linux-kernel - Re: [PATCH] block: aoenet: Replace GFP_ATOMIC with GFP_KERNEL in aoenet

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Message-Id: <219E4594-88B1-4501-A897-9A4B3296163B@cashinworks.com>
Date:   Sat, 27 Jan 2018 12:48:35 -0500
From:   Ed Cashin <ed@...hinworks.com>
To:     Jia-Ju Bai <baijiaju1990@...il.com>
Cc:     ed.cashin@....org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] block: aoenet: Replace GFP_ATOMIC with GFP_KERNEL in aoenet_rcv

If the tool cannot tell whether the protected state is manipulated by *another* piece of code called in atomic context, then it's insufficient.

> On Jan 26, 2018, at 4:37 AM, Jia-Ju Bai <baijiaju1990@...il.com> wrote:
> 
> After checking all possible call chains to aoenet_rcv(),
> my tool finds that aoenet_rcv() is never called in atomic context, 
> namely never in an interrupt handler or holding a spinlock.
> Thus GFP_ATOMIC is not necessary, and it can be replaced with GFP_KERNEL.
> 
> This is found by a static analysis tool named DCNS written by myself.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
> ---
> drivers/block/aoe/aoenet.c |    2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/block/aoe/aoenet.c b/drivers/block/aoe/aoenet.c
> index 63773a9..d5fff7a 100644
> --- a/drivers/block/aoe/aoenet.c
> +++ b/drivers/block/aoe/aoenet.c
> @@ -138,7 +138,7 @@ static int __init aoe_iflist_setup(char *str)
>    if (dev_net(ifp) != &init_net)
>        goto exit;
> 
> -    skb = skb_share_check(skb, GFP_ATOMIC);
> +    skb = skb_share_check(skb, GFP_KERNEL);
>    if (skb == NULL)
>        return 0;
>    if (!is_aoe_netif(ifp))
> -- 
> 1.7.9.5
>