Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932414AbcCBAXP (ORCPT ); Tue, 1 Mar 2016 19:23:15 -0500 Received: from mail177-1.suw61.mandrillapp.com ([198.2.177.1]:27939 "EHLO mail177-1.suw61.mandrillapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932304AbcCAX5r (ORCPT ); Tue, 1 Mar 2016 18:57:47 -0500 From: Greg Kroah-Hartman Subject: [PATCH 4.4 264/342] libceph: dont bail early from try_read() when skipping a message X-Mailer: git-send-email 2.7.2 To: Cc: Greg Kroah-Hartman , , Varada Kari , Ilya Dryomov , Alex Elder Message-Id: <20160301234536.429727564@linuxfoundation.org> In-Reply-To: <20160301234527.990448862@linuxfoundation.org> References: <20160301234527.990448862@linuxfoundation.org> X-Report-Abuse: Please forward a copy of this message, including all headers, to abuse@mandrill.com X-Report-Abuse: You can also report abuse here: http://mandrillapp.com/contact/abuse?id=30481620.66ed9a65a5f24a348df120afed69f7a9 X-Mandrill-User: md_30481620 Date: Tue, 01 Mar 2016 23:55:13 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1604 Lines: 46 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ilya Dryomov commit e7a88e82fe380459b864e05b372638aeacb0f52d upstream. The contract between try_read() and try_write() is that when called each processes as much data as possible. When instructed by osd_client to skip a message, try_read() is violating this contract by returning after receiving and discarding a single message instead of checking for more. try_write() then gets a chance to write out more requests, generating more replies/skips for try_read() to handle, forcing the messenger into a starvation loop. Reported-by: Varada Kari Signed-off-by: Ilya Dryomov Tested-by: Varada Kari Reviewed-by: Alex Elder Signed-off-by: Greg Kroah-Hartman --- net/ceph/messenger.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/net/ceph/messenger.c +++ b/net/ceph/messenger.c @@ -2340,7 +2340,7 @@ static int read_partial_message(struct c con->in_base_pos = -front_len - middle_len - data_len - sizeof(m->footer); con->in_tag = CEPH_MSGR_TAG_READY; - return 0; + return 1; } else if ((s64)seq - (s64)con->in_seq > 1) { pr_err("read_partial_message bad seq %lld expected %lld\n", seq, con->in_seq + 1); @@ -2366,7 +2366,7 @@ static int read_partial_message(struct c sizeof(m->footer); con->in_tag = CEPH_MSGR_TAG_READY; con->in_seq++; - return 0; + return 1; } BUG_ON(!con->in_msg);