From patchwork Tue Dec 21 03:21:35 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu Kuai X-Patchwork-Id: 12688975 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A6ABBC433F5 for ; Tue, 21 Dec 2021 03:10:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234383AbhLUDKE (ORCPT ); Mon, 20 Dec 2021 22:10:04 -0500 Received: from szxga08-in.huawei.com ([45.249.212.255]:30082 "EHLO szxga08-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234264AbhLUDKC (ORCPT ); Mon, 20 Dec 2021 22:10:02 -0500 Received: from kwepemi500006.china.huawei.com (unknown [172.30.72.53]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4JJ1Zj0cY1z1DKBf; Tue, 21 Dec 2021 11:06:53 +0800 (CST) Received: from kwepemm600009.china.huawei.com (7.193.23.164) by kwepemi500006.china.huawei.com (7.221.188.68) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.20; Tue, 21 Dec 2021 11:10:00 +0800 Received: from huawei.com (10.175.127.227) by kwepemm600009.china.huawei.com (7.193.23.164) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.20; Tue, 21 Dec 2021 11:09:59 +0800 From: Yu Kuai To: , , , , , CC: , , , , Subject: [PATCH 4/4] block, bfq: update pos_root for idle bfq_queue in bfq_bfqq_move() Date: Tue, 21 Dec 2021 11:21:35 +0800 Message-ID: <20211221032135.878550-5-yukuai3@huawei.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20211221032135.878550-1-yukuai3@huawei.com> References: <20211221032135.878550-1-yukuai3@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.175.127.227] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To kwepemm600009.china.huawei.com (7.193.23.164) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org During code review, we found that if bfqq is not busy in bfq_bfqq_move(), bfq_pos_tree_add_move() won't be called for the bfqq, thus bfqq->pos_root still points to the old bfqg. However, the ref that bfqq hold for the old bfqg will be released, so it's possible that the old bfqg can be freed. This is problematic because the freed bfqg can still be accessed by bfqq->pos_root. Fix the problem by calling bfq_pos_tree_add_move() for idle bfqq as well. Fixes: e21b7a0b9887 ("block, bfq: add full hierarchical scheduling and cgroups support") Signed-off-by: Yu Kuai --- block/bfq-cgroup.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c index 8e8cf6b3d946..822dd28ecf53 100644 --- a/block/bfq-cgroup.c +++ b/block/bfq-cgroup.c @@ -677,7 +677,6 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq, bfq_deactivate_bfqq(bfqd, bfqq, false, false); else if (entity->on_st_or_in_serv) bfq_put_idle_entity(bfq_entity_service_tree(entity), entity); - bfqg_and_blkg_put(old_parent); if (entity->parent && entity->parent->last_bfqq_created == bfqq) @@ -690,11 +689,16 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq, /* pin down bfqg and its associated blkg */ bfqg_and_blkg_get(bfqg); - if (bfq_bfqq_busy(bfqq)) { - if (unlikely(!bfqd->nonrot_with_queueing)) - bfq_pos_tree_add_move(bfqd, bfqq); + /* + * Don't leave the pos_root to old bfqg, since the ref to old bfqg will + * be released and the bfqg might be freed. + */ + if (unlikely(!bfqd->nonrot_with_queueing)) + bfq_pos_tree_add_move(bfqd, bfqq); + bfqg_and_blkg_put(old_parent); + + if (bfq_bfqq_busy(bfqq)) bfq_activate_bfqq(bfqd, bfqq); - } if (!bfqd->in_service_queue && !bfqd->rq_in_driver) bfq_schedule_dispatch(bfqd);