From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752699AbdKVCsB (ORCPT ); Tue, 21 Nov 2017 21:48:01 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:57452 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751732AbdKVCkd (ORCPT ); Tue, 21 Nov 2017 21:40:33 -0500 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, "Jens Axboe" , "Tang Junhui" , "Kent Overstreet" , "Eric Wheeler" Date: Wed, 22 Nov 2017 01:58:13 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 098/133] bcache: fix sequential large write IO bypass In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 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 List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.51-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Tang Junhui commit c81ffa32a214c84b08900fbc9d432187bd948eba upstream. Sequential write IOs were tested with bs=1M by FIO in writeback cache mode, these IOs were expected to be bypassed, but actually they did not. We debug the code, and find in check_should_bypass(): if (!congested && mode == CACHE_MODE_WRITEBACK && op_is_write(bio_op(bio)) && (bio-＞bi_opf & REQ_SYNC)) goto rescale that means, If in writeback mode, a write IO with REQ_SYNC flag will not be bypassed though it is a sequential large IO, It's not a correct thing to do actually, so this patch remove these codes. Signed-off-by: tang.junhui Reviewed-by: Kent Overstreet Reviewed-by: Eric Wheeler Signed-off-by: Jens Axboe [bwh: Backported to 3.16: deleted code is slightly different] Signed-off-by: Ben Hutchings --- drivers/md/bcache/request.c | 6 ------ 1 file changed, 6 deletions(-) --- a/drivers/md/bcache/request.c +++ b/drivers/md/bcache/request.c @@ -395,12 +395,6 @@ static bool check_should_bypass(struct c if (!congested && !dc->sequential_cutoff) goto rescale; - if (!congested && - mode == CACHE_MODE_WRITEBACK && - (bio->bi_rw & REQ_WRITE) && - (bio->bi_rw & REQ_SYNC)) - goto rescale; - spin_lock(&dc->io_lock); hlist_for_each_entry(i, iohash(dc, bio->bi_iter.bi_sector), hash)