v4.19.13 snapshot.
diff --git a/include/linux/interval_tree_generic.h b/include/linux/interval_tree_generic.h
new file mode 100644
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+++ b/include/linux/interval_tree_generic.h
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+/*
+ Interval Trees
+ (C) 2012 Michel Lespinasse <walken@google.com>
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+
+ include/linux/interval_tree_generic.h
+*/
+
+#include <linux/rbtree_augmented.h>
+
+/*
+ * Template for implementing interval trees
+ *
+ * ITSTRUCT: struct type of the interval tree nodes
+ * ITRB: name of struct rb_node field within ITSTRUCT
+ * ITTYPE: type of the interval endpoints
+ * ITSUBTREE: name of ITTYPE field within ITSTRUCT holding last-in-subtree
+ * ITSTART(n): start endpoint of ITSTRUCT node n
+ * ITLAST(n): last endpoint of ITSTRUCT node n
+ * ITSTATIC: 'static' or empty
+ * ITPREFIX: prefix to use for the inline tree definitions
+ *
+ * Note - before using this, please consider if generic version
+ * (interval_tree.h) would work for you...
+ */
+
+#define INTERVAL_TREE_DEFINE(ITSTRUCT, ITRB, ITTYPE, ITSUBTREE, \
+ ITSTART, ITLAST, ITSTATIC, ITPREFIX) \
+ \
+/* Callbacks for augmented rbtree insert and remove */ \
+ \
+static inline ITTYPE ITPREFIX ## _compute_subtree_last(ITSTRUCT *node) \
+{ \
+ ITTYPE max = ITLAST(node), subtree_last; \
+ if (node->ITRB.rb_left) { \
+ subtree_last = rb_entry(node->ITRB.rb_left, \
+ ITSTRUCT, ITRB)->ITSUBTREE; \
+ if (max < subtree_last) \
+ max = subtree_last; \
+ } \
+ if (node->ITRB.rb_right) { \
+ subtree_last = rb_entry(node->ITRB.rb_right, \
+ ITSTRUCT, ITRB)->ITSUBTREE; \
+ if (max < subtree_last) \
+ max = subtree_last; \
+ } \
+ return max; \
+} \
+ \
+RB_DECLARE_CALLBACKS(static, ITPREFIX ## _augment, ITSTRUCT, ITRB, \
+ ITTYPE, ITSUBTREE, ITPREFIX ## _compute_subtree_last) \
+ \
+/* Insert / remove interval nodes from the tree */ \
+ \
+ITSTATIC void ITPREFIX ## _insert(ITSTRUCT *node, \
+ struct rb_root_cached *root) \
+{ \
+ struct rb_node **link = &root->rb_root.rb_node, *rb_parent = NULL; \
+ ITTYPE start = ITSTART(node), last = ITLAST(node); \
+ ITSTRUCT *parent; \
+ bool leftmost = true; \
+ \
+ while (*link) { \
+ rb_parent = *link; \
+ parent = rb_entry(rb_parent, ITSTRUCT, ITRB); \
+ if (parent->ITSUBTREE < last) \
+ parent->ITSUBTREE = last; \
+ if (start < ITSTART(parent)) \
+ link = &parent->ITRB.rb_left; \
+ else { \
+ link = &parent->ITRB.rb_right; \
+ leftmost = false; \
+ } \
+ } \
+ \
+ node->ITSUBTREE = last; \
+ rb_link_node(&node->ITRB, rb_parent, link); \
+ rb_insert_augmented_cached(&node->ITRB, root, \
+ leftmost, &ITPREFIX ## _augment); \
+} \
+ \
+ITSTATIC void ITPREFIX ## _remove(ITSTRUCT *node, \
+ struct rb_root_cached *root) \
+{ \
+ rb_erase_augmented_cached(&node->ITRB, root, &ITPREFIX ## _augment); \
+} \
+ \
+/* \
+ * Iterate over intervals intersecting [start;last] \
+ * \
+ * Note that a node's interval intersects [start;last] iff: \
+ * Cond1: ITSTART(node) <= last \
+ * and \
+ * Cond2: start <= ITLAST(node) \
+ */ \
+ \
+static ITSTRUCT * \
+ITPREFIX ## _subtree_search(ITSTRUCT *node, ITTYPE start, ITTYPE last) \
+{ \
+ while (true) { \
+ /* \
+ * Loop invariant: start <= node->ITSUBTREE \
+ * (Cond2 is satisfied by one of the subtree nodes) \
+ */ \
+ if (node->ITRB.rb_left) { \
+ ITSTRUCT *left = rb_entry(node->ITRB.rb_left, \
+ ITSTRUCT, ITRB); \
+ if (start <= left->ITSUBTREE) { \
+ /* \
+ * Some nodes in left subtree satisfy Cond2. \
+ * Iterate to find the leftmost such node N. \
+ * If it also satisfies Cond1, that's the \
+ * match we are looking for. Otherwise, there \
+ * is no matching interval as nodes to the \
+ * right of N can't satisfy Cond1 either. \
+ */ \
+ node = left; \
+ continue; \
+ } \
+ } \
+ if (ITSTART(node) <= last) { /* Cond1 */ \
+ if (start <= ITLAST(node)) /* Cond2 */ \
+ return node; /* node is leftmost match */ \
+ if (node->ITRB.rb_right) { \
+ node = rb_entry(node->ITRB.rb_right, \
+ ITSTRUCT, ITRB); \
+ if (start <= node->ITSUBTREE) \
+ continue; \
+ } \
+ } \
+ return NULL; /* No match */ \
+ } \
+} \
+ \
+ITSTATIC ITSTRUCT * \
+ITPREFIX ## _iter_first(struct rb_root_cached *root, \
+ ITTYPE start, ITTYPE last) \
+{ \
+ ITSTRUCT *node, *leftmost; \
+ \
+ if (!root->rb_root.rb_node) \
+ return NULL; \
+ \
+ /* \
+ * Fastpath range intersection/overlap between A: [a0, a1] and \
+ * B: [b0, b1] is given by: \
+ * \
+ * a0 <= b1 && b0 <= a1 \
+ * \
+ * ... where A holds the lock range and B holds the smallest \
+ * 'start' and largest 'last' in the tree. For the later, we \
+ * rely on the root node, which by augmented interval tree \
+ * property, holds the largest value in its last-in-subtree. \
+ * This allows mitigating some of the tree walk overhead for \
+ * for non-intersecting ranges, maintained and consulted in O(1). \
+ */ \
+ node = rb_entry(root->rb_root.rb_node, ITSTRUCT, ITRB); \
+ if (node->ITSUBTREE < start) \
+ return NULL; \
+ \
+ leftmost = rb_entry(root->rb_leftmost, ITSTRUCT, ITRB); \
+ if (ITSTART(leftmost) > last) \
+ return NULL; \
+ \
+ return ITPREFIX ## _subtree_search(node, start, last); \
+} \
+ \
+ITSTATIC ITSTRUCT * \
+ITPREFIX ## _iter_next(ITSTRUCT *node, ITTYPE start, ITTYPE last) \
+{ \
+ struct rb_node *rb = node->ITRB.rb_right, *prev; \
+ \
+ while (true) { \
+ /* \
+ * Loop invariants: \
+ * Cond1: ITSTART(node) <= last \
+ * rb == node->ITRB.rb_right \
+ * \
+ * First, search right subtree if suitable \
+ */ \
+ if (rb) { \
+ ITSTRUCT *right = rb_entry(rb, ITSTRUCT, ITRB); \
+ if (start <= right->ITSUBTREE) \
+ return ITPREFIX ## _subtree_search(right, \
+ start, last); \
+ } \
+ \
+ /* Move up the tree until we come from a node's left child */ \
+ do { \
+ rb = rb_parent(&node->ITRB); \
+ if (!rb) \
+ return NULL; \
+ prev = &node->ITRB; \
+ node = rb_entry(rb, ITSTRUCT, ITRB); \
+ rb = node->ITRB.rb_right; \
+ } while (prev == rb); \
+ \
+ /* Check if the node intersects [start;last] */ \
+ if (last < ITSTART(node)) /* !Cond1 */ \
+ return NULL; \
+ else if (start <= ITLAST(node)) /* Cond2 */ \
+ return node; \
+ } \
+}