mm: fix KPF_SWAPCACHE in /proc/kpageflags

Commit 6326fec1122c ("mm: Use owner_priv bit for PageSwapCache, valid
when PageSwapBacked") aliased PG_swapcache to PG_owner_priv_1 (and
depending on PageSwapBacked being true).

As a result, the KPF_SWAPCACHE bit in '/proc/kpageflags' should now be
synthesized, instead of being shown on unrelated pages which just happen
to have PG_owner_priv_1 set.

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/proc/page.c b/fs/proc/page.c
index a2066e6dee90..2726536489b1 100644
--- a/fs/proc/page.c
+++ b/fs/proc/page.c
@@ -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);