+ if (S_ISDIR(buf.st_mode)) {
+ /*
+ * Don't descend into directories on other file systems, if this is requested. We do a simple
+ * .st_dev check here, which basically comes for free. Note that we do this check only on
+ * directories, not other kind of file system objects, for two reason:
+ *
+ * • The kernel's overlayfs pseudo file system that overlays multiple real file systems
+ * propagates the .st_dev field of the file system a file originates from all the way up
+ * through the stack to stat(). It doesn't do that for directories however. This means that
+ * comparing .st_dev on non-directories suggests that they all are mount points. To avoid
+ * confusion we hence avoid relying on this check for regular files.
+ *
+ * • The main reason we do this check at all is to protect ourselves from bind mount cycles,
+ * where we really want to avoid descending down in all eternity. However the .st_dev check
+ * is usually not sufficient for this protection anyway, as bind mount cycles from the same
+ * file system onto itself can't be detected that way. (Note we also do a recursion depth
+ * check, which is probably the better protection in this regard, which is why
+ * COPY_SAME_MOUNT is optional).
+ */
+
+ if (FLAGS_SET(copy_flags, COPY_SAME_MOUNT)) {
+ if (buf.st_dev != original_device)
+ continue;
+
+ r = fd_is_mount_point(dirfd(d), de->d_name, 0);
+ if (r < 0)
+ return r;
+ if (r > 0)
+ continue;
+ }