From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-bl2nam02on0136.outbound.protection.outlook.com ([104.47.38.136]:51875 "EHLO NAM02-BL2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753214AbeDIARu (ORCPT ); Sun, 8 Apr 2018 20:17:50 -0400 From: Sasha Levin To: "stable@vger.kernel.org" , "linux-kernel@vger.kernel.org" CC: Ming Lei , Mike Snitzer , Sasha Levin Subject: [PATCH AUTOSEL for 4.15 037/189] dm mpath: return DM_MAPIO_REQUEUE on blk-mq rq allocation failure Date: Mon, 9 Apr 2018 00:17:15 +0000 Message-ID: <20180409001637.162453-37-alexander.levin@microsoft.com> References: <20180409001637.162453-1-alexander.levin@microsoft.com> In-Reply-To: <20180409001637.162453-1-alexander.levin@microsoft.com> Content-Language: en-US Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org List-ID: From: Ming Lei [ Upstream commit 050af08ffb1b62af69196d61c22a0755f9a3cdbd ] blk-mq will rerun queue via RESTART or dispatch wake after one request is completed, so not necessary to wait random time for requeuing, we should trust blk-mq to do it. More importantly, we need to return BLK_STS_RESOURCE to blk-mq so that dequeuing from the I/O scheduler can be stopped, this results in improved I/O merging. Signed-off-by: Ming Lei Signed-off-by: Mike Snitzer Signed-off-by: Sasha Levin --- drivers/md/dm-mpath.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c index 025e033ecb78..a3223c8fbaac 100644 --- a/drivers/md/dm-mpath.c +++ b/drivers/md/dm-mpath.c @@ -534,8 +534,20 @@ static int multipath_clone_and_map(struct dm_target *t= i, struct request *rq, if (queue_dying) { atomic_inc(&m->pg_init_in_progress); activate_or_offline_path(pgpath); + return DM_MAPIO_DELAY_REQUEUE; } - return DM_MAPIO_DELAY_REQUEUE; + + /* + * blk-mq's SCHED_RESTART can cover this requeue, so we + * needn't deal with it by DELAY_REQUEUE. More importantly, + * we have to return DM_MAPIO_REQUEUE so that blk-mq can + * get the queue busy feedback (via BLK_STS_RESOURCE), + * otherwise I/O merging can suffer. + */ + if (q->mq_ops) + return DM_MAPIO_REQUEUE; + else + return DM_MAPIO_DELAY_REQUEUE; } clone->bio =3D clone->biotail =3D NULL; clone->rq_disk =3D bdev->bd_disk; --=20 2.15.1