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From: Taylor Blau <me@ttaylorr.com>
To: git@vger.kernel.org
Cc: peff@peff.net, dstolee@microsoft.com, gitster@pobox.com,
	jonathantanmy@google.com
Subject: [PATCH 08/22] midx: respect 'core.multiPackIndex' when writing
Date: Fri, 9 Apr 2021 14:11:25 -0400	[thread overview]
Message-ID: <8643174a67812f347856bef274d6b971b15dbffc.1617991824.git.me@ttaylorr.com> (raw)
In-Reply-To: <cover.1617991824.git.me@ttaylorr.com>

When writing a new multi-pack index, write_midx_internal() attempts to
load any existing one to fill in some pieces of information. But it uses
load_multi_pack_index(), which ignores the configuration
"core.multiPackIndex", which indicates whether or not Git is allowed to
read an existing multi-pack-index.

Replace this with a routine that does respect that setting, to avoid
reading multi-pack-index files when told not to.

This avoids a problem that would arise in subsequent patches due to the
combination of 'git repack' reopening the object store in-process and
the multi-pack index code not checking whether a pack already exists in
the object store when calling add_pack_to_midx().

This would ultimately lead to a cycle being created along the
'packed_git' struct's '->next' pointer. That is obviously bad, but it
has hard-to-debug downstream effects like saying a bitmap can't be
loaded for a pack because one already exists (for the same pack).

Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
 midx.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/midx.c b/midx.c
index a24c36968d..567cdf0fcf 100644
--- a/midx.c
+++ b/midx.c
@@ -908,8 +908,18 @@ static int write_midx_internal(const char *object_dir, struct multi_pack_index *
 
 	if (m)
 		ctx.m = m;
-	else
-		ctx.m = load_multi_pack_index(object_dir, 1);
+	else {
+		struct multi_pack_index *cur;
+
+		prepare_multi_pack_index_one(the_repository, object_dir, 1);
+
+		ctx.m = NULL;
+		for (cur = the_repository->objects->multi_pack_index; cur;
+		     cur = cur->next) {
+			if (!strcmp(object_dir, cur->object_dir))
+				ctx.m = cur;
+		}
+	}
 
 	ctx.nr = 0;
 	ctx.alloc = ctx.m ? ctx.m->num_packs : 16;
-- 
2.31.1.163.ga65ce7f831


  parent reply	other threads:[~2021-04-09 18:12 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-09 18:10 [PATCH 00/22] multi-pack reachability bitmaps Taylor Blau
2021-04-09 18:10 ` [PATCH 01/22] pack-bitmap.c: harden 'test_bitmap_walk()' to check type bitmaps Taylor Blau
2021-04-09 18:10 ` [PATCH 02/22] pack-bitmap-write.c: gracefully fail to write non-closed bitmaps Taylor Blau
2021-04-16  2:46   ` Jonathan Tan
2021-04-09 18:10 ` [PATCH 03/22] pack-bitmap-write.c: free existing bitmaps Taylor Blau
2021-04-09 18:10 ` [PATCH 04/22] Documentation: build 'technical/bitmap-format' by default Taylor Blau
2021-04-09 18:11 ` [PATCH 05/22] Documentation: describe MIDX-based bitmaps Taylor Blau
2021-04-09 18:11 ` [PATCH 06/22] midx: make a number of functions non-static Taylor Blau
2021-04-09 18:11 ` [PATCH 07/22] midx: clear auxiliary .rev after replacing the MIDX Taylor Blau
2021-04-09 18:11 ` Taylor Blau [this message]
2021-04-09 18:11 ` [PATCH 09/22] pack-bitmap.c: introduce 'bitmap_num_objects()' Taylor Blau
2021-04-09 18:11 ` [PATCH 10/22] pack-bitmap.c: introduce 'nth_bitmap_object_oid()' Taylor Blau
2021-04-09 18:11 ` [PATCH 11/22] pack-bitmap.c: introduce 'bitmap_is_preferred_refname()' Taylor Blau
2021-04-09 18:11 ` [PATCH 12/22] pack-bitmap: read multi-pack bitmaps Taylor Blau
2021-04-16  2:39   ` Jonathan Tan
2021-04-16  3:13     ` Taylor Blau
2021-04-09 18:11 ` [PATCH 13/22] pack-bitmap: write " Taylor Blau
2021-05-04  5:02   ` Jonathan Tan
2021-05-06 20:18     ` Taylor Blau
2021-05-06 22:00       ` Jonathan Tan
2021-04-09 18:11 ` [PATCH 14/22] t5310: move some tests to lib-bitmap.sh Taylor Blau
2021-04-09 18:11 ` [PATCH 15/22] t/helper/test-read-midx.c: add --checksum mode Taylor Blau
2021-04-09 18:12 ` [PATCH 16/22] t5326: test multi-pack bitmap behavior Taylor Blau
2021-05-04 17:51   ` Jonathan Tan
2021-04-09 18:12 ` [PATCH 17/22] t5310: disable GIT_TEST_MULTI_PACK_INDEX_WRITE_BITMAP Taylor Blau
2021-04-09 18:12 ` [PATCH 18/22] t5319: don't write MIDX bitmaps in t5319 Taylor Blau
2021-04-09 18:12 ` [PATCH 19/22] t7700: update to work with MIDX bitmap test knob Taylor Blau
2021-04-09 18:12 ` [PATCH 20/22] midx: respect 'GIT_TEST_MULTI_PACK_INDEX_WRITE_BITMAP' Taylor Blau
2021-04-09 18:12 ` [PATCH 21/22] p5310: extract full and partial bitmap tests Taylor Blau
2021-04-09 18:12 ` [PATCH 22/22] p5326: perf tests for MIDX bitmaps Taylor Blau
2021-05-04 18:00   ` Jonathan Tan
2021-05-05  0:55     ` Junio C Hamano

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