linux-kernel - Re: [PATCH 1/2] arm64/mm: Allow __create_pgd_mapping() to propagate pgtable

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Message-ID: <683f9f4e-c027-4165-a8aa-b561e304e132@arm.com>
Date: Fri, 15 Aug 2025 13:00:14 +0530
From: Dev Jain <dev.jain@....com>
To: Chaitanya S Prakash <chaitanyas.prakash@....com>,
 linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Cc: Ryan Roberts <ryan.roberts@....com>,
 Yang Shi <yang@...amperecomputing.com>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Kevin Brodsky <kevin.brodsky@....com>,
 Anshuman Khandual <anshuman.khandual@....com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Zhenhua Huang <quic_zhenhuah@...cinc.com>, Joey Gouly <joey.gouly@....com>
Subject: Re: [PATCH 1/2] arm64/mm: Allow __create_pgd_mapping() to propagate
 pgtable_alloc() errors


On 13/08/25 8:26 pm, Chaitanya S Prakash wrote:
> [-------snip-------------]
>   
> -static void __create_pgd_mapping(pgd_t *pgdir, phys_addr_t phys,
> +static int __create_pgd_mapping(pgd_t *pgdir, phys_addr_t phys,
>   				 unsigned long virt, phys_addr_t size,
>   				 pgprot_t prot,
>   				 phys_addr_t (*pgtable_alloc)(enum pgtable_type),
>   				 int flags)
>   {
> +	int ret = 0;
> +
>   	mutex_lock(&fixmap_lock);
> -	__create_pgd_mapping_locked(pgdir, phys, virt, size, prot,
> -				    pgtable_alloc, flags);
> +	ret = __create_pgd_mapping_locked(pgdir, phys, virt, size, prot,
> +					  pgtable_alloc, flags);
>   	mutex_unlock(&fixmap_lock);
> +
> +	return ret;
> +}
> +
> +static void ___create_pgd_mapping(pgd_t *pgdir, phys_addr_t phys,
> +				  unsigned long virt, phys_addr_t size,
> +				  pgprot_t prot,
> +				  phys_addr_t (*pgtable_alloc)(enum pgtable_type),
> +				  int flags)
> +{
> +	int ret = 0;
> +
> +	ret = __create_pgd_mapping(pgdir, phys, virt, size, prot, pgtable_alloc,
> +				   flags);
> +	BUG_ON(ret);
>   }

A triple underscore calling a double underscore isn't natural to reason about.
Since this is the function which must succeed, how does "must_create_pgd_mapping()"
sound?