linux-kernel - Re: [PATCH v2 1/2] arm64/mm: Allow __create_pgd_mapping() to propagate pgtable

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Message-ID: <87f23627-d0cc-4d9a-a4f8-df1f61716b04@arm.com>
Date: Tue, 14 Oct 2025 11:29:05 +0200
From: Kevin Brodsky <kevin.brodsky@....com>
To: Linu Cherian <linu.cherian@....com>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Ryan Roberts <ryan.roberts@....com>, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Cc: Anshuman Khandual <anshuman.khandual@....com>,
 Zhenhua Huang <quic_zhenhuah@...cinc.com>, Dev Jain <dev.jain@....com>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Yang Shi <yang@...amperecomputing.com>,
 Chaitanya S Prakash <chaitanyas.prakash@....com>
Subject: Re: [PATCH v2 1/2] arm64/mm: Allow __create_pgd_mapping() to
 propagate pgtable_alloc() errors

On 13/10/2025 10:02, Linu Cherian wrote:
> [...]
>
> @@ -1877,23 +1926,30 @@ int arch_add_memory(int nid, u64 start, u64 size,
>  	if (force_pte_mapping())
>  		flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
>  
> -	__create_pgd_mapping(swapper_pg_dir, start, __phys_to_virt(start),
> -			     size, params->pgprot, pgd_pgtable_alloc_init_mm,
> -			     flags);
> +	ret = __create_pgd_mapping(swapper_pg_dir, start, __phys_to_virt(start),
> +				   size, params->pgprot, pgd_pgtable_alloc_init_mm,
> +				   flags);
> +

Nit: usually no empty line between a call and a trivial if (ret).

> +	if (ret)
> +		goto out;
>  
>  	memblock_clear_nomap(start, size);
>  
>  	ret = __add_pages(nid, start >> PAGE_SHIFT, size >> PAGE_SHIFT,
>  			   params);
>  	if (ret)
> -		__remove_pgd_mapping(swapper_pg_dir,
> -				     __phys_to_virt(start), size);
> +		goto out;
>  	else {
>  		/* Address of hotplugged memory can be smaller */
>  		max_pfn = max(max_pfn, PFN_UP(start + size));
>  		max_low_pfn = max_pfn;
>  	}
>  
> +	return 0;
> +
> +out:

Nit: since this is an error path, it'd be clearer to call the label
"err" rather than "out".

- Kevin

> +	__remove_pgd_mapping(swapper_pg_dir,
> +			     __phys_to_virt(start), size);
>  	return ret;
>  }
>