From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1A47BC71122 for ; Sun, 14 Oct 2018 15:35:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DAF2020876 for ; Sun, 14 Oct 2018 15:35:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DAF2020876 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=decadent.org.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728827AbeJNXRB (ORCPT ); Sun, 14 Oct 2018 19:17:01 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:36657 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727388AbeJNXRA (ORCPT ); Sun, 14 Oct 2018 19:17:00 -0400 Received: from [2a02:8011:400e:2:cbab:f00:c93f:614] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.84_2) (envelope-from ) id 1gBiME-0004cJ-SH; Sun, 14 Oct 2018 16:31:07 +0100 Received: from ben by deadeye with local (Exim 4.91) (envelope-from ) id 1gBiLP-0000D8-3h; Sun, 14 Oct 2018 16:30:15 +0100 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Martin Schwidefsky" , "Benjamin Block" , "Julian Wiedmann" , "Ursula Braun" Date: Sun, 14 Oct 2018 16:25:40 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 057/366] s390/qdio: don't merge ERROR output buffers In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:cbab:f00:c93f:614 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.60-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Julian Wiedmann commit 0cf1e05157b9e5530dcc3ca9fec9bf617fc93375 upstream. On an Output queue, both EMPTY and PENDING buffer states imply that the buffer is ready for completion-processing by the upper-layer drivers. So for a non-QEBSM Output queue, get_buf_states() merges mixed batches of PENDING and EMPTY buffers into one large batch of EMPTY buffers. The upper-layer driver (ie. qeth) later distuingishes PENDING from EMPTY by inspecting the slsb_state for QDIO_OUTBUF_STATE_FLAG_PENDING. But the merge logic in get_buf_states() contains a bug that causes us to erronously also merge ERROR buffers into such a batch of EMPTY buffers (ERROR is 0xaf, EMPTY is 0xa1; so ERROR & EMPTY == EMPTY). Effectively, most outbound ERROR buffers are currently discarded silently and processed as if they had succeeded. Note that this affects _all_ non-QEBSM device types, not just IQD with CQ. Fix it by explicitly spelling out the exact conditions for merging. For extracting the "get initial state" part out of the loop, this relies on the fact that get_buf_states() is never called with a count of 0. The QEBSM path already strictly requires this, and the two callers with variable 'count' make sure of it. Fixes: 104ea556ee7f ("qdio: support asynchronous delivery of storage blocks") Signed-off-by: Julian Wiedmann Reviewed-by: Ursula Braun Reviewed-by: Benjamin Block Signed-off-by: Martin Schwidefsky Signed-off-by: Ben Hutchings --- drivers/s390/cio/qdio_main.c | 31 ++++++++++++++++++++----------- 1 file changed, 20 insertions(+), 11 deletions(-) --- a/drivers/s390/cio/qdio_main.c +++ b/drivers/s390/cio/qdio_main.c @@ -212,7 +212,10 @@ again: return 0; } -/* returns number of examined buffers and their common state in *state */ +/* + * Returns number of examined buffers and their common state in *state. + * Requested number of buffers-to-examine must be > 0. + */ static inline int get_buf_states(struct qdio_q *q, unsigned int bufnr, unsigned char *state, unsigned int count, int auto_ack, int merge_pending) @@ -223,17 +226,23 @@ static inline int get_buf_states(struct if (is_qebsm(q)) return qdio_do_eqbs(q, state, bufnr, count, auto_ack); - for (i = 0; i < count; i++) { - if (!__state) { - __state = q->slsb.val[bufnr]; - if (merge_pending && __state == SLSB_P_OUTPUT_PENDING) - __state = SLSB_P_OUTPUT_EMPTY; - } else if (merge_pending) { - if ((q->slsb.val[bufnr] & __state) != __state) - break; - } else if (q->slsb.val[bufnr] != __state) - break; + /* get initial state: */ + __state = q->slsb.val[bufnr]; + if (merge_pending && __state == SLSB_P_OUTPUT_PENDING) + __state = SLSB_P_OUTPUT_EMPTY; + + for (i = 1; i < count; i++) { bufnr = next_buf(bufnr); + + /* merge PENDING into EMPTY: */ + if (merge_pending && + q->slsb.val[bufnr] == SLSB_P_OUTPUT_PENDING && + __state == SLSB_P_OUTPUT_EMPTY) + continue; + + /* stop if next state differs from initial state: */ + if (q->slsb.val[bufnr] != __state) + break; } *state = __state; return i;