public FileSystemRef getMountedFilesystem(FSRLRoot fsFSRL) {
		synchronized (fsInstanceManager) {
			return fsInstanceManager.getRef(fsFSRL);
		}
	}
Returns a new FilesystemRef handle to an already mounted filesystem.
<p>
The caller is responsible for releasing the ref.
<p>
Returns null if there is no filesystem mounted at {@code fsFSRL}.

@param fsFSRL {@link FSRLRoot} of file system to get a {@link FileSystemRef} to.
@return new {@link FileSystemRef} or null if requested file system not mounted.
Ghidra/Features/Base/src/main/java/ghidra/formats/gfilesystem/FileSystemService.java