Re: [PATCH 1/3] [net/9p] Fix the size of receive buffer packing onto VirtIO ring.

[Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>]

On 07/01/2011 04:21 AM, Aneesh Kumar K.V wrote:
> On Thu, 30 Jun 2011 16:18:39 -0700, "Venkateswararao Jujjuri (JV)"<jvrao@linux.vnet.ibm.com>  wrote:
>> Signed-off-by: Venkateswararao Jujjuri "<jvrao@linux.vnet.ibm.com>
>> ---
>>   net/9p/trans_virtio.c |    2 +-
>>   1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
>> index 244e707..0ec5423 100644
>> --- a/net/9p/trans_virtio.c
>> +++ b/net/9p/trans_virtio.c
>> @@ -367,7 +367,7 @@ req_retry_pinned:
>>   		in += inp;
>>   	} else {
>>   		in = pack_sg_list(chan->sg, out, VIRTQUEUE_NUM, rdata,
>> -				client->msize);
>> +				req->rc->capacity);
>>   	}
>>
>>   	err = virtqueue_add_buf(chan->vq, chan->sg, out, in, req->tc);
> So when will req->rc->capacity be different from client->msize ? Can we
> get details for that documented in p9_tag_alloc ?
>
> The above pack_sg_list will only be called for non-zero copy case ? In
> that case won't client->size be same as rc->capacity ?
you mean client->msize?

Yes this else case is only in the non-zc case.
Basically the client->msize is the maximum pdu size.
say our msize is 128k, and we are doing a TVERSION, the logic
falls into the else case where no ZC is needed. In this case
we are operating with the rc->capacity not the entire msize.

Thanks,
JV
> -aneesh