linux-kernel - Re: [PATCH 1/2] mm: swap_cgroup: allocate swap

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Message-ID: <tygpha75uaeztnihylxyiguts2xfdzwr4arz4dwsygmbspdubr@gqwcze4d5ufd>
Date: Fri, 15 Nov 2024 12:17:43 -0800
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Roman Gushchin <roman.gushchin@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, Michal Hocko <mhocko@...nel.org>, 
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH 1/2] mm: swap_cgroup: allocate swap_cgroup map using
 vcalloc()

On Fri, Nov 15, 2024 at 07:02:28PM +0000, Roman Gushchin wrote:
> Currently swap_cgroup's map is constructed as a vmalloc()'s-based
> array of pointers to individual struct pages. This brings an
> unnecessary complexity into the code.
> 
> This patch turns the swap_cgroup's map into a single space
> allocated by vcalloc().
> 
> Signed-off-by: Roman Gushchin <roman.gushchin@...ux.dev>

Acked-by: Shakeel Butt <shakeel.butt@...ux.dev>

[...]
> @@ -215,19 +169,8 @@ void swap_cgroup_swapoff(int type)
>  	mutex_lock(&swap_cgroup_mutex);
>  	ctrl = &swap_cgroup_ctrl[type];
>  	map = ctrl->map;
> -	length = ctrl->length;
>  	ctrl->map = NULL;
> -	ctrl->length = 0;
>  	mutex_unlock(&swap_cgroup_mutex);
>  
> -	if (map) {
> -		for (i = 0; i < length; i++) {
> -			struct page *page = map[i];
> -			if (page)
> -				__free_page(page);
> -			if (!(i % SWAP_CLUSTER_MAX))
> -				cond_resched();
> -		}
> -		vfree(map);
> -	}
> +	kvfree(map);

Any reason to use kvfree() instead of just vfree()?

>  }
> -- 
> 2.47.0.338.g60cca15819-goog
>