files-reg: Don't generate ghost files for hanged out slave pty peers

We will use reg-files engine for tty c/r so lets prepare scaffolds
here preventing the engine to generate ghost files for PTY peers
(mostly because one can't create slave peers without opening
 master peers first which is a sole part of tty engine itself).
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Tycho Andersen <tycho.andersen@canonical.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

files-reg.c

@@ -680,6 +680,21 @@ static int check_path_remap(struct fd_link *link, const struct fd_parms *parms,
 		}
 
 		return 0;
+	} else if (parms->fs_type == DEVPTS_SUPER_MAGIC) {
+		/*
+		 * It's safe to call stripping here because
+		 * file paths are having predefined format for
+		 * this FS and can't have a valid " (deleted)"
+		 * postfix as a part of not deleted filename.
+		 */
+		strip_deleted(link);
+		/*
+		 * Devpts devices/files are generated by the
+		 * kernel itself so we should not try to generate
+		 * any kind of ghost files here even if file is
+		 * no longer exist.
+		 */
+		return 0;
 	}
 
 	if (ost->st_nlink == 0) {