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Subject: Re: [PATCH 03/10] hugetlb: Use LIST_HEAD() to define a list head
To:     Muchun Song <muchun.song@linux.dev>
CC:     Andrew Morton <akpm@linux-foundation.org>,
        <mike.kravetz@oracle.com>, Muchun Song <songmuchun@bytedance.com>,
        <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>
References: <20220826092422.39591-1-linmiaohe@huawei.com>
 <20220826092422.39591-4-linmiaohe@huawei.com>
 <8D011A6F-F557-4519-852C-80BBDE53E630@linux.dev>
From:   Miaohe Lin <linmiaohe@huawei.com>
Message-ID: <bb05153c-29a9-b77e-0815-506309da6da0@huawei.com>
Date:   Sat, 27 Aug 2022 10:27:46 +0800
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On 2022/8/27 9:47, Muchun Song wrote:
> 
> 
>> On Aug 26, 2022, at 17:24, Miaohe Lin <linmiaohe@huawei.com> wrote:
>>
>> We can avoid unneeded WRITE_ONCE() overhead by using LIST_HEAD() to define
>> a list head.
> 
> IIUC, the overhead doesn’t change. Right?

I think the overhead is changed. LIST_HEAD is initialized without using WRITE_ONCE():

#define LIST_HEAD_INIT(name) { &(name), &(name) }

#define LIST_HEAD(name) \
	struct list_head name = LIST_HEAD_INIT(name)

while INIT_LIST_HEAD has:

static inline void INIT_LIST_HEAD(struct list_head *list)
{
	WRITE_ONCE(list->next, list);
	WRITE_ONCE(list->prev, list);
}

Or am I miss something?

> 
> I’m fine with your changes.
> 
> Reviewed-by: Muchun Song <songmuchun@bytedance.com>

Many thanks for your review and comment. :)

Thanks,
Miaohe Lin