linux-kernel - Re: [PATCH] mm, hugetlb: Increment the number of pages to be reset on HVO

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Message-ID: <d6c415ae-4d8e-4d6b-a22d-eb2b02b5bb67@redhat.com>
Date: Tue, 15 Apr 2025 15:02:37 +0200
From: David Hildenbrand <david@...hat.com>
To: Oscar Salvador <osalvador@...e.de>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: Muchun Song <muchun.song@...ux.dev>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm, hugetlb: Increment the number of pages to be reset on
 HVO

On 15.04.25 13:18, Oscar Salvador wrote:
> commit 4eeec8c89a0c ("mm: move hugetlb specific things in folio to page[3]")
> shifted hugetlb specific stuff, and now mapping overlaps _hugetlb_cgroup field.
> 
> Upon restoring the vmemmap for HVO, only the first two tail pages are reset, and
> this causes the check in free_tail_page_prepare() to fail as it finds
> an unexpected mapping value in some tails.
> 
> Increment the number of pages to be reset to 4 (head + 3 tail pages)
> 
> Fixes: 4eeec8c89a0c ("mm: move hugetlb specific things in folio to page[3]")
> Suggested-by: David Hildenbrand <david@...hat.com>
> Signed-off-by: Oscar Salvador <osalvador@...e.de>
> ---
>   mm/hugetlb_vmemmap.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> index 9a99dfa3c495..27245e86df25 100644
> --- a/mm/hugetlb_vmemmap.c
> +++ b/mm/hugetlb_vmemmap.c
> @@ -238,11 +238,11 @@ static void vmemmap_remap_pte(pte_t *pte, unsigned long addr,
>    * struct page, the special metadata (e.g. page->flags or page->mapping)
>    * cannot copy to the tail struct page structs. The invalid value will be
>    * checked in the free_tail_page_prepare(). In order to avoid the message
> - * of "corrupted mapping in tail page". We need to reset at least 3 (one
> - * head struct page struct and two tail struct page structs) struct page
> + * of "corrupted mapping in tail page". We need to reset at least 4 (one
> + * head struct page struct and three tail struct page structs) struct page
>    * structs.
>    */
> -#define NR_RESET_STRUCT_PAGE		3
> +#define NR_RESET_STRUCT_PAGE		4
>   
>   static inline void reset_struct_pages(struct page *start)
>   {

Thanks!

Reviewed-by: David Hildenbrand <david@...hat.com>


-- 
Cheers,

David / dhildenb