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.comSigned-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/mm_types.h

@@ -60,7 +60,6 @@ struct page {
 	};
 
 	/* Second double word */
-	struct {
 	union {
 		pgoff_t index;		/* Our offset within mapping. */
 		void *freelist;		/* sl[aou]b first free object */
@@ -74,23 +73,22 @@ struct page {
 		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.
+		 * 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 {
 
 			union {
 				/*
-					 * Count of ptes mapped in mms, to show
-					 * when page is mapped & limit reverse
-					 * map searches.
+				 * Count of ptes mapped in mms, to show when
+				 * page is mapped & limit reverse map searches.
 				 */
 				atomic_t _mapcount;
 
+				unsigned int active;		/* SLAB */
 				struct {			/* SLUB */
 					unsigned inuse:16;
 					unsigned objects:15;
@@ -99,13 +97,11 @@ struct page {
 				int units;			/* SLOB */
 			};
 			/*
-				 * Usage count, *USE WRAPPER FUNCTION*
-				 * when manual accounting. See page_ref.h
+			 * Usage count, *USE WRAPPER FUNCTION* when manual
+			 * accounting. See page_ref.h
 			 */
 			atomic_t _refcount;
 		};
-			unsigned int active;	/* SLAB */
-		};
 	};
 
 	/*