1 files changed, 167 insertions, 0 deletions
diff --git a/linux/generic-radix-tree.c b/linux/generic-radix-tree.c
new file mode 100644
index 00000000..5c4a275e
--- /dev/null
+++ b/linux/generic-radix-tree.c
@@ -0,0 +1,167 @@
+
+#include <linux/export.h>
+#include <linux/generic-radix-tree.h>
+#include <linux/gfp.h>
+
+#define GENRADIX_ARY		(PAGE_SIZE / sizeof(struct genradix_node *))
+#define GENRADIX_ARY_SHIFT	ilog2(GENRADIX_ARY)
+
+struct genradix_node {
+	union {
+		/* Interior node: */
+		struct genradix_node	*children[GENRADIX_ARY];
+
+		/* Leaf: */
+		u8			data[PAGE_SIZE];
+	};
+};
+
+static inline unsigned genradix_depth_shift(unsigned depth)
+{
+	return PAGE_SHIFT + GENRADIX_ARY_SHIFT * depth;
+}
+
+/*
+ * Returns size (of data, in bytes) that a tree of a given depth holds:
+ */
+static inline size_t genradix_depth_size(unsigned depth)
+{
+	return 1UL << genradix_depth_shift(depth);
+}
+
+/*
+ * Returns pointer to the specified byte @offset within @radix, or NULL if not
+ * allocated
+ */
+void *__genradix_ptr(struct __genradix *radix, size_t offset)
+{
+	size_t level = radix->depth;
+	struct genradix_node *n = radix->root;
+
+	if (offset >= genradix_depth_size(radix->depth))
+		return NULL;
+
+	while (1) {
+		if (!n)
+			return NULL;
+		if (!level)
+			break;
+
+		level--;
+
+		n = n->children[offset >> genradix_depth_shift(level)];
+		offset &= genradix_depth_size(level) - 1;
+	}
+
+	return &n->data[offset];
+}
+EXPORT_SYMBOL(__genradix_ptr);
+
+/*
+ * Returns pointer to the specified byte @offset within @radix, allocating it if
+ * necessary - newly allocated slots are always zeroed out:
+ */
+void *__genradix_ptr_alloc(struct __genradix *radix, size_t offset,
+			   gfp_t gfp_mask)
+{
+	struct genradix_node **n;
+	size_t level;
+
+	/* Increase tree depth if necessary: */
+
+	while (offset >= genradix_depth_size(radix->depth)) {
+		struct genradix_node *new_root =
+			(void *) __get_free_page(gfp_mask|__GFP_ZERO);
+
+		if (!new_root)
+			return NULL;
+
+		new_root->children[0] = radix->root;
+		radix->root = new_root;
+		radix->depth++;
+	}
+
+	n = &radix->root;
+	level = radix->depth;
+
+	while (1) {
+		if (!*n) {
+			*n = (void *) __get_free_page(gfp_mask|__GFP_ZERO);
+			if (!*n)
+				return NULL;
+		}
+
+		if (!level)
+			break;
+
+		level--;
+
+		n = &(*n)->children[offset >> genradix_depth_shift(level)];
+		offset &= genradix_depth_size(level) - 1;
+	}
+
+	return &(*n)->data[offset];
+}
+EXPORT_SYMBOL(__genradix_ptr_alloc);
+
+void *__genradix_iter_peek(struct genradix_iter *iter,
+			   struct __genradix *radix,
+			   size_t objs_per_page)
+{
+	struct genradix_node *n;
+	size_t level, i;
+
+	if (!radix->root)
+		return NULL;
+restart:
+	if (iter->offset >= genradix_depth_size(radix->depth))
+		return NULL;
+
+	n	= radix->root;
+	level	= radix->depth;
+
+	while (level) {
+		level--;
+
+		i = (iter->offset >> genradix_depth_shift(level)) &
+			(GENRADIX_ARY - 1);
+
+		while (!n->children[i]) {
+			i++;
+			iter->offset = round_down(iter->offset +
+					   genradix_depth_size(level),
+					   genradix_depth_size(level));
+			iter->pos = (iter->offset >> PAGE_SHIFT) *
+				objs_per_page;
+			if (i == GENRADIX_ARY)
+				goto restart;
+		}
+
+		n = n->children[i];
+	}
+
+	return &n->data[iter->offset & (PAGE_SIZE - 1)];
+}
+EXPORT_SYMBOL(__genradix_iter_peek);
+
+static void genradix_free_recurse(struct genradix_node *n, unsigned level)
+{
+	if (level) {
+		unsigned i;
+
+		for (i = 0; i < GENRADIX_ARY; i++)
+			if (n->children[i])
+				genradix_free_recurse(n->children[i], level - 1);
+	}
+
+	free_page((unsigned long) n);
+}
+
+void __genradix_free(struct __genradix *radix)
+{
+	genradix_free_recurse(radix->root, radix->depth);
+
+	radix->root = NULL;
+	radix->depth = 0;
+}
+EXPORT_SYMBOL(__genradix_free);