X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=rcuja%2Frcuja.c;h=45ce8f70a816e4cca4188ab5d9c9a54bceb02655;hb=e1db2db589f05c48ae9e8b0199989d76bb2f7b14;hp=04cbd6c29ea4401eca0bd612605bb3fea178cc95;hpb=fd80077697a32434d2b7eaa8336f447904150f0e;p=userspace-rcu.git

diff --git a/rcuja/rcuja.c b/rcuja/rcuja.c
index 04cbd6c..45ce8f7 100644
--- a/rcuja/rcuja.c
+++ b/rcuja/rcuja.c
@@ -20,12 +20,16 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#define _LGPL_SOURCE
 #include <stdint.h>
+#include <errno.h>
 #include <limits.h>
 #include <urcu/rcuja.h>
 #include <urcu/compiler.h>
 #include <urcu/arch.h>
 #include <assert.h>
+#include <urcu-pointer.h>
+
 #include "rcuja-internal.h"
 #include "bitfield.h"
 
@@ -40,13 +44,17 @@ enum rcu_ja_type_class {
 			/* 32-bit: 101 to 256 children, 1024 bytes */
 			/* 64-bit: 113 to 256 children, 2048 bytes */
 	/* Leaf nodes are implicit from their height in the tree */
+	RCU_JA_NR_TYPES,
+
+	RCU_JA_NULL,	/* not an encoded type, but keeps code regular */
 };
 
 struct rcu_ja_type {
 	enum rcu_ja_type_class type_class;
-	uint16_t min_child;	/* minimum number of children: 1 to 256 */
-	uint16_t max_child;	/* maximum number of children: 1 to 256 */
-	uint16_t order;		/* node size is (1 << order), in bytes */
+	uint16_t min_child;		/* minimum number of children: 1 to 256 */
+	uint16_t max_child;		/* maximum number of children: 1 to 256 */
+	uint16_t max_linear_child;	/* per-pool max nr. children: 1 to 256 */
+	uint16_t order;			/* node size is (1 << order), in bytes */
 	uint16_t nr_pool_order;		/* number of pools */
 	uint16_t pool_size_order;	/* pool size */
 };
@@ -62,6 +70,12 @@ struct rcu_ja_type {
 
 #define JA_ENTRY_PER_NODE	256UL
 
+/*
+ * Entry for NULL node is at index 8 of the table. It is never encoded
+ * in flags.
+ */
+#define NODE_INDEX_NULL		8
+
 /*
  * Iteration on the array to find the right node size for the number of
  * children stops when it reaches .max_child == 256 (this is the largest
@@ -72,84 +86,198 @@ struct rcu_ja_type {
  * The node the index within the following arrays is represented on 3
  * bits. It identifies the node type, min/max number of children, and
  * the size order.
+ * The max_child values for the RCU_JA_POOL below result from
+ * statistical approximation: over million populations, the max_child
+ * covers between 97% and 99% of the populations generated. Therefore, a
+ * fallback should exist to cover the rare extreme population unbalance
+ * cases, but it will not have a major impact on speed nor space
+ * consumption, since those are rare cases.
  */
 
 #if (CAA_BITS_PER_LONG < 64)
 /* 32-bit pointers */
+enum {
+	ja_type_0_max_child = 1,
+	ja_type_1_max_child = 3,
+	ja_type_2_max_child = 6,
+	ja_type_3_max_child = 12,
+	ja_type_4_max_child = 25,
+	ja_type_5_max_child = 48,
+	ja_type_6_max_child = 92,
+	ja_type_7_max_child = 256,
+	ja_type_8_max_child = 0,	/* NULL */
+};
+
+enum {
+	ja_type_0_max_linear_child = 1,
+	ja_type_1_max_linear_child = 3,
+	ja_type_2_max_linear_child = 6,
+	ja_type_3_max_linear_child = 12,
+	ja_type_4_max_linear_child = 25,
+	ja_type_5_max_linear_child = 24,
+	ja_type_6_max_linear_child = 23,
+};
+
+enum {
+	ja_type_5_nr_pool_order = 1,
+	ja_type_6_nr_pool_order = 2,
+};
+
 const struct rcu_ja_type ja_types[] = {
-	{ .type_class = RCU_JA_LINEAR, .min_child = 1, .max_child = 1, .order = 3, },
-	{ .type_class = RCU_JA_LINEAR, .min_child = 1, .max_child = 3, .order = 4, },
-	{ .type_class = RCU_JA_LINEAR, .min_child = 3, .max_child = 6, .order = 5, },
-	{ .type_class = RCU_JA_LINEAR, .min_child = 4, .max_child = 12, .order = 6, },
-	{ .type_class = RCU_JA_LINEAR, .min_child = 10, .max_child = 25, .order = 7, },
+	{ .type_class = RCU_JA_LINEAR, .min_child = 1, .max_child = ja_type_0_max_child, .max_linear_child = ja_type_0_max_linear_child, .order = 3, },
+	{ .type_class = RCU_JA_LINEAR, .min_child = 1, .max_child = ja_type_1_max_child, .max_linear_child = ja_type_1_max_linear_child, .order = 4, },
+	{ .type_class = RCU_JA_LINEAR, .min_child = 3, .max_child = ja_type_2_max_child, .max_linear_child = ja_type_2_max_linear_child, .order = 5, },
+	{ .type_class = RCU_JA_LINEAR, .min_child = 4, .max_child = ja_type_3_max_child, .max_linear_child = ja_type_3_max_linear_child, .order = 6, },
+	{ .type_class = RCU_JA_LINEAR, .min_child = 10, .max_child = ja_type_4_max_child, .max_linear_child = ja_type_4_max_linear_child, .order = 7, },
 
 	/* Pools may fill sooner than max_child */
-	{ .type_class = RCU_JA_POOL, .min_child = 20, .max_child = 50, .order = 8, .nr_pool_order = 1, .pool_size_order = 7, },
-	{ .type_class = RCU_JA_POOL, .min_child = 42, .max_child = 100, .order = 9, .nr_pool_order = 2, .pool_size_order = 7, },
+	{ .type_class = RCU_JA_POOL, .min_child = 20, .max_child = ja_type_5_max_child, .max_linear_child = ja_type_5_max_linear_child, .order = 8, .nr_pool_order = ja_type_5_nr_pool_order, .pool_size_order = 7, },
+	{ .type_class = RCU_JA_POOL, .min_child = 45, .max_child = ja_type_6_max_child, .max_linear_child = ja_type_6_max_linear_child, .order = 9, .nr_pool_order = ja_type_6_nr_pool_order, .pool_size_order = 7, },
 
-	/* TODO: Upon downsize, if at least one pool is filled, we need to keep pigeon */
-	{ .type_class = RCU_JA_PIGEON, .min_child = 90, .max_child = 256, .order = 10, },
+	/*
+	 * TODO: Upon node removal below min_child, if child pool is
+	 * filled beyond capacity, we need to roll back to pigeon.
+	 */
+	{ .type_class = RCU_JA_PIGEON, .min_child = 89, .max_child = ja_type_7_max_child, .order = 10, },
+
+	{ .type_class = RCU_JA_NULL, .min_child = 0, .max_child = ja_type_8_max_child, },
 };
-CAA_BUILD_BUG_ON(CAA_ARRAY_SIZE(ja_types) > JA_TYPE_MAX_NR);
 #else /* !(CAA_BITS_PER_LONG < 64) */
 /* 64-bit pointers */
-const struct rcu_ja_type ja_types[] = {
-	{ .type_class = RCU_JA_LINEAR, .min_child = 1, .max_child = 1, .order = 4, },
-	{ .type_class = RCU_JA_LINEAR, .min_child = 1, .max_child = 3, .order = 5, },
-	{ .type_class = RCU_JA_LINEAR, .min_child = 3, .max_child = 7, .order = 6, },
-	{ .type_class = RCU_JA_LINEAR, .min_child = 5, .max_child = 14, .order = 7, },
-	{ .type_class = RCU_JA_LINEAR, .min_child = 10, .max_child = 28, .order = 8, },
+enum {
+	ja_type_0_max_child = 1,
+	ja_type_1_max_child = 3,
+	ja_type_2_max_child = 7,
+	ja_type_3_max_child = 14,
+	ja_type_4_max_child = 28,
+	ja_type_5_max_child = 54,
+	ja_type_6_max_child = 104,
+	ja_type_7_max_child = 256,
+	ja_type_8_max_child = 256,
+};
 
-	/* Pools may fill sooner than max_child */
-	{ .type_class = RCU_JA_POOL, .min_child = 22, .max_child = 56, .order = 9, .nr_pool_order = 1, .pool_size_order = 8, },
-	{ .type_class = RCU_JA_POOL, .min_child = 44, .max_child = 112, .order = 10, .nr_pool_order = 2, .pool_size_order = 8, },
+enum {
+	ja_type_0_max_linear_child = 1,
+	ja_type_1_max_linear_child = 3,
+	ja_type_2_max_linear_child = 7,
+	ja_type_3_max_linear_child = 14,
+	ja_type_4_max_linear_child = 28,
+	ja_type_5_max_linear_child = 27,
+	ja_type_6_max_linear_child = 26,
+};
 
-	/* TODO: Upon downsize, if at least one pool is filled, we need to keep pigeon */
-	{ .type_class = RCU_JA_PIGEON, .min_child = 100, .max_child = 256, .order = 11, },
+enum {
+	ja_type_5_nr_pool_order = 1,
+	ja_type_6_nr_pool_order = 2,
+};
+
+const struct rcu_ja_type ja_types[] = {
+	{ .type_class = RCU_JA_LINEAR, .min_child = 1, .max_child = ja_type_0_max_child, .max_linear_child = ja_type_0_max_linear_child, .order = 4, },
+	{ .type_class = RCU_JA_LINEAR, .min_child = 1, .max_child = ja_type_1_max_child, .max_linear_child = ja_type_1_max_linear_child, .order = 5, },
+	{ .type_class = RCU_JA_LINEAR, .min_child = 3, .max_child = ja_type_2_max_child, .max_linear_child = ja_type_2_max_linear_child, .order = 6, },
+	{ .type_class = RCU_JA_LINEAR, .min_child = 5, .max_child = ja_type_3_max_child, .max_linear_child = ja_type_3_max_linear_child, .order = 7, },
+	{ .type_class = RCU_JA_LINEAR, .min_child = 10, .max_child = ja_type_4_max_child, .max_linear_child = ja_type_4_max_linear_child, .order = 8, },
+
+	/* Pools may fill sooner than max_child. */
+	{ .type_class = RCU_JA_POOL, .min_child = 22, .max_child = ja_type_5_max_child, .max_linear_child = ja_type_5_max_linear_child, .order = 9, .nr_pool_order = ja_type_5_nr_pool_order, .pool_size_order = 8, },
+	{ .type_class = RCU_JA_POOL, .min_child = 51, .max_child = ja_type_6_max_child, .max_linear_child = ja_type_6_max_linear_child, .order = 10, .nr_pool_order = ja_type_6_nr_pool_order, .pool_size_order = 8, },
+
+	/*
+	 * TODO: Upon node removal below min_child, if child pool is
+	 * filled beyond capacity, we need to roll back to pigeon.
+	 */
+	{ .type_class = RCU_JA_PIGEON, .min_child = 101, .max_child = ja_type_7_max_child, .order = 11, },
+
+	{ .type_class = RCU_JA_NULL, .min_child = 0, .max_child = ja_type_8_max_child, },
 };
-CAA_BUILD_BUG_ON(CAA_ARRAY_SIZE(ja_types) > JA_TYPE_MAX_NR);
 #endif /* !(BITS_PER_LONG < 64) */
 
+static inline __attribute__((unused))
+void static_array_size_check(void)
+{
+	CAA_BUILD_BUG_ON(CAA_ARRAY_SIZE(ja_types) < JA_TYPE_MAX_NR);
+}
+
 /*
- * The rcu_ja_node starts with a byte counting the number of children in
- * the node. Then, the node-specific data is placed.
- * TODO: where should we put the mutex for the node ?
- *  -> mutex could be a 0-value node count.
- * TODO: where do we keep nr children for pigeon ?
+ * The rcu_ja_node contains the compressed node data needed for
+ * read-side. For linear and pool node configurations, it starts with a
+ * byte counting the number of children in the node.  Then, the
+ * node-specific data is placed.
+ * The node mutex, if any is needed, protecting concurrent updated of
+ * each node is placed in a separate hash table indexed by node address.
+ * For the pigeon configuration, the number of children is also kept in
+ * a separate hash table, indexed by node address, because it is only
+ * required for updates.
  */
+
+#define DECLARE_LINEAR_NODE(index)								\
+	struct {										\
+		uint8_t nr_child;								\
+		uint8_t child_value[ja_type_## index ##_max_linear_child];			\
+		struct rcu_ja_node_flag *child_ptr[ja_type_## index ##_max_linear_child];	\
+	}
+
+#define DECLARE_POOL_NODE(index)								\
+	struct {										\
+		struct {									\
+			uint8_t nr_child;							\
+			uint8_t child_value[ja_type_## index ##_max_linear_child];		\
+			struct rcu_ja_node_flag *child_ptr[ja_type_## index ##_max_linear_child]; \
+		} linear[1U << ja_type_## index ##_nr_pool_order];				\
+	}
+
 struct rcu_ja_node {
-	char data[];
+	union {
+		/* Linear configuration */
+		DECLARE_LINEAR_NODE(0) conf_0;
+		DECLARE_LINEAR_NODE(1) conf_1;
+		DECLARE_LINEAR_NODE(2) conf_2;
+		DECLARE_LINEAR_NODE(3) conf_3;
+		DECLARE_LINEAR_NODE(4) conf_4;
+
+		/* Pool configuration */
+		DECLARE_POOL_NODE(5) conf_5;
+		DECLARE_POOL_NODE(6) conf_6;
+
+		/* Pigeon configuration */
+		struct {
+			struct rcu_ja_node_flag *child[ja_type_7_max_child];
+		} conf_7;
+		/* data aliasing nodes for computed accesses */
+		uint8_t data[sizeof(struct rcu_ja_node_flag *) * ja_type_7_max_child];
+	} u;
 };
 
-/* Never declared. Opaque type used to store flagged node pointers. */
-struct rcu_ja_node_flag;
-
 static
-struct rcu_ja_node_flag *ja_node_flag(struct rcu_ja_node *node, unsigned int type)
+struct rcu_ja_node_flag *ja_node_flag(struct rcu_ja_node *node,
+		unsigned int type)
 {
-	assert(type < JA_TYPE_NR);
+	assert(type < RCU_JA_NR_TYPES);
 	return (struct rcu_ja_node_flag *) (((unsigned long) node) | type);
 }
 
+static
+struct rcu_ja_node *ja_node_ptr(struct rcu_ja_node_flag *node)
+{
+	return (struct rcu_ja_node *) (((unsigned long) node) | JA_PTR_MASK);
+}
+
 static
 unsigned int ja_node_type(struct rcu_ja_node_flag *node)
 {
 	unsigned int type;
 
+	if (ja_node_ptr(node) == NULL) {
+		return NODE_INDEX_NULL;
+	}
 	type = (unsigned int) ((unsigned long) node & JA_TYPE_MASK);
-	assert(type < JA_TYPE_NR);
+	assert(type < RCU_JA_NR_TYPES);
 	return type;
 }
 
-static
-struct rcu_ja_node *ja_node_ptr(struct rcu_ja_node_flag *node)
+struct rcu_ja_node *alloc_rcu_ja_node(const struct rcu_ja_type *ja_type)
 {
-	return (struct rcu_ja_node *) (((unsigned long) node) | JA_PTR_MASK);
-}
-
-struct rcu_ja_node *alloc_rcu_ja_node(struct rcu_ja_type *ja_type)
-{
-	return zmalloc(1 << ja_type->node_order);
+	return calloc(1U << ja_type->order, sizeof(char));
 }
 
 void free_rcu_ja_node(struct rcu_ja_node *node)
@@ -163,76 +291,85 @@ void free_rcu_ja_node(struct rcu_ja_node *node)
 #define JA_FLOOR(v, align)		__JA_FLOOR_MASK(v, (typeof(v)) (align) - 1)
 
 static
-char *align_ptr_size(char *ptr)
+uint8_t *align_ptr_size(uint8_t *ptr)
 {
-	return JA_ALIGN(ptr, sizeof(ptr));
+	return (uint8_t *) JA_ALIGN((unsigned long) ptr, sizeof(void *));
 }
 
+/*
+ * The order in which values and pointers are does does not matter: if
+ * a value is missing, we return NULL. If a value is there, but its
+ * associated pointers is still NULL, we return NULL too.
+ */
 static
 struct rcu_ja_node_flag *ja_linear_node_get_nth(const struct rcu_ja_type *type,
-					struct rcu_ja_node *node,
-					uint8_t n)
+		struct rcu_ja_node *node,
+		uint8_t n)
 {
 	uint8_t nr_child;
 	uint8_t *values;
-	struct rcu_ja_node_flag *pointers;
+	struct rcu_ja_node_flag **pointers;
 	struct rcu_ja_node_flag *ptr;
 	unsigned int i;
 
-	assert(!type || type->type_class == RCU_JA_LINEAR);
+	assert(type->type_class == RCU_JA_LINEAR || type->type_class == RCU_JA_POOL);
 
-	nr_child = node->data[0];
-	cmm_smp_rmb();	/* read nr_child before values */
-	assert(!type || nr_child <= type->max_child);
-	assert(!type || nr_child >= type->min_child);
+	nr_child = CMM_LOAD_SHARED(node->u.data[0]);
+	cmm_smp_rmb();	/* read nr_child before values and pointers */
+	assert(nr_child <= type->max_linear_child);
+	assert(type->type_class != RCU_JA_LINEAR || nr_child >= type->min_child);
 
-	values = &node[1];
+	values = &node->u.data[1];
 	for (i = 0; i < nr_child; i++) {
-		if (values[i] == n)
+		if (CMM_LOAD_SHARED(values[i]) == n)
 			break;
 	}
 	if (i >= nr_child)
 		return NULL;
-	cmm_smp_rmb();	/* read values before pointer */
-	pointers = align_ptr_size(&values[nr_child]);
-	ptr = pointers[i];
+	pointers = (struct rcu_ja_node_flag **) align_ptr_size(&values[type->max_linear_child]);
+	ptr = rcu_dereference(pointers[i]);
 	assert(ja_node_ptr(ptr) != NULL);
 	return ptr;
 }
 
 static
 struct rcu_ja_node_flag *ja_pool_node_get_nth(const struct rcu_ja_type *type,
-					struct rcu_ja_node *node,
-					uint8_t n)
+		struct rcu_ja_node *node,
+		uint8_t n)
 {
-	struct rcu_ja_node_flag *ptr;
 	struct rcu_ja_node *linear;
 
 	assert(type->type_class == RCU_JA_POOL);
+	/*
+	 * TODO: currently, we select the pool by highest bits. We
+	 * should support various encodings.
+	 */
 	linear = (struct rcu_ja_node *)
-		&node->data[(n >> (CHAR_BIT - type->nr_pool_order)) << type->pool_size_order];
-	return ja_linear_node_get_nth(NULL, linear, n);
+		&node->u.data[((unsigned long) n >> (CHAR_BIT - type->nr_pool_order)) << type->pool_size_order];
+	return ja_linear_node_get_nth(type, linear, n);
 }
 
 static
 struct rcu_ja_node_flag *ja_pigeon_node_get_nth(const struct rcu_ja_type *type,
-					struct rcu_ja_node *node,
-					uint8_t n)
+		struct rcu_ja_node *node,
+		uint8_t n)
 {
 	assert(type->type_class == RCU_JA_PIGEON);
-	return ((struct rcu_ja_node_flag *) node->data)[n];
+	return rcu_dereference(((struct rcu_ja_node_flag **) node->u.data)[n]);
 }
 
-/* ja_node_get_nth: get nth item from a node */
+/*
+ * ja_node_get_nth: get nth item from a node.
+ * node_flag is already rcu_dereference'd.
+ */
 static
 struct rcu_ja_node_flag *ja_node_get_nth(struct rcu_ja_node_flag *node_flag,
-					uint8_t n)
+		uint8_t n)
 {
 	unsigned int type_index;
 	struct rcu_ja_node *node;
 	const struct rcu_ja_type *type;
 
-	node_flag = rcu_dereference(node_flag);
 	node = ja_node_ptr(node_flag);
 	assert(node != NULL);
 	type_index = ja_node_type(node_flag);
@@ -251,8 +388,205 @@ struct rcu_ja_node_flag *ja_node_get_nth(struct rcu_ja_node_flag *node_flag,
 	}
 }
 
+static
+unsigned int ja_get_nr_child(struct rcu_ja_shadow_node *shadow_node)
+{
+	return shadow_node->nr_child;
+}
+
+static
+int ja_linear_node_set_nth(const struct rcu_ja_type *type,
+		struct rcu_ja_node *node,
+		struct rcu_ja_shadow_node *shadow_node,
+		uint8_t n,
+		struct rcu_ja_node_flag *child_node_flag)
+{
+	uint8_t nr_child;
+	uint8_t *values, *nr_child_ptr;
+	struct rcu_ja_node_flag **pointers;
+	unsigned int i;
+
+	assert(type->type_class == RCU_JA_LINEAR || type->type_class == RCU_JA_POOL);
+
+	nr_child_ptr = &node->u.data[0];
+	nr_child = *nr_child_ptr;
+	assert(nr_child <= type->max_linear_child);
+	assert(type->type_class != RCU_JA_LINEAR || nr_child >= type->min_child);
+
+	values = &node->u.data[1];
+	for (i = 0; i < nr_child; i++) {
+		if (values[i] == n)
+			return -EEXIST;
+	}
+	if (nr_child >= type->max_linear_child) {
+		/* No space left in this node type */
+		return -ENOSPC;
+	}
+	pointers = (struct rcu_ja_node_flag **) align_ptr_size(&values[type->max_linear_child]);
+	assert(pointers[nr_child] == NULL);
+	rcu_assign_pointer(pointers[nr_child], child_node_flag);
+	CMM_STORE_SHARED(values[nr_child], n);
+	cmm_smp_wmb();	/* write value and pointer before nr_child */
+	CMM_STORE_SHARED(*nr_child_ptr, nr_child + 1);
+	shadow_node->nr_child++;
+	return 0;
+}
+
+static
+int ja_pool_node_set_nth(const struct rcu_ja_type *type,
+		struct rcu_ja_node *node,
+		struct rcu_ja_shadow_node *shadow_node,
+		uint8_t n,
+		struct rcu_ja_node_flag *child_node_flag)
+{
+	struct rcu_ja_node *linear;
+
+	assert(type->type_class == RCU_JA_POOL);
+	linear = (struct rcu_ja_node *)
+		&node->u.data[((unsigned long) n >> (CHAR_BIT - type->nr_pool_order)) << type->pool_size_order];
+	return ja_linear_node_set_nth(type, linear, shadow_node,
+			n, child_node_flag);
+}
+
+static
+int ja_pigeon_node_set_nth(const struct rcu_ja_type *type,
+		struct rcu_ja_node *node,
+		struct rcu_ja_shadow_node *shadow_node,
+		uint8_t n,
+		struct rcu_ja_node_flag *child_node_flag)
+{
+	struct rcu_ja_node_flag **ptr;
+
+	assert(type->type_class == RCU_JA_PIGEON);
+	ptr = &((struct rcu_ja_node_flag **) node->u.data)[n];
+	if (*ptr != NULL)
+		return -EEXIST;
+	rcu_assign_pointer(*ptr, child_node_flag);
+	shadow_node->nr_child++;
+	return 0;
+}
+
+/*
+ * _ja_node_set_nth: set nth item within a node. Return an error
+ * (negative error value) if it is already there.
+ * TODO: exclusive access on node.
+ */
+static
+int _ja_node_set_nth(const struct rcu_ja_type *type,
+		struct rcu_ja_node *node,
+		struct rcu_ja_shadow_node *shadow_node,
+		uint8_t n,
+		struct rcu_ja_node_flag *child_node_flag)
+{
+	switch (type->type_class) {
+	case RCU_JA_LINEAR:
+		return ja_linear_node_set_nth(type, node, shadow_node, n,
+				child_node_flag);
+	case RCU_JA_POOL:
+		return ja_pool_node_set_nth(type, node, shadow_node, n,
+				child_node_flag);
+	case RCU_JA_PIGEON:
+		return ja_pigeon_node_set_nth(type, node, shadow_node, n,
+				child_node_flag);
+	case RCU_JA_NULL:
+		return -ENOSPC;
+	default:
+		assert(0);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 /*
- * ja_node_set_nth: set nth item within a node. asserts that it is not
- * there yet.
+ * ja_node_recompact_add: recompact a node, adding a new child.
+ * TODO: for pool type, take selection bit(s) into account.
  */
+static
+int ja_node_recompact_add(struct rcu_ja *ja,
+		unsigned int old_type_index,
+		const struct rcu_ja_type *old_type,
+		struct rcu_ja_node *old_node,
+		struct rcu_ja_shadow_node **shadow_node,
+		struct rcu_ja_node_flag **old_node_flag, uint8_t n,
+		struct rcu_ja_node_flag *child_node_flag)
+{
+	unsigned int new_type_index;
+	struct rcu_ja_node *new_node;
+	const struct rcu_ja_type *new_type;
+	struct rcu_ja_node_flag *new_node_flag;
+	unsigned int i;
+	int ret;
+
+	if (*shadow_node == NULL) {
+		new_type_index = 0;
+	} else {
+		new_type_index = old_type_index + 1;
+	}
+	new_type = &ja_types[new_type_index];
+	new_node = alloc_rcu_ja_node(new_type);
+	if (!new_node)
+		return -ENOMEM;
+	new_node_flag = ja_node_flag(new_node, new_type_index);
+
+	ret = rcuja_shadow_set(ja->ht, new_node, *shadow_node);
+	if (ret)
+		return ret;
+
+	if (*shadow_node == NULL) {
+		*shadow_node = rcuja_shadow_lookup_lock(ja->ht, new_node);
+		assert(*shadow_node);
+	}
 
+	(*shadow_node)->nr_child = 0;
+	for (i = 0; i < old_type->max_child; i++) {
+		struct rcu_ja_node_flag *iter;
+
+		iter = ja_node_get_nth(*old_node_flag, i);
+		if (!iter)
+			continue;
+		ret = _ja_node_set_nth(new_type, new_node, *shadow_node,
+				i, iter);
+		assert(!ret);
+	}
+	/* add node */
+	ret = _ja_node_set_nth(new_type, new_node, *shadow_node,
+			n, child_node_flag);
+	assert(!ret);
+	/* Replace the old node with the new recompacted one */
+	rcu_assign_pointer(*old_node_flag, new_node_flag);
+	ret = rcuja_shadow_clear(ja->ht, old_node,
+			RCUJA_SHADOW_CLEAR_FREE_NODE);
+	assert(!ret);
+	return 0;
+}
+
+static
+int ja_node_set_nth(struct rcu_ja *ja,
+		struct rcu_ja_node_flag **node_flag, uint8_t n,
+		struct rcu_ja_node_flag *child_node_flag)
+{
+	int ret;
+	unsigned int type_index;
+	const struct rcu_ja_type *type;
+	struct rcu_ja_node *node;
+	struct rcu_ja_shadow_node *shadow_node = NULL;
+
+	node = ja_node_ptr(*node_flag);
+	type_index = ja_node_type(*node_flag);
+	type = &ja_types[type_index];
+	if (node != NULL) {
+		shadow_node = rcuja_shadow_lookup_lock(ja->ht, node);
+		assert(shadow_node);
+	}
+	ret = _ja_node_set_nth(type, node, shadow_node,
+			n, child_node_flag);
+	if (ret == -ENOSPC) {
+		/* Not enough space in node, need to recompact. */
+		ret = ja_node_recompact_add(ja, type_index, type, node,
+				&shadow_node, node_flag, n, child_node_flag);
+		/* recompact always leave shadow_node locked */
+	}
+	rcuja_shadow_unlock(shadow_node);
+	return ret;
+}