Re: [PATCH 43/52] migration/rdma: Convert qemu_rdma_alloc_pd_cq() to Error

[Markus Armbruster]

"Zhijian Li (Fujitsu)" <lizhijian@fujitsu.com> writes:

> On 18/09/2023 22:41, Markus Armbruster wrote:
>> Functions that use an Error **errp parameter to return errors should
>> not also report them to the user, because reporting is the caller's
>> job.  When the caller does, the error is reported twice.  When it
>> doesn't (because it recovered from the error), there is no error to
>> report, i.e. the report is bogus.
>> 
>> qemu_rdma_source_init() violates this principle: it calls
>> error_report() via qemu_rdma_alloc_pd_cq().  I elected not to
>> investigate how callers handle the error, i.e. precise impact is not
>> known.
>> 
>> Clean this up by converting qemu_rdma_alloc_pd_cq() to Error.
>> 
>> Signed-off-by: Markus Armbruster<armbru@redhat.com>
>> ---
>>   migration/rdma.c | 27 ++++++++++++++-------------
>>   1 file changed, 14 insertions(+), 13 deletions(-)
>
> [...]
>
>
>> @@ -2451,6 +2451,7 @@ static void qemu_rdma_cleanup(RDMAContext *rdma)
>>   
>>   static int qemu_rdma_source_init(RDMAContext *rdma, bool pin_all, Error 
>> **errp)
>>   {
>> +    ERRP_GUARD();
>>       int ret, idx;
>>   
>>       /*
>> @@ -2464,12 +2465,12 @@ static int qemu_rdma_source_init(RDMAContext *rdma, 
>> bool pin_all, Error **errp)
>>           goto err_rdma_source_init;
>>       }
>>   
>> -    ret = qemu_rdma_alloc_pd_cq(rdma);
>> +    ret = qemu_rdma_alloc_pd_cq(rdma, errp);
>>       if (ret < 0) {
>> -        error_setg(errp, "RDMA ERROR: "
>> -                   "rdma migration: error allocating pd and cq! Your 
>> mlock()"
>> -                   " limits may be too low. Please check $ ulimit -a # and "
>> -                   "search for 'ulimit -l' in the output");
>> +        error_append_hint(errp,
>> +                          "Your mlock() limits may be too low. "
>> +                          "Please check $ ulimit -a # and "
>> +                          "search for 'ulimit -l' in the output\n");
>
>
> I think we could freely remove this error message as well, it may neither a 
> exact resolution
> nor some one will take care. Just report the error qemu_rdma_alloc_pd_cq() 
> tell us.

Double-checking: you recommend to drop error_append_hint()?

> Anyway
>
> Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
>
>
>>           goto err_rdma_source_init;
>>       }

Thanks!