From patchwork Mon Sep 20 16:44:06 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 514365 Delivered-To: patch@linaro.org Received: by 2002:a02:c816:0:0:0:0:0 with SMTP id p22csp2328433jao; Mon, 20 Sep 2021 11:35:56 -0700 (PDT) X-Google-Smtp-Source: ABdhPJz746tFZ2sK1NE9G+apHysvlXlivV+w00vuS9PWQ64IrE920vzFYEVvwrwl/VgGwW4T8TNU X-Received: by 2002:a17:906:3c56:: with SMTP id i22mr30385079ejg.287.1632162956773; Mon, 20 Sep 2021 11:35:56 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1632162956; cv=none; d=google.com; s=arc-20160816; b=lk7T53o0c1gDLJhbGv5/Sk82lygahQi4KOhqDCnsjH7xcnuumXWPG9gX8UDSuFIEUF 7ADdm7+6H3sXOIU8unHiFMOx/JcePtX9bmUr4d28zuBrXtB5Br8YUJbXhYFvc2C+GGtm dmmv34bszdy9PvDvnwDXC/x5kemFQDYOcPv57VGtQZE3V2XZyH+QzC8m4v1d06eaba5w dPpdzYxPXFPRqnOtxUp4ifUYa93bARt7SsyVWth0ZuyHDCgPrlEQ2u36ODX1KRoMGbuz k4Zrp29/5c0pFGzbLRsHOHINCCxU6qPUZe/l+wiIrz2rRqTpxq1b+d85MR/0r8Cebwx/ c4ww== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :user-agent:references:in-reply-to:message-id:date:subject:cc:to :from:dkim-signature; bh=nyNVLbiZKAu6RAxHoarNxRKb3YmrKDKcKwh8LbxB8eg=; b=G8RJV5NaRw84ExxU+KD2mjr/aG6LZvQm1PYmC6fYFkvc9mMB/wsc/Na8BBGgreAk+I VPJGTkr38wjPuetCWSTuHQOZM6V6vnnmTCfUu8TzOsBmgvDMkpa/MAm4TjoM3Pd8XVjb JLxYjX4de+SVSfFf6Q4sb8UkDtRs2uRUf7b2EajB+0Vs0PuUUdaXHAzJGk+6tdTmPYzJ mOEYGg6TfGvfoxMBhh25bms+NitX5w9awqvlxbJ+f/uzHEQrMFsWLAjSbRdkokuf+7xf KNSs23iKNA1fgQ2GW5oveTLANE9EzHFCoGWiAPb02R/zxe/CeEk3gfk9r5eZnxFLuxEA Fd2Q== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@linuxfoundation.org header.s=korg header.b=Ba112xSa; spf=pass (google.com: domain of stable-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=stable-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linuxfoundation.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id b1si21572484ejb.600.2021.09.20.11.35.56; Mon, 20 Sep 2021 11:35:56 -0700 (PDT) Received-SPF: pass (google.com: domain of stable-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@linuxfoundation.org header.s=korg header.b=Ba112xSa; spf=pass (google.com: domain of stable-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=stable-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linuxfoundation.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353493AbhITSgP (ORCPT + 11 others); Mon, 20 Sep 2021 14:36:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:47572 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1379745AbhITSaY (ORCPT ); Mon, 20 Sep 2021 14:30:24 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id BE64D632F0; Mon, 20 Sep 2021 17:27:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1632158826; bh=y2nuunIIMi0E1RT2BGyKCFUaFsmSdL3/puRBt2mdno0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ba112xSaJdkQ9o/ssqd4MNtqQLiJRfjwMk3q9JBIbIRLuuIm6XJ4SoZdAieIezJO4 rgBO91tS/gh0Rg6J9WwJY8OLS/XBPNCyVFlVXpmq42VPgM0m0AbaN9qPv+hCx+QjaK jCeDmAAQjKm0zF0qWT39SvjwTVZXytJaEfdVqnv8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Davide Zini , Paolo Valente , Jens Axboe , Sasha Levin Subject: [PATCH 5.10 074/122] block, bfq: honor already-setup queue merges Date: Mon, 20 Sep 2021 18:44:06 +0200 Message-Id: <20210920163918.200238472@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20210920163915.757887582@linuxfoundation.org> References: <20210920163915.757887582@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Paolo Valente [ Upstream commit 2d52c58b9c9bdae0ca3df6a1eab5745ab3f7d80b ] The function bfq_setup_merge prepares the merging between two bfq_queues, say bfqq and new_bfqq. To this goal, it assigns bfqq->new_bfqq = new_bfqq. Then, each time some I/O for bfqq arrives, the process that generated that I/O is disassociated from bfqq and associated with new_bfqq (merging is actually a redirection). In this respect, bfq_setup_merge increases new_bfqq->ref in advance, adding the number of processes that are expected to be associated with new_bfqq. Unfortunately, the stable-merging mechanism interferes with this setup. After bfqq->new_bfqq has been set by bfq_setup_merge, and before all the expected processes have been associated with bfqq->new_bfqq, bfqq may happen to be stably merged with a different queue than the current bfqq->new_bfqq. In this case, bfqq->new_bfqq gets changed. So, some of the processes that have been already accounted for in the ref counter of the previous new_bfqq will not be associated with that queue. This creates an unbalance, because those references will never be decremented. This commit fixes this issue by reestablishing the previous, natural behaviour: once bfqq->new_bfqq has been set, it will not be changed until all expected redirections have occurred. Signed-off-by: Davide Zini Signed-off-by: Paolo Valente Link: https://lore.kernel.org/r/20210802141352.74353-2-paolo.valente@linaro.org Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- block/bfq-iosched.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) -- 2.30.2 diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index b8c2ddc01aec..65c200e0ecb5 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -2526,6 +2526,15 @@ bfq_setup_merge(struct bfq_queue *bfqq, struct bfq_queue *new_bfqq) * are likely to increase the throughput. */ bfqq->new_bfqq = new_bfqq; + /* + * The above assignment schedules the following redirections: + * each time some I/O for bfqq arrives, the process that + * generated that I/O is disassociated from bfqq and + * associated with new_bfqq. Here we increases new_bfqq->ref + * in advance, adding the number of processes that are + * expected to be associated with new_bfqq as they happen to + * issue I/O. + */ new_bfqq->ref += process_refs; return new_bfqq; } @@ -2585,6 +2594,10 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq, { struct bfq_queue *in_service_bfqq, *new_bfqq; + /* if a merge has already been setup, then proceed with that first */ + if (bfqq->new_bfqq) + return bfqq->new_bfqq; + /* * Do not perform queue merging if the device is non * rotational and performs internal queueing. In fact, such a @@ -2639,9 +2652,6 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq, if (bfq_too_late_for_merging(bfqq)) return NULL; - if (bfqq->new_bfqq) - return bfqq->new_bfqq; - if (!io_struct || unlikely(bfqq == &bfqd->oom_bfqq)) return NULL;