diff --git a/ext/-test-/file/fs.c b/ext/-test-/file/fs.c
new file mode 100644
index 0000000000..ed1e64e1eb
--- /dev/null
+++ b/ext/-test-/file/fs.c
@@ -0,0 +1,60 @@
+#include "ruby/ruby.h"
+#include "ruby/io.h"
+
+#ifdef __linux__
+# define HAVE_GETMNTENT
+#endif
+
+#ifdef HAVE_GETMNTENT
+# include <stdio.h>
+# include <mntent.h>
+#endif
+
+VALUE
+get_fsname(VALUE self, VALUE str)
+{
+#ifdef HAVE_GETMNTENT
+    const char *path;
+    struct mntent mntbuf;
+    static const int buflen = 4096;
+    char *buf = alloca(buflen);
+    int len = 0;
+    FILE *fp;
+#define FSNAME_LEN 100
+    char name[FSNAME_LEN] = "";
+
+    FilePathValue(str);
+    path = RSTRING_PTR(str);
+    fp = setmntent("/etc/mtab", "r"); 
+    if (!fp) rb_sys_fail("setmntent(/etb/mtab)");;
+
+    while (getmntent_r(fp, &mntbuf, buf, buflen)) {
+	int i;
+	char *mnt_dir = mntbuf.mnt_dir;
+	for (i=0; mnt_dir[i]; i++) {
+	    if (mnt_dir[i] != path[i]) {
+		goto next_entry;
+	    }
+	}
+	if (i >= len) {
+	    len = i;
+	    strlcpy(name, mntbuf.mnt_type, FSNAME_LEN);
+	}
+next_entry:
+	;
+    }
+    endmntent(fp);
+
+    if (!len) rb_sys_fail("no matching entry");;
+    return rb_str_new_cstr(name);
+#else
+    return Qnil;
+#endif
+}
+
+void
+Init_fs(VALUE module)
+{
+    VALUE fs = rb_define_module_under(module, "Fs");
+    rb_define_module_function(fs, "fsname", get_fsname, 1);
+}