linux-kernel - Re: [PATCH v2 1/3] hugetlb: Convert hugetlb_fault() to use struct vm

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Date: Thu, 4 Apr 2024 14:27:37 +0200
From: Oscar Salvador <osalvador@...e.de>
To: "Vishal Moola (Oracle)" <vishal.moola@...il.com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, muchun.song@...ux.dev,
	willy@...radead.org
Subject: Re: [PATCH v2 1/3] hugetlb: Convert hugetlb_fault() to use struct
 vm_fault

On Mon, Apr 01, 2024 at 01:26:49PM -0700, Vishal Moola (Oracle) wrote:
> Now that hugetlb_fault() has a vm_fault available for fault tracking, use
> it throughout. This cleans up the code by removing 2 variables, and
> prepares hugetlb_fault() to take in a struct vm_fault argument.
> 
> Signed-off-by: Vishal Moola (Oracle) <vishal.moola@...il.com>

Reviewed-by: Oscar Salvador <osalvador@...e.de>

A question below:

>  mm/hugetlb.c | 84 +++++++++++++++++++++++++---------------------------
>  1 file changed, 41 insertions(+), 43 deletions(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 8267e221ca5d..360b82374a89 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
..  
>  	/*
> -	 * entry could be a migration/hwpoison entry at this point, so this
> -	 * check prevents the kernel from going below assuming that we have
> -	 * an active hugepage in pagecache. This goto expects the 2nd page
> -	 * fault, and is_hugetlb_entry_(migration|hwpoisoned) check will
> -	 * properly handle it.
> +	 * vmf.orig_pte could be a migration/hwpoison vmf.orig_pte at this

"vmf.orig_pte could be a migration/hwpoison entry at ..."

> -	entry = pte_mkyoung(entry);
> -	if (huge_ptep_set_access_flags(vma, haddr, ptep, entry,
> +	vmf.orig_pte = pte_mkyoung(vmf.orig_pte);
> +	if (huge_ptep_set_access_flags(vma, vmf.address, vmf.pte, vmf.orig_pte,
>  						flags & FAULT_FLAG_WRITE))

Would it make sense to teach huge_ptep_set_access_flags/set_huge_pte_at() to use
vm_fault struct as well? All info we are passing is stored there.
Maybe it is not worth the trouble though, just asking.


-- 
Oscar Salvador
SUSE Labs