linux-kernel - Re: [RFC PATCH 1/2] mm/khugepaged: Convert __collapse_huge_page

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Message-ID: <ZQ3vIFWOTDFtJ0Wj@casper.infradead.org>
Date:   Fri, 22 Sep 2023 20:46:40 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     "Vishal Moola (Oracle)" <vishal.moola@...il.com>
Cc:     linux-mm@...ck.org, akpm@...ux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/2] mm/khugepaged: Convert
 __collapse_huge_page_isolate() to use folios

On Fri, Sep 22, 2023 at 12:36:38PM -0700, Vishal Moola (Oracle) wrote:
> This is in preparation for the removal of the khugepaged compound_pagelist.
> 
> Replaces 11 calls to compound_head() with 1, and removes 499 bytes of
> kernel text.

Looks good to me.

> @@ -634,32 +633,33 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
>  		 * Isolate the page to avoid collapsing an hugepage
>  		 * currently in use by the VM.
>  		 */
> -		if (!isolate_lru_page(page)) {
> -			unlock_page(page);
> +		if (!folio_isolate_lru(folio)) {
> +			folio_unlock(folio);
>  			result = SCAN_DEL_PAGE_LRU;
>  			goto out;
>  		}
> -		mod_node_page_state(page_pgdat(page),
> -				NR_ISOLATED_ANON + page_is_file_lru(page),
> -				compound_nr(page));
> -		VM_BUG_ON_PAGE(!PageLocked(page), page);
> -		VM_BUG_ON_PAGE(PageLRU(page), page);
> +		node_stat_mod_folio(folio,
> +				NR_ISOLATED_ANON + folio_is_file_lru(folio),
> +				folio_nr_pages(folio));
> +		VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
> +		VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
>  
> -		if (PageCompound(page))
> -			list_add_tail(&page->lru, compound_pagelist);
> +		if (folio_test_large(folio))
> +			list_add_tail(&folio->lru, compound_pagelist);
>  next:
>  		/*
>  		 * If collapse was initiated by khugepaged, check that there is
>  		 * enough young pte to justify collapsing the page
>  		 */
>  		if (cc->is_khugepaged &&
> -		    (pte_young(pteval) || page_is_young(page) ||
> -		     PageReferenced(page) || mmu_notifier_test_young(vma->vm_mm,
> +		    (pte_young(pteval) || folio_test_young(folio) ||
> +		     folio_test_referenced(folio) || mmu_notifier_test_young(vma->vm_mm,
>  								     address)))
>  			referenced++;
>  
>  		if (pte_write(pteval))
>  			writable = true;
> +

Spurious change here.  Other than that,

Reviewed-by: Matthew Wilcox (Oracle) <willy@...radead.org>