mm: remove pointless struct in struct page definition

This patchset implements per kmemcg accounting of page tables
(x86-only), pipe buffers, and unix socket buffers.

Patches 1-3 are just cleanups that are not supposed to introduce any
functional changes.  Patches 4 and 5 move charge/uncharge to generic
page allocator paths for the sake of accounting pipe and unix socket
buffers.  Patches 5-7 make x86 page tables, pipe buffers, and unix
socket buffers accountable.

This patch (of 8):

... to reduce indentation level thus leaving more space for comments.

Link: http://lkml.kernel.org/r/f34ffe70fce2b0b9220856437f77972d67c14275.1464079537.git.vdavydov@virtuozzo.com
Signed-off-by: Vladimir Davydov <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: Minchan Kim <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: Vladimir Davydov

include/linux/mm_types.h

@@ -60,51 +60,47 @@ struct page {
 	};
 
 	/* Second double word */
-	struct {
-		union {
-			pgoff_t index;		/* Our offset within mapping. */
-			void *freelist;		/* sl[aou]b first free object */
-			/* page_deferred_list().prev	-- second tail page */
-		};
+	union {
+		pgoff_t index;		/* Our offset within mapping. */
+		void *freelist;		/* sl[aou]b first free object */
+		/* page_deferred_list().prev	-- second tail page */
+	};
 
-		union {
+	union {
 #if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \
 	defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
-			/* Used for cmpxchg_double in slub */
-			unsigned long counters;
+		/* Used for cmpxchg_double in slub */
+		unsigned long counters;
 #else
-			/*
-			 * Keep _refcount separate from slub cmpxchg_double
-			 * data.  As the rest of the double word is protected by
-			 * slab_lock but _refcount is not.
-			 */
-			unsigned counters;
+		/*
+		 * Keep _refcount separate from slub cmpxchg_double data.
+		 * As the rest of the double word is protected by slab_lock
+		 * but _refcount is not.
+		 */
+		unsigned counters;
 #endif
+		struct {
 
-			struct {
-
-				union {
-					/*
-					 * Count of ptes mapped in mms, to show
-					 * when page is mapped & limit reverse
-					 * map searches.
-					 */
-					atomic_t _mapcount;
-
-					struct { /* SLUB */
-						unsigned inuse:16;
-						unsigned objects:15;
-						unsigned frozen:1;
-					};
-					int units;	/* SLOB */
-				};
+			union {
 				/*
-				 * Usage count, *USE WRAPPER FUNCTION*
-				 * when manual accounting. See page_ref.h
+				 * Count of ptes mapped in mms, to show when
+				 * page is mapped & limit reverse map searches.
 				 */
-				atomic_t _refcount;
+				atomic_t _mapcount;
+
+				unsigned int active;		/* SLAB */
+				struct {			/* SLUB */
+					unsigned inuse:16;
+					unsigned objects:15;
+					unsigned frozen:1;
+				};
+				int units;			/* SLOB */
 			};
-			unsigned int active;	/* SLAB */
+			/*
+			 * Usage count, *USE WRAPPER FUNCTION* when manual
+			 * accounting. See page_ref.h
+			 */
+			atomic_t _refcount;
 		};
 	};