From nobody Thu Dec 18 01:02:09 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 DB2DEC25B42 for ; Sat, 21 Oct 2023 02:25:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232269AbjJUCZf (ORCPT ); Fri, 20 Oct 2023 22:25:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35660 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231201AbjJUCZV (ORCPT ); Fri, 20 Oct 2023 22:25:21 -0400 Received: from dggsgout12.his.huawei.com (unknown [45.249.212.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 91A4DD7D; Fri, 20 Oct 2023 19:25:18 -0700 (PDT) Received: from mail02.huawei.com (unknown [172.30.67.153]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTP id 4SC4zn4G3Rz4f3kG1; Sat, 21 Oct 2023 10:25:09 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.104.67]) by APP4 (Coremail) with SMTP id gCh0CgAnt9aHNjNlZ+cUDg--.5642S10; Sat, 21 Oct 2023 10:25:15 +0800 (CST) From: Yu Kuai To: song@kernel.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 -next v2 6/6] md/md-multipath: remove rcu protection to access rdev from conf Date: Sat, 21 Oct 2023 18:20:59 +0800 Message-Id: <20231021102059.3198284-7-yukuai1@huaweicloud.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20231021102059.3198284-1-yukuai1@huaweicloud.com> References: <20231021102059.3198284-1-yukuai1@huaweicloud.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: gCh0CgAnt9aHNjNlZ+cUDg--.5642S10 X-Coremail-Antispam: 1UD129KBjvJXoWxXw1kJF4UZr43uw17Wr17ZFb_yoW5Jw4kpa yaqasxtr4UXryakrnFka1Uua4Skw43tFWIkryfC3yIva15Gry5XF1rtryUXFn5AFZ5AF45 XFn8Kw4DAFyxGaUanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUPY14x267AKxVWrJVCq3wAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2jI8I6cxK62vIxIIY0VWUZVW8XwA2048vs2IY02 0E87I2jVAFwI0_JF0E3s1l82xGYIkIc2x26xkF7I0E14v26ryj6s0DM28lY4IEw2IIxxk0 rwA2F7IY1VAKz4vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6x IIjxv20xvEc7CjxVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xv wVC2z280aVCY1x0267AKxVW0oVCq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFc xC0VAKzVAqx4xG6I80ewAv7VC0I7IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_ Gr1lOx8S6xCaFVCjc4AY6r1j6r4UM4x0Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2 IErcIFxwCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E 14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_JF0_Jw1lIx kGc2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUCVW8JwCI42IY6xIIjxv20xvEc7CjxVAF wI0_Gr0_Cr1lIxAIcVCF04k26cxKx2IYs7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r1j6r 4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x0pRvJPtU UUUU= X-CM-SenderInfo: 51xn3trlr6x35dzhxuhorxvhhfrp/ X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Yu Kuai Because it's safe to accees rdev from conf: - If any spinlock is held, because synchronize_rcu() from md_kick_rdev_from_array() will prevent 'rdev' to be freed until spinlock is released; - If there is normal IO inflight, because mddev_suspend() will prevent rdev to be added or removed from array; And these will cover all the scenarios in md-multipath. Signed-off-by: Yu Kuai --- drivers/md/md-multipath.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff --git a/drivers/md/md-multipath.c b/drivers/md/md-multipath.c index aa77133f3188..51c5390c517d 100644 --- a/drivers/md/md-multipath.c +++ b/drivers/md/md-multipath.c @@ -32,17 +32,15 @@ static int multipath_map (struct mpconf *conf) * now we use the first available disk. */ =20 - rcu_read_lock(); for (i =3D 0; i < disks; i++) { - struct md_rdev *rdev =3D rcu_dereference(conf->multipaths[i].rdev); + struct md_rdev *rdev =3D conf->multipaths[i].rdev; + if (rdev && test_bit(In_sync, &rdev->flags) && !test_bit(Faulty, &rdev->flags)) { atomic_inc(&rdev->nr_pending); - rcu_read_unlock(); return i; } } - rcu_read_unlock(); =20 pr_crit_ratelimited("multipath_map(): no more operational IO paths?\n"); return (-1); @@ -137,14 +135,16 @@ static void multipath_status(struct seq_file *seq, st= ruct mddev *mddev) struct mpconf *conf =3D mddev->private; int i; =20 + lockdep_assert_held(&mddev->lock); + seq_printf (seq, " [%d/%d] [", conf->raid_disks, conf->raid_disks - mddev->degraded); - rcu_read_lock(); for (i =3D 0; i < conf->raid_disks; i++) { - struct md_rdev *rdev =3D rcu_dereference(conf->multipaths[i].rdev); - seq_printf (seq, "%s", rdev && test_bit(In_sync, &rdev->flags) ? "U" : "= _"); + struct md_rdev *rdev =3D READ_ONCE(conf->multipaths[i].rdev); + + seq_printf(seq, "%s", + rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_"); } - rcu_read_unlock(); seq_putc(seq, ']'); } =20 @@ -231,7 +231,7 @@ static int multipath_add_disk(struct mddev *mddev, stru= ct md_rdev *rdev) rdev->raid_disk =3D path; set_bit(In_sync, &rdev->flags); spin_unlock_irq(&conf->device_lock); - rcu_assign_pointer(p->rdev, rdev); + WRITE_ONCE(p->rdev, rdev); err =3D 0; break; } @@ -257,7 +257,7 @@ static int multipath_remove_disk(struct mddev *mddev, s= truct md_rdev *rdev) err =3D -EBUSY; goto abort; } - p->rdev =3D NULL; + WRITE_ONCE(p->rdev, NULL); err =3D md_integrity_register(mddev); } abort: --=20 2.39.2