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From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: git@vger.kernel.org
Cc: "Junio C Hamano" <gitster@pobox.com>, "Jeff King" <peff@peff.net>,
	"Taylor Blau" <me@ttaylorr.com>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Subject: [PATCH v2 4/4] pack-write: rename *.idx file into place last (really!)
Date: Wed,  8 Sep 2021 02:38:28 +0200	[thread overview]
Message-ID: <patch-v2-4.4-70f4a9767d-20210908T003631Z-avarab@gmail.com> (raw)
In-Reply-To: <cover-v2-0.4-0000000000-20210908T003631Z-avarab@gmail.com>

Follow-up a preceding commit (pack-write.c: rename `.idx` file into
place last, 2021-08-16)[1] and rename the *.idx file in-place after we
write the *.bitmap. The preceding commit fixed the issue of *.idx
being written before *.rev files, but did not do so for *.idx files.

See 7cc8f971085 (pack-objects: implement bitmap writing, 2013-12-21)
for commentary at the time when *.bitmap was implemented about how
those files are written out, nothing in that commit contradicts what's
being done here.

Note that the referenced earlier commit[1] is overly optimistic about
"clos[ing the] race", i.e. yes we'll now write the files in the right
order, but we might still race due to our sloppy use of fsync(). See
the thread at [2] for a rabbit hole of various discussions about
filesystem races in the face of doing and not doing fsync() (and if
doing fsync(), not doing it properly).

1. https://lore.kernel.org/git/a6a4d2154e83d41c10986c5f455279ab249a910c.1630461918.git.me@ttaylorr.com/
2. https://lore.kernel.org/git/8735qgkvv1.fsf@evledraar.gmail.com/

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 builtin/pack-objects.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index 33567aaa74..396240c25a 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -1249,7 +1249,6 @@ static void write_pack_file(void)
 			stage_tmp_packfiles(&tmpname, pack_tmp_name,
 					    written_list, nr_written,
 					    &pack_idx_opts, hash, &idx_tmp_name);
-			rename_tmp_packfile_idx(&tmpname, hash, &idx_tmp_name);
 
 			if (write_bitmap_index) {
 				struct strbuf sb = STRBUF_INIT;
@@ -1268,6 +1267,8 @@ static void write_pack_file(void)
 				strbuf_release(&sb);
 			}
 
+			rename_tmp_packfile_idx(&tmpname, hash, &idx_tmp_name);
+
 			free(idx_tmp_name);
 			strbuf_release(&tmpname);
 			free(pack_tmp_name);
-- 
2.33.0.819.gea1b153a43c


  parent reply	other threads:[~2021-09-08  0:38 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
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   ` Ævar Arnfjörð Bjarmason [this message]
2021-09-08  1:14     ` [PATCH v2 4/4] pack-write: rename *.idx file into place last (really!) 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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