Subject: Re: [PATCH v2 1/1] repack: avoid loosening promisor objects in partial clones

From: Rafael Silva <[email-masked]>
Date: Wed, 21 Apr 2021 21:25:04 +0200

Junio C Hamano <[email-masked]> writes:

> Rafael Silva <[email-masked]> writes:
>
>> When `git repack -A -d` is run in a partial clone, `pack-objects`
>> is invoked twice: once to repack all promisor objects, and once to
>> repack all non-promisor objects. The latter `pack-objects` invocation
>> is with --exclude-promisor-objects and --unpack-unreachable, which
>> loosens all unused objects. Unfortunately, this includes promisor
>> objects.
>>
>> Because the -d argument to `git repack` subsequently deletes all loose
>> objects also in packs, these just-loosened promisor objects will be
>> immediately deleted. However, this extra disk churn is unnecessary in
>> the first place.  For example, a newly-clone partial repo that filters
>
> "in a newly-cloned partial repo", I'd think.
>

Thanks, will fix on the next revision.

>> For testing, we need to validate whether any object was loosened.
>> However, the "evidence" (loosened objects) is deleted during the
>> process which prevents us from inspecting the object directory.
>> Instead, let's teach `pack-objects` to count loosened objects and
>> emit via trace2 thus allowing inspecting the debug events after the
>> process is finished. This new event is used on the added regression
>> test.
>
> Nicely designed.
>

Thanks :)

>> +	uint32_t loosened_objects_nr = 0;
>>  	struct object_id oid;
>>  
>>  	for (p = get_all_packs(the_repository); p; p = p->next) {
>> @@ -3492,11 +3493,16 @@ static void loosen_unused_packed_objects(void)
>>  			nth_packed_object_id(&oid, p, i);
>>  			if (!packlist_find(&to_pack, &oid) &&
>>  			    !has_sha1_pack_kept_or_nonlocal(&oid) &&
>> -			    !loosened_object_can_be_discarded(&oid, p->mtime))
>> +			    !loosened_object_can_be_discarded(&oid, p->mtime)) {
>>  				if (force_object_loose(&oid, p->mtime))
>>  					die(_("unable to force loose object"));
>> +				loosened_objects_nr++;
>> +			}
>>  		}
>>  	}
>> +
>> +	trace2_data_intmax("pack-objects", the_repository,
>> +			   "loosen_unused_packed_objects/loosened", loosened_objects_nr);
>>  }
>
> OK, so this is just the "stats".
>
>> diff --git a/builtin/repack.c b/builtin/repack.c
>> index 2847fdfbab..5f9bc74adc 100644
>> --- a/builtin/repack.c
>> +++ b/builtin/repack.c
>> @@ -20,7 +20,7 @@ static int delta_base_offset = 1;
>>  static int pack_kept_objects = -1;
>>  static int write_bitmaps = -1;
>>  static int use_delta_islands;
>> -static char *packdir, *packtmp;
>> +static char *packdir, *packtmp_name, *packtmp;
>>  
>>  static const char *const git_repack_usage[] = {
>>  	N_("git repack [<options>]"),
>> @@ -530,7 +530,8 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
>>  	}
>>  
>>  	packdir = mkpathdup("%s/pack", get_object_directory());
>> -	packtmp = mkpathdup("%s/.tmp-%d-pack", packdir, (int)getpid());
>> +	packtmp_name = xstrfmt(".tmp-%d-pack", (int)getpid());
>> +	packtmp = mkpathdup("%s/%s", packdir, packtmp_name);
>
> Just a mental note, but we should move away from ".tmp-$$" that is a
> remnant from the days back when this was a shell script, and use the
> tempfile.h API (#leftoverbits).  Such a change must not be part of
> this topic, of course.
>

Indeed. This should be move tempfile.h API.

>
> Thanks.  Will queue and see what others say.

Thanks for reviewing it.

-- 
Thanks
Rafael