[PATCH v2 1/8] midx-write.c: tolerate `--preferred-pack` without bitmaps
- From
Taylor Blau <me@ttaylorr.com>
- Date
- May 29, 2024, 22:55 UTC
- Message-ID
- <ad268bd264e34f02f9c32e31db696c7acc1efc2b.1717023301.git.me@ttaylorr.com>
- In-Reply-To
- <cover.1717023301.git.me@ttaylorr.com>
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 `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@ttaylorr.com> --- 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 2fa120c213..591b79bcbf 100644 --- a/midx-write.c +++ b/midx-write.c @@ -935,11 +935,17 @@ 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 '
-- 2.45.1.321.gbcadaf92783