linux-kernel - Re: [PATCH v3 3/4] mm/hugetlb: Refactor __unmap_hugepage

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Message-ID: <aBHYK3mqUyvqrGm2@localhost.localdomain>
Date: Wed, 30 Apr 2025 09:58:35 +0200
From: Oscar Salvador <osalvador@...e.de>
To: nifan.cxl@...il.com
Cc: muchun.song@...ux.dev, willy@...radead.org, mcgrof@...nel.org,
	a.manzanares@...sung.com, dave@...olabs.net,
	akpm@...ux-foundation.org, david@...hat.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Fan Ni <fan.ni@...sung.com>
Subject: Re: [PATCH v3 3/4] mm/hugetlb: Refactor __unmap_hugepage_range() to
 take folio instead of page

On Mon, Apr 28, 2025 at 10:11:46AM -0700, nifan.cxl@...il.com wrote:
> From: Fan Ni <fan.ni@...sung.com>
> 
> The function __unmap_hugepage_range() has two kinds of users:
> 1) unmap_hugepage_range(), which passes in the head page of a folio.
>    Since unmap_hugepage_range() already takes folio and there are no other
>    uses of the folio struct in the function, it is natural for
>    __unmap_hugepage_range() to take folio also.
> 2) All other uses, which pass in NULL pointer.
> 
> In both cases, we can pass in folio. Refactor __unmap_hugepage_range() to
> take folio.
> 
> Signed-off-by: Fan Ni <fan.ni@...sung.com>

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

But:

>  void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
>  			    unsigned long start, unsigned long end,
> -			    struct page *ref_page, zap_flags_t zap_flags)
> +			    struct folio *folio, zap_flags_t zap_flags)

I think we are kinda losing information here. ref_ was a good hint
and...

>  	struct mm_struct *mm = vma->vm_mm;
>  	unsigned long address;
> @@ -5885,8 +5885,8 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
>  		 * page is being unmapped, not a range. Ensure the page we
>  		 * are about to unmap is the actual page of interest.
>  		 */
> -		if (ref_page) {
> -			if (page != ref_page) {
> +		if (folio) {
> +			if (page_folio(page) != folio) {

You have to update the comment above, since we are not passing a
reference page anymore but a folio.

 

-- 
Oscar Salvador
SUSE Labs