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Re: [Xen-devel] [PATCH v5 10/18] x86/mem_sharing: Convert MEM_SHARING_DESTROY_GFN to a bool


  • To: Jan Beulich <jbeulich@xxxxxxxx>
  • From: George Dunlap <george.dunlap@xxxxxxxxxx>
  • Date: Thu, 23 Jan 2020 16:42:09 +0000
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  • Cc: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>, Tamas K Lengyel <tamas.lengyel@xxxxxxxxx>, Wei Liu <wl@xxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • Delivery-date: Thu, 23 Jan 2020 16:42:22 +0000
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  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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On 1/23/20 4:37 PM, Jan Beulich wrote:
> On 23.01.2020 17:32, George Dunlap wrote:
>> On 1/23/20 4:23 PM, Tamas K Lengyel wrote:
>>> On Thu, Jan 23, 2020 at 9:14 AM George Dunlap <george.dunlap@xxxxxxxxxx> 
>>> wrote:
>>>>
>>>> On 1/21/20 5:49 PM, Tamas K Lengyel wrote:
>>>>> MEM_SHARING_DESTROY_GFN is used on the 'flags' bitfield during unsharing.
>>>>> However, the bitfield is not used for anything else, so just convert it 
>>>>> to a
>>>>> bool instead.
>>>>>
>>>>> Signed-off-by: Tamas K Lengyel <tamas.lengyel@xxxxxxxxx>
>>>>> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
>>>>
>>>> But is there a particular advantage to getting rid of the bitfield?
>>>>
>>>> You're the maintainer, so it's your decision of course.  But if it were
>>>> me I'd leave it as a bitfield so that all the bitfield code is there if
>>>> it's needed in the future.  Flipping it to a bool, with the risk of
>>>> flipping it back to a bitfield later, seems like pointless churn to me.
>>>>
>>>> (Although perhaps the reason will become evident by the time I get to
>>>> the end of the series.)
>>>
>>> Provided its been many years since this code has been added with no
>>> need for any extra bits, and with no expectations that this would
>>> change any time soon, I wouldn't worry about that. True, there is very
>>> little difference between keeping the code as-is vs converting it to
>>> bool, but IMHO it makes the code easier to follow without you
>>> wondering what might be those non-existent situations that warranted
>>> it to be a bitmap to begin with.
>>
>> It's definitely a judgement call, and I can see where you're coming
>> from.  Like I said, if it were me I'd leave it, but it's not. :-)   Just
>> wanted to raise the issue as I was going through.  I'd Ack it but you've
>> already got an R-b.
> 
> Until your proposal gets accepted, isn't it that your ack is needed
> despite the R-b? This is also why e.g. for patch 2 I didn't see a
> point in sending any R-b, as the patch will need your ack anyway,
> and it's so simple that "reviewed" would be an overstatement.

I don't think I'm co-maintainer of this; and you're a less-specific
maintainer than Tamas, right?  Do you need my Ack?

I'm happy to go back and Ack all the mm/ ones you've given an R-b to up
until this point in the series; I just didn't think it was necessary.

I'll probably Ack patch 2 once I become convinced the change in that
patch is necessary (which I'm guessing might be when I get to 15/18).

 -George

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