On 10/16/2018 07:48 PM, Michael Ellerman wrote:
> Michael Bringmann <m...@linux.vnet.ibm.com> writes:
>> On 10/16/2018 02:57 PM, Tyrel Datwyler wrote:
>>> On 10/15/2018 05:39 PM, Michael Ellerman wrote:
>>>> Michael Bringmann <m...@linux.vnet.ibm.com> writes:
>>>>> diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c
>>>>> b/arch/powerpc/platforms/pseries/hotplug-memory.c
>>>>> index 2b796da..9c76345 100644
>>>>> --- a/arch/powerpc/platforms/pseries/hotplug-memory.c
>>>>> +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
>>>>> @@ -541,6 +549,23 @@ static int dlpar_memory_readd_by_index(u32 drc_index)
>>>>> return rc;
>>>>> }
>>>>>
>>>>> +static int dlpar_memory_readd_multiple(void)
>>>>> +{
>>>>> + struct drmem_lmb *lmb;
>>>>> + int rc;
>>>>> +
>>>>> + pr_info("Attempting to update multiple LMBs\n");
>>>>> +
>>>>> + for_each_drmem_lmb(lmb) {
>>>>> + if (drmem_lmb_update(lmb)) {
>>>>> + rc = dlpar_memory_readd_helper(lmb);
>>>>> + drmem_remove_lmb_update(lmb);
>>>>> + }
>>>>> + }
>>>>> +
>>>>> + return rc;
>>>>> +}
>>>>
>>>> This leaves rc potentially uninitialised.
>>>>
>>>> What should the result be in that case, -EINVAL ?
>>>
>>> On another note if there are multiple LMBs to update the value of rc only
>>> reflects the final dlpar_memory_readd_helper() call.
>>
>> Correct. But that is what happens when we compress common code
>> between two disparate uses i.e. updating memory association after
>> a migration event with no reporting mechanism other than the console
>> log, vs re-adding a single LMB by index for the purposes of DLPAR / drmgr.
>>
>> I could discard the return value from dlpar_memory_readd_helper entirely
>> in this function and just return 0, but in my experience, once errors start
>> to occur in memory dlpar ops, they tend to keep on occurring, so I was
>> returning the last one. We could also make the code smart enough to
>> capture and return the first/last non-zero return code. I didn't believe
>> that the frequency of errors for this operation warranted the overhead.
>
> The actual error value is probably not very relevant.
>
> But dropping errors entirely is almost always a bad idea.
>
> So I think you should at least return an error if any error occurred,
> that way at least an error will be returned up to the caller(s).
>
> Something like:
>
> int rc;
>
> rc = 0;
> for_each_drmem_lmb(lmb) {
> if (drmem_lmb_update(lmb)) {
> rc |= dlpar_memory_readd_helper(lmb);
> drmem_remove_lmb_update(lmb);
> }
> }
>
> if (rc)
> return -EIO;
Okay.
>
> cheers
>
Thanks.
--
Michael W. Bringmann
Linux Technology Center
IBM Corporation
Tie-Line 363-5196
External: (512) 286-5196
Cell: (512) 466-0650
m...@linux.vnet.ibm.com
