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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 C2C6EC2BA83 for ; Fri, 14 Feb 2020 18:16:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 960062187F for ; Fri, 14 Feb 2020 18:16:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581704167; bh=hhHJKlpWN495uh2vdO0TDhEHxnvrpn3GndEc5iHu2kc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=lMpuzGNnScQcjiO/rY4MR+tuFrO8vX7/5B9kIJka6l5/2Un/louD0LijI5KKDoF7Q ZpkA4XMTkeypzE0nbJRnOhaf33CEPgFZQzPEKkBDYZdXYo0Q7dLgfEwBBz3lkM0aaE vZJ0ajHwqZqBIuwMKh6wthZM4EwgSe1YyxTALHAY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404758AbgBNSQG (ORCPT ); Fri, 14 Feb 2020 13:16:06 -0500 Received: from mail.kernel.org ([198.145.29.99]:56780 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730838AbgBNPvk (ORCPT ); Fri, 14 Feb 2020 10:51:40 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6BCB42465D; Fri, 14 Feb 2020 15:51:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581695500; bh=hhHJKlpWN495uh2vdO0TDhEHxnvrpn3GndEc5iHu2kc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MC0v5jSerDEMIctzOL6gY9SMHktpShHC95BWW09nl/HWmvHwqgHZHUpy+pFWKiFoF ChQNFUmOa0BXXK6KoUjE4TtCAUX6hu+fhYtJrkpI4r35+eJYjotUO1/oXnMZaYy2ls lJoGFoam2CpEHfsUupdJdAngj/cdYTuSN7CgMR/Y= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Paolo Valente , Oleksandr Natalenko , Patrick Dung , Jens Axboe , Sasha Levin , linux-block@vger.kernel.org Subject: [PATCH AUTOSEL 5.5 127/542] block, bfq: do not plug I/O for bfq_queues with no proc refs Date: Fri, 14 Feb 2020 10:41:59 -0500 Message-Id: <20200214154854.6746-127-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200214154854.6746-1-sashal@kernel.org> References: <20200214154854.6746-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Paolo Valente [ Upstream commit f718b093277df582fbf8775548a4f163e664d282 ] Commit 478de3380c1c ("block, bfq: deschedule empty bfq_queues not referred by any process") fixed commit 3726112ec731 ("block, bfq: re-schedule empty queues if they deserve I/O plugging") by descheduling an empty bfq_queue when it remains with not process reference. Yet, this still left a case uncovered: an empty bfq_queue with not process reference that remains in service. This happens for an in-service sync bfq_queue that is deemed to deserve I/O-dispatch plugging when it remains empty. Yet no new requests will arrive for such a bfq_queue if no process sends requests to it any longer. Even worse, the bfq_queue may happen to be prematurely freed while still in service (because there may remain no reference to it any longer). This commit solves this problem by preventing I/O dispatch from being plugged for the in-service bfq_queue, if the latter has no process reference (the bfq_queue is then prevented from remaining in service). Fixes: 3726112ec731 ("block, bfq: re-schedule empty queues if they deserve I/O plugging") Tested-by: Oleksandr Natalenko Reported-by: Patrick Dung Tested-by: Patrick Dung Signed-off-by: Paolo Valente Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- block/bfq-iosched.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index ad4af4aaf2ced..5c239c540c47a 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -3444,6 +3444,10 @@ static void bfq_dispatch_remove(struct request_queue *q, struct request *rq) static bool idling_needed_for_service_guarantees(struct bfq_data *bfqd, struct bfq_queue *bfqq) { + /* No point in idling for bfqq if it won't get requests any longer */ + if (unlikely(!bfqq_process_refs(bfqq))) + return false; + return (bfqq->wr_coeff > 1 && (bfqd->wr_busy_queues < bfq_tot_busy_queues(bfqd) || @@ -4077,6 +4081,10 @@ static bool idling_boosts_thr_without_issues(struct bfq_data *bfqd, bfqq_sequential_and_IO_bound, idling_boosts_thr; + /* No point in idling for bfqq if it won't get requests any longer */ + if (unlikely(!bfqq_process_refs(bfqq))) + return false; + bfqq_sequential_and_IO_bound = !BFQQ_SEEKY(bfqq) && bfq_bfqq_IO_bound(bfqq) && bfq_bfqq_has_short_ttime(bfqq); @@ -4170,6 +4178,10 @@ static bool bfq_better_to_idle(struct bfq_queue *bfqq) struct bfq_data *bfqd = bfqq->bfqd; bool idling_boosts_thr_with_no_issue, idling_needed_for_service_guar; + /* No point in idling for bfqq if it won't get requests any longer */ + if (unlikely(!bfqq_process_refs(bfqq))) + return false; + if (unlikely(bfqd->strict_guarantees)) return true; -- 2.20.1