Re: [PATCH 4/7] maccess: Use a scoped guard for page faults

["David Hildenbrand (Arm)" <david@kernel.org>]

On 8/24/26 18:04, Muhammad Usama Anjum wrote:
> Kernel nofault copy and string paths open-code page-fault disable and
> enable around label-based loops, duplicating cleanup on success and
> failure.
> 
> Use a page-fault scope guard instead. Leaving the scope now re-enables
> page faults on both paths without separate cleanup at the fault label.
> 
> No functional change.
> 
> Signed-off-by: Muhammad Usama Anjum <usama.anjum@arm.com>
> ---
>  mm/maccess.c | 53 +++++++++++++++++++++++++---------------------------
>  1 file changed, 25 insertions(+), 28 deletions(-)
> 
> diff --git a/mm/maccess.c b/mm/maccess.c
> index c59a0e092d24a..f695ceefe6fcc 100644
> --- a/mm/maccess.c
> +++ b/mm/maccess.c
> @@ -38,18 +38,17 @@ long copy_from_kernel_nofault(void *dst, const void *src, size_t size)
>  	if (!size)
>  		return 0;
>  
> -	pagefault_disable();
> -	if (!(align & 7))
> -		copy_from_kernel_nofault_loop(dst, src, size, u64, Efault);
> -	if (!(align & 3))
> -		copy_from_kernel_nofault_loop(dst, src, size, u32, Efault);
> -	if (!(align & 1))
> -		copy_from_kernel_nofault_loop(dst, src, size, u16, Efault);
> -	copy_from_kernel_nofault_loop(dst, src, size, u8, Efault);
> -	pagefault_enable();
> +	scoped_guard(pagefault) {
> +		if (!(align & 7))
> +			copy_from_kernel_nofault_loop(dst, src, size, u64, Efault);
> +		if (!(align & 3))
> +			copy_from_kernel_nofault_loop(dst, src, size, u32, Efault);
> +		if (!(align & 1))
> +			copy_from_kernel_nofault_loop(dst, src, size, u16, Efault);
> +		copy_from_kernel_nofault_loop(dst, src, size, u8, Efault);
> +	}

While I understand what pagefault_disable+pagefault_enable does, it is
completely unclear what scoped_guard(pagefault) does.

Should this be scoped_guard(disabled_pagefaults) or sth like that?

-- 
Cheers,

David