Received-SPF: pass (google.com: domain of linux-kernel+bounces-14078-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) client-ip=2604:1380:4601:e00::3;
Subject: Re: [PATCH] md: get rdev->mddev with READ_ONCE()
To: Li Lingfeng <lilingfeng@huaweicloud.com>, song@kernel.org
Cc: linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org,
 linan122@huawei.com, yi.zhang@huawei.com, yangerkun@huawei.com,
 lilingfeng3@huawei.com, "yukuai (C)" <yukuai3@huawei.com>
References: <20231229070500.3602712-1-lilingfeng@huaweicloud.com>
From: Yu Kuai <yukuai1@huaweicloud.com>
Message-ID: <a5d9a13b-6b95-b2ba-203a-f8bb8dfb4936@huaweicloud.com>
Date: Tue, 2 Jan 2024 14:16:32 +0800
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101
 Thunderbird/60.8.0
Precedence: bulk
MIME-Version: 1.0
In-Reply-To: <20231229070500.3602712-1-lilingfeng@huaweicloud.com>
Content-Type: text/plain; charset=gbk; format=flowed
Content-Transfer-Encoding: 8bit

?? 2023/12/29 15:05, Li Lingfeng д??:
> From: Li Lingfeng <lilingfeng3@huawei.com>
> 
> Users may get rdev->mddev by sysfs while rdev is releasing.
> So use both READ_ONCE() and WRITE_ONCE() to prevent load/store tearing
> and to read/write mddev atomically.

LGTM
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
> 
> Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com>
> ---
>   drivers/md/md.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 9bdd57324c37..3b38a565bffa 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -2562,7 +2562,7 @@ static void md_kick_rdev_from_array(struct md_rdev *rdev)
>   	list_del_rcu(&rdev->same_set);
>   	pr_debug("md: unbind<%pg>\n", rdev->bdev);
>   	mddev_destroy_serial_pool(rdev->mddev, rdev);
> -	rdev->mddev = NULL;
> +	WRITE_ONCE(rdev->mddev, NULL);
>   	sysfs_remove_link(&rdev->kobj, "block");
>   	sysfs_put(rdev->sysfs_state);
>   	sysfs_put(rdev->sysfs_unack_badblocks);
> @@ -3646,7 +3646,7 @@ rdev_attr_store(struct kobject *kobj, struct attribute *attr,
>   	struct kernfs_node *kn = NULL;
>   	bool suspend = false;
>   	ssize_t rv;
> -	struct mddev *mddev = rdev->mddev;
> +	struct mddev *mddev = READ_ONCE(rdev->mddev);
>   
>   	if (!entry->store)
>   		return -EIO;
>