On Mon, Nov 28 2022, René Scharfe wrote: > Am 28.11.2022 um 13:24 schrieb Ævar Arnfjörð Bjarmason: >> >> On Mon, Nov 28 2022, Ævar Arnfjörð Bjarmason wrote: >> >> René: >> >>> On Mon, Nov 28 2022, René Scharfe wrote: >>> >>>> Am 28.11.2022 um 11:03 schrieb Junio C Hamano: >>>>> René Scharfe <l.s.r@xxxxxx> writes: >>>>> >>>>>> This reverts commit 5cb28270a1ff94a0a23e67b479bbbec3bc993518. >>>>>> >>>>>> 5cb28270a1 (pack-objects: lazily set up "struct rev_info", don't leak, >>>>>> 2022-03-28) avoided leaking rev_info allocations in many cases by >>>>>> calling repo_init_revisions() only when the .filter member was actually >>>>>> needed, but then still leaking it. That was fixed later by 2108fe4a19 >>>>>> (revisions API users: add straightforward release_revisions(), >>>>>> 2022-04-13), making the reverted commit unnecessary. >>>>> >>>>> Hmph, with this merged, 'seen' breaks linux-leaks job in a strange >>>>> way. >>>>> >>>>> https://github.com/git/git/actions/runs/3563546608/jobs/5986458300#step:5:3917 >>>>> >>>>> Does anybody want to help looking into it? >>> >>> [I see we crossed E-Mails]: >>> https://lore.kernel.org/git/221128.868rjvmi3l.gmgdl@xxxxxxxxxxxxxxxxxxx/ >>> >>>> The patch exposes that release_revisions() leaks the diffopt allocations >>>> as we're yet to address the TODO added by 54c8a7c379 (revisions API: add >>>> a TODO for diff_free(&revs->diffopt), 2022-04-14). >>> >>> That's correct, and we have that leak in various places in our codebase, >>> but per the above side-thread I think this is primarily exposing that >>> we're setting up the "struct rev_info" with your change when we don't >>> need to. Why can't we just skip it? >>> >>> Yeah, if we do set it up we'll run into an outstanding leak, and that >>> should also be fixed (I have some local patches...), but the other cases >>> I know of where we'll leak that data is where we're actually using the >>> "struct rev_info". >>> >>> I haven't tried tearing your change apart to poke at it myself, and >>> maybe there's some really good reason for why you can't separate getting >>> rid of the J.5.7 dependency and removing the lazy-init. >>> >>>> The patch below plugs it locally. >>>> >>>> --- >8 --- >>>> Subject: [PATCH 4/3] fixup! revision: free diffopt in release_revisions() >>>> >>>> Signed-off-by: René Scharfe <l.s.r@xxxxxx> >>>> --- >>>> builtin/pack-objects.c | 1 + >>>> 1 file changed, 1 insertion(+) >>>> >>>> diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c >>>> index 3e74fbb0cd..a47a3f0fba 100644 >>>> --- a/builtin/pack-objects.c >>>> +++ b/builtin/pack-objects.c >>>> @@ -4462,6 +4462,7 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix) >>>> } else { >>>> get_object_list(&revs, rp.nr, rp.v); >>>> } >>>> + diff_free(&revs.diffopt); >>>> release_revisions(&revs); >>>> cleanup_preferred_base(); >>>> if (include_tag && nr_result) >>> >>> So, the main motivation for the change was paranoia that a compiler or >>> platform might show up without J.5.7 support and that would bite us, but >>> we're now adding a double-free-in-waiting? >>> >>> I think we're both a bit paranoid, but clearly have different >>> paranoia-priorities :) >>> >>> If we do end up with some hack like this instead of fixing the >>> underlying problem I'd much prefer that such a hack just be an UNLEAK() >>> here. >>> >>> I.e. we have a destructor for "revs.*" already, let's not bypass it and >>> start freeing things from under it, which will result in a double-free >>> if we forget this callsite once the TODO in 54c8a7c379 is addressed. >>> >>> As you'd see if you made release_revisions() simply call >>> diff_free(&revs.diffopt) doing so would reveal some really gnarly edge >>> cases. >>> >>> I haven't dug into this one, but offhand I'm not confident in saying >>> that this isn't exposing us to some aspect of that gnarlyness (maybe >>> not, it's been a while since I looked). >>> >>> (IIRC some of the most gnarly edge cases will only show up as CI >>> failures on Windows, to do with the ordering of when we'll fclose() >>> files hanging off that "diffopt"). >> >> This squashed into 3/3 seems to me to be a proper fix to a change that >> wants to refactor the code for non-J.5.7 compatibility. I.e. this just >> does the data<->fp casting part of the change, without refactoring the >> "lazy init". > > That works, but lazy code is more complicated and there is no benefit > here -- eager allocations are not noticably slow or big. Laziness > hides leaks in corners, i.e. requiring invocations with uncommon > options to trigger them. Yes, sometimes it's easier to just set everything up at the beginning. As for hiding leaks I think the empirical data here is going against that, i.e. your change introduced a leak. I don't think it's realistic that we'll have the side that assigns to "have_revs" drift from the corresponding code in cmd_pack_objects(). >> But I think you should check this a bit more carefully. Your 3/3 says >> that your change "mak[es] the reverted commit unnecessary" > > No, it says that _your_ change 2108fe4a19 (revisions API users: add > straightforward release_revisions(), 2022-04-13) made it unnecessary. Yes, I'm saying that's not correct, because if you run the command that 5cb28270a1 prominently notes we'll now leak with this revert: echo e83c5163316f89bfbde7d9ab23ca2e25604af290 | ./git pack-objects initial But yes with just 5cb28270a1 didn't add release_revisions(), that came shortly afterwards in 2108fe4a19. >> , but as I >> noted if you'd run the command that commit shows, you'd have seen you're >> re-introducing the leak it fixed. So I wonder what else has been missed >> here. > > 5cb28270a1 (pack-objects: lazily set up "struct rev_info", don't leak, > 2022-03-28) did not plug the leak. It only moved it to the corner that > handles the --filter option. I think we're using "the leak" here differently. I mean callstacks that LeakSanitizer emits & tests we have that do & don't pass with SANITIZE=leak. But yes, there may be multiple paths through a function, some of which leak, some of which don't. I'm not saying that the entire set of API features that builtin/pack-objects.c uses in the revision API is leak-free. > That leak is only interesting to Git developers and harmless for users. > But if the goal is to become free of trivial leaks in order to allow > using tools like LeakSanitizer to find real ones then pushing them into > the shadows not yet reached by our test coverage won't help for long. It's clearly helping in this case, as our CI had multiple failing tests. >> I vaguely recall that one reason I ended up with that J.5.7 dependency >> was because there was an objection to mocking up the "struct option" as >> I'm doing here. I.e. here we assume that the >> opt_parse_list_objects_filter() is only ever going to care about the >> "value" member. > > It's probably fine, but unnecessarily complicated compared to calling > repo_init_revisions() eagerly. I'm leaving aside the question of whether we should go for some version of the refactoring in your 3/3. What I am saying is that such refactoring should be split up from the more narrow bug fix to the existing code. I.e. this as a replacement for your 3/3 is all that's needed to pass the test you're adding in 2/3. -- >8 -- From: =?UTF-8?q?Ren=C3=A9=20Scharfe?= <l.s.r@xxxxxx> Subject: [PATCH] pack-objects: support multiple --filter options again 5cb28270a1f (pack-objects: lazily set up "struct rev_info", don't leak, 2022-03-28) broke support for multiple --filter options by calling repo_init_revisions() every time "--filter" was seen. Instead we should only do so the first time, and subsequently append to the existing filter data. Helped-by: Jeff King <peff@xxxxxxxx> Signed-off-by: René Scharfe <l.s.r@xxxxxx> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx> --- builtin/pack-objects.c | 3 ++- t/t5317-pack-objects-filter-objects.sh | 2 +- 2 files changed, 3 insertions(+), 2 deletions(-) diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c index 573d0b20b76..c702c09dd45 100644 --- a/builtin/pack-objects.c +++ b/builtin/pack-objects.c @@ -4158,7 +4158,8 @@ static struct list_objects_filter_options *po_filter_revs_init(void *value) { struct po_filter_data *data = value; - repo_init_revisions(the_repository, &data->revs, NULL); + if (!data->have_revs) + repo_init_revisions(the_repository, &data->revs, NULL); data->have_revs = 1; return &data->revs.filter; diff --git a/t/t5317-pack-objects-filter-objects.sh b/t/t5317-pack-objects-filter-objects.sh index 25faebaada8..5b707d911b5 100755 --- a/t/t5317-pack-objects-filter-objects.sh +++ b/t/t5317-pack-objects-filter-objects.sh @@ -265,7 +265,7 @@ test_expect_success 'verify normal and blob:limit packfiles have same commits/tr test_cmp expected observed ' -test_expect_failure 'verify small limit and big limit results in small limit' ' +test_expect_success 'verify small limit and big limit results in small limit' ' git -C r2 ls-files -s large.1000 >ls_files_result && test_parse_ls_files_stage_oids <ls_files_result | sort >expected && -- 2.39.0.rc0.993.g0c499e58e3b
