[patch] only update dcache after write succeeds

[Michael Snyder]

Doug Evans wrote:
> On Mon, Sep 14, 2009 at 12:26 PM, Michael Snyder <msnyder@vmware.com> wrote:
>> Doug Evans wrote:
>>> Hi.
>>>
>>> Marc, Greg: Can you see if this patch fixes things for you?
>> Hey Doug,
> 
> Hey Michael, :-)
> 
>> I tested this change, and it does indeed seem to fix the problem
>> with target record -- but.   ;-)
>>
>> Part of the reason that it works is that record_xfer_partial
>> calls error() instead of returning -1.  If I change it so that
>> it returns -1, things get more complicated.
>>
>> The do-while loop that used to follow and now preceeds this code
>> calls target-beneath, which in our case results in several different
>> target methods being called, one of which eventually returns > 0.
>>
>> That just means that in the present case, calling error is correct.
>> But I worry about some of the other cases where the target method
>> returns -1, and whether badness might occur in some other cases.
> 
> How does one reconcile  "eventually returns > 0" with "badness"?
> 
> IOW, if some target method does return > 0, then the write succeeded, right?
> Are there different kinds of "success" in effect here?

Well, maybe only in our case.  ;-)

If nobody else has any worries about it, I'm OK with it.

----
* In our case (process record), it's a bad thing for the target
beneath to be called after the user has said "no".