linux-kernel - Re: [PATCH v2 02/15] mm: pgtable: introduce generic p4d_alloc_one() and p4d

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Message-ID: <Z2RKpdv7pL34MIEt@tuxmaker.boeblingen.de.ibm.com>
Date: Thu, 19 Dec 2024 17:32:37 +0100
From: Alexander Gordeev <agordeev@...ux.ibm.com>
To: Qi Zheng <zhengqi.arch@...edance.com>
Cc: peterz@...radead.org, tglx@...utronix.de, david@...hat.com,
        jannh@...gle.com, hughd@...gle.com, yuzhao@...gle.com,
        willy@...radead.org, muchun.song@...ux.dev, vbabka@...nel.org,
        lorenzo.stoakes@...cle.com, akpm@...ux-foundation.org,
        rientjes@...gle.com, vishal.moola@...il.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 02/15] mm: pgtable: introduce generic p4d_alloc_one()
 and p4d_free()

On Wed, Dec 18, 2024 at 09:04:38PM +0800, Qi Zheng wrote:
> For these architectures, provide a generic implementation in
> asm-generic/pgalloc.h and convert them to use it. And like other levels
> of page tables, add statistics for P4D level page table.

FWIW, introducing the generic implementation and adding ctor|dtors
look as separate changes to me.

...
>  static inline void p4d_free(struct mm_struct *mm, p4d_t *p4d)
>  {
> -	if (!pgtable_l5_enabled())
> -		return;
> -	BUG_ON((unsigned long)p4d & (PAGE_SIZE-1));

Or maybe?

	BUG_ON(!IS_ALIGNED((unsigned long)p4d, PAGE_SIZE));

> -	free_page((unsigned long)p4d);
> +	if (pgtable_l5_enabled())
> +		__p4d_free(mm, p4d);
>  }