From 8bcfd8b451b619d0c00acac6f23c4c1102400b78 Mon Sep 17 00:00:00 2001
From: Hugh Dickins <hughd@google.com>
Date: Fri, 22 Feb 2013 16:36:07 -0800
Subject: [PATCH] --- yaml --- r: 356630 b: refs/heads/master c:
 5117b3b835f288314a2d4e5512bc1747e3a7c8ed h: refs/heads/master v: v3

---
 [refs]                   |  2 +-
 trunk/include/linux/mm.h |  1 +
 trunk/mm/ksm.c           |  2 +-
 trunk/mm/memory.c        | 20 ++++++++++++++++++--
 4 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/[refs] b/[refs]
index 24a5c8c5cb8a..36ab4690383d 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: bc56620b493496b8a6962080b644ccc537f4d526
+refs/heads/master: 5117b3b835f288314a2d4e5512bc1747e3a7c8ed
diff --git a/trunk/include/linux/mm.h b/trunk/include/linux/mm.h
index 6124f1db50fe..e7c3f9a0111a 100644
--- a/trunk/include/linux/mm.h
+++ b/trunk/include/linux/mm.h
@@ -1651,6 +1651,7 @@ static inline struct page *follow_page(struct vm_area_struct *vma,
 #define FOLL_SPLIT	0x80	/* don't return transhuge pages, split them */
 #define FOLL_HWPOISON	0x100	/* check page is hwpoisoned */
 #define FOLL_NUMA	0x200	/* force NUMA hinting page fault */
+#define FOLL_MIGRATION	0x400	/* wait for page to replace migration entry */
 
 typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, unsigned long addr,
 			void *data);
diff --git a/trunk/mm/ksm.c b/trunk/mm/ksm.c
index 0320327b8a6c..d61cba6fa1dc 100644
--- a/trunk/mm/ksm.c
+++ b/trunk/mm/ksm.c
@@ -364,7 +364,7 @@ static int break_ksm(struct vm_area_struct *vma, unsigned long addr)
 
 	do {
 		cond_resched();
-		page = follow_page(vma, addr, FOLL_GET);
+		page = follow_page(vma, addr, FOLL_GET | FOLL_MIGRATION);
 		if (IS_ERR_OR_NULL(page))
 			break;
 		if (PageKsm(page))
diff --git a/trunk/mm/memory.c b/trunk/mm/memory.c
index 5d2ef1217d0c..ec8ba011fa7d 100644
--- a/trunk/mm/memory.c
+++ b/trunk/mm/memory.c
@@ -1548,8 +1548,24 @@ struct page *follow_page_mask(struct vm_area_struct *vma,
 	ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
 
 	pte = *ptep;
-	if (!pte_present(pte))
-		goto no_page;
+	if (!pte_present(pte)) {
+		swp_entry_t entry;
+		/*
+		 * KSM's break_ksm() relies upon recognizing a ksm page
+		 * even while it is being migrated, so for that case we
+		 * need migration_entry_wait().
+		 */
+		if (likely(!(flags & FOLL_MIGRATION)))
+			goto no_page;
+		if (pte_none(pte) || pte_file(pte))
+			goto no_page;
+		entry = pte_to_swp_entry(pte);
+		if (!is_migration_entry(entry))
+			goto no_page;
+		pte_unmap_unlock(ptep, ptl);
+		migration_entry_wait(mm, pmd, address);
+		goto split_fallthrough;
+	}
 	if ((flags & FOLL_NUMA) && pte_numa(pte))
 		goto no_page;
 	if ((flags & FOLL_WRITE) && !pte_write(pte))