Resource handling: add 'insert_resource_expand_to_fit()' function

Not used anywhere yet, but this complements the existing plain
'insert_resource()' functionality with a version that can expand the
resource we are adding in order to fix up any conflicts it has with
existing resources.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 63 insertions, 25 deletions

diff --git a/kernel/resource.c b/kernel/resource.c
index f5b518e..cf0a178 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -362,35 +362,21 @@ int allocate_resource(struct resource *root, struct resource *new,
 
 EXPORT_SYMBOL(allocate_resource);
 
-/**
- * insert_resource - Inserts a resource in the resource tree
- * @parent: parent of the new resource
- * @new: new resource to insert
- *
- * Returns 0 on success, -EBUSY if the resource can't be inserted.
- *
- * This function is equivalent to request_resource when no conflict
- * happens. If a conflict happens, and the conflicting resources
- * entirely fit within the range of the new resource, then the new
- * resource is inserted and the conflicting resources become children of
- * the new resource.
+/*
+ * Insert a resource into the resource tree. If successful, return NULL,
+ * otherwise return the conflicting resource (compare to __request_resource())
  */
-int insert_resource(struct resource *parent, struct resource *new)
+static struct resource * __insert_resource(struct resource *parent, struct resource *new)
 {
-	int result;
 	struct resource *first, *next;
 
-	write_lock(&resource_lock);
-
 	for (;; parent = first) {
-	 	result = 0;
 		first = __request_resource(parent, new);
 		if (!first)
-			goto out;
+			return first;
 
-		result = -EBUSY;
 		if (first == parent)
-			goto out;
+			return first;
 
 		if ((first->start > new->start) || (first->end < new->end))
 			break;
@@ -401,15 +387,13 @@ int insert_resource(struct resource *parent, struct resource *new)
 	for (next = first; ; next = next->sibling) {
 		/* Partial overlap? Bad, and unfixable */
 		if (next->start < new->start || next->end > new->end)
-			goto out;
+			return next;
 		if (!next->sibling)
 			break;
 		if (next->sibling->start > new->end)
 			break;
 	}
 
-	result = 0;
-
 	new->parent = parent;
 	new->sibling = next->sibling;
 	new->child = first;
@@ -426,10 +410,64 @@ int insert_resource(struct resource *parent, struct resource *new)
 			next = next->sibling;
 		next->sibling = new;
 	}
+	return NULL;
+}
 
- out:
+/**
+ * insert_resource - Inserts a resource in the resource tree
+ * @parent: parent of the new resource
+ * @new: new resource to insert
+ *
+ * Returns 0 on success, -EBUSY if the resource can't be inserted.
+ *
+ * This function is equivalent to request_resource when no conflict
+ * happens. If a conflict happens, and the conflicting resources
+ * entirely fit within the range of the new resource, then the new
+ * resource is inserted and the conflicting resources become children of
+ * the new resource.
+ */
+int insert_resource(struct resource *parent, struct resource *new)
+{
+	struct resource *conflict;
+
+	write_lock(&resource_lock);
+	conflict = __insert_resource(parent, new);
+	write_unlock(&resource_lock);
+	return conflict ? -EBUSY : 0;
+}
+
+/**
+ * insert_resource_expand_to_fit - Insert a resource into the resource tree
+ * @parent: parent of the new resource
+ * @new: new resource to insert
+ *
+ * Insert a resource into the resource tree, possibly expanding it in order
+ * to make it encompass any conflicting resources.
+ */
+void insert_resource_expand_to_fit(struct resource *root, struct resource *new)
+{
+	if (new->parent)
+		return;
+
+	write_lock(&resource_lock);
+	for (;;) {
+		struct resource *conflict;
+
+		conflict = __insert_resource(root, new);
+		if (!conflict)
+			break;
+		if (conflict == root)
+			break;
+
+		/* Ok, expand resource to cover the conflict, then try again .. */
+		if (conflict->start < new->start)
+			new->start = conflict->start;
+		if (conflict->end > new->end)
+			new->end = conflict->end;
+
+		printk("Expanded resource %s due to conflict with %s\n", new->name, conflict->name);
+	}
 	write_unlock(&resource_lock);
-	return result;
 }
 
 /**