[PATCH] mm: fix KPF_SWAPCACHE

[Hugh Dickins]

4.10-rc1 commit 6326fec1122c ("mm: Use owner_priv bit for PageSwapCache,
valid when PageSwapBacked") aliased PG_swapcache to PG_owner_priv_1:
so /proc/kpageflags' KPF_SWAPCACHE should now be synthesized, instead
of being shown on unrelated pages which have PG_owner_priv_1 set.

Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
---

 fs/proc/page.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- 4.10-rc7/fs/proc/page.c	2016-12-25 18:40:50.618454962 -0800
+++ linux/fs/proc/page.c	2017-02-07 10:28:51.019640392 -0800
@@ -173,7 +173,8 @@ u64 stable_page_flags(struct page *page)
 	u |= kpf_copy_bit(k, KPF_ACTIVE,	PG_active);
 	u |= kpf_copy_bit(k, KPF_RECLAIM,	PG_reclaim);
 
-	u |= kpf_copy_bit(k, KPF_SWAPCACHE,	PG_swapcache);
+	if (PageSwapCache(page))
+		u |= 1 << KPF_SWAPCACHE;
 	u |= kpf_copy_bit(k, KPF_SWAPBACKED,	PG_swapbacked);
 
 	u |= kpf_copy_bit(k, KPF_UNEVICTABLE,	PG_unevictable);