Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754077AbdIXVED (ORCPT ); Sun, 24 Sep 2017 17:04:03 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:60254 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932832AbdIXUkR (ORCPT ); Sun, 24 Sep 2017 16:40:17 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Peter Hurley , Arnd Bergmann Subject: [PATCH 4.13 011/109] tty: improve tty_insert_flip_char() slow path Date: Sun, 24 Sep 2017 22:32:32 +0200 Message-Id: <20170924203353.552775914@linuxfoundation.org> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20170924203353.104695385@linuxfoundation.org> References: <20170924203353.104695385@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1550 Lines: 45 4.13-stable review patch. If anyone has any objections, please let me know. ------------------ From: Arnd Bergmann commit 065ea0a7afd64d6cf3464bdd1d8cd227527e2045 upstream. While working on improving the fast path of tty_insert_flip_char(), I noticed that by calling tty_buffer_request_room(), we needlessly move to the separate flag buffer mode for the tty, even when all characters use TTY_NORMAL as the flag. This changes the code to call __tty_buffer_request_room() with the correct flag, which will then allocate a regular buffer when it rounds out of space but no special flags have been used. I'm guessing that this is the behavior that Peter Hurley intended when he introduced the compacted flip buffers. Fixes: acc0f67f307f ("tty: Halve flip buffer GFP_ATOMIC memory consumption") Cc: Peter Hurley Signed-off-by: Arnd Bergmann Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_buffer.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- a/drivers/tty/tty_buffer.c +++ b/drivers/tty/tty_buffer.c @@ -375,10 +375,11 @@ int __tty_insert_flip_char(struct tty_po struct tty_buffer *tb = port->buf.tail; int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0; - if (!tty_buffer_request_room(port, 1)) + if (!__tty_buffer_request_room(port, 1, flags)) return 0; - *flag_buf_ptr(tb, tb->used) = flag; + if (~tb->flags & TTYB_NORMAL) + *flag_buf_ptr(tb, tb->used) = flag; *char_buf_ptr(tb, tb->used++) = ch; return 1;