linux-kernel - Re: [PATCH 2/2] mm: cma: simplify cma_maxchunk

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Message-ID: <2cae64a2-7fd4-46ae-b4ab-8924db99154b@redhat.com>
Date: Mon, 21 Jul 2025 12:59:53 +0200
From: David Hildenbrand <david@...hat.com>
To: Yury Norov <yury.norov@...il.com>,
 Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] mm: cma: simplify cma_maxchunk_get()

On 19.07.25 22:54, Yury Norov wrote:
> From: Yury Norov (NVIDIA) <yury.norov@...il.com>
> 
> The function opencodes for_each_clear_bitrange(). Fix that and drop most
> of housekeeping code.

Not sure if talking about a "fix" it the right word here.

Acked-by: David Hildenbrand <david@...hat.com>

> 
> Signed-off-by: Yury Norov (NVIDIA) <yury.norov@...il.com>
> ---
>   mm/cma_debug.c | 10 +---------
>   1 file changed, 1 insertion(+), 9 deletions(-)
> 
> diff --git a/mm/cma_debug.c b/mm/cma_debug.c
> index fdf899532ca0..8c7d7f8e8fbd 100644
> --- a/mm/cma_debug.c
> +++ b/mm/cma_debug.c
> @@ -56,16 +56,8 @@ static int cma_maxchunk_get(void *data, u64 *val)
>   	for (r = 0; r < cma->nranges; r++) {
>   		cmr = &cma->ranges[r];
>   		bitmap_maxno = cma_bitmap_maxno(cma, cmr);
> -		end = 0;
> -		for (;;) {
> -			start = find_next_zero_bit(cmr->bitmap,
> -						   bitmap_maxno, end);
> -			if (start >= bitmap_maxno)
> -				break;
> -			end = find_next_bit(cmr->bitmap, bitmap_maxno,
> -					    start);
> +		for_each_clear_bitrange(start, end, cmr->bitmap, bitmap_maxno)
>   			maxchunk = max(end - start, maxchunk);
> -		}
>   	}
>   	spin_unlock_irq(&cma->lock);
>   	*val = (u64)maxchunk << cma->order_per_bit;


-- 
Cheers,

David / dhildenb