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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 2D096C4360C for ; Sun, 6 Oct 2019 17:59:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 074DF20673 for ; Sun, 6 Oct 2019 17:59:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570384740; bh=6U0DUglx+sJiUGe4E43ESyfD7KbgwoFb8onbvz+2Zoc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=obqQXDlOYbF3tr5zPauXriFj1kiImws48uvp0Pa4Wq3yX5wTOz9LSBSr6WEIZp4eA rxZZv4DroHbHG4Ou3GPWusZdpYVJSPKOzHOwRYW9nvKUWpGNUD20p+LaNo/36whhK4 fVHr6n7iri5U8qLqHjseH8E6fQWInguA4Vf4Q/70= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729424AbfJFRb2 (ORCPT ); Sun, 6 Oct 2019 13:31:28 -0400 Received: from mail.kernel.org ([198.145.29.99]:57648 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729412AbfJFRbZ (ORCPT ); Sun, 6 Oct 2019 13:31:25 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 30A5E2080F; Sun, 6 Oct 2019 17:31:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570383083; bh=6U0DUglx+sJiUGe4E43ESyfD7KbgwoFb8onbvz+2Zoc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0kbSlWCwfua3AAwvHFO9OL1C2mob/2Pw3clOWS28w4Yrjq1Wz0NKjZfVpGW4Du7+u Ln31YxhZQnGUejceKu1S7wT5VKDh8rKyQhTjFv2b7V7e/93R99EfX+OhL2Rxlyv2t5 uIp4VxyIUvx7Imbmks9zoQN7qMkf7fdpMC/qTNUI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Hans Holmberg , Hans Holmberg , Christoph Hellwig , Damien Le Moal , Jens Axboe , Sasha Levin Subject: [PATCH 4.19 078/106] block: mq-deadline: Fix queue restart handling Date: Sun, 6 Oct 2019 19:21:24 +0200 Message-Id: <20191006171156.638428126@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191006171124.641144086@linuxfoundation.org> References: <20191006171124.641144086@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Damien Le Moal [ Upstream commit cb8acabbe33b110157955a7425ee876fb81e6bbc ] Commit 7211aef86f79 ("block: mq-deadline: Fix write completion handling") added a call to blk_mq_sched_mark_restart_hctx() in dd_dispatch_request() to make sure that write request dispatching does not stall when all target zones are locked. This fix left a subtle race when a write completion happens during a dispatch execution on another CPU: CPU 0: Dispatch CPU1: write completion dd_dispatch_request() lock(&dd->lock); ... lock(&dd->zone_lock); dd_finish_request() rq = find request lock(&dd->zone_lock); unlock(&dd->zone_lock); zone write unlock unlock(&dd->zone_lock); ... __blk_mq_free_request check restart flag (not set) -> queue not run ... if (!rq && have writes) blk_mq_sched_mark_restart_hctx() unlock(&dd->lock) Since the dispatch context finishes after the write request completion handling, marking the queue as needing a restart is not seen from __blk_mq_free_request() and blk_mq_sched_restart() not executed leading to the dispatch stall under 100% write workloads. Fix this by moving the call to blk_mq_sched_mark_restart_hctx() from dd_dispatch_request() into dd_finish_request() under the zone lock to ensure full mutual exclusion between write request dispatch selection and zone unlock on write request completion. Fixes: 7211aef86f79 ("block: mq-deadline: Fix write completion handling") Cc: stable@vger.kernel.org Reported-by: Hans Holmberg Reviewed-by: Hans Holmberg Reviewed-by: Christoph Hellwig Signed-off-by: Damien Le Moal Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- block/mq-deadline.c | 23 +++++++++++++---------- 1 file changed, 13 insertions(+), 10 deletions(-) diff --git a/block/mq-deadline.c b/block/mq-deadline.c index d5e21ce44d2cc..69094d6410623 100644 --- a/block/mq-deadline.c +++ b/block/mq-deadline.c @@ -376,13 +376,6 @@ static struct request *__dd_dispatch_request(struct deadline_data *dd) * hardware queue, but we may return a request that is for a * different hardware queue. This is because mq-deadline has shared * state for all hardware queues, in terms of sorting, FIFOs, etc. - * - * For a zoned block device, __dd_dispatch_request() may return NULL - * if all the queued write requests are directed at zones that are already - * locked due to on-going write requests. In this case, make sure to mark - * the queue as needing a restart to ensure that the queue is run again - * and the pending writes dispatched once the target zones for the ongoing - * write requests are unlocked in dd_finish_request(). */ static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx) { @@ -391,9 +384,6 @@ static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx) spin_lock(&dd->lock); rq = __dd_dispatch_request(dd); - if (!rq && blk_queue_is_zoned(hctx->queue) && - !list_empty(&dd->fifo_list[WRITE])) - blk_mq_sched_mark_restart_hctx(hctx); spin_unlock(&dd->lock); return rq; @@ -559,6 +549,13 @@ static void dd_prepare_request(struct request *rq, struct bio *bio) * spinlock so that the zone is never unlocked while deadline_fifo_request() * or deadline_next_request() are executing. This function is called for * all requests, whether or not these requests complete successfully. + * + * For a zoned block device, __dd_dispatch_request() may have stopped + * dispatching requests if all the queued requests are write requests directed + * at zones that are already locked due to on-going write requests. To ensure + * write request dispatch progress in this case, mark the queue as needing a + * restart to ensure that the queue is run again after completion of the + * request and zones being unlocked. */ static void dd_finish_request(struct request *rq) { @@ -570,6 +567,12 @@ static void dd_finish_request(struct request *rq) spin_lock_irqsave(&dd->zone_lock, flags); blk_req_zone_write_unlock(rq); + if (!list_empty(&dd->fifo_list[WRITE])) { + struct blk_mq_hw_ctx *hctx; + + hctx = blk_mq_map_queue(q, rq->mq_ctx->cpu); + blk_mq_sched_mark_restart_hctx(hctx); + } spin_unlock_irqrestore(&dd->zone_lock, flags); } } -- 2.20.1