From nobody Wed Dec 17 14:01:17 2025 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 308CBC4167B for ; Wed, 29 Nov 2023 02:03:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1376738AbjK2CDQ (ORCPT ); Tue, 28 Nov 2023 21:03:16 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40478 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229885AbjK2CDO (ORCPT ); Tue, 28 Nov 2023 21:03:14 -0500 Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1E9ED198D; Tue, 28 Nov 2023 18:03:19 -0800 (PST) Received: from mail.maildlp.com (unknown [172.19.163.235]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4Sg2fT1Hrhz4f3jZB; Wed, 29 Nov 2023 10:03:13 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.112]) by mail.maildlp.com (Postfix) with ESMTP id 0CB171A0C0D; Wed, 29 Nov 2023 10:03:16 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.104.67]) by APP1 (Coremail) with SMTP id cCh0CgDHyhDim2ZlfZTmCA--.8717S4; Wed, 29 Nov 2023 10:03:15 +0800 (CST) From: Yu Kuai To: song@kernel.org, neilb@suse.de, maan@systemlinux.org Cc: linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, yukuai3@huawei.com, yukuai1@huaweicloud.com, yi.zhang@huawei.com, yangerkun@huawei.com Subject: [PATCH v3] md: synchronize flush io with array reconfiguration Date: Wed, 29 Nov 2023 10:02:34 +0800 Message-Id: <20231129020234.1586910-1-yukuai1@huaweicloud.com> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: cCh0CgDHyhDim2ZlfZTmCA--.8717S4 X-Coremail-Antispam: 1UD129KBjvJXoWxWry8uFW5Kw1DZw4xtr1UWrg_yoW5AFy3p3 yFq3Zxtr4UXFZ8KwsxJa1kGr1rWa1jvFW0yay3Z343Zw13Xrn8G3yfKF95Xr98CFyfu3y3 ur4qgw4Dua4jqFUanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUyK14x267AKxVW8JVW5JwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK02 1l84ACjcxK6xIIjxv20xvE14v26w1j6s0DM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26r4U JVWxJr1l84ACjcxK6I8E87Iv67AKxVW0oVCq3wA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_Gc CE3s1le2I262IYc4CY6c8Ij28IcVAaY2xG8wAqx4xG64xvF2IEw4CE5I8CrVC2j2WlYx0E 2Ix0cI8IcVAFwI0_Jr0_Jr4lYx0Ex4A2jsIE14v26r1j6r4UMcvjeVCFs4IE7xkEbVWUJV W8JwACjcxG0xvY0x0EwIxGrwACjI8F5VA0II8E6IAqYI8I648v4I1l42xK82IYc2Ij64vI r41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4xG67AKxVWUJVWUGwC20s026x8Gjc xK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r1q6r43MIIYrxkI7VAKI48JMIIF0xvE2Ix0 cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6xkF7I0E14v26r1j6r4UMIIF0xvE42xK8V AvwI8IcIk0rVWrJr0_WFyUJwCI42IY6I8E87Iv67AKxVWUJVW8JwCI42IY6I8E87Iv6xkF 7I0E14v26r4j6r4UJbIYCTnIWIevJa73UjIFyTuYvjfUoOJ5UUUUU X-CM-SenderInfo: 51xn3trlr6x35dzhxuhorxvhhfrp/ Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Yu Kuai Currently rcu is used to protect iterating rdev from submit_flushes(): submit_flushes remove_and_add_spares synchronize_rcu pers->hot_remove_disk() rcu_read_lock() rdev_for_each_rcu if (rdev->raid_disk >=3D 0) rdev->radi_disk =3D -1; atomic_inc(&rdev->nr_pending) rcu_read_unlock() bi =3D bio_alloc_bioset() bi->bi_end_io =3D md_end_flush bi->private =3D rdev submit_bio // issue io for removed rdev Fix this problem by grabbing 'acive_io' before iterating rdev, make sure that remove_and_add_spares() won't concurrent with submit_flushes(). Fixes: a2826aa92e2e ("md: support barrier requests on all personalities.") Signed-off-by: Yu Kuai --- Changes in v3: - use WARN_ON(percpu_ref_is_zero()) and use percpu_ref_get(). Changes in v2: - Add WARN_ON in case md_flush_request() is not called from md_handle_request() in future. drivers/md/md.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index 05902e36db66..75ff96d53266 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -529,6 +529,9 @@ static void md_end_flush(struct bio *bio) rdev_dec_pending(rdev, mddev); =20 if (atomic_dec_and_test(&mddev->flush_pending)) { + /* The pair is percpu_ref_get() from md_flush_request() */ + percpu_ref_put(&mddev->active_io); + /* The pre-request flush has finished */ queue_work(md_wq, &mddev->flush_work); } @@ -548,12 +551,8 @@ static void submit_flushes(struct work_struct *ws) rdev_for_each_rcu(rdev, mddev) if (rdev->raid_disk >=3D 0 && !test_bit(Faulty, &rdev->flags)) { - /* Take two references, one is dropped - * when request finishes, one after - * we reclaim rcu_read_lock - */ struct bio *bi; - atomic_inc(&rdev->nr_pending); + atomic_inc(&rdev->nr_pending); rcu_read_unlock(); bi =3D bio_alloc_bioset(rdev->bdev, 0, @@ -564,7 +563,6 @@ static void submit_flushes(struct work_struct *ws) atomic_inc(&mddev->flush_pending); submit_bio(bi); rcu_read_lock(); - rdev_dec_pending(rdev, mddev); } rcu_read_unlock(); if (atomic_dec_and_test(&mddev->flush_pending)) @@ -617,6 +615,18 @@ bool md_flush_request(struct mddev *mddev, struct bio = *bio) /* new request after previous flush is completed */ if (ktime_after(req_start, mddev->prev_flush_start)) { WARN_ON(mddev->flush_bio); + /* + * Grab a reference to make sure mddev_suspend() will wait for + * this flush to be done. + * + * md_flush_reqeust() is called under md_handle_request() and + * 'active_io' is already grabbed, hence percpu_ref_is_zero() + * won't pass, percpu_ref_tryget_live() can't be used because + * percpu_ref_kill() can be called by mddev_suspend() + * concurrently. + */ + WARN_ON(percpu_ref_is_zero(&mddev->active_io)); + percpu_ref_get(&mddev->active_io); mddev->flush_bio =3D bio; bio =3D NULL; } --=20 2.39.2