linux-kernel - Re: [PATCH v2 1/3] blk-cgroup: check for pd_(alloc|free)_fn in blkcg_activate

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Message-ID: <febb4bcb-5908-382f-db9a-42b62347aa7e@huaweicloud.com>
Date: Sat, 20 Jul 2024 15:17:22 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Bart Van Assche <bvanassche@....org>,
 Christoph Hellwig <hch@...radead.org>, Yu Kuai <yukuai1@...weicloud.com>
Cc: jack@...e.cz, tj@...nel.org, josef@...icpanda.com, axboe@...nel.dk,
 cgroups@...r.kernel.org, linux-block@...r.kernel.org,
 linux-kernel@...r.kernel.org, yi.zhang@...wei.com, yangerkun@...wei.com,
 "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH v2 1/3] blk-cgroup: check for pd_(alloc|free)_fn in
 blkcg_activate_policy()

Hi,

在 2024/07/20 0:25, Bart Van Assche 写道:
> On 7/18/24 10:29 PM, Christoph Hellwig wrote:
>> On Fri, Jul 19, 2024 at 10:34:29AM +0800, Yu Kuai wrote:
>>> +    /*
>>> +     * Make sure cpd/pd_alloc_fn and cpd/pd_free_fn in pairs, and 
>>> policy
>>> +     * without pd_alloc_fn/pd_free_fn can't be activated.
>>> +     */
>>>       if ((!pol->cpd_alloc_fn ^ !pol->cpd_free_fn) ||
>>>           (!pol->pd_alloc_fn ^ !pol->pd_free_fn))
>>>           goto err_unlock;
>>> -- 
>>
>> I know this is existing code, but can you fix up the incorrect
>> indentation while you touch this:
>>
>>       if ((!pol->cpd_alloc_fn ^ !pol->cpd_free_fn) ||
>>           (!pol->pd_alloc_fn ^ !pol->pd_free_fn))
> 
> Using xor (^) for booleans seems weird to me. Is there any preference in
> Linux kernel code whether to use ^ or != to check whether to booleans
> are different?

I don't know, but I feel more comfortable to use '!=' myself.

Thanks,
Kuai

> 
> Thanks,
> 
> Bart.
> 
> .
>