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SubjectRe: [PATCH v5 09/13] xen/pvcalls: implement sendmsg
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On 10/19/2017 09:41 PM, Stefano Stabellini wrote:
> On Tue, 17 Oct 2017, Boris Ostrovsky wrote:
>>> +static int __write_ring(struct pvcalls_data_intf *intf,
>>> + struct pvcalls_data *data,
>>> + struct iov_iter *msg_iter,
>>> + int len)
>>> +{
>>> + RING_IDX cons, prod, size, masked_prod, masked_cons;
>>> + RING_IDX array_size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
>>> + int32_t error;
>>> +
>>> + error = intf->out_error;
>>> + if (error < 0)
>>> + return error;
>>> + cons = intf->out_cons;
>>> + prod = intf->out_prod;
>>> + /* read indexes before continuing */
>>> + virt_mb();
>>> +
>>> + size = pvcalls_queued(prod, cons, array_size);
>>> + if (size >= array_size)
>>> + return 0;
>>
>> I thought you were going to return an error here? If this can only be
>> due to someone messing up indexes is there a reason to continue trying
>> to write? What are the chances that the index will get corrected?
> Sorry, I forgot. I'll change it to return an error, maybe EFAULT.

I think EINVAL might be more appropriate. But either way you can tack on
my R-b to the patch.

-boris

>
>
>>> + if (len > array_size - size)
>>> + len = array_size - size;
>>> +
>>> + masked_prod = pvcalls_mask(prod, array_size);
>>> + masked_cons = pvcalls_mask(cons, array_size);
>>> +
>>> + if (masked_prod < masked_cons) {
>>> + copy_from_iter(data->out + masked_prod, len, msg_iter);
>>> + } else {
>>> + if (len > array_size - masked_prod) {
>>> + copy_from_iter(data->out + masked_prod,
>>> + array_size - masked_prod, msg_iter);
>>> + copy_from_iter(data->out,
>>> + len - (array_size - masked_prod),
>>> + msg_iter);
>>> + } else {
>>> + copy_from_iter(data->out + masked_prod, len, msg_iter);
>>> + }
>>> + }
>>> + /* write to ring before updating pointer */
>>> + virt_wmb();
>>> + intf->out_prod += len;
>>> +
>>> + return len;
>>> +}

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