When passing a preferred pack to the MIDX write machinery, we ensure
that the given preferred pack is non-empty since 5d3cd09a808 (midx:
reject empty `--preferred-pack`'s, 2021-08-31).
However packs are only loaded (via `write_midx_internal()`, though a
subsequent patch will refactor this code out to its own function) when
the `MIDX_WRITE_REV_INDEX` flag is set.
So if a caller runs:
$ git multi-pack-index write --preferred-pack=...
with both (a) an existing MIDX, and (b) specifies a pack from that MIDX
as the preferred one, without passing `--bitmap`, then the check added
in 5d3cd09a808 will result in a segfault.
Note that packs loaded from disk which don't appear in an existing MIDX
do not trigger this issue, as those packs are loaded unconditionally. We
conditionally load packs from a MIDX since we tolerate MIDXs whose
packs do not resolve (i.e., via the MIDX write after removing
unreferenced packs via 'git multi-pack-index expire').
In practice, this isn't possible to trigger when running `git
multi-pack-index write` from via `git repack`, as the latter always
passes `--stdin-packs`, which prevents us from loading an existing MIDX,
as it forces all packs to be read from disk.
But a future commit in this series will change that behavior to
unconditionally load an existing MIDX, even with `--stdin-packs`, making
this behavior trigger-able from 'repack' much more easily.
Prevent this from being an issue by removing the segfault altogether by
calling `prepare_midx_pack()` on packs loaded from an existing MIDX when
either the `MIDX_WRITE_REV_INDEX` flag is set *or* we specified a
`--preferred-pack`.
Signed-off-by: Taylor Blau <me@xxxxxxxxxxxx>
---
midx-write.c | 8 +++++++-
t/t5319-multi-pack-index.sh | 23 +++++++++++++++++++++++
2 files changed, 30 insertions(+), 1 deletion(-)
diff --git a/midx-write.c b/midx-write.c
index 9d096d5a28..03e95ae821 100644
--- a/midx-write.c
+++ b/midx-write.c
@@ -930,11 +930,17 @@ static int write_midx_internal(const char *object_dir,
for (i = 0; i < ctx.m->num_packs; i++) {
ALLOC_GROW(ctx.info, ctx.nr + 1, ctx.alloc);
- if (flags & MIDX_WRITE_REV_INDEX) {
+ if (flags & MIDX_WRITE_REV_INDEX ||
+ preferred_pack_name) {
/*
* If generating a reverse index, need to have
* packed_git's loaded to compare their
* mtimes and object count.
+ *
+ * If a preferred pack is specified,
+ * need to have packed_git's loaded to
+ * ensure the chosen preferred pack has
+ * a non-zero object count.
*/
if (prepare_midx_pack(the_repository, ctx.m, i)) {
error(_("could not load pack"));
diff --git a/t/t5319-multi-pack-index.sh b/t/t5319-multi-pack-index.sh
index dd09134db0..10d2a6bf92 100755
--- a/t/t5319-multi-pack-index.sh
+++ b/t/t5319-multi-pack-index.sh
@@ -350,6 +350,29 @@ test_expect_success 'preferred packs must be non-empty' '
)
'
+test_expect_success 'preferred pack from existing MIDX without bitmaps' '
+ git init preferred-without-bitmaps &&
+ (
+ cd preferred-without-bitmaps &&
+
+ test_commit one &&
+ pack="$(git pack-objects --all $objdir/pack/pack </dev/null)" &&
+
+ git multi-pack-index write &&
+
+ # make another pack so that the subsequent MIDX write
+ # has something to do
+ test_commit two &&
+ git repack -d &&
+
+ # write a new MIDX without bitmaps reusing the singular
+ # pack from the existing MIDX as the preferred pack in
+ # the new MIDX
+ git multi-pack-index write --preferred-pack=pack-$pack.pack
+ )
+
+'
+
test_expect_success 'verify multi-pack-index success' '
git multi-pack-index verify --object-dir=$objdir
'
--
2.45.1.217.g9bb58e2bf5a.dirty
