Re: [PATCHv3 0/5] Fix --recurse-submodules for submodule worktree changes

From: Stefan Beller <sbeller@google.com>
Date: Jan 3, 2018, 21:16 UTC
Message-ID: <CAGZ79kbC5tsL8R-tUBxHoZzxYiqiWwYS61F7cLfTZeb0Wu1LGA@mail.gmail.com>
In-Reply-To: <xmqqo9mahdll.fsf@gitster.mtv.corp.google.com>

On Wed, Jan 3, 2018 at 12:49 PM, Junio C Hamano <gitster@pobox.com> wrote:

Show 26 quoted lines

> Stefan Beller <sbeller@google.com> writes:
>
>> Thanks Junio for review of this series!
>> The only change in this version of the series is
>>
>> --- a/unpack-trees.c
>> +++ b/unpack-trees.c
>> @@ -2140,7 +2140,7 @@ int oneway_merge(const struct cache_entry * const *src,
>>                                 update |= CE_UPDATE;
>>                 }
>>                 if (S_ISGITLINK(old->ce_mode) && should_update_submodules() &&
>> -                   !verify_uptodate(old, o))
>> +                   o->update && !verify_uptodate(old, o))
>>                         update |= CE_UPDATE;
>>                 add_entry(o, old, update, 0);
>>
>
> Sounds OK.
>
> I wonder why o->update is not at the very beginning of the &&-chain,
> though.  After all, the one above this addition begins with o->reset
> && o->update *not* because of the performance concern, but primarily
> due to logic flow.  I.e. "if we are resetting and updating the
> working tree, then..." comes first before saying "we may need to
> flip CE_UPDATE bit in update variable if the file in the working
> tree is not up to date and it is within a narrow checkout area".

It shows that I work too much with submodules. ;) "If we have a submodule and ..." seemed to be the important part when writing the patch.

> Of course, because verify_uptodate() is rather expensive, checking
> o->update before that makes sense from micro-optimization's point of
> view, too.

I would think S_ISGITLINK, should_update_submodules as well as o->update are all on the same order of magnitude of costs (some couple number of operations) when compared to verify_uptodate (spawning processes), so as long as verify_uptodate goes last we'd be fine.

>
> So after thinking aloud like the above, I am reasonably sure that
> you want to check o->update as the very first thing in this new if
> statement.

Thanks for double checking and thinking about the code base with a less submodule centric point of view.

Mind to squash it locally or want me to resend? For a resend I'll wait a couple of days to see if there are more comments needing to be addressed.

Show 16 quoted lines

>
>> v2:
>> I dropped the patch to `same()` as I realized we only need to fix the
>> oneway_merge function, the others (two, three way merge) are fine as
>> they have the checks already in place.
>
> This is a bit flawed argument, no?  Checking working tree paths
> unconditionally in same(), which does not even know if we are
> touching the working tree paths, is broken.  Unless "they have the
> checks already in place" refers to checks that bypasses calls to
> same() when we are not touching working tree paths, that is, but
> obviously that is not what is going on.
>
> Will queue.  Thanks for working on this.
>
>