linux-kernel - Re: [PATCH 3/4] md: fix is_mddev

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Message-ID: <4358e07e-f78b-cd32-bbed-c597b8bb4c19@huaweicloud.com>
Date: Wed, 16 Apr 2025 17:28:58 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Yu Kuai <yukuai1@...weicloud.com>, Xiao Ni <xni@...hat.com>,
 axboe@...nel.dk, song@...nel.org
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-raid@...r.kernel.org, yi.zhang@...wei.com, yangerkun@...wei.com,
 "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH 3/4] md: fix is_mddev_idle()

Hi,

在 2025/04/16 15:42, Yu Kuai 写道:
> Hi,
> 
> 在 2025/04/16 14:20, Xiao Ni 写道:
>>> +static bool is_rdev_idle(struct md_rdev *rdev, bool init)
>>> +{
>>> +    unsigned long last_events = rdev->last_events;
>>> +
>>> +    if (!bdev_is_partition(rdev->bdev))
>>> +        return true;
>>
>>
>> For md array, I think is_rdev_idle is not useful. Because 
>> mddev->last_events must be increased while upper ios come in and idle 
>> will be set to false. For dm array, mddev->last_events can't work. So 
>> is_rdev_idle is for dm array. If member disk is one partition, 
>> is_rdev_idle alwasy returns true, and is_mddev_idle always return 
>> true. It's a bug here. Do we need to check bdev_is_partition here?
> 
> is_rdev_idle() is not used for current array, for example:
> 
> sda1 is used for array md0, and user doesn't issue IO to md0, while
> user issues IO to sda2. In this case, is_mddev_idle() still fail for
> array md0 because is_rdev_idle() fail.

Perhaps the name is_rdev_holder_idle() is better.

Thanks,
Kuai

> 
> This is just inherited from the old behaviour.
> 
> Thanks,
> Kuai
> 
>>
>> Best Regards
>>
>> Xiao
> 
> .
>