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[08/22] midx: respect 'core.multiPackIndex' when writing

Message ID 8643174a67812f347856bef274d6b971b15dbffc.1617991824.git.me@ttaylorr.com (mailing list archive)
State New
Headers show
Series multi-pack reachability bitmaps | expand

Commit Message

Taylor Blau April 9, 2021, 6:11 p.m. UTC
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(-)
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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;