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reftable/stack: allow locking of outdated stacks

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In `reftable_stack_new_addition()` we first lock the stack and then
check whether it is still up-to-date. If it is not we return an error to
the caller indicating that the stack is outdated.

This is overly restrictive in our ref transaction interface though: we
lock the stack right before we start to verify the transaction, so we do
not really care whether it is outdated or not. What we really want is
that the stack is up-to-date after it has been locked so that we can
verify queued updates against its current state while we know that it is
locked for concurrent modification.

Introduce a new flag `REFTABLE_STACK_NEW_ADDITION_RELOAD` that alters
the behaviour of `reftable_stack_init_addition()` in this case: when we
notice that it is out-of-date we reload it instead of returning an error
to the caller.

This logic will be wired up in the reftable backend in the next commit.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Patrick Steinhardt
2024-09-24 07:33:05 +02:00
committed by Junio C Hamano
parent bc39b6a796
commit 80e7342ea8
4 changed files with 91 additions and 13 deletions
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67
t/unit-tests/t-reftable-stack.c
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@ -271,7 +271,7 @@ static void t_reftable_stack_transaction_api(void)
reftable_addition_destroy(add);
err = reftable_stack_new_addition(&add, st);
err = reftable_stack_new_addition(&add, st, 0);
check(!err);
err = reftable_addition_add(add, write_test_ref, &ref);
@ -292,6 +292,68 @@ static void t_reftable_stack_transaction_api(void)
clear_dir(dir);
}
static void t_reftable_stack_transaction_with_reload(void)
{
char *dir = get_tmp_dir(__LINE__);
struct reftable_stack *st1 = NULL, *st2 = NULL;
int err;
struct reftable_addition *add = NULL;
struct reftable_ref_record refs[2] = {
{
.refname = (char *) "refs/heads/a",
.update_index = 1,
.value_type = REFTABLE_REF_VAL1,
.value.val1 = { '1' },
},
{
.refname = (char *) "refs/heads/b",
.update_index = 2,
.value_type = REFTABLE_REF_VAL1,
.value.val1 = { '1' },
},
};
struct reftable_ref_record ref = { 0 };
err = reftable_new_stack(&st1, dir, NULL);
check(!err);
err = reftable_new_stack(&st2, dir, NULL);
check(!err);
err = reftable_stack_new_addition(&add, st1, 0);
check(!err);
err = reftable_addition_add(add, write_test_ref, &refs[0]);
check(!err);
err = reftable_addition_commit(add);
check(!err);
reftable_addition_destroy(add);
/*
* The second stack is now outdated, which we should notice. We do not
* create the addition and lock the stack by default, but allow the
* reload to happen when REFTABLE_STACK_NEW_ADDITION_RELOAD is set.
*/
err = reftable_stack_new_addition(&add, st2, 0);
check_int(err, ==, REFTABLE_OUTDATED_ERROR);
err = reftable_stack_new_addition(&add, st2, REFTABLE_STACK_NEW_ADDITION_RELOAD);
check(!err);
err = reftable_addition_add(add, write_test_ref, &refs[1]);
check(!err);
err = reftable_addition_commit(add);
check(!err);
reftable_addition_destroy(add);
for (size_t i = 0; i < ARRAY_SIZE(refs); i++) {
err = reftable_stack_read_ref(st2, refs[i].refname, &ref);
check(!err);
check(reftable_ref_record_equal(&refs[i], &ref, GIT_SHA1_RAWSZ));
}
reftable_ref_record_release(&ref);
reftable_stack_destroy(st1);
reftable_stack_destroy(st2);
clear_dir(dir);
}
static void t_reftable_stack_transaction_api_performs_auto_compaction(void)
{
char *dir = get_tmp_dir(__LINE__);
@ -322,7 +384,7 @@ static void t_reftable_stack_transaction_api_performs_auto_compaction(void)
*/
st->opts.disable_auto_compact = i != n;
err = reftable_stack_new_addition(&add, st);
err = reftable_stack_new_addition(&add, st, 0);
check(!err);
err = reftable_addition_add(add, write_test_ref, &ref);
@ -1314,6 +1376,7 @@ int cmd_main(int argc UNUSED, const char *argv[] UNUSED)
TEST(t_reftable_stack_reload_with_missing_table(), "stack iteration with garbage tables");
TEST(t_reftable_stack_tombstone(), "'tombstone' refs in stack");
TEST(t_reftable_stack_transaction_api(), "update transaction to stack");
TEST(t_reftable_stack_transaction_with_reload(), "transaction with reload");
TEST(t_reftable_stack_transaction_api_performs_auto_compaction(), "update transaction triggers auto-compaction");
TEST(t_reftable_stack_update_index_check(), "update transactions with equal update indices");
TEST(t_reftable_stack_uptodate(), "stack must be reloaded before ref update");