linux-kernel - Re: [RFC PATCH net-next 01/12] vhost_net: introduce helper to initialize tx iov iter

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Date:   Tue, 22 May 2018 20:26:37 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Jesse Brandeburg <jesse.brandeburg@...el.com>
Cc:     mst@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [RFC PATCH net-next 01/12] vhost_net: introduce helper to
 initialize tx iov iter



On 2018年05月22日 00:24, Jesse Brandeburg wrote:
> Hi Jason, a few nits.
>
> On Mon, 21 May 2018 17:04:22 +0800 Jason wrote:
>> Signed-off-by: Jason Wang <jasowang@...hat.com>
>> ---
>>   drivers/vhost/net.c | 34 +++++++++++++++++++++++-----------
>>   1 file changed, 23 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
>> index c4b49fc..15d191a 100644
>> --- a/drivers/vhost/net.c
>> +++ b/drivers/vhost/net.c
>> @@ -459,6 +459,26 @@ static bool vhost_exceeds_maxpend(struct vhost_net *net)
>>   	       min_t(unsigned int, VHOST_MAX_PEND, vq->num >> 2);
>>   }
>>   
>> +static size_t init_iov_iter(struct vhost_virtqueue *vq, struct iov_iter *iter,
>> +			    size_t hdr_size, int out)
>> +{
>> +	/* Skip header. TODO: support TSO. */
>> +	size_t len = iov_length(vq->iov, out);
>> +
>> +	iov_iter_init(iter, WRITE, vq->iov, out, len);
>> +	iov_iter_advance(iter, hdr_size);
>> +	/* Sanity check */
>> +	if (!iov_iter_count(iter)) {
>> +		vq_err(vq, "Unexpected header len for TX: "
>> +			"%zd expected %zd\n",
>> +			len, hdr_size);
> ok, it was like this before, but please unwrap the string in " ", there
> should be no line breaks in string declarations and they are allowed to
> go over 80 characters.

Ok.

>
>> +		return -EFAULT;
>> +	}
>> +	len = iov_iter_count(iter);
>> +
>> +	return len;
>> +}
>> +
>>   /* Expects to be always run from workqueue - which acts as
>>    * read-size critical section for our kind of RCU. */
>>   static void handle_tx(struct vhost_net *net)
>> @@ -521,18 +541,10 @@ static void handle_tx(struct vhost_net *net)
>>   			       "out %d, int %d\n", out, in);
>>   			break;
>>   		}
>> -		/* Skip header. TODO: support TSO. */
>> -		len = iov_length(vq->iov, out);
>> -		iov_iter_init(&msg.msg_iter, WRITE, vq->iov, out, len);
>> -		iov_iter_advance(&msg.msg_iter, hdr_size);
>> -		/* Sanity check */
>> -		if (!msg_data_left(&msg)) {
>> -			vq_err(vq, "Unexpected header len for TX: "
>> -			       "%zd expected %zd\n",
>> -			       len, hdr_size);
>> +
>> +		len = init_iov_iter(vq, &msg.msg_iter, hdr_size, out);
>> +		if (len < 0)
> len is declared as size_t, which is unsigned, and can never be
> negative.  I'm pretty sure this is a bug.

Yes, let me fix it in next version.

Thanks

>
>
>>   			break;
>> -		}
>> -		len = msg_data_left(&msg);
>>   
>>   		zcopy_used = zcopy && len >= VHOST_GOODCOPY_LEN
>>   				   && !vhost_exceeds_maxpend(net)