linux-kernel - Re: [PATCH 2/3] LoongArch: Code cleanup in function pcpu_populate

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Date:   Mon, 31 Jul 2023 22:15:20 +0800
From:   Huacai Chen <chenhuacai@...nel.org>
To:     Bibo Mao <maobibo@...ngson.cn>
Cc:     Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, WANG Xuerui <kernel@...0n.name>
Subject: Re: [PATCH 2/3] LoongArch: Code cleanup in function pcpu_populate_pte

On Wed, Jul 12, 2023 at 11:16 AM Bibo Mao <maobibo@...ngson.cn> wrote:
>
> There are some code cleanups in function pcpu_populate_pte:
> 1. Replace memblock_alloc with memblock_alloc_raw for pud and pmd since
> they will be reinitialized with pud_init and pmd_init.
>
> 2. Add memory allocation failure handling
>
> 3. Replace pgd_populate with p4d_populate, it will be useful if there
> four-level page tables.
>
> Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
> ---
>  arch/loongarch/kernel/numa.c | 33 ++++++++++++++++++++-------------
>  1 file changed, 20 insertions(+), 13 deletions(-)
>
> diff --git a/arch/loongarch/kernel/numa.c b/arch/loongarch/kernel/numa.c
> index 708665895b47..778e1c20bfb0 100644
> --- a/arch/loongarch/kernel/numa.c
> +++ b/arch/loongarch/kernel/numa.c
> @@ -73,33 +73,40 @@ void __init pcpu_populate_pte(unsigned long addr)
>         pmd_t *pmd;
>
>         if (p4d_none(*p4d)) {
> -               pud_t *new;
> -
> -               new = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
> -               pgd_populate(&init_mm, pgd, new);
> +               pud = memblock_alloc_raw(PAGE_SIZE, PAGE_SIZE);
Don't use memblock_alloc_raw() here, it is better to keep consistency
with mm/percpu.c.


Huacai
> +               if (!pud)
> +                       goto err_alloc;
> +               p4d_populate(&init_mm, p4d, pud);
>  #ifndef __PAGETABLE_PUD_FOLDED
> -               pud_init(new);
> +               pud_init(pud);
>  #endif
>         }
>
>         pud = pud_offset(p4d, addr);
>         if (pud_none(*pud)) {
> -               pmd_t *new;
> -
> -               new = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
> -               pud_populate(&init_mm, pud, new);
> +               pmd = memblock_alloc_raw(PAGE_SIZE, PAGE_SIZE);
> +               if (!pmd)
> +                       goto err_alloc;
> +               pud_populate(&init_mm, pud, pmd);
>  #ifndef __PAGETABLE_PMD_FOLDED
> -               pmd_init(new);
> +               pmd_init(pmd);
>  #endif
>         }
>
>         pmd = pmd_offset(pud, addr);
>         if (!pmd_present(*pmd)) {
> -               pte_t *new;
> +               pte_t *pte;
>
> -               new = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
> -               pmd_populate_kernel(&init_mm, pmd, new);
> +               pte = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
> +               if (!pte)
> +                       goto err_alloc;
> +               pmd_populate_kernel(&init_mm, pmd, pte);
>         }
> +
> +       return;
> +
> +err_alloc:
> +       panic("%s: Failed to allocate memory\n", __func__);
>  }
>
>  void __init setup_per_cpu_areas(void)
> --
> 2.27.0
>