linux-kernel - Re: [PATCH] goldfish_pipe: use GFP

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Message-ID: <20170521074836.GA24459@dhcp22.suse.cz>
Date:   Sun, 21 May 2017 09:48:37 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Wei Yongjun <weiyj.lk@...il.com>
Cc:     jinqian@...roid.com, gregkh@...uxfoundation.org,
        lstoakes@...il.com, jack@...e.cz, christian.koenig@....com,
        Wei Yongjun <weiyongjun1@...wei.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] goldfish_pipe: use GFP_ATOMIC under spin lock

On Sun 21-05-17 00:45:46, Wei Yongjun wrote:
> From: Wei Yongjun <weiyongjun1@...wei.com>
> 
> The function get_free_pipe_id_locked() is called from
> goldfish_pipe_open() with a lock is held, so we should
> use GFP_ATOMIC instead of GFP_KERNEL.

Why is GFP_NOWAIT insufficient? Does this path needs an access to memory
reserves?

> Signed-off-by: Wei Yongjun <weiyongjun1@...wei.com>
> ---
>  drivers/platform/goldfish/goldfish_pipe.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/goldfish/goldfish_pipe.c b/drivers/platform/goldfish/goldfish_pipe.c
> index 2de1e60..5f36721 100644
> --- a/drivers/platform/goldfish/goldfish_pipe.c
> +++ b/drivers/platform/goldfish/goldfish_pipe.c
> @@ -704,7 +704,7 @@ static int get_free_pipe_id_locked(struct goldfish_pipe_dev *dev)
>  		/* Reallocate the array */
>  		u32 new_capacity = 2 * dev->pipes_capacity;
>  		struct goldfish_pipe **pipes =
> -			kcalloc(new_capacity, sizeof(*pipes), GFP_KERNEL);
> +			kcalloc(new_capacity, sizeof(*pipes), GFP_ATOMIC);
>  		if (!pipes)
>  			return -ENOMEM;
>  		memcpy(pipes, dev->pipes, sizeof(*pipes) * dev->pipes_capacity);
> 

-- 
Michal Hocko
SUSE Labs