linux-kernel - Re: [RFC v2 3/4] mm: add largest_zero

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Message-ID: <87seibr7do.fsf@gmail.com>
Date: Fri, 01 Aug 2025 10:00:27 +0530
From: Ritesh Harjani (IBM) <ritesh.list@...il.com>
To: "Pankaj Raghav (Samsung)" <kernel@...kajraghav.com>, Suren Baghdasaryan <surenb@...gle.com>, Ryan Roberts <ryan.roberts@....com>, Baolin Wang <baolin.wang@...ux.alibaba.com>, Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>, "H . Peter Anvin" <hpa@...or.com>, Vlastimil Babka <vbabka@...e.cz>, Zi Yan <ziy@...dia.com>, Mike Rapoport <rppt@...nel.org>, Dave Hansen <dave.hansen@...ux.intel.com>, Michal Hocko <mhocko@...e.com>, David Hildenbrand <david@...hat.com>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Andrew Morton <akpm@...ux-foundation.org>, Thomas Gleixner <tglx@...utronix.de>, Nico Pache <npache@...hat.com>, Dev Jain <dev.jain@....com>, "Liam R . Howlett" <Liam.Howlett@...cle.com>, Jens Axboe <axboe@...nel.dk>
Cc: linux-kernel@...r.kernel.org, willy@...radead.org, linux-mm@...ck.org, x86@...nel.org, linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org, "Darrick J . Wong" <djwong@...nel.org>, mcgrof@...nel.org, gost.dev@...sung.com, kernel@...kajraghav.com, hch@....de, Pankaj Raghav <p.raghav@...sung.com>
Subject: Re: [RFC v2 3/4]  mm: add largest_zero_folio() routine

"Pankaj Raghav (Samsung)" <kernel@...kajraghav.com> writes:

> From: Pankaj Raghav <p.raghav@...sung.com>
>
> Add largest_zero_folio() routine so that huge_zero_folio can be

[largest]_zero_folio() can sound a bit confusing with largest in it's
name. Maybe optimal_zero_folio()? 

No hard opinion though. Will leave it upto you. 

-ritesh

> used directly when CONFIG_STATIC_HUGE_ZERO_FOLIO is enabled. This will
> return ZERO_PAGE folio if CONFIG_STATIC_HUGE_ZERO_FOLIO is disabled or
> if we failed to allocate a huge_zero_folio.
>
> Co-developed-by: David Hildenbrand <david@...hat.com>
> Signed-off-by: David Hildenbrand <david@...hat.com>
> Signed-off-by: Pankaj Raghav <p.raghav@...sung.com>
> ---
>  include/linux/huge_mm.h | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
>
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index 78ebceb61d0e..c44a6736704b 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -716,4 +716,21 @@ static inline int split_folio_to_order(struct folio *folio, int new_order)
>  	return split_folio_to_list_to_order(folio, NULL, new_order);
>  }
>  
> +/*
> + * largest_zero_folio - Get the largest zero size folio available
> + *
> + * This function will return huge_zero_folio if CONFIG_STATIC_HUGE_ZERO_FOLIO
> + * is enabled. Otherwise, a ZERO_PAGE folio is returned.
> + *
> + * Deduce the size of the folio with folio_size instead of assuming the
> + * folio size.
> + */
> +static inline struct folio *largest_zero_folio(void)
> +{
> +	struct folio *folio = get_static_huge_zero_folio();
> +
> +	if (folio)
> +		return folio;
> +	return page_folio(ZERO_PAGE(0));
> +}
>  #endif /* _LINUX_HUGE_MM_H */
> -- 
> 2.49.0