linux-kernel - Re: [PATCH v1] mm/memory: fix folio_set_dirty() vs. folio_mark_dirty() in zap_pte

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Message-ID: <d2272d63-1999-4cb3-be61-4a9fbd00e728@arm.com>
Date: Mon, 22 Jan 2024 17:22:42 +0000
From: Ryan Roberts <ryan.roberts@....com>
To: David Hildenbrand <david@...hat.com>, linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org, Matthew Wilcox <willy@...radead.org>,
 Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v1] mm/memory: fix folio_set_dirty() vs.
 folio_mark_dirty() in zap_pte_range()

On 22/01/2024 17:17, David Hildenbrand wrote:
> The correct folio replacement for "set_page_dirty()" is
> "folio_mark_dirty()", not "folio_set_dirty()". Using the latter won't
> properly inform the FS using the dirty_folio() callback.

That set_page_dirty() naming is pretty nasty, hey.

> 
> This has been found by code inspection, but likely this can result in
> some real trouble when zapping dirty PTEs that point at clean pagecache
> folios.
> 
> Reported-by: Ryan Roberts <ryan.roberts@....com>
> Closes: https://lkml.kernel.org/r/2445cedb-61fb-422c-8bfb-caf0a2beed62@arm.com
> Fixes: c46265030b0f ("mm/memory: page_remove_rmap() -> folio_remove_rmap_pte()")
> Cc: Matthew Wilcox (Oracle) <willy@...radead.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Signed-off-by: David Hildenbrand <david@...hat.com>

Reviewed-by: Ryan Roberts <ryan.roberts@....com>

> ---
>  mm/memory.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index 7e1f4849463aa..89bcae0b224d6 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1464,7 +1464,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
>  			delay_rmap = 0;
>  			if (!folio_test_anon(folio)) {
>  				if (pte_dirty(ptent)) {
> -					folio_set_dirty(folio);
> +					folio_mark_dirty(folio);
>  					if (tlb_delay_rmap(tlb)) {
>  						delay_rmap = 1;
>  						force_flush = 1;