[RBTREE] Merge colour and parent fields of struct rb_node.

We only used a single bit for colour information, so having a whole
machine word of space allocated for it was a bit wasteful. Instead,
store it in the lowest bit of the 'parent' pointer, since that was
always going to be aligned anyway.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

diff --git a/include/linux/rbtree.h b/include/linux/rbtree.h
index ffee81c..748be50 100644 (file)
--- a/include/linux/rbtree.h
+++ b/include/linux/rbtree.h
@@ -99,28 +99,35 @@ static inline struct page * rb_insert_page_cache(struct inode * inode,
 
 struct rb_node
 {
-       struct rb_node *rb_parent;
-       int rb_color;
+       unsigned long  rb_parent_colour;
 #define        RB_RED          0
 #define        RB_BLACK        1
        struct rb_node *rb_right;
        struct rb_node *rb_left;
 };
 
-#define rb_parent(r)           ((r)->rb_parent)
-#define rb_set_parent(r,p)     do { (r)->rb_parent = p; } while (0)
-#define rb_colour(r)           ((r)->rb_colour)
-#define rb_is_red(r)           ((r)->colour == RB_RED)
-#define rb_is_black(r)         ((r)->colour == RB_BLACK)
-#define rb_set_red(r)          do { (r)->colour = RB_RED; } while (0)
-#define rb_set_black(r)                do { (r)->colour = RB_BLACK; } while (0)
-#define rb_set_colour(r,c)     do { (r)->colour = (c); } while (0)
-
 struct rb_root
 {
        struct rb_node *rb_node;
 };
 
+
+#define rb_parent(r)   ((struct rb_node *)((r)->rb_parent_colour & ~3))
+#define rb_colour(r)   ((r)->rb_parent_colour & 1)
+#define rb_is_red(r)   (!rb_colour(r))
+#define rb_is_black(r) rb_colour(r)
+#define rb_set_red(r)  do { (r)->rb_parent_colour &= ~1; } while (0)
+#define rb_set_black(r)  do { (r)->rb_parent_colour |= 1; } while (0)
+
+static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
+{
+       rb->rb_parent_colour = (rb->rb_parent_colour & 3) | (unsigned long)p;
+}
+static inline void rb_set_colour(struct rb_node *rb, int colour)
+{
+       rb->rb_parent_colour = (rb->rb_parent_colour & ~1) | colour;
+}
+
 #define RB_ROOT        (struct rb_root) { NULL, }
 #define        rb_entry(ptr, type, member) container_of(ptr, type, member)
 
@@ -140,8 +147,7 @@ extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
 static inline void rb_link_node(struct rb_node * node, struct rb_node * parent,
                                struct rb_node ** rb_link)
 {
-       node->rb_parent = parent;
-       node->rb_color = RB_RED;
+       node->rb_parent_colour = (unsigned long )parent;
        node->rb_left = node->rb_right = NULL;
 
        *rb_link = node;

diff --git a/lib/rbtree.c b/lib/rbtree.c
index 63473e0..4a7173c 100644 (file)
--- a/lib/rbtree.c
+++ b/lib/rbtree.c
@@ -26,60 +26,66 @@
 static void __rb_rotate_left(struct rb_node *node, struct rb_root *root)
 {
        struct rb_node *right = node->rb_right;
+       struct rb_node *parent = rb_parent(node);
 
        if ((node->rb_right = right->rb_left))
-               right->rb_left->rb_parent = node;
+               rb_set_parent(right->rb_left, node);
        right->rb_left = node;
 
-       if ((right->rb_parent = node->rb_parent))
+       rb_set_parent(right, parent);
+
+       if (parent)
        {
-               if (node == node->rb_parent->rb_left)
-                       node->rb_parent->rb_left = right;
+               if (node == parent->rb_left)
+                       parent->rb_left = right;
                else
-                       node->rb_parent->rb_right = right;
+                       parent->rb_right = right;
        }
        else
                root->rb_node = right;
-       node->rb_parent = right;
+       rb_set_parent(node, right);
 }
 
 static void __rb_rotate_right(struct rb_node *node, struct rb_root *root)
 {
        struct rb_node *left = node->rb_left;
+       struct rb_node *parent = rb_parent(node);
 
        if ((node->rb_left = left->rb_right))
-               left->rb_right->rb_parent = node;
+               rb_set_parent(left->rb_right, node);
        left->rb_right = node;
 
-       if ((left->rb_parent = node->rb_parent))
+       rb_set_parent(left, parent);
+
+       if (parent)
        {
-               if (node == node->rb_parent->rb_right)
-                       node->rb_parent->rb_right = left;
+               if (node == parent->rb_right)
+                       parent->rb_right = left;
                else
-                       node->rb_parent->rb_left = left;
+                       parent->rb_left = left;
        }
        else
                root->rb_node = left;
-       node->rb_parent = left;
+       rb_set_parent(node, left);
 }
 
 void rb_insert_color(struct rb_node *node, struct rb_root *root)
 {
        struct rb_node *parent, *gparent;
 
-       while ((parent = node->rb_parent) && parent->rb_color == RB_RED)
+       while ((parent = rb_parent(node)) && rb_is_red(parent))
        {
-               gparent = parent->rb_parent;
+               gparent = rb_parent(parent);
 
                if (parent == gparent->rb_left)
                {
                        {
                                register struct rb_node *uncle = gparent->rb_right;
-                               if (uncle && uncle->rb_color == RB_RED)
+                               if (uncle && rb_is_red(uncle))
                                {
-                                       uncle->rb_color = RB_BLACK;
-                                       parent->rb_color = RB_BLACK;
-                                       gparent->rb_color = RB_RED;
+                                       rb_set_black(uncle);
+                                       rb_set_black(parent);
+                                       rb_set_red(gparent);
                                        node = gparent;
                                        continue;
                                }
@@ -94,17 +100,17 @@ void rb_insert_color(struct rb_node *node, struct rb_root *root)
                                node = tmp;
                        }
 
-                       parent->rb_color = RB_BLACK;
-                       gparent->rb_color = RB_RED;
+                       rb_set_black(parent);
+                       rb_set_red(gparent);
                        __rb_rotate_right(gparent, root);
                } else {
                        {
                                register struct rb_node *uncle = gparent->rb_left;
-                               if (uncle && uncle->rb_color == RB_RED)
+                               if (uncle && rb_is_red(uncle))
                                {
-                                       uncle->rb_color = RB_BLACK;
-                                       parent->rb_color = RB_BLACK;
-                                       gparent->rb_color = RB_RED;
+                                       rb_set_black(uncle);
+                                       rb_set_black(parent);
+                                       rb_set_red(gparent);
                                        node = gparent;
                                        continue;
                                }
@@ -119,13 +125,13 @@ void rb_insert_color(struct rb_node *node, struct rb_root *root)
                                node = tmp;
                        }
 
-                       parent->rb_color = RB_BLACK;
-                       gparent->rb_color = RB_RED;
+                       rb_set_black(parent);
+                       rb_set_red(gparent);
                        __rb_rotate_left(gparent, root);
                }
        }
 
-       root->rb_node->rb_color = RB_BLACK;
+       rb_set_black(root->rb_node);
 }
 EXPORT_SYMBOL(rb_insert_color);
 
@@ -134,43 +140,40 @@ static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
 {
        struct rb_node *other;
 
-       while ((!node || node->rb_color == RB_BLACK) && node != root->rb_node)
+       while ((!node || rb_is_black(node)) && node != root->rb_node)
        {
                if (parent->rb_left == node)
                {
                        other = parent->rb_right;
-                       if (other->rb_color == RB_RED)
+                       if (rb_is_red(other))
                        {
-                               other->rb_color = RB_BLACK;
-                               parent->rb_color = RB_RED;
+                               rb_set_black(other);
+                               rb_set_red(parent);
                                __rb_rotate_left(parent, root);
                                other = parent->rb_right;
                        }
-                       if ((!other->rb_left ||
-                            other->rb_left->rb_color == RB_BLACK)
-                           && (!other->rb_right ||
-                               other->rb_right->rb_color == RB_BLACK))
+                       if ((!other->rb_left || rb_is_black(other->rb_left)) &&
+                           (!other->rb_right || rb_is_black(other->rb_right)))
                        {
-                               other->rb_color = RB_RED;
+                               rb_set_red(other);
                                node = parent;
-                               parent = node->rb_parent;
+                               parent = rb_parent(node);
                        }
                        else
                        {
-                               if (!other->rb_right ||
-                                   other->rb_right->rb_color == RB_BLACK)
+                               if (!other->rb_right || rb_is_black(other->rb_right))
                                {
-                                       register struct rb_node *o_left;
+                                       struct rb_node *o_left;
                                        if ((o_left = other->rb_left))
-                                               o_left->rb_color = RB_BLACK;
-                                       other->rb_color = RB_RED;
+                                               rb_set_black(o_left);
+                                       rb_set_red(other);
                                        __rb_rotate_right(other, root);
                                        other = parent->rb_right;
                                }
-                               other->rb_color = parent->rb_color;
-                               parent->rb_color = RB_BLACK;
+                               rb_set_colour(other, rb_colour(parent));
+                               rb_set_black(parent);
                                if (other->rb_right)
-                                       other->rb_right->rb_color = RB_BLACK;
+                                       rb_set_black(other->rb_right);
                                __rb_rotate_left(parent, root);
                                node = root->rb_node;
                                break;
@@ -179,38 +182,35 @@ static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
                else
                {
                        other = parent->rb_left;
-                       if (other->rb_color == RB_RED)
+                       if (rb_is_red(other))
                        {
-                               other->rb_color = RB_BLACK;
-                               parent->rb_color = RB_RED;
+                               rb_set_black(other);
+                               rb_set_red(parent);
                                __rb_rotate_right(parent, root);
                                other = parent->rb_left;
                        }
-                       if ((!other->rb_left ||
-                            other->rb_left->rb_color == RB_BLACK)
-                           && (!other->rb_right ||
-                               other->rb_right->rb_color == RB_BLACK))
+                       if ((!other->rb_left || rb_is_black(other->rb_left)) &&
+                           (!other->rb_right || rb_is_black(other->rb_right)))
                        {
-                               other->rb_color = RB_RED;
+                               rb_set_red(other);
                                node = parent;
-                               parent = node->rb_parent;
+                               parent = rb_parent(node);
                        }
                        else
                        {
-                               if (!other->rb_left ||
-                                   other->rb_left->rb_color == RB_BLACK)
+                               if (!other->rb_left || rb_is_black(other->rb_left))
                                {
                                        register struct rb_node *o_right;
                                        if ((o_right = other->rb_right))
-                                               o_right->rb_color = RB_BLACK;
-                                       other->rb_color = RB_RED;
+                                               rb_set_black(o_right);
+                                       rb_set_red(other);
                                        __rb_rotate_left(other, root);
                                        other = parent->rb_left;
                                }
-                               other->rb_color = parent->rb_color;
-                               parent->rb_color = RB_BLACK;
+                               rb_set_colour(other, rb_colour(parent));
+                               rb_set_black(parent);
                                if (other->rb_left)
-                                       other->rb_left->rb_color = RB_BLACK;
+                                       rb_set_black(other->rb_left);
                                __rb_rotate_right(parent, root);
                                node = root->rb_node;
                                break;
@@ -218,7 +218,7 @@ static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
                }
        }
        if (node)
-               node->rb_color = RB_BLACK;
+               rb_set_black(node);
 }
 
 void rb_erase(struct rb_node *node, struct rb_root *root)
@@ -238,43 +238,41 @@ void rb_erase(struct rb_node *node, struct rb_root *root)
                while ((left = node->rb_left) != NULL)
                        node = left;
                child = node->rb_right;
-               parent = node->rb_parent;
-               color = node->rb_color;
+               parent = rb_parent(node);
+               color = rb_colour(node);
 
                if (child)
-                       child->rb_parent = parent;
-
-               if (node->rb_parent == old) {
+                       rb_set_parent(child, parent);
+               if (parent == old) {
                        parent->rb_right = child;
                        parent = node;
-               } else                  
+               } else
                        parent->rb_left = child;
 
-               node->rb_parent = old->rb_parent;
-               node->rb_color = old->rb_color;
+               node->rb_parent_colour = old->rb_parent_colour;
                node->rb_right = old->rb_right;
                node->rb_left = old->rb_left;
 
-               if (old->rb_parent)
+               if (rb_parent(old))
                {
-                       if (old->rb_parent->rb_left == old)
-                               old->rb_parent->rb_left = node;
+                       if (rb_parent(old)->rb_left == old)
+                               rb_parent(old)->rb_left = node;
                        else
-                               old->rb_parent->rb_right = node;
+                               rb_parent(old)->rb_right = node;
                } else
                        root->rb_node = node;
 
-               old->rb_left->rb_parent = node;
+               rb_set_parent(old->rb_left, node);
                if (old->rb_right)
-                       old->rb_right->rb_parent = node;
+                       rb_set_parent(old->rb_right, node);
                goto color;
        }
 
-       parent = node->rb_parent;
-       color = node->rb_color;
+       parent = rb_parent(node);
+       color = rb_colour(node);
 
        if (child)
-               child->rb_parent = parent;
+               rb_set_parent(child, parent);
        if (parent)
        {
                if (parent->rb_left == node)
@@ -322,6 +320,8 @@ EXPORT_SYMBOL(rb_last);
 
 struct rb_node *rb_next(struct rb_node *node)
 {
+       struct rb_node *parent;
+
        /* If we have a right-hand child, go down and then left as far
           as we can. */
        if (node->rb_right) {
@@ -337,15 +337,17 @@ struct rb_node *rb_next(struct rb_node *node)
           ancestor is a right-hand child of its parent, keep going
           up. First time it's a left-hand child of its parent, said
           parent is our 'next' node. */
-       while (node->rb_parent && node == node->rb_parent->rb_right)
-               node = node->rb_parent;
+       while ((parent = rb_parent(node)) && node == parent->rb_right)
+               node = parent;
 
-       return node->rb_parent;
+       return parent;
 }
 EXPORT_SYMBOL(rb_next);
 
 struct rb_node *rb_prev(struct rb_node *node)
 {
+       struct rb_node *parent;
+
        /* If we have a left-hand child, go down and then right as far
           as we can. */
        if (node->rb_left) {
@@ -357,17 +359,17 @@ struct rb_node *rb_prev(struct rb_node *node)
 
        /* No left-hand children. Go up till we find an ancestor which
           is a right-hand child of its parent */
-       while (node->rb_parent && node == node->rb_parent->rb_left)
-               node = node->rb_parent;
+       while ((parent = rb_parent(node)) && node == parent->rb_left)
+               node = parent;
 
-       return node->rb_parent;
+       return parent;
 }
 EXPORT_SYMBOL(rb_prev);
 
 void rb_replace_node(struct rb_node *victim, struct rb_node *new,
                     struct rb_root *root)
 {
-       struct rb_node *parent = victim->rb_parent;
+       struct rb_node *parent = rb_parent(victim);
 
        /* Set the surrounding nodes to point to the replacement */
        if (parent) {
@@ -379,9 +381,9 @@ void rb_replace_node(struct rb_node *victim, struct rb_node *new,
                root->rb_node = new;
        }
        if (victim->rb_left)
-               victim->rb_left->rb_parent = new;
+               rb_set_parent(victim->rb_left, new);
        if (victim->rb_right)
-               victim->rb_right->rb_parent = new;
+               rb_set_parent(victim->rb_right, new);
 
        /* Copy the pointers/colour from the victim to the replacement */
        *new = *victim;