Re: [Xen-devel] [PATCH] MAINTAINERS: Add explicit check-in policy section

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 1/7/20 1:05 PM, Jan Beulich wrote:
> On 07.01.2020 13:03, George Dunlap wrote:
>> DISCUSSION
>>
>> This seems to be a change from people's understanding of the current
>> policy.  Most people's understanding of the current policy seems to be:
>>
>> 1.  In order to get a change to a given file committed, it must have
>> an Ack or Review from at least one *maintainer* of that file other
>> than the submitter.
>>
>> 2. In the case where a file has only one maintainer, it must have an
>> Ack or Review from a "nested" maintainer.
>>
>> I.e., if I submitted something to x86/mm, it would require an Ack from
>> Jan or Andy, or (in exceptional circumstances) The Rest; but an Ack from
>> (say) Roger or Juergen wouldn't suffice.
>>
>> Let's call this the "maintainer-ack" approach (because it must have an
>> ack or r-b from a maintainer to be checked in), and the proposal in
>> this patch the "maintainer-approval" (since SoB from a maintainer
>> indicates approval).
>>
>> The core issue I have with "maintainer-ack" is that it makes the
>> maintainer less privileged with regard to writing code than
>> non-maintainers.  If component X has maintainers A and B, then a
>> non-maintainer can have code checked in if reviewed either by A or B.
>> If A or B wants code checked in, they have to wait for exactly one
>> person to review it.
>>
>> In fact, if B is quite busy, the easiest way for A really to get their
>> code checked in might be to hand it to a non-maintainer N, and ask N
>> to submit it as their own.  Then A can Ack the patches and check them
>> in.
>>
>> The current system, therefore, either sets up a perverse incentive (if
>> you think the behavior described above is unacceptable) or unnecessary
>> bureaucracy (if you think it's acceptable).  Either way I think we
>> should set up our system to avoid it.
> 
> I much appreciate this initiative of yours.
> 
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -104,7 +104,53 @@ Descriptions of section entries:
>>         xen-maintainers-<version format number of this file>
>>  
>>  
>> -The meaning of nesting:
>> +    Check-in policy
>> +    ===============
>> +
>> +In order for a patch to be checked in, in general, several conditions
>> +must be met:
>> +
>> +1. In order to get a change to a given file committed, it must have
>> +   the approval of at least one maintainer of that file.
>> +
>> +   A patch of course needs Acks from the maintainers of each file that
>> +   it changes; so a patch which changes xen/arch/x86/traps.c,
>> +   xen/arch/x86/mm/p2m.c, and xen/arch/x86/mm/shadow/multi.c would
>> +   require an Ack from each of the three sets of maintainers.
>> +
>> +   See below for rules on nested maintainership.
>> +
>> +2. It must have an Acked-by or a Reviewed-by from someone other than
>> +   the submitter.
> 
> I'd like to propose some further distinction here, albeit I'm not sure
> this isn't implied anyway. It might be that making explicit the
> distinction between A-b and R-b is sufficient - our current common
> understanding looks to be that only maintainers can "ack", and others
> would "review".

Well first of all, I don't think that's strictly true.  If a
non-maintainer raises a concern, the patch can't be checked in unless
that person is satisfied.  We sometimes assume silence is consent, but
it's much better for the person who raised the concern to say, "I am now
satisfied with this patch"; and the clearest and most concise way to do
that is to say "Acked-by".

But that sort of "Acked-by" isn't really what is meant by this section.
 I guess you'd like to say that such an Acked-by would not be sufficient
to check in a patch; it would have to be the stronger Reviewed-by.

The point of this sentence is not to define what Ack and Reviewed-by
mean, but that it must come from someone who is not the submitter.
However, it is true that someone may read that and be confused;
particularly as we don't seem to define it anywhere else in the tree, so
perhaps it's worth trying to clarify.

> Since the latter is implying a more thorough look at a
> patch, I think it wouldn't be right to allow (quoting text further
> down) "anyone in the community" to ack a random patch (I could probably
> talk my son into ack-ing my patches ;-) ). Perhaps, rather than
> limiting acks to maintainers of the changed code, we could extend this
> to maintainers of just some code for maintainer submitted patches (i.e.
> anyone named as M: at least once in ./MAINTAINERS)? People outside of
> whatever subset we might pick would be eligible to offer R-b only,
> implying of course that they actually did do a review.

I do actually prefer that only people in a "direct line" of
maintainership for that exact code (i.e., is a maintainer at whatever
level of specificity) be able to get Acks; and that anyone else should
be required to give a Reviewed-by.

This is of course again slightly more aggregate work for a maintianer
than for someone else, but I think that makes sense in this case.

How about this:

2. It must have either a an Acked-by from a maintainer, or a
   Reviewed-by.  This must come from someone other than the submitter.

>> +3. Sufficient time and/or warning must have been given for anyone to
>> +   respond.  This depends in large part upon the urgency and nature of
>> +   the patch.  For a straightforward uncontroversial patch, a day or
>> +   two is sufficient; for a controversial patch, perhaps waiting a
>> +   week and then saying "I intend to check this in tomorrow unless I
>> +   hear otherwise".
> 
> To me as non-native speaker, this last sentence looks incomplete (as
> in missing e.g. "would be appropriate" at the end), or alternatively
> it would feel like wanting the two "ing" dropped from the verbs.

I see what you mean.  But on reflection, I think the intent of this
paragraph has gotten skewed.  Patches should be given sufficent time for
*anyone* to give input before being checked in.

What about changing this as follows:

---
3. Sufficient time must have been given for anyone to respond.  This
   depends in large part upon the urgency and nature of the patch.
   For a straightforward uncontroversial patch, a day or two may be
   sufficient; for a controversial patch, a week or two may be better.
---

And then adding a para below:

---
Before a maintainer checks in their own patch with another community
member's R-b but no co-maintainer Ack, it is especially important to
give their co-maintainer opportunity to give feedback, perhaps
declaring their intention to check it in without their co-maintainers
ack a day before doing so.
---

 -George



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