move page writeback acounting out of macros

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

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

Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 12 insertions, 30 deletions

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index a454176c3e30..209d3a47f50f 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -189,37 +189,15 @@ static inline void SetPageUptodate(struct page *page)
 #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 PageBuddy(page)         test_bit(PG_buddy, &(page)->flags)
 #define __SetPageBuddy(page)    __set_bit(PG_buddy, &(page)->flags)
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 51b3eb6ab445..63512a9ed57e 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -987,6 +987,8 @@ int test_clear_page_writeback(struct page *page)
         } else {
                 ret = TestClearPageWriteback(page);
         }
+        if (ret)
+                dec_zone_page_state(page, NR_WRITEBACK);
         return ret;
 }
 
@@ -1012,6 +1014,8 @@ int test_set_page_writeback(struct page *page)
         } else {
                 ret = TestSetPageWriteback(page);
         }
+        if (!ret)
+                inc_zone_page_state(page, NR_WRITEBACK);
         return ret;
 
 }