef3640..a4be307 100644
--- v4.9-rc2-mmotm-2016-10-27-18-27/mm/rmap.c
+++ v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/rmap.c
@@ -1449,7 +1449,7 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 
 	if (flags & TTU_SPLIT_HUGE_PMD) {
 		split_huge_pmd_address(vma, address,
-				flags & TTU_MIGRATION, page);
+				flags & TTU_SPLIT_FREEZE, page);
 		/* check if we have anything to do after split */
 		if (page_mapcount(page) == 0)
 			goto out;
@@ -1527,7 +1527,8 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 		 * will take care of the rest.
 		 */
 		dec_mm_counter(mm, mm_counter(page));
-	} else if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION)) {
+	} else if (IS_ENABLED(CONFIG_MIGRATION) &&
+		   (flags & (TTU_MIGRATION|TTU_SPLIT_FREEZE))) {
 		swp_entry_t entry;
 		pte_t swp_pte;
 		/*
@@ -1649,7 +1650,8 @@ int try_to_unmap(struct page *page, enum ttu_flags flags)
 	 * locking requirements of exec(), migration skips
 	 * temporary VMAs until after exec() completes.
 	 */
-	if ((flags & TTU_MIGRATION) && !PageKsm(page) && PageAnon(page))
+	if ((flags & (TTU_MIGRATION|TTU_SPLIT_FREEZE))
+	    && !PageKsm(page) && PageAnon(page))
 		rwc.invalid_vma = invalid_migration_vma;
 
 	if (flags & TTU_RMAP_LOCKED)
-- 
2.7.0