ram_disk: Add note about code duplication with ramfs.

src/add-ons/kernel/drivers/disk/virtual/ram_disk/ram_disk.cpp

@@ -651,6 +651,9 @@ private:
 
 	void _GetPages(off_t offset, off_t length, bool isWrite, vm_page** pages)
 	{
+		// TODO: This method is duplicated in ramfs' DataContainer. Perhaps it
+		// should be put into a common location?
+
 		// get the pages, we already have
 		AutoLocker<VMCache> locker(fCache);
 
@@ -701,6 +704,9 @@ private:
 
 	void _PutPages(off_t offset, off_t length, vm_page** pages, bool success)
 	{
+		// TODO: This method is duplicated in ramfs' DataContainer. Perhaps it
+		// should be put into a common location?
+
 		AutoLocker<VMCache> locker(fCache);
 
 		// Mark all pages unbusy. On error free the newly allocated pages.