linux-kernel - Re: [PATCH] net: tap: remove redundant assignments

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Message-ID: <20210222165344.533bc87e@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Mon, 22 Feb 2021 16:53:44 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Tang Bin <tangbin@...s.chinamobile.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: tap: remove redundant assignments

On Mon, 22 Feb 2021 22:57:48 +0800 Tang Bin wrote:
> In the function tap_get_user, the assignment of 'err' at both places
> is redundant, so remove one.
> 
> Signed-off-by: Tang Bin <tangbin@...s.chinamobile.com>
> ---
>  drivers/net/tap.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/net/tap.c b/drivers/net/tap.c
> index 1f4bdd944..3e9c72738 100644
> --- a/drivers/net/tap.c
> +++ b/drivers/net/tap.c
> @@ -625,7 +625,7 @@ static ssize_t tap_get_user(struct tap_queue *q, void *msg_control,
>  	struct tap_dev *tap;
>  	unsigned long total_len = iov_iter_count(from);
>  	unsigned long len = total_len;
> -	int err;
> +	int err = -EINVAL;
>  	struct virtio_net_hdr vnet_hdr = { 0 };
>  	int vnet_hdr_len = 0;
>  	int copylen = 0;
> @@ -636,7 +636,6 @@ static ssize_t tap_get_user(struct tap_queue *q, void *msg_control,
>  	if (q->flags & IFF_VNET_HDR) {
>  		vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz);
>  
> -		err = -EINVAL;
>  		if (len < vnet_hdr_len)
>  			goto err;
>  		len -= vnet_hdr_len;
> @@ -657,7 +656,6 @@ static ssize_t tap_get_user(struct tap_queue *q, void *msg_control,
>  			goto err;
>  	}
>  
> -	err = -EINVAL;
>  	if (unlikely(len < ETH_HLEN))
>  		goto err;
>  

Assigning err close to the gotos makes the code more robust and easier
to read. No applying this, sorry.