+
+/*
+ * check if a given path is a mountpoint
+ */
+
+#include <string.h>
+#include <malloc.h>
+#include <sys/stat.h>
+
+int
+is_mountpoint(char *path)
+{
+ /* Check if 'path' is a current mountpoint.
+ * Possibly we should also check it is the mountpoint of the
+ * filesystem holding the target directory, but there doesn't
+ * seem a lot of point.
+ *
+ * We deem it to be a mountpoint if appending a ".." gives a different
+ * device or the same inode number.
+ */
+ char *dotdot;
+ struct stat stb, pstb;
+
+ dotdot = malloc(strlen(path)+4);
+ strcat(strcpy(dotdot, path), "/..");
+ if (lstat(path, &stb) != 0 ||
+ lstat(dotdot, &pstb) != 0)
+ return 0;
+
+ if (stb.st_dev != pstb.st_dev
+ || stb.st_ino == pstb.st_ino)
+ return 1;
+ return 0;
+}