1 files changed, 103 insertions, 0 deletions
diff --git a/kernel/resource.c b/kernel/resource.c
index ae246f97c5d..4aef8867fd4 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1021,6 +1021,109 @@ void __release_region(struct resource *parent, resource_size_t start,
 }
 EXPORT_SYMBOL(__release_region);
 
+#ifdef CONFIG_MEMORY_HOTREMOVE
+/**
+ * release_mem_region_adjustable - release a previously reserved memory region
+ * @parent: parent resource descriptor
+ * @start: resource start address
+ * @size: resource region size
+ *
+ * This interface is intended for memory hot-delete.  The requested region
+ * is released from a currently busy memory resource.  The requested region
+ * must either match exactly or fit into a single busy resource entry.  In
+ * the latter case, the remaining resource is adjusted accordingly.
+ * Existing children of the busy memory resource must be immutable in the
+ * request.
+ *
+ * Note:
+ * - Additional release conditions, such as overlapping region, can be
+ *   supported after they are confirmed as valid cases.
+ * - When a busy memory resource gets split into two entries, the code
+ *   assumes that all children remain in the lower address entry for
+ *   simplicity.  Enhance this logic when necessary.
+ */
+int release_mem_region_adjustable(struct resource *parent,
+			resource_size_t start, resource_size_t size)
+{
+	struct resource **p;
+	struct resource *res;
+	struct resource *new_res;
+	resource_size_t end;
+	int ret = -EINVAL;
+
+	end = start + size - 1;
+	if ((start < parent->start) || (end > parent->end))
+		return ret;
+
+	/* The kzalloc() result gets checked later */
+	new_res = kzalloc(sizeof(struct resource), GFP_KERNEL);
+
+	p = &parent->child;
+	write_lock(&resource_lock);
+
+	while ((res = *p)) {
+		if (res->start >= end)
+			break;
+
+		/* look for the next resource if it does not fit into */
+		if (res->start > start || res->end < end) {
+			p = &res->sibling;
+			continue;
+		}
+
+		if (!(res->flags & IORESOURCE_MEM))
+			break;
+
+		if (!(res->flags & IORESOURCE_BUSY)) {
+			p = &res->child;
+			continue;
+		}
+
+		/* found the target resource; let's adjust accordingly */
+		if (res->start == start && res->end == end) {
+			/* free the whole entry */
+			*p = res->sibling;
+			kfree(res);
+			ret = 0;
+		} else if (res->start == start && res->end != end) {
+			/* adjust the start */
+			ret = __adjust_resource(res, end + 1,
+						res->end - end);
+		} else if (res->start != start && res->end == end) {
+			/* adjust the end */
+			ret = __adjust_resource(res, res->start,
+						start - res->start);
+		} else {
+			/* split into two entries */
+			if (!new_res) {
+				ret = -ENOMEM;
+				break;
+			}
+			new_res->name = res->name;
+			new_res->start = end + 1;
+			new_res->end = res->end;
+			new_res->flags = res->flags;
+			new_res->parent = res->parent;
+			new_res->sibling = res->sibling;
+			new_res->child = NULL;
+
+			ret = __adjust_resource(res, res->start,
+						start - res->start);
+			if (ret)
+				break;
+			res->sibling = new_res;
+			new_res = NULL;
+		}
+
+		break;
+	}
+
+	write_unlock(&resource_lock);
+	kfree(new_res);
+	return ret;
+}
+#endif	/* CONFIG_MEMORY_HOTREMOVE */
+
 /*
  * Managed region resource
  */