From: Andrew Morton <akpm@osdl.org>

page-writeback accounting is presently performed in the page-flags macros. 
This is inconsistent and makes it awkward to implement per-backing_dev
under-writeback page accounting.

So move this accounting down to the callsite(s).

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/page-flags.h |   38 +++++++----------------------------
 mm/page-writeback.c        |    4 +++
 2 files changed, 12 insertions(+), 30 deletions(-)

diff -puN include/linux/page-flags.h~move-page-writeback-acounting-out-of-macros include/linux/page-flags.h
--- a/include/linux/page-flags.h~move-page-writeback-acounting-out-of-macros
+++ a/include/linux/page-flags.h
@@ -182,37 +182,15 @@ static inline void SetPageUptodate(struc
 #define __SetPagePrivate(page)  __set_bit(PG_private, &(page)->flags)
 #define __ClearPagePrivate(page) __clear_bit(PG_private, &(page)->flags)
 
+/*
+ * Only test-and-set exist for PG_writeback.  The unconditional operators are
+ * risky: they bypass page accounting.
+ */
 #define PageWriteback(page)	test_bit(PG_writeback, &(page)->flags)
-#define SetPageWriteback(page)						\
-	do {								\
-		if (!test_and_set_bit(PG_writeback,			\
-				&(page)->flags))			\
-			inc_zone_page_state(page, NR_WRITEBACK);	\
-	} while (0)
-#define TestSetPageWriteback(page)					\
-	({								\
-		int ret;						\
-		ret = test_and_set_bit(PG_writeback,			\
-					&(page)->flags);		\
-		if (!ret)						\
-			inc_zone_page_state(page, NR_WRITEBACK);	\
-		ret;							\
-	})
-#define ClearPageWriteback(page)					\
-	do {								\
-		if (test_and_clear_bit(PG_writeback,			\
-				&(page)->flags))			\
-			dec_zone_page_state(page, NR_WRITEBACK);	\
-	} while (0)
-#define TestClearPageWriteback(page)					\
-	({								\
-		int ret;						\
-		ret = test_and_clear_bit(PG_writeback,			\
-				&(page)->flags);			\
-		if (ret)						\
-			dec_zone_page_state(page, NR_WRITEBACK);	\
-		ret;							\
-	})
+#define TestSetPageWriteback(page) test_and_set_bit(PG_writeback,	\
+							&(page)->flags)
+#define TestClearPageWriteback(page) test_and_clear_bit(PG_writeback,	\
+							&(page)->flags)
 
 #define PageNosave(page)	test_bit(PG_nosave, &(page)->flags)
 #define SetPageNosave(page)	set_bit(PG_nosave, &(page)->flags)
diff -puN mm/page-writeback.c~move-page-writeback-acounting-out-of-macros mm/page-writeback.c
--- a/mm/page-writeback.c~move-page-writeback-acounting-out-of-macros
+++ a/mm/page-writeback.c
@@ -980,6 +980,8 @@ int test_clear_page_writeback(struct pag
 	} else {
 		ret = TestClearPageWriteback(page);
 	}
+	if (ret)
+		dec_zone_page_state(page, NR_WRITEBACK);
 	return ret;
 }
 
@@ -1005,6 +1007,8 @@ int test_set_page_writeback(struct page 
 	} else {
 		ret = TestSetPageWriteback(page);
 	}
+	if (!ret)
+		inc_zone_page_state(page, NR_WRITEBACK);
 	return ret;
 
 }
_