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". But I think you should check this a bit more carefully. Your 3/3 says that your change "mak[es] the reverted commit unnecessary", 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. 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. I think that's probably fine, but I may be misrecalling, or missing some crucial detail. I'll leave digging that up & convincing us that it's fine to the person pushing for refactoring all of this :) diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c index 3e74fbb0cd5..faf210bfe8c 100644 --- a/builtin/pack-objects.c +++ b/builtin/pack-objects.c @@ -4149,6 +4149,27 @@ static int option_parse_cruft_expiration(const struct option *opt, return 0; } +struct po_filter_data { + unsigned have_revs:1; + struct rev_info revs; +}; + +static int opt_parse_list_objects_filter_init(const struct option *opt, + const char *arg, int unset) +{ + struct po_filter_data *data = opt->value; + struct rev_info *revs = &data->revs; + const struct option opt_rev = { + .value = (void *)&revs->filter, + }; + + if (!data->have_revs) + repo_init_revisions(the_repository, revs, NULL); + data->have_revs = 1; + + return opt_parse_list_objects_filter(&opt_rev, arg, unset); +} + int cmd_pack_objects(int argc, const char **argv, const char *prefix) { int use_internal_rev_list = 0; @@ -4159,7 +4180,7 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix) int rev_list_index = 0; int stdin_packs = 0; struct string_list keep_pack_list = STRING_LIST_INIT_NODUP; - struct rev_info revs; + struct po_filter_data pfd = { .have_revs = 0 }; struct option pack_objects_options[] = { OPT_SET_INT('q', "quiet", &progress, @@ -4250,7 +4271,8 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix) &write_bitmap_index, N_("write a bitmap index if possible"), WRITE_BITMAP_QUIET, PARSE_OPT_HIDDEN), - OPT_PARSE_LIST_OBJECTS_FILTER(&revs.filter), + OPT_CALLBACK(0, "filter", &pfd, N_("args"), N_("object filtering"), + opt_parse_list_objects_filter_init), OPT_CALLBACK_F(0, "missing", NULL, N_("action"), N_("handling for missing objects"), PARSE_OPT_NONEG, option_parse_missing_action), @@ -4269,8 +4291,6 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix) read_replace_refs = 0; - repo_init_revisions(the_repository, &revs, NULL); - sparse = git_env_bool("GIT_TEST_PACK_SPARSE", -1); if (the_repository->gitdir) { prepare_repo_settings(the_repository); @@ -4372,7 +4392,7 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix) if (!rev_list_all || !rev_list_reflog || !rev_list_index) unpack_unreachable_expiration = 0; - if (revs.filter.choice) { + if (pfd.have_revs && pfd.revs.filter.choice) { if (!pack_to_stdout) die(_("cannot use --filter without --stdout")); if (stdin_packs) @@ -4459,10 +4479,16 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix) read_cruft_objects(); } else if (!use_internal_rev_list) { read_object_list_from_stdin(); + } else if (pfd.have_revs) { + get_object_list(&pfd.revs, rp.nr, rp.v); + release_revisions(&pfd.revs); } else { + struct rev_info revs; + + repo_init_revisions(the_repository, &revs, NULL); get_object_list(&revs, rp.nr, rp.v); + release_revisions(&revs); } - release_revisions(&revs); cleanup_preferred_base(); if (include_tag && nr_result) for_each_tag_ref(add_ref_tag, NULL);
