Re: [PATCH 03/11] block: add rq->resid_len

Boaz Harrosh
2009-05-12T15:08:52Z

On 05/12/2009 06:00 PM, FUJITA Tomonori wrote:
> On Tue, 12 May 2009 11:58:28 +0300
> Boaz Harrosh <bharrosh@panasas.com> wrote:
>
>> On 05/11/2009 05:59 PM, FUJITA Tomonori wrote:
>>> On Mon, 11 May 2009 14:31:41 +0300
>>> Boaz Harrosh <bharrosh@panasas.com> wrote:
>>>
>>>>>>> diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
>>>>>>> index 3da02e4..6605ec9 100644
>>>>>>> --- a/drivers/scsi/libsas/sas_expander.c
>>>>>>> +++ b/drivers/scsi/libsas/sas_expander.c
>>>>>>> @@ -1936,12 +1936,8 @@ int sas_smp_handler(struct Scsi_Host *shost, struct sas_rphy *rphy,
>>>>>>> bio_data(rsp->bio), rsp->data_len);
>>>>>>> if (ret > 0) {
>>>>>>> /* positive number is the untransferred residual */
>>>>>>> - rsp->data_len = ret;
>>>>>>> - req->data_len = 0;
>>>>>>> + rsp->resid_len = ret;
>>>>>>> ret = 0;
>>>>>>> - } else if (ret == 0) {
>>>>>>> - rsp->data_len = 0;
>>>>>>> - req->data_len = 0;
>>>>>>> }
>>>>>>>
>>>>>>> return ret;
>>>>>> This is actually a bug fix, as well as a strait conversion
>>>>> Can you elaborate a bit about the bug fix part?
>>>>>
>>>> Nothing big really, just that before (according to the comment), the theoretical
>>>> negative case would be full-residual. and now it is zero (untouched).
>>>>
>>>> I know that in iscsi a negative residual is possible which means over-flow. That is:
>>>> the target had more data to give then the buffer had space for. (which is not an error at all)
>>> Hmm, iSCSI? This code is for SAS management Protocol.
>>>
>> I gave that as an example of what the scsi standard says about negative
>> residual count return from the target. If SAS as sepecific and different
>> meaning to negative residual, it should be noted and handled.
>
> Please read the code first.
>
> If sas_smp_handler() returns a negative value, a lld doesn't transfer
> anything. The original code used full-residual. The original code is
> fine. Your 'this is a bug fix' claim is wrong. We need to revert the
> original behavior though.

Please read my full reply, I said yes old code was better, but not
good enough, error status must be returned also in this case.

This code is already submitted are you sending a fix?

Thanks
Boaz