From: Taylor Blau <me@ttaylorr.com>
To: Jeff King <peff@peff.net>
Cc: Taylor Blau <me@ttaylorr.com>, git@vger.kernel.org
Subject: Re: [PATCH 0/2] pack-write,repack: prevent opening packs too early
Date: Wed, 1 Sep 2021 00:29:54 -0400 [thread overview]
Message-ID: <YS8BwgfurPzhT4xh@nand.local> (raw)
In-Reply-To: <YS75P7r33NIBmFh2@coredump.intra.peff.net>
On Tue, Aug 31, 2021 at 11:53:35PM -0400, Jeff King wrote:
> So far so good. But the other obvious way to get a pack idx is via
> index-pack (especially "--stdin").
>
> It looks like we'd want the same re-ordering to happen in
> builtin/index-pack.c:final(), which is where we rename the temporary
> files into place.
Sure, that's easy enough.
> We _might_ also want to re-order the calls to write_idx_file() and
> write_rev_file() in its caller, given that simultaneous readers are
> happy to read our tmp_pack_* files. I guess the same might apply to the
> actual file write order pack-objects, too? I'm not sure if that's even
> possible, though; do we rely on side effects of generating the .idx when
> generating the other meta files?
These are a little trickier. write_idx_file() is also responsible for
rearranging the objects array into index (name) order on the way out,
which write_rev_file() depends on in order to build up its mapping.
So you could sort the array at the call-site before calling either
function, but it gets awkward since there are a handful of other callers
of write_idx_file() besides the two we're discussing.
It could be done, but it feels like the wrong approach, because...
> I think it might be more sensible if the reading side was taught to
> ignore ".tmp-*" and "tmp_*" (and possibly even ".*", though it's
> possible somebody is relying on that).
...this seems like the much-better way to go. Git shouldn't have to
worry about what order it writes the temporary files in, only what order
those temporary files are made non-temporary.
But I need to do some more investigation to make sure there aren't any
other implications. So I'm happy to wait on that, or send a new version
of this series with a patch to fix the race in
builtin/index-pack.c:final(), too.
(Unrelated to your suggestions above) another consideration for "stuff
to do later" would be to flip the default of pack.writeReverseIndex. I
had intentions to do that in the 2.32 cycle, but I forgot about it.
> -Peff
Thanks,
Taylor
next prev parent reply other threads:[~2021-09-01 4:30 UTC|newest]
Thread overview: 81+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-01 2:05 [PATCH 0/2] pack-write,repack: prevent opening packs too early Taylor Blau
2021-09-01 2:06 ` [PATCH 1/2] pack-write.c: rename `.idx` file into place last Taylor Blau
2021-09-01 2:06 ` [PATCH 2/2] builtin/repack.c: move `.idx` files " Taylor Blau
2021-09-01 3:53 ` [PATCH 0/2] pack-write,repack: prevent opening packs too early Jeff King
2021-09-01 4:29 ` Taylor Blau [this message]
2021-09-01 4:59 ` Jeff King
2021-09-01 5:12 ` Taylor Blau
2021-09-01 6:08 ` Jeff King
2021-09-01 21:40 ` Taylor Blau
2021-09-07 16:07 ` Jeff King
2021-09-07 19:42 ` [PATCH 0/3] rename *.idx file into place last (also after *.bitmap) Ævar Arnfjörð Bjarmason
2021-09-07 19:42 ` [PATCH 1/3] pack-write: use more idiomatic strbuf usage for packname construction Ævar Arnfjörð Bjarmason
2021-09-07 22:21 ` Taylor Blau
2021-09-07 23:22 ` Ævar Arnfjörð Bjarmason
2021-09-07 19:42 ` [PATCH 2/3] pack-write: split up finish_tmp_packfile() function Ævar Arnfjörð Bjarmason
2021-09-07 22:28 ` Taylor Blau
2021-09-07 19:42 ` [PATCH 3/3] pack-write: rename *.idx file into place last (really!) Ævar Arnfjörð Bjarmason
2021-09-07 22:31 ` Taylor Blau
2021-09-07 22:36 ` [PATCH 0/3] rename *.idx file into place last (also after *.bitmap) Taylor Blau
2021-09-07 19:48 ` [PATCH 0/2] pack-write,repack: prevent opening packs too early Ævar Arnfjörð Bjarmason
2021-09-08 0:38 ` [PATCH v2 0/4] rename *.idx file into place last (also after *.bitmap) Ævar Arnfjörð Bjarmason
2021-09-08 0:38 ` [PATCH v2 1/4] pack.h: line-wrap the definition of finish_tmp_packfile() Ævar Arnfjörð Bjarmason
2021-09-08 0:38 ` [PATCH v2 2/4] pack-write: refactor renaming in finish_tmp_packfile() Ævar Arnfjörð Bjarmason
2021-09-08 4:22 ` Taylor Blau
2021-09-08 0:38 ` [PATCH v2 3/4] pack-write: split up finish_tmp_packfile() function Ævar Arnfjörð Bjarmason
2021-09-08 0:38 ` [PATCH v2 4/4] pack-write: rename *.idx file into place last (really!) Ævar Arnfjörð Bjarmason
2021-09-08 1:14 ` Ævar Arnfjörð Bjarmason
2021-09-08 9:18 ` Ævar Arnfjörð Bjarmason
2021-09-08 4:24 ` Taylor Blau
2021-09-08 22:17 ` [PATCH v2 0/3] prevent opening packs too early Taylor Blau
2021-09-08 22:17 ` [PATCH v2 1/3] pack-write.c: rename `.idx` files into place last Taylor Blau
2021-09-08 22:17 ` [PATCH v2 2/3] builtin/repack.c: move " Taylor Blau
2021-09-08 22:17 ` [PATCH v2 3/3] builtin/index-pack.c: " Taylor Blau
2021-09-08 23:52 ` [PATCH v2 0/3] prevent opening packs too early Ævar Arnfjörð Bjarmason
2021-09-09 0:50 ` Ævar Arnfjörð Bjarmason
2021-09-09 1:13 ` Taylor Blau
2021-09-09 1:33 ` Ævar Arnfjörð Bjarmason
2021-09-09 2:36 ` Ævar Arnfjörð Bjarmason
2021-09-09 2:49 ` Taylor Blau
2021-09-09 3:24 ` [PATCH 0/9] packfile: avoid .idx rename races Taylor Blau
2021-09-09 3:24 ` [PATCH 1/9] pack.h: line-wrap the definition of finish_tmp_packfile() Taylor Blau
2021-09-09 3:24 ` [PATCH 2/9] bulk-checkin.c: store checksum directly Taylor Blau
2021-09-09 7:38 ` Ævar Arnfjörð Bjarmason
2021-09-09 3:24 ` [PATCH 3/9] pack-write: refactor renaming in finish_tmp_packfile() Taylor Blau
2021-09-09 19:29 ` Junio C Hamano
2021-09-09 21:07 ` Taylor Blau
2021-09-09 23:30 ` Junio C Hamano
2021-09-09 23:31 ` Taylor Blau
2021-09-10 1:29 ` Junio C Hamano
2021-09-09 3:24 ` [PATCH 4/9] pack-write.c: rename `.idx` files after `*.rev` Taylor Blau
2021-09-09 7:46 ` Ævar Arnfjörð Bjarmason
2021-09-09 14:37 ` Taylor Blau
2021-09-09 19:32 ` Junio C Hamano
2021-09-09 3:25 ` [PATCH 5/9] builtin/repack.c: move `.idx` files into place last Taylor Blau
2021-09-09 19:38 ` Junio C Hamano
2021-09-09 21:08 ` Taylor Blau
2021-09-09 3:25 ` [PATCH 6/9] index-pack: refactor renaming in final() Taylor Blau
2021-09-09 19:45 ` Junio C Hamano
2021-09-09 21:11 ` Taylor Blau
2021-09-09 3:25 ` [PATCH 7/9] builtin/index-pack.c: move `.idx` files into place last Taylor Blau
2021-09-09 7:52 ` Ævar Arnfjörð Bjarmason
2021-09-09 19:45 ` Junio C Hamano
2021-09-09 3:25 ` [PATCH 8/9] pack-write: split up finish_tmp_packfile() function Taylor Blau
2021-09-09 3:25 ` [PATCH 9/9] pack-objects: rename .idx files into place after .bitmap files Taylor Blau
2021-09-09 7:54 ` Ævar Arnfjörð Bjarmason
2021-09-09 19:52 ` Junio C Hamano
2021-09-09 21:13 ` Taylor Blau
2021-09-09 8:06 ` [PATCH 0/9] packfile: avoid .idx rename races Ævar Arnfjörð Bjarmason
2021-09-09 14:40 ` Taylor Blau
2021-09-09 19:52 ` Junio C Hamano
2021-09-09 23:24 ` [PATCH v2 " Taylor Blau
2021-09-09 23:24 ` [PATCH v2 1/9] pack.h: line-wrap the definition of finish_tmp_packfile() Taylor Blau
2021-09-09 23:24 ` [PATCH v2 2/9] bulk-checkin.c: store checksum directly Taylor Blau
2021-09-09 23:24 ` [PATCH v2 3/9] pack-write: refactor renaming in finish_tmp_packfile() Taylor Blau
2021-09-09 23:24 ` [PATCH v2 4/9] pack-write.c: rename `.idx` files after `*.rev` Taylor Blau
2021-09-09 23:24 ` [PATCH v2 5/9] builtin/repack.c: move `.idx` files into place last Taylor Blau
2021-09-09 23:24 ` [PATCH v2 6/9] index-pack: refactor renaming in final() Taylor Blau
2021-09-09 23:24 ` [PATCH v2 7/9] builtin/index-pack.c: move `.idx` files into place last Taylor Blau
2021-09-09 23:24 ` [PATCH v2 8/9] pack-write: split up finish_tmp_packfile() function Taylor Blau
2021-09-09 23:25 ` [PATCH v2 9/9] pack-objects: rename .idx files into place after .bitmap files Taylor Blau
2021-09-10 1:35 ` [PATCH v2 0/9] packfile: avoid .idx rename races Junio C Hamano
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