linux-kernel - Re: [PATCH linux-next] mm/huge_memory: remove redundant locking when parsing THP sysfs input

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Date: Mon, 13 May 2024 17:58:21 +0200
From: David Hildenbrand <david@...hat.com>
To: xu.xin16@....com.cn, akpm@...ux-foundation.org
Cc: willy@...radead.org, shy828301@...il.com, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org
Subject: Re: [PATCH linux-next] mm/huge_memory: remove redundant locking when
 parsing THP sysfs input

On 11.05.24 08:40, xu.xin16@....com.cn wrote:
> From: Ran Xiaokai <ran.xiaokai@....com.cn>
> 
> Since sysfs_streq() only performs a simple memory comparison operation
> and will not introduce any sleepable operation, So there is no
> need to drop the lock when parsing input. Remove redundant lock
> and unlock operations to make code cleaner.
> 
> Signed-off-by: Ran Xiaokai <ran.xiaokai@....com.cn>
> ---
>   mm/huge_memory.c | 10 ++--------
>   1 file changed, 2 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 89f58c7603b2..87123a87cb21 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -478,32 +478,26 @@ static ssize_t thpsize_enabled_store(struct kobject *kobj,
>   	int order = to_thpsize(kobj)->order;
>   	ssize_t ret = count;
> 
> +	spin_lock(&huge_anon_orders_lock);
>   	if (sysfs_streq(buf, "always")) {
> -		spin_lock(&huge_anon_orders_lock);
>   		clear_bit(order, &huge_anon_orders_inherit);
>   		clear_bit(order, &huge_anon_orders_madvise);
>   		set_bit(order, &huge_anon_orders_always);
> -		spin_unlock(&huge_anon_orders_lock);
>   	} else if (sysfs_streq(buf, "inherit")) {
> -		spin_lock(&huge_anon_orders_lock);
>   		clear_bit(order, &huge_anon_orders_always);
>   		clear_bit(order, &huge_anon_orders_madvise);
>   		set_bit(order, &huge_anon_orders_inherit);
> -		spin_unlock(&huge_anon_orders_lock);
>   	} else if (sysfs_streq(buf, "madvise")) {
> -		spin_lock(&huge_anon_orders_lock);
>   		clear_bit(order, &huge_anon_orders_always);
>   		clear_bit(order, &huge_anon_orders_inherit);
>   		set_bit(order, &huge_anon_orders_madvise);
> -		spin_unlock(&huge_anon_orders_lock);
>   	} else if (sysfs_streq(buf, "never")) {
> -		spin_lock(&huge_anon_orders_lock);
>   		clear_bit(order, &huge_anon_orders_always);
>   		clear_bit(order, &huge_anon_orders_inherit);
>   		clear_bit(order, &huge_anon_orders_madvise);
> -		spin_unlock(&huge_anon_orders_lock);
>   	} else
>   		ret = -EINVAL;
> +	spin_unlock(&huge_anon_orders_lock);
> 
>   	return ret;
>   }

No strong opinion

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

-- 
Cheers,

David / dhildenb