From patchwork Sun Jun 28 17:20:40 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dmitry Monakhov X-Patchwork-Id: 11630243 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 35297618 for ; Sun, 28 Jun 2020 17:20:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B8F9420771 for ; Sun, 28 Jun 2020 17:20:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=yandex-team.ru header.i=@yandex-team.ru header.b="i7o08oxK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726143AbgF1RUt (ORCPT ); Sun, 28 Jun 2020 13:20:49 -0400 Received: from forwardcorp1o.mail.yandex.net ([95.108.205.193]:53770 "EHLO forwardcorp1o.mail.yandex.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726060AbgF1RUs (ORCPT ); Sun, 28 Jun 2020 13:20:48 -0400 Received: from iva8-d077482f1536.qloud-c.yandex.net (iva8-d077482f1536.qloud-c.yandex.net [IPv6:2a02:6b8:c0c:2f26:0:640:d077:482f]) by forwardcorp1o.mail.yandex.net (Yandex) with ESMTP id 53EF32E19C0; Sun, 28 Jun 2020 20:20:45 +0300 (MSK) Received: from iva8-88b7aa9dc799.qloud-c.yandex.net (iva8-88b7aa9dc799.qloud-c.yandex.net [2a02:6b8:c0c:77a0:0:640:88b7:aa9d]) by iva8-d077482f1536.qloud-c.yandex.net (mxbackcorp/Yandex) with ESMTP id pM0SH2ClET-Khn0egtc; Sun, 28 Jun 2020 20:20:45 +0300 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex-team.ru; s=default; t=1593364845; bh=kKRrfxb90VfzoXGfhNPYe5HmgW3st+L4rXe9X50lhVE=; h=Message-Id:Date:Subject:To:From:Cc; b=i7o08oxKIQ6LebaGj7RjcZEmSQ/jVIhZDVLMmqRI5fPe18FKATrS6E0JMF8eqIxrZ XF6/8cgk8a3BSlMoAkM5sGF/Scgfdd0e5Rr6C6WZgOWK8K6cLHW9Gn/94/EyvsuU5J SHA3MAurrEWt/OvZdYhzCX0cDPeOdCjVT/MGbacQ= Authentication-Results: iva8-d077482f1536.qloud-c.yandex.net; dkim=pass header.i=@yandex-team.ru Received: from 95.108.174.193-red.dhcp.yndx.net (95.108.174.193-red.dhcp.yndx.net [95.108.174.193]) by iva8-88b7aa9dc799.qloud-c.yandex.net (smtpcorp/Yandex) with ESMTPSA id UGedWxu57L-KhhKEAMr; Sun, 28 Jun 2020 20:20:43 +0300 (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client certificate not present) From: Dmitry Monakhov To: linux-kernel@vger.kernel.org Cc: linux-block@vger.kernel.org, axboe@kernel.dk, paolo.valente@linaro.org, khlebnikov@yandex-team.ru, Dmitry Monakhov Subject: [PATCH] bfq: fix blkio cgroup leakage Date: Sun, 28 Jun 2020 17:20:40 +0000 Message-Id: <20200628172040.1869-1-dmonakhov@gmail.com> X-Mailer: git-send-email 2.18.0 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org commit db37a34c563b ("block, bfq: get a ref to a group when adding it to a service tree") introduce leak forbfq_group and blkcg_gq objects because of get/put imbalance. See trace balow: -> blkg_alloc -> bfq_pq_alloc -> bfqg_get (+1) ->bfq_activate_bfqq ->bfq_activate_requeue_entity -> __bfq_activate_entity ->bfq_get_entity ->bfqg_and_blkg_get (+1) <==== : Note1 ->bfq_del_bfqq_busy ->bfq_deactivate_entity+0x53/0xc0 [bfq] ->__bfq_deactivate_entity+0x1b8/0x210 [bfq] -> bfq_forget_entity(is_in_service = true) entity->on_st_or_in_serv = false <=== :Note2 if (is_in_service) return; ==> do not touch reference -> blkcg_css_offline -> blkcg_destroy_blkgs -> blkg_destroy -> bfq_pd_offline -> __bfq_deactivate_entity if (!entity->on_st_or_in_serv) /* true, because (Note2) return false; -> bfq_pd_free -> bfqg_put() (-1, byt bfqg->ref == 2) because of (Note2) So bfq_group and blkcg_gq will leak forever, see test-case below. If fact bfq_group objects reference counting are quite different from bfq_queue. bfq_groups object are referenced by blkcg_gq via blkg_policy_data pointer, so neither nor blkg_get() neither bfqg_get required here. This patch drop commit db37a34c563b ("block, bfq: get a ref to a group when adding it to a service tree") and add corresponding comment. ##TESTCASE_BEGIN: #!/bin/bash max_iters=${1:-100} #prep cgroup mounts mount -t tmpfs cgroup_root /sys/fs/cgroup mkdir /sys/fs/cgroup/blkio mount -t cgroup -o blkio none /sys/fs/cgroup/blkio # Prepare blkdev grep blkio /proc/cgroups truncate -s 1M img losetup /dev/loop0 img echo bfq > /sys/block/loop0/queue/scheduler grep blkio /proc/cgroups for ((i=0;i /sys/fs/cgroup/blkio/a/cgroup.procs dd if=/dev/loop0 bs=4k count=1 of=/dev/null iflag=direct 2> /dev/null echo 0 > /sys/fs/cgroup/blkio/cgroup.procs rmdir /sys/fs/cgroup/blkio/a grep blkio /proc/cgroups done ##TESTCASE_END: Signed-off-by: Dmitry Monakhov --- block/bfq-cgroup.c | 2 +- block/bfq-iosched.h | 1 - block/bfq-wf2q.c | 15 +++++---------- 3 files changed, 6 insertions(+), 12 deletions(-) diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c index 68882b9..b791e20 100644 --- a/block/bfq-cgroup.c +++ b/block/bfq-cgroup.c @@ -332,7 +332,7 @@ static void bfqg_put(struct bfq_group *bfqg) kfree(bfqg); } -void bfqg_and_blkg_get(struct bfq_group *bfqg) +static void bfqg_and_blkg_get(struct bfq_group *bfqg) { /* see comments in bfq_bic_update_cgroup for why refcounting bfqg */ bfqg_get(bfqg); diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h index cd224aa..7038952 100644 --- a/block/bfq-iosched.h +++ b/block/bfq-iosched.h @@ -986,7 +986,6 @@ struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd, struct blkcg_gq *bfqg_to_blkg(struct bfq_group *bfqg); struct bfq_group *bfqq_group(struct bfq_queue *bfqq); struct bfq_group *bfq_create_group_hierarchy(struct bfq_data *bfqd, int node); -void bfqg_and_blkg_get(struct bfq_group *bfqg); void bfqg_and_blkg_put(struct bfq_group *bfqg); #ifdef CONFIG_BFQ_GROUP_IOSCHED diff --git a/block/bfq-wf2q.c b/block/bfq-wf2q.c index 34ad095..6a363bb 100644 --- a/block/bfq-wf2q.c +++ b/block/bfq-wf2q.c @@ -529,13 +529,14 @@ static void bfq_get_entity(struct bfq_entity *entity) { struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); + /* Grab reference only for bfq_queue's objects, bfq_group ones + * are owned by blkcg_gq + */ if (bfqq) { bfqq->ref++; bfq_log_bfqq(bfqq->bfqd, bfqq, "get_entity: %p %d", bfqq, bfqq->ref); - } else - bfqg_and_blkg_get(container_of(entity, struct bfq_group, - entity)); + } } /** @@ -649,14 +650,8 @@ static void bfq_forget_entity(struct bfq_service_tree *st, entity->on_st_or_in_serv = false; st->wsum -= entity->weight; - if (is_in_service) - return; - - if (bfqq) + if (bfqq && !is_in_service) bfq_put_queue(bfqq); - else - bfqg_and_blkg_put(container_of(entity, struct bfq_group, - entity)); } /**