Re: [Xen-devel] [PATCH net-next v7 4/9] xen-netback: Introduce TX grant mapping

[Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>]

On 13/03/14 13:56, Ian Campbell wrote:
> On Thu, 2014-03-13 at 13:17 +0000, Zoltan Kiss wrote:
> > On 13/03/14 10:33, Ian Campbell wrote:
> > > On Thu, 2014-03-06 at 21:48 +0000, Zoltan Kiss wrote:
> > >
> > > > +                               netdev_err(vif->dev,
> > > > +                                          "Page still granted! Index: %x\n",
> > > > +                                          i);
> > > > +                       i = -1;
> > > Should there not be a break here? Otherwise don't we restart the for
> > > loop from 0 again? If that is intentional then a comment would be very
> > > useful.
> > Yes, that's intentional, we shouldn't exit this loop until everything is
> > unmapped. An i-- would be fine as well. I will put a comment there.
> Yes please do, it's very non-obvious what is going on. I'm almost
> inclined to suggest that this is one of the few places where a goto
> retry might be appropriate.
>
> Can you also add a comment saying what is doing the actual unmap work
> which we are waiting for here since it is not actually part of the loop.
> Might a barrier be needed to ensure we see that work happening?
I don't think a barrier is necessary here, if this function ran into 
!NETBACK_INVALID_HANDLE, it just starts again the checking.
On 13/03/14 13:17, Zoltan Kiss wrote:>>
>> [...]
>>> +    /* Btw. already unmapped? */
>>
>> What does this comment mean? Is it a fixme? An indicator that
>> xenvif_grant_handle_reset is supposed to handle this case or something
>> else?
> It comes from the time when xenvif_grant_handle_reset was not a
> standalone function. Yes, it refers to the check in the beginning of
> that function, and it should go there.

I ended up removing that comment, the error message in the function 
tells the same.
Zoli

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