linux-kernel - Re: [PATCH 1/2] mm/page_ext: Add page_ext_get

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Message-ID: <qu5oksvcaytolppeeale6rwf4bzvckvfdg3iw77kowrg4fn24a@p4hmieukkttu>
Date: Mon, 19 Jan 2026 16:48:59 +0100
From: Jörg Rödel <joro@...tes.org>
To: Mostafa Saleh <smostafa@...gle.com>
Cc: linux-mm@...ck.org, iommu@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org, corbet@....net, will@...nel.org, 
	robin.murphy@....com, akpm@...ux-foundation.org, vbabka@...e.cz, surenb@...gle.com, 
	mhocko@...e.com, jackmanb@...gle.com, hannes@...xchg.org, ziy@...dia.com, 
	david@...hat.com, lorenzo.stoakes@...cle.com, Liam.Howlett@...cle.com, 
	rppt@...nel.org, xiaqinxin@...wei.com, baolu.lu@...ux.intel.com, 
	rdunlap@...radead.org
Subject: Re: [PATCH 1/2] mm/page_ext: Add page_ext_get_phys()

On Mon, Jan 19, 2026 at 02:22:45PM +0000, Mostafa Saleh wrote:
> +static inline struct page_ext *page_ext_get_phys(phys_addr_t phys)

The name is misleading as it indicates that the function returns a physical
address. Maybe name it page_ext_from_phys()?

> +{
> +	return NULL;
> +}
> +
>  static inline void page_ext_put(struct page_ext *page_ext)
>  {
>  }
> diff --git a/mm/page_ext.c b/mm/page_ext.c
> index 297e4cd8ce90..5fe65a0ac4f3 100644
> --- a/mm/page_ext.c
> +++ b/mm/page_ext.c
> @@ -538,6 +538,29 @@ struct page_ext *page_ext_get(const struct page *page)
>  	return page_ext;
>  }
>  
> +/**
> + * page_ext_get_phys() - Get the page_ext structure for a physical address.
> + * @phys: The physical address to query.
> + *
> + * This function safely gets the `struct page_ext` associated with a given
> + * physical address. It performs validation to ensure the address corresponds
> + * to a valid, online struct page before attempting to access it.
> + * It should return NULL for (MMIO, ZONE_DEVICE, holes, offline memory)

It should?

-Joerg