mm: don't assume anonymous pages have SwapBacked flag

There are a few places the code assumes anonymous pages should have
SwapBacked flag set.  MADV_FREE pages are anonymous pages but we are
going to add them to LRU_INACTIVE_FILE list and clear SwapBacked flag
for them.  The assumption doesn't hold any more, so fix them.

Link: http://lkml.kernel.org/r/3945232c0df3dd6c4ef001976f35a95f18dcb407.1487965799.git.shli@fb.com
Signed-off-by: Shaohua Li <shli@fb.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index 5c5df09ac962..b32630d10329 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1944,7 +1944,8 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm,
 
         /* Prepare a page as a migration target */
         __SetPageLocked(new_page);
-        __SetPageSwapBacked(new_page);
+        if (PageSwapBacked(page))
+                __SetPageSwapBacked(new_page);
 
         /* anon mapping, we can simply copy page->mapping to the new page: */
         new_page->mapping = page->mapping;