Avoid duplicate _count variables in page_struct

Restructure the union / struct cascade in struct page so that
we only have one definition of _count.

Tested-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

1 files changed, 19 insertions, 18 deletions

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 3d76a433d52f..774b8952deb4 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -49,30 +49,31 @@ struct page {
                                          * see PAGE_MAPPING_ANON below.
                                          */
         /* Second double word */
-        union {
-                struct {
+        struct {
+                union {
                         pgoff_t index;          /* Our offset within mapping. */
-                        atomic_t _mapcount;     /* Count of ptes mapped in mms,
+                        void *freelist;         /* slub first free object */
+                };
+
+                union {
+                        /* Used for cmpxchg_double in slub */
+                        unsigned long counters;
+
+                        struct {
+
+                                union {
+                                        atomic_t _mapcount;     /* Count of ptes mapped in mms,
                                                          * to show when page is mapped
                                                          * & limit reverse map searches.
                                                          */
-                        atomic_t _count;                /* Usage count, see below. */
-                };
 
-                struct {                        /* SLUB cmpxchg_double area */
-                        void *freelist;
-                        union {
-                                unsigned long counters;
-                                struct {
-                                        unsigned inuse:16;
-                                        unsigned objects:15;
-                                        unsigned frozen:1;
-                                        /*
-                                         * Kernel may make use of this field even when slub
-                                         * uses the rest of the double word!
-                                         */
-                                        atomic_t _count;
+                                        struct {
+                                                unsigned inuse:16;
+                                                unsigned objects:15;
+                                                unsigned frozen:1;
+                                        };
                                 };
+                                atomic_t _count;                /* Usage count, see below. */
                         };
                 };
         };