linux-kernel - Re: [PATCH][next] vhost: only return early if ret indicates an error or no iovecs have been processed

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Date:   Tue, 19 Feb 2019 11:35:34 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Colin King <colin.king@...onical.com>
Cc:     Jason Wang <jasowang@...hat.com>, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] vhost: only return early if ret indicates an error
 or no iovecs have been processed

On Tue, Feb 19, 2019 at 01:57:13PM +0000, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> Currently the loop that calls log_write_hva on each iovec is never
> executed because of an incorrect error check on the return from the
> call to translate_desc.  The check should be checking for a -ve error
> return and because it makes no sense to iterate over zero items, the
> checks should also check for zero too.
> 
> Detected by CoverityScan, CID#1476969 ("Logically dead code")
> 
> Fixes: cc5e71075947 ("vhost: log dirty page correctly")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>

Jason posted a similar patch recently.

Are you happy with that one?

> ---
>  drivers/vhost/vhost.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 24a129fcdd61..a9a1709a859a 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -1788,7 +1788,7 @@ static int log_used(struct vhost_virtqueue *vq, u64 used_offset, u64 len)
>  
>  	ret = translate_desc(vq, (uintptr_t)vq->used + used_offset,
>  			     len, iov, 64, VHOST_ACCESS_WO);
> -	if (ret)
> +	if (ret <= 0)
>  		return ret;
>  
>  	for (i = 0; i < ret; i++) {
> -- 
> 2.20.1