linux-kernel - Re: [PATCH 2/3] md/raid10: factor out get_rdev_repl_from

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Message-ID: <0af5c40f-ccc5-0d4c-3371-6473da9083b7@huaweicloud.com>
Date:   Sat, 1 Jul 2023 09:40:19 +0800
From:   Li Nan <linan666@...weicloud.com>
To:     Song Liu <song@...nel.org>, linan666@...weicloud.com
Cc:     guoqing.jiang@...ud.ionos.com, colyli@...e.de, xni@...hat.com,
        linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
        yukuai3@...wei.com, yi.zhang@...wei.com, houtao1@...wei.com,
        yangerkun@...wei.com
Subject: Re: [PATCH 2/3] md/raid10: factor out get_rdev_repl_from_mirror()



在 2023/7/1 7:53, Song Liu 写道:
> On Tue, Jun 27, 2023 at 6:58 PM <linan666@...weicloud.com> wrote:
>>
> [...]
> 
>>
>> +static void get_rdev_repl_from_mirror(struct raid10_info *mirror,
>> +                                struct md_rdev **prdev,
>> +                                struct md_rdev **prrdev)
>> +{
>> +       struct md_rdev *rdev, *rrdev;
>> +
>> +       rrdev = rcu_dereference(mirror->replacement);
>> +       /*
>> +        * Read replacement first to prevent reading both rdev and
>> +        * replacement as NULL during replacement replace rdev.
>> +        */
>> +       smp_mb();
>> +       rdev = rcu_dereference(mirror->rdev);
>> +       if (rdev == rrdev)
>> +               rrdev = NULL;
>> +
>> +       *prrdev = rrdev;
>> +       *prdev = rdev;
> 
> I don't think the reduction in duplicated code justifies two output arguments.
> 
> How about
> 
> static struct md_rdev *dereference_rdev_and_rrdev(struct raid10_info *mirror,
>                                 struct md_rdev **prrdev)
> {
>      ...
>      *prrdev = xxx;
>      return rdev;
> }
> 
> So we only have one argument for output.
> 
> Also, "from_mirror" in the function name doesn't really add more value.
> 
> Thanks,
> Song
> .

I agree. Let me improve this.

-- 
Thanks,
Nan