Re: [Qemu-devel] [PATCH 04/18] savevm: set right return value for qemu_file_rate_limit

[Lei Li <lilei@linux.vnet.ibm.com>]

On 08/21/2013 06:42 PM, Paolo Bonzini wrote:
> Il 21/08/2013 09:18, Lei Li ha scritto:
>> Commit 1964a397063967acc5ce71a2a24ed26e74824ee1 refactors rate
>> limiting to QEMUFile, but set the return value for qemu_file_rate_limit
>> to 1 in the case of qemu_file_get_error. It is wrong and should be negative
>> compared to the original function buffered_rate_limit and the current logic
>> in ram_save_iterate. As qemu_file_rate_limit is called manually to determine
>> if it has to exit, add the definition of the meaning of the return values
>> as well.
> When there is an error it returns "time to stop" so that ultimately we
> get to the migration_thread function and check qemu_file_get_error there.
>
> Why doesn't this work for you?

Hi Paolo,

Say, In ram_save_iterate(), the current logic is:

ret = qemu_file_rate_limit();
while(ret == 0) {
     save RAM blocks until no more to send.
}
if (ret < 0) {
     return ret;
}
...

And in savevm layer, qemu_savevm_state_iterate() set an error if the return
value of ram_save_iterate < 0.

Obviously the return value of qemu_file_rate_limit() should have an negative
value for there has been an error. Otherwise we need to modify the logic above.

> Paolo
>
>> Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
>> ---
>>   savevm.c |   14 ++++++++++++--
>>   1 files changed, 12 insertions(+), 2 deletions(-)
>>
>> diff --git a/savevm.c b/savevm.c
>> index 68552a7..6362275 100644
>> --- a/savevm.c
>> +++ b/savevm.c
>> @@ -904,10 +904,20 @@ int64_t qemu_ftell(QEMUFile *f)
>>       return f->pos;
>>   }
>>   
>> +/*
>> + * The meaning of the return values is:
>> + *   0: We can continue sending
>> + *   1: Time to stop
>> + *   negative: There has been an error
>> + */
>> +
>>   int qemu_file_rate_limit(QEMUFile *f)
>>   {
>> -    if (qemu_file_get_error(f)) {
>> -        return 1;
>> +    int ret;
>> +
>> +    ret = qemu_file_get_error(f);
>> +    if (ret) {
>> +        return ret;
>>       }
>>       if (f->xfer_limit > 0 && f->bytes_xfer > f->xfer_limit) {
>>           return 1;
>>
>


-- 
Lei