@Override
	public synchronized void onFilesystemRefChange(GFileSystem fs,
			FileSystemRefManager refManager) {
		//Msg.info(this, "Filesystem " + fs.getFSRL() + " ref changed");
		// TODO: could move unused filesystems to their own waiting-to-be-purged list
		// if its too much work to walk the entire list of current filesystems.
	}
Returns a new {@link FileSystemRef} to a already mounted {@link GFileSystem filesystem}
(keeping the filesystem pinned in memory without the risk of it being closed during
a race condition).
<p>
The caller is responsible for {@link FileSystemRef#close() closing} it when done.
<p>
Returns null if there is no filesystem mounted at the requested container fsrl.

@param containerFSRL {@link FSRL} location where a filesystem is already mounted
@return new {@link FileSystemRef} to the already mounted filesystem, or null
Ghidra/Features/Base/src/main/java/ghidra/formats/gfilesystem/FileSystemInstanceManager.java