[PATCH 13/17] refs/reftable: fix consistency checks with worktrees

From: Patrick Steinhardt <ps@pks.im>
Date: Jan 9, 2026, 12:39 UTC
Message-ID: <20260109-pks-refs-verify-fixes-v1-13-3587dba18294@pks.im>
In-Reply-To: <20260109-pks-refs-verify-fixes-v1-0-3587dba18294@pks.im>

The ref consistency checks are driven via `cmd_refs_verify()`. That function loops through all worktrees (including the main worktree) and then checks the ref store for each of them individually. It follows that the backend is expected to only verify refs that belong to the specified worktree.

While the "files" backend handles this correctly, the "reftable" backend doesn't. In fact, it completely ignores the passed worktree and instead verifies refs of _all_ worktrees. The consequence is that we'll end up every ref store N times, where N is the number of worktrees.

Or rather, that would be the case if we actually iterated through the worktree reftable stacks correctly. But we use `strmap_for_each_entry()` to iterate through the stacks, but the map is in fact not even properly populated. So instead of checking stacks N^2 times, we actually only end up checking the reftable stack of the main worktree.

Fix this bug by only verifying the stack of the passed-in worktree and constructing the backends via `backend_for_worktree()`.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 refs/reftable-backend.c  | 29 ++++++++++++++---------------
 t/t0614-reftable-fsck.sh | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 15 deletions(-)

diff --git a/refs/reftable-backend.c b/refs/reftable-backend.c
index dda961a32b..6361b27015 100644
--- a/refs/reftable-backend.c
+++ b/refs/reftable-backend.c
@@ -26,6 +26,7 @@
 #include "../setup.h"
 #include "../strmap.h"
 #include "../trace2.h"
+#include "../worktree.h"
 #include "../write-or-die.h"
 #include "refs-internal.h"
 
@@ -2762,25 +2763,23 @@ static int reftable_fsck_error_handler(struct reftable_fsck_info *info,
 }
 
 static int reftable_be_fsck(struct ref_store *ref_store, struct fsck_options *o,
-			    struct worktree *wt UNUSED)
+			    struct worktree *wt)
 {
-	struct reftable_ref_store *refs;
-	struct strmap_entry *entry;
-	struct hashmap_iter iter;
-	int ret = 0;
-
-	refs = reftable_be_downcast(ref_store, REF_STORE_READ, "fsck");
-
-	ret |= reftable_fsck_check(refs->main_backend.stack, reftable_fsck_error_handler,
-				   reftable_fsck_verbose_handler, o);
+	struct reftable_ref_store *refs =
+		reftable_be_downcast(ref_store, REF_STORE_READ, "fsck");
+	struct reftable_backend *backend;
 
-	strmap_for_each_entry(&refs->worktree_backends, &iter, entry) {
-		struct reftable_backend *b = (struct reftable_backend *)entry->value;
-		ret |= reftable_fsck_check(b->stack, reftable_fsck_error_handler,
-					   reftable_fsck_verbose_handler, o);
+	if (is_main_worktree(wt)) {
+		backend = &refs->main_backend;
+	} else {
+		int ret = backend_for_worktree(&backend, refs, wt->id);
+		if (ret < 0)
+			return error(_("reftable stack for worktree '%s' is broken"),
+				     wt->id);
 	}
 
-	return ret;
+	return reftable_fsck_check(backend->stack, reftable_fsck_error_handler,
+				   reftable_fsck_verbose_handler, o);
 }
 
 struct ref_storage_be refs_be_reftable = {
diff --git a/t/t0614-reftable-fsck.sh b/t/t0614-reftable-fsck.sh
index 677eb9143c..4757eb5931 100755
--- a/t/t0614-reftable-fsck.sh
+++ b/t/t0614-reftable-fsck.sh
@@ -55,4 +55,36 @@ for TABLE_NAME in "foo-bar-e4d12d59.ref" \
 	'
 done
 
+test_expect_success 'worktree stacks can be verified' '
+	test_when_finished "rm -rf repo worktree" &&
+	git init repo &&
+	test_commit -C repo initial &&
+	git -C repo worktree add ../worktree &&
+
+	git -C worktree refs verify 2>err &&
+	test_must_be_empty err &&
+
+	REFTABLE_DIR=$(git -C worktree rev-parse --git-dir)/reftable &&
+	EXISTING_TABLE=$(head -n1 "$REFTABLE_DIR/tables.list") &&
+	mv "$REFTABLE_DIR/$EXISTING_TABLE" "$REFTABLE_DIR/broken.ref" &&
+
+	for d in repo worktree
+	do
+		echo "broken.ref" >"$REFTABLE_DIR/tables.list" &&
+		git -C "$d" refs verify 2>err &&
+		cat >expect <<-EOF &&
+		warning: broken.ref: badReftableTableName: invalid reftable table name
+		EOF
+		test_cmp expect err &&
+
+		echo garbage >"$REFTABLE_DIR/tables.list" &&
+		test_must_fail git -C "$d" refs verify 2>err &&
+		cat >expect <<-EOF &&
+		error: reftable stack for worktree ${SQ}worktree${SQ} is broken
+		EOF
+		test_cmp expect err || return 1
+
+	done
+'
+
 test_done

-- 
2.52.0.542.g9473a8513b.dirty