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Date: Fri, 23 Aug 2013 01:34:17 -0400 (EDT)
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 04/18] savevm: set right return value for
 qemu_file_rate_limit
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To: Lei Li <lilei@linux.vnet.ibm.com>
Cc: aarcange@redhat.com, aliguori@us.ibm.com, quintela@redhat.com, qemu-devel@nongnu.org, mrhines@linux.vnet.ibm.com, lagarcia@br.ibm.com, rcj@linux.vnet.ibm.com

> 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.

But that is to report errors *not in the QEMUFile*.  Errors in the
QEMUFile are already reported by qemu_file_get_error(), and
qemu_savevm_state_iterate() will not overwrite them.

qemu_file_rate_limit() returning 1 is enough to exit the loop,
which is all that is needed.

> 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.

It is not obvious to me... what is, again, the bug that you're observing?
I think it is happening only because you're modifying the migration thread's
body.  If you use the normal code of the migration thread, it will just work.

Paolo