From 6326fec1122cde256bd2a8c63f2606e08e44ce1d Mon Sep 17 00:00:00 2001
From: Nicholas Piggin <npiggin@gmail.com>
Date: Sun, 25 Dec 2016 13:00:29 +1000
Subject: mm: Use owner_priv bit for PageSwapCache, valid when PageSwapBacked

A page is not added to the swap cache without being swap backed,
so PageSwapBacked mappings can use PG_owner_priv_1 for PageSwapCache.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Bob Peterson <rpeterso@redhat.com>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Andrew Lutomirski <luto@kernel.org>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 mm/memory-failure.c |  4 +---
 mm/migrate.c        | 14 ++++++++------
 2 files changed, 9 insertions(+), 9 deletions(-)

(limited to 'mm')

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 19e796d36a62..f283c7e0a2a3 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -764,12 +764,11 @@ static int me_huge_page(struct page *p, unsigned long pfn)
  */
 
 #define dirty		(1UL << PG_dirty)
-#define sc		(1UL << PG_swapcache)
+#define sc		((1UL << PG_swapcache) | (1UL << PG_swapbacked))
 #define unevict		(1UL << PG_unevictable)
 #define mlock		(1UL << PG_mlocked)
 #define writeback	(1UL << PG_writeback)
 #define lru		(1UL << PG_lru)
-#define swapbacked	(1UL << PG_swapbacked)
 #define head		(1UL << PG_head)
 #define slab		(1UL << PG_slab)
 #define reserved	(1UL << PG_reserved)
@@ -819,7 +818,6 @@ static struct page_state {
 #undef mlock
 #undef writeback
 #undef lru
-#undef swapbacked
 #undef head
 #undef slab
 #undef reserved
diff --git a/mm/migrate.c b/mm/migrate.c
index 0ed24b1fa77b..87f4d0f81819 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -466,13 +466,15 @@ int migrate_page_move_mapping(struct address_space *mapping,
 	 */
 	newpage->index = page->index;
 	newpage->mapping = page->mapping;
-	if (PageSwapBacked(page))
-		__SetPageSwapBacked(newpage);
-
 	get_page(newpage);	/* add cache reference */
-	if (PageSwapCache(page)) {
-		SetPageSwapCache(newpage);
-		set_page_private(newpage, page_private(page));
+	if (PageSwapBacked(page)) {
+		__SetPageSwapBacked(newpage);
+		if (PageSwapCache(page)) {
+			SetPageSwapCache(newpage);
+			set_page_private(newpage, page_private(page));
+		}
+	} else {
+		VM_BUG_ON_PAGE(PageSwapCache(page), page);
 	}
 
 	/* Move dirty while page refs frozen and newpage not yet exposed */
-- 
cgit