From patchwork Tue Jan 3 08:47:55 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu Kuai X-Patchwork-Id: 13087303 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 9401BC3DA7D for ; Tue, 3 Jan 2023 08:23:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232992AbjACIX1 (ORCPT ); Tue, 3 Jan 2023 03:23:27 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46858 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232838AbjACIX0 (ORCPT ); Tue, 3 Jan 2023 03:23:26 -0500 Received: from dggsgout12.his.huawei.com (dggsgout12.his.huawei.com [45.249.212.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 763291036; Tue, 3 Jan 2023 00:23:21 -0800 (PST) Received: from mail02.huawei.com (unknown [172.30.67.153]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTP id 4NmQjH3z7yz4f3kpC; Tue, 3 Jan 2023 16:23:15 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.127.227]) by APP4 (Coremail) with SMTP id gCh0CgBH_rH05bNjFOASBA--.23491S4; Tue, 03 Jan 2023 16:23:18 +0800 (CST) From: Yu Kuai To: jack@suse.cz, paolo.valente@linaro.org, axboe@kernel.dk, tj@kernel.org, josef@toxicpanda.com Cc: linux-block@vger.kernel.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, yukuai3@huawei.com, yukuai1@huaweicloud.com, yi.zhang@huawei.com, yangerkun@huawei.com Subject: [PATCH] block, bfq: switch 'bfqg->ref' to use atomic refcount apis Date: Tue, 3 Jan 2023 16:47:55 +0800 Message-Id: <20230103084755.1256479-1-yukuai1@huaweicloud.com> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 X-CM-TRANSID: gCh0CgBH_rH05bNjFOASBA--.23491S4 X-Coremail-Antispam: 1UD129KBjvJXoW7uFyfuw15JryDWrWDury3Arb_yoW8Zr1kpF n0qa45G34rGr1fXF4UAa4UXry8Jw1fCryrK3yqg3sYyry7Xw1Sg3Z0yrWrJ34SvF93ArWU Zr1Ygay0vr12qFUanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUvY14x267AKxVW8JVW5JwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK02 1l84ACjcxK6xIIjxv20xvE14v26w1j6s0DM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26r4U JVWxJr1l84ACjcxK6I8E87Iv67AKxVW0oVCq3wA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_Gc CE3s1le2I262IYc4CY6c8Ij28IcVAaY2xG8wAqx4xG64xvF2IEw4CE5I8CrVC2j2WlYx0E 2Ix0cI8IcVAFwI0_Jr0_Jr4lYx0Ex4A2jsIE14v26r1j6r4UMcvjeVCFs4IE7xkEbVWUJV W8JwACjcxG0xvY0x0EwIxGrwACjI8F5VA0II8E6IAqYI8I648v4I1lFIxGxcIEc7CjxVA2 Y2ka0xkIwI1l42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4 xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r1q6r43 MIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6xkF7I 0E14v26r4j6F4UMIIF0xvE42xK8VAvwI8IcIk0rVWrZr1j6s0DMIIF0xvEx4A2jsIE14v2 6r1j6r4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x0J UdHUDUUUUU= X-CM-SenderInfo: 51xn3trlr6x35dzhxuhorxvhhfrp/ X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org From: Yu Kuai The updating of 'bfqg->ref' should be protected by 'bfqd->lock', however, during code review, we found that bfq_pd_free() update 'bfqg->ref' without holding the lock, which is problematic: 1) bfq_pd_free() triggered by removing cgroup is called asynchronously; 2) bfqq will grab bfqg reference, and exit bfqq will drop the reference, which can concurrent with 1). Unfortunately, 'bfqd->lock' can't be held here because 'bfqd' might already be freed in bfq_pd_free(). Fix the problem by using atomic refcount apis. Signed-off-by: Yu Kuai Reviewed-by: Jan Kara --- Changes from RFC: - refcount_dec_and_test(bfqg->ref) -> refcount_dec_and_test(&bfqg->ref) block/bfq-cgroup.c | 8 +++----- block/bfq-iosched.h | 2 +- 2 files changed, 4 insertions(+), 6 deletions(-) diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c index 1b2829e99dad..7d9b15f0dbd5 100644 --- a/block/bfq-cgroup.c +++ b/block/bfq-cgroup.c @@ -316,14 +316,12 @@ struct bfq_group *bfqq_group(struct bfq_queue *bfqq) static void bfqg_get(struct bfq_group *bfqg) { - bfqg->ref++; + refcount_inc(&bfqg->ref); } static void bfqg_put(struct bfq_group *bfqg) { - bfqg->ref--; - - if (bfqg->ref == 0) + if (refcount_dec_and_test(&bfqg->ref)) kfree(bfqg); } @@ -530,7 +528,7 @@ static struct blkg_policy_data *bfq_pd_alloc(gfp_t gfp, struct request_queue *q, } /* see comments in bfq_bic_update_cgroup for why refcounting */ - bfqg_get(bfqg); + refcount_set(&bfqg->ref, 1); return &bfqg->pd; } diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h index 41aa151ccc22..466e4865ace6 100644 --- a/block/bfq-iosched.h +++ b/block/bfq-iosched.h @@ -928,7 +928,7 @@ struct bfq_group { char blkg_path[128]; /* reference counter (see comments in bfq_bic_update_cgroup) */ - int ref; + refcount_t ref; /* Is bfq_group still online? */ bool online;