UBIFS: improve error reporting when reading bad node

When an error happens during validation of read node, the typical situation is that
the LEB we read is unmapped (due to some bug). It is handy to include the mapping
status into the error message.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

fs/ubifs/io.c

@@ -815,7 +815,8 @@ int ubifs_read_node(const struct ubifs_info *c, void *buf, int type, int len,
 	return 0;
 
 out:
-	ubifs_err("bad node at LEB %d:%d", lnum, offs);
+	ubifs_err("bad node at LEB %d:%d, LEB mapping status %d", lnum, offs,
+		  ubi_is_mapped(c->ubi, lnum));
 	dbg_dump_node(c, buf);
 	dbg_dump_stack();
 	return -EINVAL;