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[62.195.237.193]) by smtp.gmail.com with ESMTPSA id d44sm434767eda.75.2019.06.28.00.21.19 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Fri, 28 Jun 2019 00:21:19 -0700 (PDT) From: =?utf-8?B?w4Z2YXIgQXJuZmrDtnLDsA==?= Bjarmason To: Eric Wong Cc: Jeff King , Janos Farkas , git@vger.kernel.org Subject: Re: [PATCH] repack: disable bitmaps-by-default if .keep files exist References: <875zow8i85.fsf@evledraar.gmail.com> <20190623180226.GA1100@sigill.intra.peff.net> <20190623180825.3ospajjgat3clwiu@dcvr> <20190623224244.GB1100@sigill.intra.peff.net> <20190628070211.hfweqcons6c6gy52@dcvr> User-agent: Debian GNU/Linux 10 (buster); Emacs 26.1; mu4e 1.1.0 In-reply-to: <20190628070211.hfweqcons6c6gy52@dcvr> Date: Fri, 28 Jun 2019 09:21:18 +0200 Message-ID: <87zhm26uq9.fsf@evledraar.gmail.com> MIME-Version: 1.0 Content-Type: text/plain Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Fri, Jun 28 2019, Eric Wong wrote: > Jeff King wrote: >> On Sun, Jun 23, 2019 at 06:08:25PM +0000, Eric Wong wrote: >> >> > > I'm not sure of the right solution. For maximal backwards-compatibility, >> > > the default for bitmaps could become "if not bare and if there are no >> > > .keep files". But that would mean bitmaps sometimes not getting >> > > generated because of the problems that ee34a2bead was trying to solve. >> > > >> > > That's probably OK, though; you can always flip the bitmap config to >> > > "true" yourself if you _must_ have bitmaps. >> > >> > What about something like this? Needs tests but I need to leave, now. >> >> Yeah, I think that's the right direction. > > OK. I have a real patch with one additional test, below. > (don't have a lot of time for hacking) > >> Though... >> >> > +static int has_pack_keep_file(void) >> > +{ >> > + DIR *dir; >> > + struct dirent *e; >> > + int found = 0; >> > + >> > + if (!(dir = opendir(packdir))) >> > + return found; >> > + >> > + while ((e = readdir(dir)) != NULL) { >> > + if (ends_with(e->d_name, ".keep")) { >> > + found = 1; >> > + break; >> > + } >> > + } >> > + closedir(dir); >> > + return found; >> > +} >> >> I think this can be replaced with just checking p->pack_keep for each >> item in the packed_git list. > > Good point, I tend to forget git C API internals as soon as I > learn them :x > >> That's racy, but then so is your code here, since it's really the child >> pack-objects which is going to deal with the .keep. I don't think we >> need to care much about the race, though. Either: > > Agreed. > > --------8<------- > Subject: [PATCH] repack: disable bitmaps-by-default if .keep files exist > > Bitmaps aren't useful with multiple packs, and users with > .keep files ended up with redundant packs when bitmaps > got enabled by default in bare repos. > > So detect when .keep files exist and stop enabling bitmaps > by default in that case. > > Wasteful (but otherwise harmless) race conditions with .keep files > documented by Jeff King still apply and there's a chance we'd > still end up with redundant data on the FS: > > https://public-inbox.org/git/20190623224244.GB1100@sigill.intra.peff.net/ > > Fixes: 36eba0323d3288a8 ("repack: enable bitmaps by default on bare repos") > Signed-off-by: Eric Wong > Helped-by: Jeff King > Reported-by: Janos Farkas > --- > builtin/repack.c | 18 ++++++++++++++++-- > t/t7700-repack.sh | 10 ++++++++++ > 2 files changed, 26 insertions(+), 2 deletions(-) > > diff --git a/builtin/repack.c b/builtin/repack.c > index caca113927..a9529d1afc 100644 > --- a/builtin/repack.c > +++ b/builtin/repack.c > @@ -89,6 +89,17 @@ static void remove_pack_on_signal(int signo) > raise(signo); > } > > +static int has_pack_keep_file(void) > +{ > + struct packed_git *p; > + > + for (p = get_packed_git(the_repository); p; p = p->next) { > + if (p->pack_keep) > + return 1; > + } > + return 0; > +} > + > /* > * Adds all packs hex strings to the fname list, which do not > * have a corresponding .keep file. These packs are not to > @@ -343,9 +354,12 @@ int cmd_repack(int argc, const char **argv, const char *prefix) > (unpack_unreachable || (pack_everything & LOOSEN_UNREACHABLE))) > die(_("--keep-unreachable and -A are incompatible")); > > - if (write_bitmaps < 0) > + if (write_bitmaps < 0) { > write_bitmaps = (pack_everything & ALL_INTO_ONE) && > - is_bare_repository(); > + is_bare_repository() && > + keep_pack_list.nr == 0 && > + !has_pack_keep_file(); > + } > if (pack_kept_objects < 0) > pack_kept_objects = write_bitmaps; > > diff --git a/t/t7700-repack.sh b/t/t7700-repack.sh > index 86d05160a3..0acde3b1f8 100755 > --- a/t/t7700-repack.sh > +++ b/t/t7700-repack.sh > @@ -239,4 +239,14 @@ test_expect_success 'bitmaps can be disabled on bare repos' ' > test -z "$bitmap" > ' I have the feedback I posted before this patch in https://public-inbox.org/git/874l4f8h4c.fsf@evledraar.gmail.com/ In particular "b" there since "a" is clearly more work. I.e. shouldn't we at least in interactive mode on a "gc" print something about skipping what we'd otherwise do. Maybe that's tricky with the gc.log functionality, but I think we should at least document this before the next guy shows up with "sometimes my .bitmap files aren't generated...". > +test_expect_success 'no bitmaps created if .keep files present' ' > + pack=$(ls bare.git/objects/pack/*.pack) && > + test_path_is_file "$pack" && > + keep=${pack%.pack}.keep && > + >"$keep" && > + git -C bare.git repack -ad && > + bitmap=$(ls bare.git/objects/pack/*.bitmap 2>/dev/null || :) && > + test -z "$bitmap" Maybe more readable as: find .git/objects/pack/ -type f -name '*.bitmap' >actual && test_must_be_empty actual I.e. it avoids the "|| :" & subshell. > +' > + > test_done