mm: page-writeback: inline account_page_dirtied() into single caller

A follow-up patch would have changed the call signature.  To save the
trouble, just fold it instead.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Cc: <stable@vger.kernel.org>	[3.17.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/mm.h

@@ -1235,7 +1235,6 @@ int __set_page_dirty_no_writeback(struct page *page);
 int redirty_page_for_writepage(struct writeback_control *wbc,
 				struct page *page);
 void account_page_dirtied(struct page *page, struct address_space *mapping);
-void account_page_writeback(struct page *page);
 int set_page_dirty(struct page *page);
 int set_page_dirty_lock(struct page *page);
 int clear_page_dirty_for_io(struct page *page);

mm/page-writeback.c

@@ -2115,23 +2115,6 @@ void account_page_dirtied(struct page *page, struct address_space *mapping)
 }
 EXPORT_SYMBOL(account_page_dirtied);
 
-/*
- * Helper function for set_page_writeback family.
- *
- * The caller must hold mem_cgroup_begin/end_update_page_stat() lock
- * while calling this function.
- * See test_set_page_writeback for example.
- *
- * NOTE: Unlike account_page_dirtied this does not rely on being atomic
- * wrt interrupts.
- */
-void account_page_writeback(struct page *page)
-{
-	mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_WRITEBACK);
-	inc_zone_page_state(page, NR_WRITEBACK);
-}
-EXPORT_SYMBOL(account_page_writeback);
-
 /*
  * For address_spaces which do not use buffers.  Just tag the page as dirty in
  * its radix tree.
@@ -2410,8 +2393,10 @@ int __test_set_page_writeback(struct page *page, bool keep_write)
 	} else {
 		ret = TestSetPageWriteback(page);
 	}
-	if (!ret)
-		account_page_writeback(page);
+	if (!ret) {
+		mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_WRITEBACK);
+		inc_zone_page_state(page, NR_WRITEBACK);
+	}
 	mem_cgroup_end_update_page_stat(page, &locked, &memcg_flags);
 	return ret;