linux-kernel - Re: [PATCH] mm/cma: Remove CONFIG_CMA

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Message-ID: <20251114010928.151974-1-sj@kernel.org>
Date: Thu, 13 Nov 2025 17:09:27 -0800
From: SeongJae Park <sj@...nel.org>
To: Jean Delvare <jdelvare@...e.de>
Cc: SeongJae Park <sj@...nel.org>,
	linux-mm@...ck.org,
	LKML <linux-kernel@...r.kernel.org>,
	David Hildenbrand <david@...hat.com>
Subject: Re: [PATCH] mm/cma: Remove CONFIG_CMA_SYSFS option

On Thu, 13 Nov 2025 14:56:36 +0100 Jean Delvare <jdelvare@...e.de> wrote:

> The sysfs interface to CMA has a marginal runtime cost and a small
> footprint, there's no reason not to include it in all kernels where
> the dependencies are satisfied.

Overall change looks good to me.  I have a question below, though.

> 
> Signed-off-by: Jean Delvare <jdelvare@...e.de>
> ---
> As discussed with David:
>   https://lkml.org/lkml/2025/8/6/371
> 
>  arch/loongarch/configs/loongson3_defconfig |    1 -
>  arch/s390/configs/debug_defconfig          |    1 -
>  arch/s390/configs/defconfig                |    1 -
>  mm/Kconfig                                 |    7 -------
>  mm/Makefile                                |    4 +++-
>  mm/cma.h                                   |    4 ++--
>  6 files changed, 5 insertions(+), 13 deletions(-)
> 
> --- linux-6.17.orig/arch/loongarch/configs/loongson3_defconfig
> +++ linux-6.17/arch/loongarch/configs/loongson3_defconfig
[...]
> --- linux-6.17.orig/mm/cma.h
> +++ linux-6.17/mm/cma.h
> @@ -49,7 +49,7 @@ struct cma {
>  	char name[CMA_MAX_NAME];
>  	int nranges;
>  	struct cma_memrange ranges[CMA_MAX_RANGES];
> -#ifdef CONFIG_CMA_SYSFS
> +#ifdef CONFIG_SYSFS
>  	/* the number of CMA page successful allocations */
>  	atomic64_t nr_pages_succeeded;
>  	/* the number of CMA page allocation failures */
> @@ -80,7 +80,7 @@ static inline unsigned long cma_bitmap_m
>  	return cmr->count >> cma->order_per_bit;
>  }
>  
> -#ifdef CONFIG_CMA_SYSFS
> +#ifdef CONFIG_SYSFS
>  void cma_sysfs_account_success_pages(struct cma *cma, unsigned long nr_pages);
>  void cma_sysfs_account_fail_pages(struct cma *cma, unsigned long nr_pages);
>  void cma_sysfs_account_release_pages(struct cma *cma, unsigned long nr_pages);

Why don't you check CONFIG_CMA together?  I think that makes the change more
complete and safe.

I found there is no file that can be compiled without CONFIG_CMA but still
including this header file, so I expect no real issue for now, though.


Thanks,
SJ

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