linux-kernel - Re: [PATCH v4 07/15] mm: pgtable: introduce pagetable

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Message-ID: <bce4bb4e-459a-44c8-945b-8889149377fd@bytedance.com>
Date: Mon, 6 Jan 2025 21:23:10 +0800
From: Qi Zheng <zhengqi.arch@...edance.com>
To: Alexander Gordeev <agordeev@...ux.ibm.com>
Cc: peterz@...radead.org, kevin.brodsky@....com, palmer@...belt.com,
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Subject: Re: [PATCH v4 07/15] mm: pgtable: introduce pagetable_dtor()



On 2025/1/6 20:36, Alexander Gordeev wrote:
> On Mon, Jan 06, 2025 at 06:55:58PM +0800, Qi Zheng wrote:
>>>> +static inline void pagetable_dtor(struct ptdesc *ptdesc)
>>>> +{
>>>> +	struct folio *folio = ptdesc_folio(ptdesc);
>>>> +
>>>> +	ptlock_free(ptdesc);
>>>> +	__folio_clear_pgtable(folio);
>>>> +	lruvec_stat_sub_folio(folio, NR_PAGETABLE);
>>>> +}
>>>> +
>>>
>>> If I am not mistaken, it is just pagetable_pte_dtor() rename.
>>> What is the point in moving the code around?
>>
>> No, this is to unify pagetable_p*_dtor() into pagetable_dtor(), so
>> that we can move pagetable_dtor() to __tlb_remove_table(), and then
>> ptlock and PTE page can be freed together through RCU, which is
>> also the main purpose of this patch series.
> 
> I am only talking about this patch. pagetable_dtor() code above is
> the same pagetable_pte_dtor() below - it is only the function name
> that changed. So why to move the function body? Anyway, that is

Ah, I just don't want to put pagetable_dtor() in between
pagetable_pte_ctor() and ___pte_offset_map(), so I moved it above
pagetable_pte_ctor(). No other special reason. ;)

Thanks!

> just a nit.
> 
>> Thanks!
> 
>>>> -static inline void pagetable_pte_dtor(struct ptdesc *ptdesc)
>>>> -{
>>>> -	struct folio *folio = ptdesc_folio(ptdesc);
>>>> -
>>>> -	ptlock_free(ptdesc);
>>>> -	__folio_clear_pgtable(folio);
>>>> -	lruvec_stat_sub_folio(folio, NR_PAGETABLE);
>>>> -}
> 
> Thank you!