linux-kernel - Re: [PATCH] mm/kasan: use kasan_zero

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Date:   Mon, 15 May 2017 11:29:57 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     <js1304@...il.com>, Andrew Morton <akpm@...ux-foundation.org>
CC:     "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        <kasan-dev@...glegroups.com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, <kernel-team@....com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH] mm/kasan: use kasan_zero_pud for p4d table

On 05/15/2017 09:20 AM, js1304@...il.com wrote:
> From: Joonsoo Kim <iamjoonsoo.kim@....com>
> 
> There is missing optimization in zero_p4d_populate() that can save
> some memory when mapping zero shadow. Implement it like as others.
> 
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>

Acked-by: Andrey Ryabinin <aryabinin@...tuozzo.com>


> ---
>  mm/kasan/kasan_init.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/mm/kasan/kasan_init.c b/mm/kasan/kasan_init.c
> index b96a5f7..554e4c0 100644
> --- a/mm/kasan/kasan_init.c
> +++ b/mm/kasan/kasan_init.c
> @@ -118,6 +118,18 @@ static void __init zero_p4d_populate(pgd_t *pgd, unsigned long addr,
>  
>  	do {
>  		next = p4d_addr_end(addr, end);
> +		if (IS_ALIGNED(addr, P4D_SIZE) && end - addr >= P4D_SIZE) {
> +			pud_t *pud;
> +			pmd_t *pmd;
> +
> +			p4d_populate(&init_mm, p4d, lm_alias(kasan_zero_pud));
> +			pud = pud_offset(p4d, addr);
> +			pud_populate(&init_mm, pud, lm_alias(kasan_zero_pmd));
> +			pmd = pmd_offset(pud, addr);
> +			pmd_populate_kernel(&init_mm, pmd,
> +						lm_alias(kasan_zero_pte));
> +			continue;
> +		}
>  
>  		if (p4d_none(*p4d)) {
>  			p4d_populate(&init_mm, p4d,
>