[PATCH 1/2] mm: Move PageDoubleMap bit

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

PG_private_2 is defined as being PF_ANY (applicable to tail pages
as well as regular & head pages).  That means that the first tail
page of a double-map page will appear to have Private2 set.  Use the
Workingset bit instead which is defined as PF_HEAD so any attempt to
access the Workingset bit on a tail page will redirect to the head page's
Workingset bit.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/page-flags.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 6be1aa559b1e..b4e6051aa311 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -164,7 +164,7 @@ enum pageflags {
 	PG_slob_free = PG_private,
 
 	/* Compound pages. Stored in first tail page's flags */
-	PG_double_map = PG_private_2,
+	PG_double_map = PG_workingset,
 
 	/* non-lru isolated movable page */
 	PG_isolated = PG_reclaim,
-- 
2.27.0