linux-kernel - Re: [PATCH] fs: quota: Replace GFP_ATOMIC with GFP_KERNEL in dquot

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Date:   Mon, 9 Apr 2018 17:49:16 +0200
From:   Jan Kara <jack@...e.cz>
To:     Jia-Ju Bai <baijiaju1990@...il.com>
Cc:     jack@...e.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs: quota: Replace GFP_ATOMIC with GFP_KERNEL in
 dquot_init

On Mon 09-04-18 22:31:19, Jia-Ju Bai wrote:
> dquot_init() is never called in atomic context.
> This function is only set as a parameter of fs_initcall().
> 
> Despite never getting called from atomic context,
> dquot_init() calls __get_free_pages() with GFP_ATOMIC,
> which waits busily for allocation.
> GFP_ATOMIC is not necessary and can be replaced with GFP_KERNEL,
> to avoid busy waiting and improve the possibility of sucessful allocation.
> 
> This is found by a static analysis tool named DCNS written by myself.
> And I also manually check it.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>

Thanks, I have added the patch to my tree.

								Honza


> ---
>  fs/quota/dquot.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
> index 8381db9..d6e111e 100644
> --- a/fs/quota/dquot.c
> +++ b/fs/quota/dquot.c
> @@ -2944,7 +2944,7 @@ static int __init dquot_init(void)
>  			NULL);
>  
>  	order = 0;
> -	dquot_hash = (struct hlist_head *)__get_free_pages(GFP_ATOMIC, order);
> +	dquot_hash = (struct hlist_head *)__get_free_pages(GFP_KERNEL, order);
>  	if (!dquot_hash)
>  		panic("Cannot create dquot hash table");
>  
> -- 
> 1.9.1
> 
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR