include/linux/rbtree_augmented.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /*
   3   Red Black Trees
   4   (C) 1999  Andrea Arcangeli <andrea@suse.de>
   5   (C) 2002  David Woodhouse <dwmw2@infradead.org>
   6   (C) 2012  Michel Lespinasse <walken@google.com>
   7
   8
   9   linux/include/linux/rbtree_augmented.h
  10 */
  11
  12 #ifndef _LINUX_RBTREE_AUGMENTED_H
  13 #define _LINUX_RBTREE_AUGMENTED_H
  14
  15 #include <linux/compiler.h>
  16 #include <linux/rbtree.h>
  17 #include <linux/rcupdate.h>
  18
  19 /*
  20  * Please note - only struct rb_augment_callbacks and the prototypes for
  21  * rb_insert_augmented() and rb_erase_augmented() are intended to be public.
  22  * The rest are implementation details you are not expected to depend on.
  23  *
  24  * See Documentation/rbtree.txt for documentation and samples.
  25  */
  26
  27 struct rb_augment_callbacks {
  28         void (*propagate)(struct rb_node *node, struct rb_node *stop);
  29         void (*copy)(struct rb_node *old, struct rb_node *new);
  30         void (*rotate)(struct rb_node *old, struct rb_node *new);
  31 };
  32
  33 extern void __rb_insert_augmented(struct rb_node *node,
  34                                   struct rb_root *root,
  35                                   bool newleft, struct rb_node **leftmost,
  36         void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
  37 /*
  38  * Fixup the rbtree and update the augmented information when rebalancing.
  39  *
  40  * On insertion, the user must update the augmented information on the path
  41  * leading to the inserted node, then call rb_link_node() as usual and
  42  * rb_insert_augmented() instead of the usual rb_insert_color() call.
  43  * If rb_insert_augmented() rebalances the rbtree, it will callback into
  44  * a user provided function to update the augmented information on the
  45  * affected subtrees.
  46  */
  47 static inline void
  48 rb_insert_augmented(struct rb_node *node, struct rb_root *root,
  49                     const struct rb_augment_callbacks *augment)
  50 {
  51         __rb_insert_augmented(node, root, false, NULL, augment->rotate);
  52 }
  53
  54 static inline void
  55 rb_insert_augmented_cached(struct rb_node *node,
  56                            struct rb_root_cached *root, bool newleft,
  57                            const struct rb_augment_callbacks *augment)
  58 {
  59         __rb_insert_augmented(node, &root->rb_root,
  60                               newleft, &root->rb_leftmost, augment->rotate);
  61 }
  62
  63 #define RB_DECLARE_CALLBACKS(rbstatic, rbname, rbstruct, rbfield,       \
  64                              rbtype, rbaugmented, rbcompute)            \
  65 static inline void                                                      \
  66 rbname ## _propagate(struct rb_node *rb, struct rb_node *stop)          \
  67 {                                                                       \
  68         while (rb != stop) {                                            \
  69                 rbstruct *node = rb_entry(rb, rbstruct, rbfield);       \
  70                 rbtype augmented = rbcompute(node);                     \
  71                 if (node->rbaugmented == augmented)                     \
  72                         break;                                          \
  73                 node->rbaugmented = augmented;                          \
  74                 rb = rb_parent(&node->rbfield);                         \
  75         }                                                               \
  76 }                                                                       \
  77 static inline void                                                      \
  78 rbname ## _copy(struct rb_node *rb_old, struct rb_node *rb_new)         \
  79 {                                                                       \
  80         rbstruct *old = rb_entry(rb_old, rbstruct, rbfield);            \
  81         rbstruct *new = rb_entry(rb_new, rbstruct, rbfield);            \
  82         new->rbaugmented = old->rbaugmented;                            \
  83 }                                                                       \
  84 static void                                                             \
  85 rbname ## _rotate(struct rb_node *rb_old, struct rb_node *rb_new)       \
  86 {                                                                       \
  87         rbstruct *old = rb_entry(rb_old, rbstruct, rbfield);            \
  88         rbstruct *new = rb_entry(rb_new, rbstruct, rbfield);            \
  89         new->rbaugmented = old->rbaugmented;                            \
  90         old->rbaugmented = rbcompute(old);                              \
  91 }                                                                       \
  92 rbstatic const struct rb_augment_callbacks rbname = {                   \
  93         .propagate = rbname ## _propagate,                              \
  94         .copy = rbname ## _copy,                                        \
  95         .rotate = rbname ## _rotate                                     \
  96 };
  97
  98
  99 #define RB_RED          0
 100 #define RB_BLACK        1
 101
 102 #define __rb_parent(pc)    ((struct rb_node *)(pc & ~3))
 103
 104 #define __rb_color(pc)     ((pc) & 1)
 105 #define __rb_is_black(pc)  __rb_color(pc)
 106 #define __rb_is_red(pc)    (!__rb_color(pc))
 107 #define rb_color(rb)       __rb_color((rb)->__rb_parent_color)
 108 #define rb_is_red(rb)      __rb_is_red((rb)->__rb_parent_color)
 109 #define rb_is_black(rb)    __rb_is_black((rb)->__rb_parent_color)
 110
 111 static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
 112 {
 113         rb->__rb_parent_color = rb_color(rb) | (unsigned long)p;
 114 }
 115
 116 static inline void rb_set_parent_color(struct rb_node *rb,
 117                                        struct rb_node *p, int color)
 118 {
 119         rb->__rb_parent_color = (unsigned long)p | color;
 120 }
 121
 122 static inline void
 123 __rb_change_child(struct rb_node *old, struct rb_node *new,
 124                   struct rb_node *parent, struct rb_root *root)
 125 {
 126         if (parent) {
 127                 if (parent->rb_left == old)
 128                         WRITE_ONCE(parent->rb_left, new);
 129                 else
 130                         WRITE_ONCE(parent->rb_right, new);
 131         } else
 132                 WRITE_ONCE(root->rb_node, new);
 133 }
 134
 135 static inline void
 136 __rb_change_child_rcu(struct rb_node *old, struct rb_node *new,
 137                       struct rb_node *parent, struct rb_root *root)
 138 {
 139         if (parent) {
 140                 if (parent->rb_left == old)
 141                         rcu_assign_pointer(parent->rb_left, new);
 142                 else
 143                         rcu_assign_pointer(parent->rb_right, new);
 144         } else
 145                 rcu_assign_pointer(root->rb_node, new);
 146 }
 147
 148 extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
 149         void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
 150
 151 static __always_inline struct rb_node *
 152 __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
 153                      struct rb_node **leftmost,
 154                      const struct rb_augment_callbacks *augment)
 155 {
 156         struct rb_node *child = node->rb_right;
 157         struct rb_node *tmp = node->rb_left;
 158         struct rb_node *parent, *rebalance;
 159         unsigned long pc;
 160
 161         if (leftmost && node == *leftmost)
 162                 *leftmost = rb_next(node);
 163
 164         if (!tmp) {
 165                 /*
 166                  * Case 1: node to erase has no more than 1 child (easy!)
 167                  *
 168                  * Note that if there is one child it must be red due to 5)
 169                  * and node must be black due to 4). We adjust colors locally
 170                  * so as to bypass __rb_erase_color() later on.
 171                  */
 172                 pc = node->__rb_parent_color;
 173                 parent = __rb_parent(pc);
 174                 __rb_change_child(node, child, parent, root);
 175                 if (child) {
 176                         child->__rb_parent_color = pc;
 177                         rebalance = NULL;
 178                 } else
 179                         rebalance = __rb_is_black(pc) ? parent : NULL;
 180                 tmp = parent;
 181         } else if (!child) {
 182                 /* Still case 1, but this time the child is node->rb_left */
 183                 tmp->__rb_parent_color = pc = node->__rb_parent_color;
 184                 parent = __rb_parent(pc);
 185                 __rb_change_child(node, tmp, parent, root);
 186                 rebalance = NULL;
 187                 tmp = parent;
 188         } else {
 189                 struct rb_node *successor = child, *child2;
 190
 191                 tmp = child->rb_left;
 192                 if (!tmp) {
 193                         /*
 194                          * Case 2: node's successor is its right child
 195                          *
 196                          *    (n)          (s)
 197                          *    / \          / \
 198                          *  (x) (s)  ->  (x) (c)
 199                          *        \
 200                          *        (c)
 201                          */
 202                         parent = successor;
 203                         child2 = successor->rb_right;
 204
 205                         augment->copy(node, successor);
 206                 } else {
 207                         /*
 208                          * Case 3: node's successor is leftmost under
 209                          * node's right child subtree
 210                          *
 211                          *    (n)          (s)
 212                          *    / \          / \
 213                          *  (x) (y)  ->  (x) (y)
 214                          *      /            /
 215                          *    (p)          (p)
 216                          *    /            /
 217                          *  (s)          (c)
 218                          *    \
 219                          *    (c)
 220                          */
 221                         do {
 222                                 parent = successor;
 223                                 successor = tmp;
 224                                 tmp = tmp->rb_left;
 225                         } while (tmp);
 226                         child2 = successor->rb_right;
 227                         WRITE_ONCE(parent->rb_left, child2);
 228                         WRITE_ONCE(successor->rb_right, child);
 229                         rb_set_parent(child, successor);
 230
 231                         augment->copy(node, successor);
 232                         augment->propagate(parent, successor);
 233                 }
 234
 235                 tmp = node->rb_left;
 236                 WRITE_ONCE(successor->rb_left, tmp);
 237                 rb_set_parent(tmp, successor);
 238
 239                 pc = node->__rb_parent_color;
 240                 tmp = __rb_parent(pc);
 241                 __rb_change_child(node, successor, tmp, root);
 242
 243                 if (child2) {
 244                         successor->__rb_parent_color = pc;
 245                         rb_set_parent_color(child2, parent, RB_BLACK);
 246                         rebalance = NULL;
 247                 } else {
 248                         unsigned long pc2 = successor->__rb_parent_color;
 249                         successor->__rb_parent_color = pc;
 250                         rebalance = __rb_is_black(pc2) ? parent : NULL;
 251                 }
 252                 tmp = successor;
 253         }
 254
 255         augment->propagate(tmp, NULL);
 256         return rebalance;
 257 }
 258
 259 static __always_inline void
 260 rb_erase_augmented(struct rb_node *node, struct rb_root *root,
 261                    const struct rb_augment_callbacks *augment)
 262 {
 263         struct rb_node *rebalance = __rb_erase_augmented(node, root,
 264                                                          NULL, augment);
 265         if (rebalance)
 266                 __rb_erase_color(rebalance, root, augment->rotate);
 267 }
 268
 269 static __always_inline void
 270 rb_erase_augmented_cached(struct rb_node *node, struct rb_root_cached *root,
 271                           const struct rb_augment_callbacks *augment)
 272 {
 273         struct rb_node *rebalance = __rb_erase_augmented(node, &root->rb_root,
 274                                                          &root->rb_leftmost,
 275                                                          augment);
 276         if (rebalance)
 277                 __rb_erase_color(rebalance, &root->rb_root, augment->rotate);
 278 }
 279
 280 #endif  /* _LINUX_RBTREE_AUGMENTED_H */