linux-kernel - Re: [PATCH v2] mm/memory: Don't require head page for do_set

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Date: Tue, 11 Jun 2024 17:33:17 +0200
From: David Hildenbrand <david@...hat.com>
To: Andrew Bresticker <abrestic@...osinc.com>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm/memory: Don't require head page for do_set_pmd()

On 11.06.24 17:32, Andrew Bresticker wrote:
> The requirement that the head page be passed to do_set_pmd() was added
> in commit ef37b2ea08ac ("mm/memory: page_add_file_rmap() ->
> folio_add_file_rmap_[pte|pmd]()") and prevents pmd-mapping in the
> finish_fault() and filemap_map_pages() paths if the page to be inserted
> is anything but the head page for an otherwise suitable vma and pmd-sized
> page.
> 
> Fixes: ef37b2ea08ac ("mm/memory: page_add_file_rmap() -> folio_add_file_rmap_[pte|pmd]()")
> Signed-off-by: Andrew Bresticker <abrestic@...osinc.com>
> ---
>   mm/memory.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index 0f47a533014e..a1fce5ddacb3 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4614,8 +4614,9 @@ vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page)
>   	if (!thp_vma_suitable_order(vma, haddr, PMD_ORDER))
>   		return ret;
>   
> -	if (page != &folio->page || folio_order(folio) != HPAGE_PMD_ORDER)
> +	if (folio_order(folio) != HPAGE_PMD_ORDER)
>   		return ret;
> +	page = &folio->page;
>   
>   	/*
>   	 * Just backoff if any subpage of a THP is corrupted otherwise

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

-- 
Cheers,

David / dhildenb