s390/numa: add topology tree infrastructure

NUMA emulation needs proper means to mangle the book/mc/core topology
of the machine. The topology tree (toptree) consistently maintains cpu
masks for the root, each node, and all leaves of the tree while the
user may use the toptree functions to rearrange the tree in various
ways.

This patch contains several changes from Michael Holzheu.
Signed-off-by: Philipp Hachtmann <phacht@linux.vnet.ibm.com>
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/numa/Makefile

 obj-y			+= numa.o
+obj-y			+= toptree.o

arch/s390/numa/toptree.c

+/*
+ * NUMA support for s390
+ *
+ * A tree structure used for machine topology mangling
+ *
+ * Copyright IBM Corp. 2015
+ */
+
+#include <linux/kernel.h>
+#include <linux/cpumask.h>
+#include <linux/list.h>
+#include <linux/list_sort.h>
+#include <linux/slab.h>
+#include <asm/numa.h>
+
+#include "toptree.h"
+
+/**
+ * toptree_alloc - Allocate and initialize a new tree node.
+ * @level: The node's vertical level; level 0 contains the leaves.
+ * @id: ID number, explicitly not unique beyond scope of node's siblings
+ *
+ * Allocate a new tree node and initialize it.
+ *
+ * RETURNS:
+ * Pointer to the new tree node or NULL on error
+ */
+struct toptree *toptree_alloc(int level, int id)
+{
+	struct toptree *res = kzalloc(sizeof(struct toptree), GFP_KERNEL);
+
+	if (!res)
+		return res;
+
+	INIT_LIST_HEAD(&res->children);
+	INIT_LIST_HEAD(&res->sibling);
+	cpumask_clear(&res->mask);
+	res->level = level;
+	res->id = id;
+	return res;
+}
+
+/**
+ * toptree_remove - Remove a tree node from a tree
+ * @cand: Pointer to the node to remove
+ *
+ * The node is detached from its parent node. The parent node's
+ * masks will be updated to reflect the loss of the child.
+ */
+static void toptree_remove(struct toptree *cand)
+{
+	struct toptree *oldparent;
+
+	list_del_init(&cand->sibling);
+	oldparent = cand->parent;
+	cand->parent = NULL;
+	toptree_update_mask(oldparent);
+}
+
+/**
+ * toptree_free - discard a tree node
+ * @cand: Pointer to the tree node to discard
+ *
+ * Checks if @cand is attached to a parent node. Detaches it
+ * cleanly using toptree_remove. Possible children are freed
+ * recursively. In the end @cand itself is freed.
+ */
+void toptree_free(struct toptree *cand)
+{
+	struct toptree *child, *tmp;
+
+	if (cand->parent)
+		toptree_remove(cand);
+	toptree_for_each_child_safe(child, tmp, cand)
+		toptree_free(child);
+	kfree(cand);
+}
+
+/**
+ * toptree_update_mask - Update node bitmasks
+ * @cand: Pointer to a tree node
+ *
+ * The node's cpumask will be updated by combining all children's
+ * masks. Then toptree_update_mask is called recursively for the
+ * parent if applicable.
+ *
+ * NOTE:
+ * This must not be called on leaves. If called on a leaf, its
+ * CPU mask is cleared and lost.
+ */
+void toptree_update_mask(struct toptree *cand)
+{
+	struct toptree *child;
+
+	cpumask_clear(&cand->mask);
+	list_for_each_entry(child, &cand->children, sibling)
+		cpumask_or(&cand->mask, &cand->mask, &child->mask);
+	if (cand->parent)
+		toptree_update_mask(cand->parent);
+}
+
+/**
+ * toptree_insert - Insert a tree node into tree
+ * @cand: Pointer to the node to insert
+ * @target: Pointer to the node to which @cand will added as a child
+ *
+ * Insert a tree node into a tree. Masks will be updated automatically.
+ *
+ * RETURNS:
+ * 0 on success, -1 if NULL is passed as argument or the node levels
+ * don't fit.
+ */
+static int toptree_insert(struct toptree *cand, struct toptree *target)
+{
+	if (!cand || !target)
+		return -1;
+	if (target->level != (cand->level + 1))
+		return -1;
+	list_add_tail(&cand->sibling, &target->children);
+	cand->parent = target;
+	toptree_update_mask(target);
+	return 0;
+}
+
+/**
+ * toptree_move_children - Move all child nodes of a node to a new place
+ * @cand: Pointer to the node whose children are to be moved
+ * @target: Pointer to the node to which @cand's children will be attached
+ *
+ * Take all child nodes of @cand and move them using toptree_move.
+ */
+static void toptree_move_children(struct toptree *cand, struct toptree *target)
+{
+	struct toptree *child, *tmp;
+
+	toptree_for_each_child_safe(child, tmp, cand)
+		toptree_move(child, target);
+}
+
+/**
+ * toptree_unify - Merge children with same ID
+ * @cand: Pointer to node whose direct children should be made unique
+ *
+ * When mangling the tree it is possible that a node has two or more children
+ * which have the same ID. This routine merges these children into one and
+ * moves all children of the merged nodes into the unified node.
+ */
+void toptree_unify(struct toptree *cand)
+{
+	struct toptree *child, *tmp, *cand_copy;
+
+	/* Threads cannot be split, cores are not split */
+	if (cand->level < 2)
+		return;
+
+	cand_copy = toptree_alloc(cand->level, 0);
+	toptree_for_each_child_safe(child, tmp, cand) {
+		struct toptree *tmpchild;
+
+		if (!cpumask_empty(&child->mask)) {
+			tmpchild = toptree_get_child(cand_copy, child->id);
+			toptree_move_children(child, tmpchild);
+		}
+		toptree_free(child);
+	}
+	toptree_move_children(cand_copy, cand);
+	toptree_free(cand_copy);
+
+	toptree_for_each_child(child, cand)
+		toptree_unify(child);
+}
+
+/**
+ * toptree_move - Move a node to another context
+ * @cand: Pointer to the node to move
+ * @target: Pointer to the node where @cand should go
+ *
+ * In the easiest case @cand is exactly on the level below @target
+ * and will be immediately moved to the target.
+ *
+ * If @target's level is not the direct parent level of @cand,
+ * nodes for the missing levels are created and put between
+ * @cand and @target. The "stacking" nodes' IDs are taken from
+ * @cand's parents.
+ *
+ * After this it is likely to have redundant nodes in the tree
+ * which are addressed by means of toptree_unify.
+ */
+void toptree_move(struct toptree *cand, struct toptree *target)
+{
+	struct toptree *stack_target, *real_insert_point, *ptr, *tmp;
+
+	if (cand->level + 1 == target->level) {
+		toptree_remove(cand);
+		toptree_insert(cand, target);
+		return;
+	}
+
+	real_insert_point = NULL;
+	ptr = cand;
+	stack_target = NULL;
+
+	do {
+		tmp = stack_target;
+		stack_target = toptree_alloc(ptr->level + 1,
+					     ptr->parent->id);
+		toptree_insert(tmp, stack_target);
+		if (!real_insert_point)
+			real_insert_point = stack_target;
+		ptr = ptr->parent;
+	} while (stack_target->level < (target->level - 1));
+
+	toptree_remove(cand);
+	toptree_insert(cand, real_insert_point);
+	toptree_insert(stack_target, target);
+}
+
+/**
+ * toptree_get_child - Access a tree node's child by its ID
+ * @cand: Pointer to tree node whose child is to access
+ * @id: The desired child's ID
+ *
+ * @cand's children are searched for a child with matching ID.
+ * If no match can be found, a new child with the desired ID
+ * is created and returned.
+ */
+struct toptree *toptree_get_child(struct toptree *cand, int id)
+{
+	struct toptree *child;
+
+	toptree_for_each_child(child, cand)
+		if (child->id == id)
+			return child;
+	child = toptree_alloc(cand->level-1, id);
+	toptree_insert(child, cand);
+	return child;
+}
+
+/**
+ * toptree_first - Find the first descendant on specified level
+ * @context: Pointer to tree node whose descendants are to be used
+ * @level: The level of interest
+ *
+ * RETURNS:
+ * @context's first descendant on the specified level, or NULL
+ * if there is no matching descendant
+ */
+struct toptree *toptree_first(struct toptree *context, int level)
+{
+	struct toptree *child, *tmp;
+
+	if (context->level == level)
+		return context;
+
+	if (!list_empty(&context->children)) {
+		list_for_each_entry(child, &context->children, sibling) {
+			tmp = toptree_first(child, level);
+			if (tmp)
+				return tmp;
+		}
+	}
+	return NULL;
+}
+
+/**
+ * toptree_next_sibling - Return next sibling
+ * @cur: Pointer to a tree node
+ *
+ * RETURNS:
+ * If @cur has a parent and is not the last in the parent's children list,
+ * the next sibling is returned. Or NULL when there are no siblings left.
+ */
+static struct toptree *toptree_next_sibling(struct toptree *cur)
+{
+	if (cur->parent == NULL)
+		return NULL;
+
+	if (cur == list_last_entry(&cur->parent->children,
+				   struct toptree, sibling))
+		return NULL;
+	return (struct toptree *) list_next_entry(cur, sibling);
+}
+
+/**
+ * toptree_next - Tree traversal function
+ * @cur: Pointer to current element
+ * @context: Pointer to the root node of the tree or subtree to
+ * be traversed.
+ * @level: The level of interest.
+ *
+ * RETURNS:
+ * Pointer to the next node on level @level
+ * or NULL when there is no next node.
+ */
+struct toptree *toptree_next(struct toptree *cur, struct toptree *context,
+			     int level)
+{
+	struct toptree *cur_context, *tmp;
+
+	if (!cur)
+		return NULL;
+
+	if (context->level == level)
+		return NULL;
+
+	tmp = toptree_next_sibling(cur);
+	if (tmp != NULL)
+		return tmp;
+
+	cur_context = cur;
+	while (cur_context->level < context->level - 1) {
+		/* Step up */
+		cur_context = cur_context->parent;
+		/* Step aside */
+		tmp = toptree_next_sibling(cur_context);
+		if (tmp != NULL) {
+			/* Step down */
+			tmp = toptree_first(tmp, level);
+			if (tmp != NULL)
+				return tmp;
+		}
+	}
+	return NULL;
+}
+
+/**
+ * toptree_count - Count descendants on specified level
+ * @context: Pointer to node whose descendants are to be considered
+ * @level: Only descendants on the specified level will be counted
+ *
+ * RETURNS:
+ * Number of descendants on the specified level
+ */
+int toptree_count(struct toptree *context, int level)
+{
+	struct toptree *cur;
+	int cnt = 0;
+
+	toptree_for_each(cur, context, level)
+		cnt++;
+	return cnt;
+}

arch/s390/numa/toptree.h

+/*
+ * NUMA support for s390
+ *
+ * A tree structure used for machine topology mangling
+ *
+ * Copyright IBM Corp. 2015
+ */
+#ifndef S390_TOPTREE_H
+#define S390_TOPTREE_H
+
+#include <linux/cpumask.h>
+#include <linux/list.h>
+
+struct toptree {
+	int level;
+	int id;
+	cpumask_t mask;
+	struct toptree *parent;
+	struct list_head sibling;
+	struct list_head children;
+};
+
+struct toptree *toptree_alloc(int level, int id);
+void toptree_free(struct toptree *cand);
+void toptree_update_mask(struct toptree *cand);
+void toptree_unify(struct toptree *cand);
+struct toptree *toptree_get_child(struct toptree *cand, int id);
+void toptree_move(struct toptree *cand, struct toptree *target);
+int toptree_count(struct toptree *context, int level);
+
+struct toptree *toptree_first(struct toptree *context, int level);
+struct toptree *toptree_next(struct toptree *cur, struct toptree *context,
+			     int level);
+
+#define toptree_for_each_child(child, ptree)				\
+	list_for_each_entry(child,  &ptree->children, sibling)
+
+#define toptree_for_each_child_safe(child, ptmp, ptree)			\
+	list_for_each_entry_safe(child, ptmp, &ptree->children, sibling)
+
+#define toptree_is_last(ptree)					\
+	((ptree->parent == NULL) ||				\
+	 (ptree->parent->children.prev == &ptree->sibling))
+
+#define toptree_for_each(ptree, cont, ttype)		\
+	for (ptree = toptree_first(cont, ttype);	\
+	     ptree != NULL;				\
+	     ptree = toptree_next(ptree, cont, ttype))
+
+#define toptree_for_each_safe(ptree, tmp, cont, ttype)		\
+	for (ptree = toptree_first(cont, ttype),		\
+		     tmp = toptree_next(ptree, cont, ttype);	\
+	     ptree != NULL;					\
+	     ptree = tmp,					\
+		     tmp = toptree_next(ptree, cont, ttype))
+
+#define toptree_for_each_sibling(ptree, start)			\
+	toptree_for_each(ptree, start->parent, start->level)
+
+#endif /* S390_TOPTREE_H */