augmented rbtree: rework the RB_DECLARE_CALLBACKS macro definition

Change the definition of the RBCOMPUTE function.  The propagate callback
repeatedly calls RBCOMPUTE as it moves from leaf to root.  it wants to
stop recomputing once the augmented subtree information doesn't change.
This was previously checked using the == operator, but that only works
when the augmented subtree information is a scalar field.  This commit
modifies the RBCOMPUTE function so that it now sets the augmented subtree
information instead of returning it, and returns a boolean value
indicating if the propagate callback should stop.

The motivation for this change is that I want to introduce augmented
rbtree uses where the augmented data for the subtree is a struct instead
of a scalar.

Link: http://lkml.kernel.org/r/20190703040156.56953-4-walken@google.comSigned-off-by: Michel Lespinasse <walken@google.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: Uladzislau Rezki <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/rbtree_augmented.h

@@ -67,22 +67,19 @@ rb_insert_augmented_cached(struct rb_node *node,
  * RBNAME:      name of the rb_augment_callbacks structure
  * RBSTRUCT:    struct type of the tree nodes
  * RBFIELD:     name of struct rb_node field within RBSTRUCT
- * RBTYPE:      type of the RBAUGMENTED field
- * RBAUGMENTED: name of RBTYPE field within RBSTRUCT holding data for subtree
+ * RBAUGMENTED: name of field within RBSTRUCT holding data for subtree
  * RBCOMPUTE:   name of function that recomputes the RBAUGMENTED data
  */
 
-#define RB_DECLARE_CALLBACKS(RBSTATIC, RBNAME, RBSTRUCT, RBFIELD,	\
-			     RBTYPE, RBAUGMENTED, RBCOMPUTE)		\
+#define RB_DECLARE_CALLBACKS(RBSTATIC, RBNAME,				\
+			     RBSTRUCT, RBFIELD, RBAUGMENTED, RBCOMPUTE)	\
 static inline void							\
 RBNAME ## _propagate(struct rb_node *rb, struct rb_node *stop)		\
 {									\
 	while (rb != stop) {						\
 		RBSTRUCT *node = rb_entry(rb, RBSTRUCT, RBFIELD);	\
-		RBTYPE augmented = RBCOMPUTE(node);			\
-		if (node->RBAUGMENTED == augmented)			\
+		if (RBCOMPUTE(node, true))				\
 			break;						\
-		node->RBAUGMENTED = augmented;				\
 		rb = rb_parent(&node->RBFIELD);				\
 	}								\
 }									\
@@ -99,7 +96,7 @@ RBNAME ## _rotate(struct rb_node *rb_old, struct rb_node *rb_new)	\
 	RBSTRUCT *old = rb_entry(rb_old, RBSTRUCT, RBFIELD);		\
 	RBSTRUCT *new = rb_entry(rb_new, RBSTRUCT, RBFIELD);		\
 	new->RBAUGMENTED = old->RBAUGMENTED;				\
-	old->RBAUGMENTED = RBCOMPUTE(old);				\
+	RBCOMPUTE(old, false);						\
 }									\
 RBSTATIC const struct rb_augment_callbacks RBNAME = {			\
 	.propagate = RBNAME ## _propagate,				\
@@ -122,7 +119,7 @@ RBSTATIC const struct rb_augment_callbacks RBNAME = {			\
 
 #define RB_DECLARE_CALLBACKS_MAX(RBSTATIC, RBNAME, RBSTRUCT, RBFIELD,	      \
 				 RBTYPE, RBAUGMENTED, RBCOMPUTE)	      \
-static inline RBTYPE RBNAME ## _compute_max(RBSTRUCT *node)		      \
+static inline bool RBNAME ## _compute_max(RBSTRUCT *node, bool exit)	      \
 {									      \
 	RBSTRUCT *child;						      \
 	RBTYPE max = RBCOMPUTE(node);					      \
@@ -136,10 +133,13 @@ static inline RBTYPE RBNAME ## _compute_max(RBSTRUCT *node)		      \
 		if (child->RBAUGMENTED > max)				      \
 			max = child->RBAUGMENTED;			      \
 	}								      \
-	return max;							      \
+	if (exit && node->RBAUGMENTED == max)				      \
+		return true;						      \
+	node->RBAUGMENTED = max;					      \
+	return false;							      \
 }									      \
-RB_DECLARE_CALLBACKS(RBSTATIC, RBNAME, RBSTRUCT, RBFIELD,		      \
-		     RBTYPE, RBAUGMENTED, RBNAME ## _compute_max)
+RB_DECLARE_CALLBACKS(RBSTATIC, RBNAME,					      \
+		     RBSTRUCT, RBFIELD, RBAUGMENTED, RBNAME ## _compute_max)
 
 
 #define	RB_RED		0

tools/include/linux/rbtree_augmented.h

@@ -69,22 +69,19 @@ rb_insert_augmented_cached(struct rb_node *node,
  * RBNAME:      name of the rb_augment_callbacks structure
  * RBSTRUCT:    struct type of the tree nodes
  * RBFIELD:     name of struct rb_node field within RBSTRUCT
- * RBTYPE:      type of the RBAUGMENTED field
- * RBAUGMENTED: name of RBTYPE field within RBSTRUCT holding data for subtree
+ * RBAUGMENTED: name of field within RBSTRUCT holding data for subtree
  * RBCOMPUTE:   name of function that recomputes the RBAUGMENTED data
  */
 
-#define RB_DECLARE_CALLBACKS(RBSTATIC, RBNAME, RBSTRUCT, RBFIELD,	\
-			     RBTYPE, RBAUGMENTED, RBCOMPUTE)		\
+#define RB_DECLARE_CALLBACKS(RBSTATIC, RBNAME,				\
+			     RBSTRUCT, RBFIELD, RBAUGMENTED, RBCOMPUTE)	\
 static inline void							\
 RBNAME ## _propagate(struct rb_node *rb, struct rb_node *stop)		\
 {									\
 	while (rb != stop) {						\
 		RBSTRUCT *node = rb_entry(rb, RBSTRUCT, RBFIELD);	\
-		RBTYPE augmented = RBCOMPUTE(node);			\
-		if (node->RBAUGMENTED == augmented)			\
+		if (RBCOMPUTE(node, true))				\
 			break;						\
-		node->RBAUGMENTED = augmented;				\
 		rb = rb_parent(&node->RBFIELD);				\
 	}								\
 }									\
@@ -101,7 +98,7 @@ RBNAME ## _rotate(struct rb_node *rb_old, struct rb_node *rb_new)	\
 	RBSTRUCT *old = rb_entry(rb_old, RBSTRUCT, RBFIELD);		\
 	RBSTRUCT *new = rb_entry(rb_new, RBSTRUCT, RBFIELD);		\
 	new->RBAUGMENTED = old->RBAUGMENTED;				\
-	old->RBAUGMENTED = RBCOMPUTE(old);				\
+	RBCOMPUTE(old, false);						\
 }									\
 RBSTATIC const struct rb_augment_callbacks RBNAME = {			\
 	.propagate = RBNAME ## _propagate,				\
@@ -124,7 +121,7 @@ RBSTATIC const struct rb_augment_callbacks RBNAME = {			\
 
 #define RB_DECLARE_CALLBACKS_MAX(RBSTATIC, RBNAME, RBSTRUCT, RBFIELD,	      \
 				 RBTYPE, RBAUGMENTED, RBCOMPUTE)	      \
-static inline RBTYPE RBNAME ## _compute_max(RBSTRUCT *node)		      \
+static inline bool RBNAME ## _compute_max(RBSTRUCT *node, bool exit)	      \
 {									      \
 	RBSTRUCT *child;						      \
 	RBTYPE max = RBCOMPUTE(node);					      \
@@ -138,10 +135,13 @@ static inline RBTYPE RBNAME ## _compute_max(RBSTRUCT *node)		      \
 		if (child->RBAUGMENTED > max)				      \
 			max = child->RBAUGMENTED;			      \
 	}								      \
-	return max;							      \
+	if (exit && node->RBAUGMENTED == max)				      \
+		return true;						      \
+	node->RBAUGMENTED = max;					      \
+	return false;							      \
 }									      \
-RB_DECLARE_CALLBACKS(RBSTATIC, RBNAME, RBSTRUCT, RBFIELD,		      \
-		     RBTYPE, RBAUGMENTED, RBNAME ## _compute_max)
+RB_DECLARE_CALLBACKS(RBSTATIC, RBNAME,					      \
+		     RBSTRUCT, RBFIELD, RBAUGMENTED, RBNAME ## _compute_max)
 
 
 #define	RB_RED		0