lib/rbtree: avoid generating code twice for the cached versions

As was already noted in rbtree.h, the logic to cache rb_first (or
rb_last) can easily be implemented externally to the core rbtree api.

Change the implementation to do just that.  Previously the update of
rb_leftmost was wired deeper into the implmentation, but there were some
disadvantages to that - mostly, lib/rbtree.c had separate instantiations
for rb_insert_color() vs rb_insert_color_cached(), as well as rb_erase()
vs rb_erase_cached(), which were doing exactly the same thing save for
the rb_leftmost update at the start of either function.

   text	   data	    bss	    dec	    hex	filename
   5405	    120	      0	   5525	   1595	lib/rbtree.o-vanilla
   3827	     96	      0	   3923	    f53	lib/rbtree.o-patch

[dave@stgolabs.net: changelog addition]
Link: http://lkml.kernel.org/r/20190628171416.by5gdizl3rcxk5h5@linux-r8p5
[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20190628045008.39926-1-walken@google.com
Signed-off-by: Michel Lespinasse <walken@google.com>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/rbtree.h b/include/linux/rbtree.h
index e6337fc..1fd61a9 100644 (file)
--- a/include/linux/rbtree.h
+++ b/include/linux/rbtree.h
@@ -32,25 +32,9 @@ struct rb_root {
        struct rb_node *rb_node;
 };
 
-/*
- * Leftmost-cached rbtrees.
- *
- * We do not cache the rightmost node based on footprint
- * size vs number of potential users that could benefit
- * from O(1) rb_last(). Just not worth it, users that want
- * this feature can always implement the logic explicitly.
- * Furthermore, users that want to cache both pointers may
- * find it a bit asymmetric, but that's ok.
- */
-struct rb_root_cached {
-       struct rb_root rb_root;
-       struct rb_node *rb_leftmost;
-};
-
 #define rb_parent(r)   ((struct rb_node *)((r)->__rb_parent_color & ~3))
 
 #define RB_ROOT        (struct rb_root) { NULL, }
-#define RB_ROOT_CACHED (struct rb_root_cached) { {NULL, }, NULL }
 #define        rb_entry(ptr, type, member) container_of(ptr, type, member)
 
 #define RB_EMPTY_ROOT(root)  (READ_ONCE((root)->rb_node) == NULL)
@@ -72,12 +56,6 @@ extern struct rb_node *rb_prev(const struct rb_node *);
 extern struct rb_node *rb_first(const struct rb_root *);
 extern struct rb_node *rb_last(const struct rb_root *);
 
-extern void rb_insert_color_cached(struct rb_node *,
-                                  struct rb_root_cached *, bool);
-extern void rb_erase_cached(struct rb_node *node, struct rb_root_cached *);
-/* Same as rb_first(), but O(1) */
-#define rb_first_cached(root) (root)->rb_leftmost
-
 /* Postorder iteration - always visit the parent after its children */
 extern struct rb_node *rb_first_postorder(const struct rb_root *);
 extern struct rb_node *rb_next_postorder(const struct rb_node *);
@@ -87,8 +65,6 @@ extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
                            struct rb_root *root);
 extern void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new,
                                struct rb_root *root);
-extern void rb_replace_node_cached(struct rb_node *victim, struct rb_node *new,
-                                  struct rb_root_cached *root);
 
 static inline void rb_link_node(struct rb_node *node, struct rb_node *parent,
                                struct rb_node **rb_link)
@@ -136,4 +112,50 @@ static inline void rb_link_node_rcu(struct rb_node *node, struct rb_node *parent
                        typeof(*pos), field); 1; }); \
             pos = n)
 
+/*
+ * Leftmost-cached rbtrees.
+ *
+ * We do not cache the rightmost node based on footprint
+ * size vs number of potential users that could benefit
+ * from O(1) rb_last(). Just not worth it, users that want
+ * this feature can always implement the logic explicitly.
+ * Furthermore, users that want to cache both pointers may
+ * find it a bit asymmetric, but that's ok.
+ */
+struct rb_root_cached {
+       struct rb_root rb_root;
+       struct rb_node *rb_leftmost;
+};
+
+#define RB_ROOT_CACHED (struct rb_root_cached) { {NULL, }, NULL }
+
+/* Same as rb_first(), but O(1) */
+#define rb_first_cached(root) (root)->rb_leftmost
+
+static inline void rb_insert_color_cached(struct rb_node *node,
+                                         struct rb_root_cached *root,
+                                         bool leftmost)
+{
+       if (leftmost)
+               root->rb_leftmost = node;
+       rb_insert_color(node, &root->rb_root);
+}
+
+static inline void rb_erase_cached(struct rb_node *node,
+                                  struct rb_root_cached *root)
+{
+       if (root->rb_leftmost == node)
+               root->rb_leftmost = rb_next(node);
+       rb_erase(node, &root->rb_root);
+}
+
+static inline void rb_replace_node_cached(struct rb_node *victim,
+                                         struct rb_node *new,
+                                         struct rb_root_cached *root)
+{
+       if (root->rb_leftmost == victim)
+               root->rb_leftmost = new;
+       rb_replace_node(victim, new, &root->rb_root);
+}
+
 #endif /* _LINUX_RBTREE_H */

diff --git a/include/linux/rbtree_augmented.h b/include/linux/rbtree_augmented.h
index 0f902cc..179faab 100644 (file)
--- a/include/linux/rbtree_augmented.h
+++ b/include/linux/rbtree_augmented.h
@@ -30,10 +30,9 @@ struct rb_augment_callbacks {
        void (*rotate)(struct rb_node *old, struct rb_node *new);
 };
 
-extern void __rb_insert_augmented(struct rb_node *node,
-                                 struct rb_root *root,
-                                 bool newleft, struct rb_node **leftmost,
+extern void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
        void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
+
 /*
  * Fixup the rbtree and update the augmented information when rebalancing.
  *
@@ -48,7 +47,7 @@ static inline void
 rb_insert_augmented(struct rb_node *node, struct rb_root *root,
                    const struct rb_augment_callbacks *augment)
 {
-       __rb_insert_augmented(node, root, false, NULL, augment->rotate);
+       __rb_insert_augmented(node, root, augment->rotate);
 }
 
 static inline void
@@ -56,8 +55,9 @@ rb_insert_augmented_cached(struct rb_node *node,
                           struct rb_root_cached *root, bool newleft,
                           const struct rb_augment_callbacks *augment)
 {
-       __rb_insert_augmented(node, &root->rb_root,
-                             newleft, &root->rb_leftmost, augment->rotate);
+       if (newleft)
+               root->rb_leftmost = node;
+       rb_insert_augmented(node, &root->rb_root, augment);
 }
 
 #define RB_DECLARE_CALLBACKS(rbstatic, rbname, rbstruct, rbfield,      \
@@ -150,7 +150,6 @@ extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
 
 static __always_inline struct rb_node *
 __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
-                    struct rb_node **leftmost,
                     const struct rb_augment_callbacks *augment)
 {
        struct rb_node *child = node->rb_right;
@@ -158,9 +157,6 @@ __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
        struct rb_node *parent, *rebalance;
        unsigned long pc;
 
-       if (leftmost && node == *leftmost)
-               *leftmost = rb_next(node);
-
        if (!tmp) {
                /*
                 * Case 1: node to erase has no more than 1 child (easy!)
@@ -260,8 +256,7 @@ static __always_inline void
 rb_erase_augmented(struct rb_node *node, struct rb_root *root,
                   const struct rb_augment_callbacks *augment)
 {
-       struct rb_node *rebalance = __rb_erase_augmented(node, root,
-                                                        NULL, augment);
+       struct rb_node *rebalance = __rb_erase_augmented(node, root, augment);
        if (rebalance)
                __rb_erase_color(rebalance, root, augment->rotate);
 }
@@ -270,11 +265,9 @@ static __always_inline void
 rb_erase_augmented_cached(struct rb_node *node, struct rb_root_cached *root,
                          const struct rb_augment_callbacks *augment)
 {
-       struct rb_node *rebalance = __rb_erase_augmented(node, &root->rb_root,
-                                                        &root->rb_leftmost,
-                                                        augment);
-       if (rebalance)
-               __rb_erase_color(rebalance, &root->rb_root, augment->rotate);
+       if (root->rb_leftmost == node)
+               root->rb_leftmost = rb_next(node);
+       rb_erase_augmented(node, &root->rb_root, augment);
 }
 
 #endif /* _LINUX_RBTREE_AUGMENTED_H */

diff --git a/lib/rbtree.c b/lib/rbtree.c
index 1ef6e25..abc86c6 100644 (file)
--- a/lib/rbtree.c
+++ b/lib/rbtree.c
@@ -83,14 +83,10 @@ __rb_rotate_set_parents(struct rb_node *old, struct rb_node *new,
 
 static __always_inline void
 __rb_insert(struct rb_node *node, struct rb_root *root,
-           bool newleft, struct rb_node **leftmost,
            void (*augment_rotate)(struct rb_node *old, struct rb_node *new))
 {
        struct rb_node *parent = rb_red_parent(node), *gparent, *tmp;
 
-       if (newleft)
-               *leftmost = node;
-
        while (true) {
                /*
                 * Loop invariant: node is red.
@@ -437,38 +433,19 @@ static const struct rb_augment_callbacks dummy_callbacks = {
 
 void rb_insert_color(struct rb_node *node, struct rb_root *root)
 {
-       __rb_insert(node, root, false, NULL, dummy_rotate);
+       __rb_insert(node, root, dummy_rotate);
 }
 EXPORT_SYMBOL(rb_insert_color);
 
 void rb_erase(struct rb_node *node, struct rb_root *root)
 {
        struct rb_node *rebalance;
-       rebalance = __rb_erase_augmented(node, root,
-                                        NULL, &dummy_callbacks);
+       rebalance = __rb_erase_augmented(node, root, &dummy_callbacks);
        if (rebalance)
                ____rb_erase_color(rebalance, root, dummy_rotate);
 }
 EXPORT_SYMBOL(rb_erase);
 
-void rb_insert_color_cached(struct rb_node *node,
-                           struct rb_root_cached *root, bool leftmost)
-{
-       __rb_insert(node, &root->rb_root, leftmost,
-                   &root->rb_leftmost, dummy_rotate);
-}
-EXPORT_SYMBOL(rb_insert_color_cached);
-
-void rb_erase_cached(struct rb_node *node, struct rb_root_cached *root)
-{
-       struct rb_node *rebalance;
-       rebalance = __rb_erase_augmented(node, &root->rb_root,
-                                        &root->rb_leftmost, &dummy_callbacks);
-       if (rebalance)
-               ____rb_erase_color(rebalance, &root->rb_root, dummy_rotate);
-}
-EXPORT_SYMBOL(rb_erase_cached);
-
 /*
  * Augmented rbtree manipulation functions.
  *
@@ -477,10 +454,9 @@ EXPORT_SYMBOL(rb_erase_cached);
  */
 
 void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
-                          bool newleft, struct rb_node **leftmost,
        void (*augment_rotate)(struct rb_node *old, struct rb_node *new))
 {
-       __rb_insert(node, root, newleft, leftmost, augment_rotate);
+       __rb_insert(node, root, augment_rotate);
 }
 EXPORT_SYMBOL(__rb_insert_augmented);
 
@@ -591,16 +567,6 @@ void rb_replace_node(struct rb_node *victim, struct rb_node *new,
 }
 EXPORT_SYMBOL(rb_replace_node);
 
-void rb_replace_node_cached(struct rb_node *victim, struct rb_node *new,
-                           struct rb_root_cached *root)
-{
-       rb_replace_node(victim, new, &root->rb_root);
-
-       if (root->rb_leftmost == victim)
-               root->rb_leftmost = new;
-}
-EXPORT_SYMBOL(rb_replace_node_cached);
-
 void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new,
                         struct rb_root *root)
 {