Re: [PATCH 1/4] mm: factor out the order calculation into a new helper

[David Hildenbrand <david@redhat.com>]

On 08.11.24 05:12, Baolin Wang wrote:
> Factor out the order calculation into a new helper, which can be reused
> by shmem in the following patch.
> 
> Suggested-by: Matthew Wilcox <willy@infradead.org>
> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> ---
>   include/linux/pagemap.h | 16 +++++++++++++---
>   1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index bcf0865a38ae..d796c8a33647 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -727,6 +727,16 @@ typedef unsigned int __bitwise fgf_t;
>   
>   #define FGP_WRITEBEGIN		(FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE)
>   
> +static inline unsigned int filemap_get_order(size_t size)
> +{
> +	unsigned int shift = ilog2(size);
> +
> +	if (shift <= PAGE_SHIFT)
> +		return 0;
> +
> +	return shift - PAGE_SHIFT;
> +}
> +

I'd have added some words somewhere, how this differs to get_order() 
[calculated order might not have space to fit the complete size] and why 
[avoid over-allocation].

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb