[RFC 8/8] mm: simplify page_ref_* functions

[Pasha Tatashin]

Now, that we are using atomic_return variants to add/sub/inc/dec page
_refcount, it makes sense to combined page_ref_* return and non return
functions.

Also remove some extra trace points for non-return  variants. This
improves the tracability by always recording the new _refcount value
after the modifications has occurred.

Signed-off-by: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
---
 include/linux/page_ref.h        | 79 +++++++--------------------------
 include/trace/events/page_ref.h | 26 +++--------
 mm/debug_page_ref.c             | 14 ------
 3 files changed, 22 insertions(+), 97 deletions(-)

diff --git a/include/linux/page_ref.h b/include/linux/page_ref.h
index 06f5760fcd06..2a91dbc33486 100644
--- a/include/linux/page_ref.h
+++ b/include/linux/page_ref.h
@@ -8,8 +8,6 @@
 #include <linux/tracepoint-defs.h>
 
 DECLARE_TRACEPOINT(page_ref_init);
-DECLARE_TRACEPOINT(page_ref_mod);
-DECLARE_TRACEPOINT(page_ref_mod_and_test);
 DECLARE_TRACEPOINT(page_ref_mod_and_return);
 DECLARE_TRACEPOINT(page_ref_mod_unless);
 DECLARE_TRACEPOINT(page_ref_freeze);
@@ -27,8 +25,6 @@ DECLARE_TRACEPOINT(page_ref_unfreeze);
 #define page_ref_tracepoint_active(t) tracepoint_enabled(t)
 
 extern void __page_ref_init(struct page *page);
-extern void __page_ref_mod(struct page *page, int v);
-extern void __page_ref_mod_and_test(struct page *page, int v, int ret);
 extern void __page_ref_mod_and_return(struct page *page, int v, int ret);
 extern void __page_ref_mod_unless(struct page *page, int v, int u);
 extern void __page_ref_freeze(struct page *page, int v, int ret);
@@ -41,12 +37,6 @@ extern void __page_ref_unfreeze(struct page *page, int v);
 static inline void __page_ref_init(struct page *page)
 {
 }
-static inline void __page_ref_mod(struct page *page, int v)
-{
-}
-static inline void __page_ref_mod_and_test(struct page *page, int v, int ret)
-{
-}
 static inline void __page_ref_mod_and_return(struct page *page, int v, int ret)
 {
 }
@@ -102,26 +92,7 @@ static inline int page_ref_add_return(struct page *page, int nr)
 
 static inline void page_ref_add(struct page *page, int nr)
 {
-	int ret;
-
-	VM_BUG_ON(nr <= 0);
-	ret = atomic_add_return(nr, &page->_refcount);
-	VM_BUG_ON_PAGE(ret <= 0, page);
-
-	if (page_ref_tracepoint_active(page_ref_mod))
-		__page_ref_mod(page, nr);
-}
-
-static inline void page_ref_sub(struct page *page, int nr)
-{
-	int ret;
-
-	VM_BUG_ON(nr <= 0);
-	ret = atomic_sub_return(nr, &page->_refcount);
-	VM_BUG_ON_PAGE(ret < 0, page);
-
-	if (page_ref_tracepoint_active(page_ref_mod))
-		__page_ref_mod(page, -nr);
+	page_ref_add_return(page, nr);
 }
 
 static inline int page_ref_sub_return(struct page *page, int nr)
@@ -137,37 +108,14 @@ static inline int page_ref_sub_return(struct page *page, int nr)
 	return ret;
 }
 
-static inline void page_ref_inc(struct page *page)
-{
-	int ret = atomic_inc_return(&page->_refcount);
-
-	VM_BUG_ON_PAGE(ret <= 0, page);
-
-	if (page_ref_tracepoint_active(page_ref_mod))
-		__page_ref_mod(page, 1);
-}
-
-static inline void page_ref_dec(struct page *page)
+static inline void page_ref_sub(struct page *page, int nr)
 {
-	int ret = atomic_dec_return(&page->_refcount);
-
-	VM_BUG_ON_PAGE(ret < 0, page);
-
-	if (page_ref_tracepoint_active(page_ref_mod))
-		__page_ref_mod(page, -1);
+	page_ref_sub_return(page, nr);
 }
 
 static inline int page_ref_sub_and_test(struct page *page, int nr)
 {
-	int ret;
-
-	VM_BUG_ON(nr <= 0);
-	ret = atomic_sub_return(nr, &page->_refcount);
-	VM_BUG_ON_PAGE(ret < 0, page);
-
-	if (page_ref_tracepoint_active(page_ref_mod_and_test))
-		__page_ref_mod_and_test(page, -nr, ret);
-	return ret == 0;
+	return page_ref_sub_return(page, nr) == 0;
 }
 
 static inline int page_ref_inc_return(struct page *page)
@@ -181,15 +129,10 @@ static inline int page_ref_inc_return(struct page *page)
 	return ret;
 }
 
-static inline int page_ref_dec_and_test(struct page *page)
+static inline void page_ref_inc(struct page *page)
 {
-	int ret = atomic_dec_return(&page->_refcount);
 
-	VM_BUG_ON_PAGE(ret < 0, page);
-
-	if (page_ref_tracepoint_active(page_ref_mod_and_test))
-		__page_ref_mod_and_test(page, -1, ret);
-	return ret == 0;
+	page_ref_inc_return(page);
 }
 
 static inline int page_ref_dec_return(struct page *page)
@@ -203,6 +146,16 @@ static inline int page_ref_dec_return(struct page *page)
 	return ret;
 }
 
+static inline void page_ref_dec(struct page *page)
+{
+	page_ref_dec_return(page);
+}
+
+static inline int page_ref_dec_and_test(struct page *page)
+{
+	return page_ref_dec_return(page) == 0;
+}
+
 static inline int page_ref_add_unless(struct page *page, int nr, int u)
 {
 	int ret;
diff --git a/include/trace/events/page_ref.h b/include/trace/events/page_ref.h
index 87551bb1df9e..883d90508ca2 100644
--- a/include/trace/events/page_ref.h
+++ b/include/trace/events/page_ref.h
@@ -49,7 +49,7 @@ DEFINE_EVENT(page_ref_init_template, page_ref_init,
 	TP_ARGS(page)
 );
 
-DECLARE_EVENT_CLASS(page_ref_mod_template,
+DECLARE_EVENT_CLASS(page_ref_unfreeze_template,
 
 	TP_PROTO(struct page *page, int v),
 
@@ -83,14 +83,7 @@ DECLARE_EVENT_CLASS(page_ref_mod_template,
 		__entry->val)
 );
 
-DEFINE_EVENT(page_ref_mod_template, page_ref_mod,
-
-	TP_PROTO(struct page *page, int v),
-
-	TP_ARGS(page, v)
-);
-
-DECLARE_EVENT_CLASS(page_ref_mod_and_test_template,
+DECLARE_EVENT_CLASS(page_ref_mod_template,
 
 	TP_PROTO(struct page *page, int v, int ret),
 
@@ -126,35 +119,28 @@ DECLARE_EVENT_CLASS(page_ref_mod_and_test_template,
 		__entry->val, __entry->ret)
 );
 
-DEFINE_EVENT(page_ref_mod_and_test_template, page_ref_mod_and_test,
-
-	TP_PROTO(struct page *page, int v, int ret),
-
-	TP_ARGS(page, v, ret)
-);
-
-DEFINE_EVENT(page_ref_mod_and_test_template, page_ref_mod_and_return,
+DEFINE_EVENT(page_ref_mod_template, page_ref_mod_and_return,
 
 	TP_PROTO(struct page *page, int v, int ret),
 
 	TP_ARGS(page, v, ret)
 );
 
-DEFINE_EVENT(page_ref_mod_and_test_template, page_ref_mod_unless,
+DEFINE_EVENT(page_ref_mod_template, page_ref_mod_unless,
 
 	TP_PROTO(struct page *page, int v, int ret),
 
 	TP_ARGS(page, v, ret)
 );
 
-DEFINE_EVENT(page_ref_mod_and_test_template, page_ref_freeze,
+DEFINE_EVENT(page_ref_mod_template, page_ref_freeze,
 
 	TP_PROTO(struct page *page, int v, int ret),
 
 	TP_ARGS(page, v, ret)
 );
 
-DEFINE_EVENT(page_ref_mod_template, page_ref_unfreeze,
+DEFINE_EVENT(page_ref_unfreeze_template, page_ref_unfreeze,
 
 	TP_PROTO(struct page *page, int v),
 
diff --git a/mm/debug_page_ref.c b/mm/debug_page_ref.c
index e32149734122..1de9d93cca25 100644
--- a/mm/debug_page_ref.c
+++ b/mm/debug_page_ref.c
@@ -12,20 +12,6 @@ void __page_ref_init(struct page *page)
 EXPORT_SYMBOL(__page_ref_init);
 EXPORT_TRACEPOINT_SYMBOL(page_ref_init);
 
-void __page_ref_mod(struct page *page, int v)
-{
-	trace_page_ref_mod(page, v);
-}
-EXPORT_SYMBOL(__page_ref_mod);
-EXPORT_TRACEPOINT_SYMBOL(page_ref_mod);
-
-void __page_ref_mod_and_test(struct page *page, int v, int ret)
-{
-	trace_page_ref_mod_and_test(page, v, ret);
-}
-EXPORT_SYMBOL(__page_ref_mod_and_test);
-EXPORT_TRACEPOINT_SYMBOL(page_ref_mod_and_test);
-
 void __page_ref_mod_and_return(struct page *page, int v, int ret)
 {
 	trace_page_ref_mod_and_return(page, v, ret);
-- 
2.33.0.1079.g6e70778dc9-goog