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/migrate.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

(limited to 'mm/migrate.c')

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