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Subject: [RFC PATCH 1/1] Lib: btree_blue - A simple btree with linear
 travesal and more V3
From:   liuwf <liuwf@mailbox.org>
To:     linux-kernel@vger.kernel.org
Date:   Tue, 25 Apr 2023 02:39:51 -0400
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This (V3) is a explanation-fixed version, some text "node" should be "keys"
in note.

btree_blue is a simple btree whose algorithm implementation comes from 
Joern Engel's lib/btree. btree_blue extended lib/btree with several features
and optimizations:

	Add Two-Way links between leaf-nodes to offer a fast linear traversal.
	
	Insert, search, delete are relatively fast comparing with lib/btree, rbtee
	when an extended plain bytes searching is applied, even if choosing a big
	node size(4K) btree_blue is still a bit faster than other trees.
	I implememted the extended plain bytes search which is some faster than 
	binary search, although it is targeted to work in 64 slots, it seems 
	still faster than binary search in 256 slots (in 4096 bytes node size).
	
	The 0 for the value of key itself is allowed.
	
	Node size can be variable in 256, 512, 1024, 2K, 4K, or 192, 384 ...
	
	Key has sizes of one long, two long, four long (32-bit OS).


Joern Engel's lib/btree represents an elegance in logical and is fast and 
effective(100% slots usage ...). When I decided to add features based on it
like two-way links between leaf-nodes, bigger node sizes (and more, hope in 
the feature) which are required in many practices, I found it is a challenge 
to keep speed and slots usage with lib/btree, so I have to give several 
optimizings to keep or get more performance. 

Here are results of a simple test, the results may be unfair for some objects, 
for example, maple tree is RCU-safe and can deal with many complex cases, 
rbtree support duplicated keys, lib/btree's grace has virtue itself ....

For the fast linear traversal, I do not give a contrast test, and I think 
results would not be on an order of magnitude over those who have not direct 
links between nodes.


1. btree_blue with a fast plain byte comparing version

btree_blue use node size of 512 bytes in header part of the test, then 4096
bytes size.

On 512 bytes size node, leaf node has slots usage of 15/16 and can be higher
like 31/32 in 1K size node ..., non-leaf nodes keep 100% slots usage.


# 1000000 keys inserts to a empty tree ...

btree_blue is faster than 29% (btree),	130% (rbtree),	313% (maple tree)

maple tree 1000000 inserts use time: 	989232430 ns
rbtree 1000000 inserts use time: 	552244351 ns
btree 1000000 inserts use time: 	310080508 ns
btree_blue 1000000 inserts use time: 	238926066 ns


# 1000000 keys searches ...

btree_blue, btree and maple_tree got almost the same rate, and are all faster 
nealy 100% than rbtree.

maple tree 1000000 searches use time: 	241619833 ns
rbtree 1000000 searches use time: 	421757078 ns
btree 1000000 searches use time: 	232226540 ns
btree_blue 1000000 searches use time: 	220941629 ns


# 1000000 mixed insert + delete based on a tree which has 1000000 keys ...

btree_blue is faster than 28% (btree),	132% (rbtree),	307% (maple_tree)

maple tree 1000000 mixed insert + delete use time: 	2321929510 ns
rbtree 1000000 mixed insert + delete use time: 		1325037376 ns
btree 1000000 mixed insert + delete use time: 		 734110187 ns
btree_blue 1000000 mixed insert + delete use time: 	 569514235 ns


# delete a tree which has 1000000 keys to empty ...

btree_blue is faster than 34% (btree),	117% (rbtree),	613% (maple_tree)

maple tree 1000000 deletes use time: 	1606556096 ns
rbtree 1000000 deletes use time: 	 489245700 ns
btree 1000000 deletes use time: 	 301982693 ns
btree_blue 1000000 deletes use time: 	 224875145 ns


btree_blue uses a big node size of 4096 bytes


# 1000000 keys inserts to a empty tree ...

maple tree 1000000 inserts use time: 	1006161194 ns
rbtree 1000000 inserts use time: 	 582635990 ns
btree 1000000 inserts use time: 	 311212510 ns
btree_blue 1000000 inserts use time: 	 323870887 ns


# 1000000 keys searches ...

maple tree 1000000 searches use time: 	260520956 ns
rbtree 1000000 searches use time: 	459984150 ns
btree 1000000 searches use time: 	242243634 ns
btree_blue 1000000 searches use time: 	207793404 ns


# 1000000 mixed insert + delete based on a tree which has 1000000 keys ...

maple tree 1000000 mixed insert + delete use time: 		2316355888 ns
rbtree 1000000 mixed insert + delete use time: 			1499731734 ns
btree 1000000 mixed insert + delete use time: 			 761392377 ns
btree_blue 1000000 mixed insert + delete use time: 		 737142324 ns


# delete a tree which has 1000000 keys to empty ...

maple tree 1000000 deletes use time: 				1616467751 ns
rbtree 1000000 deletes use time: 				 570675402 ns
btree 1000000 deletes use time: 				 299528612 ns
btree_blue 1000000 deletes use time: 				 226293835 ns


2. btree_blue with binary search version

btree_blue uses node size of 512 bytes in header part of the test then 4096 
bytes size.


# 1000000 keys inserts to a empty tree ...

maple tree 1000000 inserts use time: 	1007482573 ns
rbtree 1000000 inserts use time:	 552520109 ns
btree 1000000 inserts use time: 	 311470955 ns
btree_blue 1000000 inserts use time: 	 305165271 ns


# 1000000 keys searches ...

maple tree 1000000 searches use time: 	248842879 ns
rbtree 1000000 searches use time: 	459954315 ns
btree 1000000 searches use time: 	239902063 ns
btree_blue 1000000 searches use time: 	251252337 ns


# 1000000 mixed insert + delete based on a tree which has 1000000 keys ...

maple tree 1000000 mixed insert + delete use time: 	2279468017 ns
rbtree 1000000 mixed insert + delete use time: 		1567305915 ns
btree 1000000 mixed insert + delete use time: 		 742089882 ns
btree_blue 1000000 mixed insert + delete use time: 	 679494846 ns


# delete a tree which has 1000000 keys to empty ...

maple tree 1000000 deletes use time: 	1630034161 ns
rbtree 1000000 deletes use time: 	 561434384 ns
btree 1000000 deletes use time: 	 317263337 ns
btree_blue 1000000 deletes use time: 	 252872063 ns


# btree_blue uses node size of 4096 bytes


# 1000000 keys inserts to a empty tree ...

maple tree 1000000 inserts use time: 	1013781694 ns
rbtree 1000000 inserts use time: 	 549275685 ns
btree 1000000 inserts use time: 	 314653894 ns
btree_blue 1000000 inserts use time: 	 395352766 ns


# 1000000 keys searches ...

maple tree 1000000 searches use time: 	256280986 ns
rbtree 1000000 searches use time: 	453439598 ns
btree 1000000 searches use time: 	243705745 ns
btree_blue 1000000 searches use time: 	241042481 ns


# 1000000 mixed insert + delete based on a tree which has 1000000 keys ...

maple tree 1000000 mixed insert + delete use time: 	2319430653 ns
rbtree 1000000 mixed insert + delete use time: 		1440130422 ns
btree 1000000 mixed insert + delete use time: 		 742443694 ns
btree_blue 1000000 mixed insert + delete use time: 	 886005615 ns


# delete a tree which has 1000000 keys to empty ...

maple tree 1000000 deletes use time: 		1618646788 ns
rbtree 1000000 deletes use time: 		 554263247 ns
btree 1000000 deletes use time: 		 314184624 ns
btree_blue 1000000 deletes use time: 		 258111208 ns

Signed-off-by: Liu Weifeng 4019c26b5c0d5f6b <liuwf@mailbox.org>
---
 include/linux/btree_blue.h |   83 +++
 lib/Kconfig                |    4 +
 lib/Makefile               |    1 +
 lib/btree_blue.c           | 1007 ++++++++++++++++++++++++++++++++++++
 4 files changed, 1095 insertions(+)
 create mode 100644 include/linux/btree_blue.h
 create mode 100644 lib/btree_blue.c

diff --git a/include/linux/btree_blue.h b/include/linux/btree_blue.h
new file mode 100644
index 000000000000..67a20752d0f6
--- /dev/null
+++ b/include/linux/btree_blue.h
@@ -0,0 +1,83 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef BTREE_BLUE_H
+#define BTREE_BLUE_H
+
+#include <linux/kernel.h>
+#include <linux/mempool.h>
+
+#define MAX_TREE_HEIGHT 8
+#define MIN_SLOTS_NUMBER 16
+#define MIN_NODE_SIZE (MIN_SLOTS_NUMBER * 2 * sizeof(unsigned long))
+
+#define GET_PREV 0
+#define GET_NEXT 1
+
+struct btree_blue_head;
+struct btree_blue_node_cb;
+
+struct btree_blue_head {
+	unsigned long *node;
+	mempool_t *mempool;
+
+	u16 node_size;
+	u16 stub_base;
+	u8 keylen;
+	u8 slot_width;
+	u8 height;
+	u8 reserved[1];
+
+	u16 vols[MAX_TREE_HEIGHT + 1];
+};
+
+void *btree_blue_alloc(gfp_t gfp_mask, void *pool_data);
+
+void btree_blue_free(void *element, void *pool_data);
+
+int __must_check btree_blue_init(struct btree_blue_head *head,
+				 int node_size_in_byte, int key_len_in_byte,
+				 int flags);
+
+void btree_blue_destroy(struct btree_blue_head *head);
+
+void *btree_blue_lookup(struct btree_blue_head *head, unsigned long *key);
+
+int __must_check btree_blue_insert(struct btree_blue_head *head,
+				   unsigned long *key, void *val, gfp_t gfp);
+
+int btree_blue_update(struct btree_blue_head *head, unsigned long *key,
+		      void *val);
+
+void *btree_blue_remove(struct btree_blue_head *head, unsigned long *key);
+
+void *btree_blue_first(struct btree_blue_head *head, unsigned long *__key);
+void *btree_blue_last(struct btree_blue_head *head, unsigned long *__key);
+
+void *btree_blue_get_prev(struct btree_blue_head *head, unsigned long *__key);
+void *btree_blue_get_next(struct btree_blue_head *head, unsigned long *__key);
+
+typedef bool (*btree_blue_traverse_FN_T)(const unsigned long *key,
+					 const void *val);
+
+/*
+ * Visit each key-value pair started from the @key and continue toward
+ * @prev_or_next until the last or fisrt.
+ *
+ * IF @key is given NULL, visit starts with the last(the biggest) key and walk
+ * toward the smallest.
+ *
+ * @prev_or_next, bool value to specify the visit direction.
+ *
+ * @callback. Your function that is called in the visit loop with each key-value
+ * visited.
+ * If a function like : bool myfunc(const unsigned long *key, const void *val)
+ * is given to the param @callback, you will see every *key and *val from the
+ * start @key(included, and it's value). Your function's return value of 0
+ * indicates to continue visit and 1 to exit the loop.
+ *
+ * */
+size_t btree_blue_traverse_from_key(struct btree_blue_head *head,
+				    unsigned long *key,
+				    btree_blue_traverse_FN_T callback,
+				    bool prev_or_next);
+
+#endif
diff --git a/lib/Kconfig b/lib/Kconfig
index 9bbf8a4b2108..a0e185ddf389 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -464,6 +464,10 @@ config TEXTSEARCH_FSM
 
 config BTREE
 	bool
+	
+config BTREE_BLUE
+	tristate
+	default m
 
 config INTERVAL_TREE
 	bool
diff --git a/lib/Makefile b/lib/Makefile
index 59bd7c2f793a..fe37f467d219 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -154,6 +154,7 @@ obj-$(CONFIG_TRACE_MMIO_ACCESS) += trace_readwrite.o
 obj-$(CONFIG_GENERIC_HWEIGHT) += hweight.o
 
 obj-$(CONFIG_BTREE) += btree.o
+obj-$(CONFIG_BTREE_BLUE) += btree_blue.o
 obj-$(CONFIG_INTERVAL_TREE) += interval_tree.o
 obj-$(CONFIG_ASSOCIATIVE_ARRAY) += assoc_array.o
 obj-$(CONFIG_DEBUG_PREEMPT) += smp_processor_id.o
diff --git a/lib/btree_blue.c b/lib/btree_blue.c
new file mode 100644
index 000000000000..57412f52a7f0
--- /dev/null
+++ b/lib/btree_blue.c
@@ -0,0 +1,1007 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/btree_blue.h>
+#include <linux/cache.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+
+#define LONG_PER_U64 (64 / BITS_PER_LONG)
+#define MAX_KEYLEN (2 * LONG_PER_U64)
+#define VALUE_LEN (sizeof(unsigned long))
+
+struct btree_blue_slots_info {
+#if (BITS_PER_LONG == 32)
+	u16 slots_nr;
+	u16 offset;
+#else
+	u16 slots_nr;
+	u16 offset;
+	u16 reserved_a;
+	u16 reserved_b;
+#endif
+};
+
+struct btree_blue_node_cb {
+	struct btree_blue_slots_info slots_info;
+	unsigned long slots_base[];
+};
+
+struct btree_blue_stub {
+	unsigned long *prev;
+	unsigned long *next;
+};
+
+static struct kmem_cache *btree_blue_cachep;
+
+void *btree_blue_alloc(gfp_t gfp_mask, void *pool_data)
+{
+	return kmem_cache_alloc(btree_blue_cachep, gfp_mask);
+}
+EXPORT_SYMBOL_GPL(btree_blue_alloc);
+
+void btree_blue_free(void *element, void *pool_data)
+{
+	kmem_cache_free(btree_blue_cachep, element);
+}
+EXPORT_SYMBOL_GPL(btree_blue_free);
+
+static unsigned long *btree_blue_node_alloc(struct btree_blue_head *head,
+					    gfp_t gfp)
+{
+	unsigned long *node;
+
+	node = mempool_alloc(head->mempool, gfp);
+	if (likely(node))
+		memset(node, 0, head->node_size);
+	return node;
+}
+
+static int longcmp(const unsigned long *l1, const unsigned long *l2, size_t n)
+{
+	size_t i;
+
+	for (i = 0; i < n; i++) {
+		if (l1[i] < l2[i])
+			return -1;
+		if (l1[i] > l2[i])
+			return 1;
+	}
+	return 0;
+}
+
+static unsigned long *longcpy(unsigned long *dest, const unsigned long *src,
+			      size_t n)
+{
+	size_t i;
+
+	for (i = 0; i < n; i++)
+		dest[i] = src[i];
+	return dest;
+}
+
+static unsigned long *bkey(struct btree_blue_head *head,
+			   struct btree_blue_node_cb *cb, int n)
+{
+	return cb->slots_base + (cb->slots_info.offset + n) * head->slot_width +
+	       1;
+}
+
+static void *bval(struct btree_blue_head *head, struct btree_blue_node_cb *cb,
+		  int n)
+{
+	return (void *)(cb->slots_base[(cb->slots_info.offset + n) *
+				       head->slot_width]);
+}
+
+static void setkey(struct btree_blue_head *head, struct btree_blue_node_cb *cb,
+		   int n, unsigned long *key)
+{
+	longcpy(bkey(head, cb, n), key, head->keylen);
+}
+
+static void setval(struct btree_blue_head *head, struct btree_blue_node_cb *cb,
+		   int n, void *val)
+{
+	cb->slots_base[(cb->slots_info.offset + n) * head->slot_width] =
+		(unsigned long)val;
+}
+
+static int keycmp(struct btree_blue_head *head, struct btree_blue_node_cb *cb,
+		  int pos, unsigned long *key)
+{
+	return longcmp(bkey(head, cb, pos), key, head->keylen);
+}
+
+static int getpos(struct btree_blue_head *head, struct btree_blue_node_cb *cb,
+		  unsigned long *key)
+{
+	int i, o, x, nr, p, c;
+
+	nr = cb->slots_info.slots_nr;
+	x = nr / 8;
+
+	for (i = 1; i <= x; i++) {
+		p = i * 8 - 1;
+		c = keycmp(head, cb, p, key);
+		if (c < 0) {
+			o = (i - 1) * 8;
+			for (i = 0; i < 7; i++) {
+				p = o + i;
+				c = keycmp(head, cb, p, key);
+				if (c <= 0)
+					return p;
+			}
+			return o + 7;
+		} else if (c == 0)
+			return p;
+	}
+
+	o = x * 8;
+	for (i = 0; i < nr % 8; i++) {
+		p = o + i;
+		c = keycmp(head, cb, p, key);
+		if (c <= 0)
+			return p;
+	}
+
+	return nr;
+}
+
+static int geteqv(struct btree_blue_head *head, struct btree_blue_node_cb *cb,
+		  unsigned long *key)
+{
+	int i, o, x, nr, p, c;
+
+	nr = cb->slots_info.slots_nr;
+	x = nr / 8;
+
+	for (i = 1; i <= x; i++) {
+		p = i * 8 - 1;
+		c = keycmp(head, cb, p, key);
+		if (c < 0) {
+			o = (i - 1) * 8;
+			for (i = 0; i < 7; i++) {
+				p = o + i;
+				c = keycmp(head, cb, p, key);
+				if (c == 0)
+					return p;
+			}
+			return nr;
+		} else if (c == 0)
+			return p;
+	}
+
+	o = x * 8;
+	for (i = 0; i < nr % 8; i++) {
+		p = o + i;
+		c = keycmp(head, cb, p, key);
+		if (c == 0)
+			return p;
+	}
+
+	return nr;
+}
+
+/*
+static int getpos_bin(struct btree_blue_head *head,
+		      struct btree_blue_node_cb *cb, unsigned long *key)
+{
+	int l = 0;
+	int h = cb->slots_info.slots_nr;
+	int m, ret;
+
+	while (l < h) {
+		m = (l + h) / 2;
+		ret = keycmp(head, cb, m, key);
+
+		if (ret < 0)
+			h = m;
+		else if (ret > 0)
+			l = m + 1;
+		else
+			return m;
+	}
+
+	return h;
+}
+
+static int geteqv_bin(struct btree_blue_head *head,
+		      struct btree_blue_node_cb *cb, unsigned long *key)
+{
+	int l = 0;
+	int h = cb->slots_info.slots_nr;
+	int m, ret;
+
+	while (l < h) {
+		m = (l + h) / 2;
+		ret = keycmp(head, cb, m, key);
+
+		if (ret < 0)
+			h = m;
+		else if (ret > 0)
+			l = m + 1;
+		else
+			return m;
+	}
+
+	return cb->slots_info.slots_nr;
+}
+ */
+
+static inline struct btree_blue_stub *__get_stub(struct btree_blue_head *head,
+						 struct btree_blue_node_cb *cb)
+{
+	return (struct btree_blue_stub *)((char *)cb + head->stub_base);
+}
+
+static inline void _shift_slots(struct btree_blue_head *head,
+				struct btree_blue_node_cb *cb, int dest_slot,
+				int src_slot, size_t slots_nr)
+{
+	unsigned long *d =
+		cb->slots_base +
+		(cb->slots_info.offset + dest_slot) * head->slot_width;
+	unsigned long *s = cb->slots_base + (cb->slots_info.offset + src_slot) *
+						    head->slot_width;
+
+	size_t n = slots_nr * head->slot_width * sizeof(long);
+
+	memmove(d, s, n);
+}
+
+static inline void _transfer_slots(struct btree_blue_head *head,
+				   struct btree_blue_node_cb *dest,
+				   struct btree_blue_node_cb *src,
+				   int dest_slot, int src_slot, size_t slots_nr)
+{
+	unsigned long *d =
+		dest->slots_base +
+		(dest->slots_info.offset + dest_slot) * head->slot_width;
+	unsigned long *s =
+		src->slots_base +
+		(src->slots_info.offset + src_slot) * head->slot_width;
+
+	size_t n = slots_nr * head->slot_width * sizeof(long);
+
+	memmove(d, s, n);
+}
+
+static inline int shift_slots_on_insert(struct btree_blue_head *head,
+					struct btree_blue_node_cb *node,
+					int pos, int level)
+{
+	int slots_nr = node->slots_info.slots_nr;
+	_shift_slots(head, node, pos + 1, pos, slots_nr - pos);
+	node->slots_info.slots_nr++;
+	return pos;
+}
+
+static inline void delete_slot(struct btree_blue_head *head,
+			       struct btree_blue_node_cb *node, int pos,
+			       int level)
+{
+	int slots_nr = node->slots_info.slots_nr;
+	_shift_slots(head, node, pos, pos + 1, slots_nr - pos - 1);
+	node->slots_info.slots_nr--;
+}
+
+static inline void split_to_empty(struct btree_blue_head *head,
+				  struct btree_blue_node_cb *dest,
+				  struct btree_blue_node_cb *src, int level)
+{
+	int slots_nr = src->slots_info.slots_nr / 2;
+
+	_transfer_slots(head, dest, src, 0, 0, slots_nr);
+	dest->slots_info.slots_nr += slots_nr;
+
+	_shift_slots(head, src, 0, slots_nr,
+		     src->slots_info.slots_nr - slots_nr);
+	src->slots_info.slots_nr -= slots_nr;
+}
+
+static inline void merge_nodes(struct btree_blue_head *head,
+			       struct btree_blue_node_cb *dest,
+			       struct btree_blue_node_cb *src, int level)
+{
+	int dest_nr, src_nr;
+
+	dest_nr = dest->slots_info.slots_nr;
+	src_nr = src->slots_info.slots_nr;
+
+	_transfer_slots(head, dest, src, dest_nr, 0, src_nr);
+	dest->slots_info.slots_nr += src_nr;
+}
+
+void *btree_blue_first(struct btree_blue_head *head, unsigned long *__key)
+{
+	int height = head->height;
+	struct btree_blue_node_cb *node =
+		(struct btree_blue_node_cb *)head->node;
+
+	if (height == 0)
+		return NULL;
+
+	for (; height > 1; height--)
+		node = bval(head, node, node->slots_info.slots_nr - 1);
+
+	longcpy(__key, bkey(head, node, node->slots_info.slots_nr - 1),
+		head->keylen);
+	return bval(head, node, node->slots_info.slots_nr - 1);
+}
+EXPORT_SYMBOL_GPL(btree_blue_first);
+
+void *btree_blue_last(struct btree_blue_head *head, unsigned long *__key)
+{
+	int height = head->height;
+	struct btree_blue_node_cb *node =
+		(struct btree_blue_node_cb *)head->node;
+
+	if (height == 0)
+		return NULL;
+	for (; height > 1; height--)
+		node = bval(head, node, 0);
+
+	longcpy(__key, bkey(head, node, 0), head->keylen);
+	return bval(head, node, 0);
+}
+EXPORT_SYMBOL_GPL(btree_blue_last);
+
+static unsigned long *btree_blue_lookup_node(struct btree_blue_head *head,
+					     unsigned long *key)
+{
+	int height = head->height;
+	int pos;
+	struct btree_blue_node_cb *node =
+		(struct btree_blue_node_cb *)head->node;
+
+	if (height == 0)
+		return NULL;
+
+	for (; height > 1; height--) {
+		pos = getpos(head, node, key);
+		/*pos = getpos_bin(head, node, key);*/
+		if (pos == node->slots_info.slots_nr)
+			return NULL;
+
+		node = bval(head, node, pos);
+	}
+	return (unsigned long *)node;
+}
+
+void *btree_blue_lookup(struct btree_blue_head *head, unsigned long *key)
+{
+	int i;
+	struct btree_blue_node_cb *node;
+
+	node = (struct btree_blue_node_cb *)btree_blue_lookup_node(head, key);
+	if (!node)
+		return NULL;
+
+	i = geteqv(head, node, key);
+	/*i = geteqv_bin(head, node, key);*/
+	if (i == node->slots_info.slots_nr)
+		return NULL;
+
+	return bval(head, node, i);
+}
+EXPORT_SYMBOL_GPL(btree_blue_lookup);
+
+int btree_blue_update(struct btree_blue_head *head, unsigned long *key,
+		      void *val)
+{
+	int pos;
+	struct btree_blue_node_cb *node;
+
+	node = (struct btree_blue_node_cb *)btree_blue_lookup_node(head, key);
+	if (!node)
+		return -ENOENT;
+
+	pos = geteqv(head, node, key);
+	/*pos = geteqv_bin(head, node, key);*/
+
+	if (pos == node->slots_info.slots_nr)
+		return -ENOENT;
+
+	setval(head, node, pos, val);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(btree_blue_update);
+
+void *btree_blue_prev_or_next(struct btree_blue_head *head,
+			      unsigned long *__key, int flag)
+{
+	int i;
+	struct btree_blue_node_cb *node;
+	unsigned long key[MAX_KEYLEN];
+	int slots_nr;
+
+	if (head->height == 0)
+		return NULL;
+
+	longcpy(key, __key, head->keylen);
+
+	node = (struct btree_blue_node_cb *)btree_blue_lookup_node(head, key);
+	if (!node)
+		return NULL;
+
+	slots_nr = node->slots_info.slots_nr;
+	for (i = 0; i < slots_nr; i++)
+		if (keycmp(head, node, i, key) == 0)
+			break;
+	if (i == slots_nr)
+		return NULL;
+
+	if (flag == GET_PREV) {
+		if (++i < slots_nr) {
+			longcpy(__key, bkey(head, node, i), head->keylen);
+			return bval(head, node, i);
+		} else {
+			struct btree_blue_stub *stub = __get_stub(head, node);
+			if (stub->next) {
+				node = (struct btree_blue_node_cb *)(stub->next);
+				longcpy(__key, bkey(head, node, 0),
+					head->keylen);
+				return bval(head, node, 0);
+			} else
+				return NULL;
+		}
+	}
+
+	/* GET_NEXT  */
+
+	if (i > 0) {
+		--i;
+		longcpy(__key, bkey(head, node, i), head->keylen);
+		return bval(head, node, i);
+	} else {
+		struct btree_blue_stub *stub = __get_stub(head, node);
+		if (stub->prev) {
+			node = (struct btree_blue_node_cb *)(stub->prev);
+			longcpy(__key,
+				bkey(head, node, node->slots_info.slots_nr - 1),
+				head->keylen);
+			return bval(head, node, 0);
+		} else
+			return NULL;
+	}
+}
+
+void *btree_blue_get_prev(struct btree_blue_head *head, unsigned long *__key)
+{
+	return btree_blue_prev_or_next(head, __key, GET_PREV);
+}
+EXPORT_SYMBOL_GPL(btree_blue_get_prev);
+
+void *btree_blue_get_next(struct btree_blue_head *head, unsigned long *__key)
+{
+	return btree_blue_prev_or_next(head, __key, GET_NEXT);
+}
+EXPORT_SYMBOL_GPL(btree_blue_get_next);
+
+size_t btree_blue_traverse_from_key(struct btree_blue_head *head,
+				    unsigned long *key,
+				    btree_blue_traverse_FN_T callback,
+				    bool prev_or_next)
+{
+	struct btree_blue_node_cb *node;
+	struct btree_blue_stub *stub;
+	int i, slots_nr, height;
+	bool term;
+	unsigned long found_key[MAX_KEYLEN];
+	unsigned long found_val;
+	size_t total = 0;
+
+	height = head->height;
+	if (height == 0)
+		return total;
+
+	node = (struct btree_blue_node_cb *)(head->node);
+
+	if (key == NULL) {
+		for (; height > 1; height--)
+			node = bval(head, node, 0);
+
+		i = 0;
+		slots_nr = node->slots_info.slots_nr;
+		longcpy(found_key, bkey(head, node, i), head->keylen);
+		found_val = (unsigned long)bval(head, node, i);
+		term = callback((const unsigned long *)(&found_key),
+				(const void *)found_val);
+		total++;
+		if (term)
+			return total;
+		else
+			goto TRAVERSE;
+	}
+
+	node = (struct btree_blue_node_cb *)btree_blue_lookup_node(head, key);
+	if (!node)
+		return total;
+
+	slots_nr = node->slots_info.slots_nr;
+	for (i = 0; i < slots_nr; i++)
+		if (keycmp(head, node, i, (unsigned long *)key) == 0)
+			break;
+
+	if (i == slots_nr)
+		return total;
+
+	longcpy(found_key, bkey(head, node, i), head->keylen);
+	found_val = (unsigned long)bval(head, node, i);
+	term = callback((const unsigned long *)(&found_key),
+			(const void *)found_val);
+	total++;
+	if (term)
+		return total;
+
+TRAVERSE:
+
+	if (prev_or_next == GET_PREV) {
+		i = i + 1;
+		do {
+			if (i < slots_nr) {
+				longcpy(found_key, bkey(head, node, i),
+					head->keylen);
+				found_val = (unsigned long)bval(head, node, i);
+				term = callback(
+					(const unsigned long *)(&found_key),
+					(const void *)found_val);
+				total++;
+				if (term)
+					return total;
+				i++;
+			} else {
+				stub = __get_stub(head, node);
+				if (stub->next) {
+					node = (struct btree_blue_node_cb
+							*)(stub->next);
+					slots_nr = node->slots_info.slots_nr;
+					i = 0;
+				} else
+					return total;
+			}
+		} while (true);
+	}
+
+	/* GET_NEXT */
+	i = i - 1;
+	do {
+		if (i >= 0) {
+			longcpy(found_key, bkey(head, node, i), head->keylen);
+			found_val = (unsigned long)bval(head, node, i);
+			term = callback((const unsigned long *)(&found_key),
+					(const void *)found_val);
+			total++;
+			if (term)
+				return total;
+			i--;
+		} else {
+			stub = __get_stub(head, node);
+			if (stub->prev) {
+				node = (struct btree_blue_node_cb *)(stub->prev);
+				i = node->slots_info.slots_nr - 1;
+			} else
+				return total;
+		}
+	} while (true);
+}
+EXPORT_SYMBOL_GPL(btree_blue_traverse_from_key);
+
+static unsigned long *find_level(struct btree_blue_head *head,
+				 unsigned long *key, int level,
+				 struct btree_blue_node_cb **cb_p)
+{
+	struct btree_blue_node_cb *node =
+		(struct btree_blue_node_cb *)head->node;
+	struct btree_blue_node_cb *node_p = node;
+	int height = head->height;
+	int pos;
+
+	for (; height > level; height--) {
+		pos = getpos(head, node, key);
+		/*pos = getpos_bin(head, node, key);*/
+		if (pos == node->slots_info.slots_nr) {
+			/* right-most key is too large, update it */
+			/* FIXME: If the right-most key on higher levels is
+			 * always zero, this wouldn't be necessary. */
+			pos--;
+			setkey(head, node, pos, key);
+		}
+
+		BUG_ON(pos < 0);
+		node_p = node;
+		node = bval(head, node, pos);
+	}
+
+	BUG_ON(!node);
+
+	if (cb_p)
+		*cb_p = node_p;
+
+	return (unsigned long *)node;
+}
+
+static int btree_blue_grow(struct btree_blue_head *head, gfp_t gfp)
+{
+	struct btree_blue_node_cb *node, *node_h;
+
+	node = (struct btree_blue_node_cb *)btree_blue_node_alloc(head, gfp);
+	if (!node)
+		return -ENOMEM;
+
+	if (likely(head->node)) {
+		node_h = (struct btree_blue_node_cb *)head->node;
+		setkey(head, node, 0,
+		       bkey(head, node_h, node_h->slots_info.slots_nr - 1));
+		setval(head, node, 0, head->node);
+		node->slots_info.slots_nr = 1;
+	}
+
+	head->node = (unsigned long *)node;
+	head->height++;
+
+	return 0;
+}
+
+static void btree_blue_shrink(struct btree_blue_head *head)
+{
+	struct btree_blue_node_cb *node;
+
+	if (head->height <= 1)
+		return;
+
+	node = (struct btree_blue_node_cb *)head->node;
+	BUG_ON(node->slots_info.slots_nr > 1);
+
+	head->node = bval(head, node, 0);
+	head->height--;
+
+	mempool_free(node, head->mempool);
+}
+
+static int btree_blue_insert_level(struct btree_blue_head *head,
+				   unsigned long *key, void *val, int level,
+				   struct btree_blue_node_cb *found, gfp_t gfp)
+{
+	struct btree_blue_node_cb *cb, *cb_new, *cb_p;
+	int pos, slots_nr, err;
+
+	BUG_ON(!val);
+
+	if (head->height < level) {
+		err = btree_blue_grow(head, gfp);
+		if (err)
+			return err;
+
+		found = 0;
+	}
+
+	//retry:
+
+	if (found) {
+		cb = found;
+		cb_p = NULL;
+	} else
+		cb = (struct btree_blue_node_cb *)find_level(head, key, level,
+							     &cb_p);
+
+	pos = getpos(head, cb, key);
+	/*pos = getpos_bin(head, cb, key);*/
+
+	slots_nr = cb->slots_info.slots_nr;
+
+	/* two identical keys are not allowed */
+	BUG_ON(pos < slots_nr && keycmp(head, cb, pos, key) == 0);
+
+	if (slots_nr == head->vols[level]) {
+		/* need to split node */
+		struct btree_blue_node_cb *cb_prev;
+		struct btree_blue_stub *stub, *stub_new, *stub_prev;
+
+		cb_new = (struct btree_blue_node_cb *)btree_blue_node_alloc(
+			head, gfp);
+		if (!cb_new)
+			return -ENOMEM;
+
+		err = btree_blue_insert_level(head,
+					      bkey(head, cb, slots_nr / 2 - 1),
+					      cb_new, level + 1, cb_p, gfp);
+		if (err) {
+			mempool_free(cb_new, head->mempool);
+			return err;
+		}
+
+		if (level == 1) {
+			stub = __get_stub(head, cb);
+			stub_new = __get_stub(head, cb_new);
+			stub_new->next = (unsigned long *)cb;
+
+			if (stub->prev) {
+				cb_prev = (struct btree_blue_node_cb
+						   *)(stub->prev);
+				stub_prev = __get_stub(head, cb_prev);
+				stub_prev->next = (unsigned long *)cb_new;
+				stub_new->prev = stub->prev;
+			}
+			stub->prev = (unsigned long *)cb_new;
+		}
+
+		split_to_empty(head, cb_new, cb, level);
+
+		if (pos <= (slots_nr / 2 - 1)) {
+			slots_nr = slots_nr / 2;
+			cb = cb_new;
+		} else {
+			pos = pos - slots_nr / 2;
+			slots_nr = slots_nr - slots_nr / 2;
+		}
+	}
+
+	BUG_ON(slots_nr >= head->vols[level]);
+
+	/* shift and insert */
+	pos = shift_slots_on_insert(head, cb, pos, level);
+	setkey(head, cb, pos, key);
+	setval(head, cb, pos, val);
+
+	return 0;
+}
+
+int btree_blue_insert(struct btree_blue_head *head, unsigned long *key,
+		      void *val, gfp_t gfp)
+{
+	BUG_ON(!val);
+	return btree_blue_insert_level(head, key, val, 1, 0, gfp);
+}
+EXPORT_SYMBOL_GPL(btree_blue_insert);
+
+static void *btree_blue_remove_level(struct btree_blue_head *head,
+				     unsigned long *key, int level);
+
+static void merge(struct btree_blue_head *head, int level,
+		  struct btree_blue_node_cb *cb_left,
+		  struct btree_blue_node_cb *cb_right,
+		  struct btree_blue_node_cb *cb_parent, int lpos)
+{
+	struct btree_blue_node_cb *cb_right_right;
+
+	struct btree_blue_stub *stub_left, *stub_right, *stub_right_right;
+
+	/* Move all keys to the left */
+	merge_nodes(head, cb_left, cb_right, level);
+
+	if (level == 1) {
+		stub_left = __get_stub(head, cb_left);
+		stub_right = __get_stub(head, cb_right);
+
+		if (stub_right->next) {
+			stub_left->next = stub_right->next;
+
+			cb_right_right =
+				(struct btree_blue_node_cb *)(stub_right->next);
+			stub_right_right = __get_stub(head, cb_right_right);
+			stub_right_right->prev = (unsigned long *)cb_left;
+		} else
+			stub_left->next = NULL;
+	}
+
+	/* Exchange left and right child in parent */
+	setval(head, cb_parent, lpos, cb_right);
+	setval(head, cb_parent, lpos + 1, cb_left);
+	/* Remove left (formerly right) child from parent */
+	btree_blue_remove_level(head, bkey(head, cb_parent, lpos), level + 1);
+	mempool_free(cb_right, head->mempool);
+}
+
+static void rebalance(struct btree_blue_head *head, unsigned long *key,
+		      int level, struct btree_blue_node_cb *cb_child,
+		      struct btree_blue_node_cb *cb_p)
+{
+	struct btree_blue_node_cb *cb_parent, *cb_left, *cb_right;
+	struct btree_blue_stub *stub_child, *stub_left, *stub_right;
+	int i;
+	int slots_nr, slots_nr_left, slots_nr_right;
+
+	slots_nr = cb_child->slots_info.slots_nr;
+
+	if (slots_nr == 0) {
+		/* Because we don't steal entries from a neighbour, this case
+		 * can happen.  Parent node contains a single child, this
+		 * node, so merging with a sibling never happens.
+		 */
+		btree_blue_remove_level(head, key, level + 1);
+
+		if (level == 1) {
+			stub_child = __get_stub(head, cb_child);
+			if (stub_child->prev) {
+				cb_left = (struct btree_blue_node_cb
+						   *)(stub_child->prev);
+				stub_left = __get_stub(head, cb_left);
+				stub_left->next = stub_child->next ?
+								stub_child->next :
+								NULL;
+			}
+
+			if (stub_child->next) {
+				cb_right = (struct btree_blue_node_cb
+						    *)(stub_child->next);
+				stub_right = __get_stub(head, cb_right);
+				stub_right->prev = stub_child->prev ?
+								 stub_child->prev :
+								 NULL;
+			}
+		}
+
+		mempool_free(cb_child, head->mempool);
+		return;
+	}
+
+	cb_parent = cb_p;
+
+	i = getpos(head, cb_parent, key);
+	/*i = getpos_bin(head, cb_parent, key);*/
+
+	BUG_ON(bval(head, cb_parent, i) != cb_child);
+
+	if (i > 0) {
+		cb_left = bval(head, cb_parent, i - 1);
+		slots_nr_left = cb_left->slots_info.slots_nr;
+
+		if (slots_nr_left + slots_nr <= head->vols[level]) {
+			merge(head, level, cb_left, cb_child, cb_parent, i - 1);
+			return;
+		}
+	}
+
+	if (i + 1 < cb_parent->slots_info.slots_nr) {
+		cb_right = bval(head, cb_parent, i + 1);
+
+		slots_nr_right = cb_right->slots_info.slots_nr;
+
+		if (slots_nr + slots_nr_right <= head->vols[level]) {
+			merge(head, level, cb_child, cb_right, cb_parent, i);
+			return;
+		}
+	}
+	/*
+	 * We could also try to steal one entry from the left or right
+	 * neighbor.  By not doing so we changed the invariant from
+	 * "all nodes are at least half full" to "no two neighboring
+	 * nodes can be merged".  Which means that the average fill of
+	 * all nodes is still half or better.
+	 */
+}
+
+static void *btree_blue_remove_level(struct btree_blue_head *head,
+				     unsigned long *key, int level)
+{
+	struct btree_blue_node_cb *cb, *cb_p;
+	int pos;
+	void *ret;
+
+	if (level > head->height) {
+		/* we recursed all the way up */
+		head->height = 0;
+		head->node = NULL;
+		return NULL;
+	}
+
+	cb = (struct btree_blue_node_cb *)find_level(head, key, level, &cb_p);
+	pos = getpos(head, cb, key);
+	/*pos = getpos_bin(head, cb, key);*/
+
+	if ((level == 1) && (pos == cb->slots_info.slots_nr))
+		return NULL;
+
+	ret = bval(head, cb, pos);
+
+	/* remove and shift */
+	delete_slot(head, cb, pos, level);
+
+	if (cb->slots_info.slots_nr < head->vols[level] / 2) {
+		if (level < head->height)
+			rebalance(head, key, level, cb, cb_p);
+		else if (cb->slots_info.slots_nr == 1)
+			btree_blue_shrink(head);
+	}
+
+	return ret;
+}
+
+void *btree_blue_remove(struct btree_blue_head *head, unsigned long *key)
+{
+	if (head->height == 0)
+		return NULL;
+
+	return btree_blue_remove_level(head, key, 1);
+}
+EXPORT_SYMBOL_GPL(btree_blue_remove);
+
+static inline void __btree_blue_init(struct btree_blue_head *head,
+				     int node_size, int keylen, int flags)
+{
+	int vol;
+
+	head->node = NULL;
+	head->height = 0;
+
+	head->node_size = node_size;
+
+	head->keylen = (keylen * 8) / BITS_PER_LONG;
+
+	head->slot_width = (VALUE_LEN * 8) / BITS_PER_LONG + head->keylen;
+
+	vol = (node_size - sizeof(struct btree_blue_node_cb)) /
+	      (head->slot_width * sizeof(long));
+	for (int i = 2; i < MAX_TREE_HEIGHT + 1; i++)
+		head->vols[i] = vol;
+	vol = (node_size - sizeof(struct btree_blue_node_cb) -
+	       sizeof(struct btree_blue_stub)) /
+	      (head->slot_width * sizeof(long));
+	head->vols[0] = head->vols[1] = vol;
+
+	head->stub_base = sizeof(struct btree_blue_node_cb) +
+			  head->vols[1] * (head->slot_width * sizeof(long));
+}
+
+int __must_check btree_blue_init(struct btree_blue_head *head,
+				 int node_size_in_byte, int key_len_in_byte,
+				 int flags)
+{
+	if (node_size_in_byte % L1_CACHE_BYTES)
+		return -EINVAL;
+
+	if ((node_size_in_byte < MIN_NODE_SIZE) ||
+	    (node_size_in_byte > PAGE_SIZE))
+		return -EINVAL;
+
+#if defined(CONFIG_64BIT) || defined(BUILD_VDSO32_64)
+	if ((key_len_in_byte != sizeof(unsigned long)) &&
+	    (key_len_in_byte != 2 * sizeof(unsigned long)))
+		return -EINVAL;
+#else
+	if ((key_len_in_byte != sizeof(unsigned long)) &&
+	    (key_len_in_byte != 2 * sizeof(unsigned long)) &&
+	    (key_len_in_byte != 4 * sizeof(unsigned long)))
+		return -EINVAL;
+#endif
+
+	btree_blue_cachep = kmem_cache_create("btree_blue_node_cb",
+					      node_size_in_byte, 0,
+					      SLAB_HWCACHE_ALIGN, NULL);
+	if (!btree_blue_cachep)
+		return -ENOMEM;
+
+	__btree_blue_init(head, node_size_in_byte, key_len_in_byte, flags);
+
+	head->mempool =
+		mempool_create(0, btree_blue_alloc, btree_blue_free, NULL);
+	if (!head->mempool)
+		return -ENOMEM;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(btree_blue_init);
+
+void btree_blue_destroy(struct btree_blue_head *head)
+{
+	mempool_free(head->node, head->mempool);
+	mempool_destroy(head->mempool);
+	head->mempool = NULL;
+}
+EXPORT_SYMBOL_GPL(btree_blue_destroy);
+
+static int __init btree_blue_module_init(void)
+{
+	return 0;
+}
+
+static void __exit btree_blue_module_exit(void)
+{
+	kmem_cache_destroy(btree_blue_cachep);
+}
+
+module_init(btree_blue_module_init);
+module_exit(btree_blue_module_exit);
+
+MODULE_LICENSE("GPL");

base-commit: 93f875a8526a291005e7f38478079526c843cbec
-- 
2.30.2