storage: skip local housekeeping and gc for cloud topics

disk_log_impl gc() and housekeeping() are no-ops for cloud topics:
is_locally_collectable() and is_locally_compacted() are both false, so
do_gc returns nullopt and local compaction is skipped. The local log is
trimmed by ctp_stm and compaction happens at L1.

do_gc asserts it is not reached for tiered_cloud, so returning early for
cloud topics also keeps that invariant true: housekeeping_scan calls
gc()/housekeeping() for every registered log, cloud topics included.

Signed-off-by: Oren Leiman <oren.leiman@redpanda.com>

Author: oleiman

src/v/storage/disk_log_impl.cc

@@ -1362,6 +1362,11 @@ gc_config disk_log_impl::apply_overrides(gc_config defaults) const {
 }
 
 ss::future<> disk_log_impl::housekeeping(housekeeping_config cfg) {
+    // Cloud topics do local retention/compaction elsewhere (ctp_stm trims the
+    // local log; compaction is at L1), so this loop does nothing for them.
+    if (config().cloud_topic_enabled()) {
+        co_return;
+    }
     ss::gate::holder holder{_compaction_housekeeping_gate};
     vlog(
       gclog.trace,
@@ -1767,12 +1772,21 @@ ss::future<> disk_log_impl::rewrite_segment_with_offset_map(
 }
 
 ss::future<> disk_log_impl::gc(gc_config cfg) {
+    // Cloud topics do local retention/compaction elsewhere (ctp_stm trims the
+    // local log; compaction is at L1), so disk_log_impl gc does not apply.
+    if (config().cloud_topic_enabled()) {
+        co_return;
+    }
     ss::gate::holder holder{_compaction_housekeeping_gate};
     co_await do_gc(cfg);
 }
 
 ss::future<std::optional<model::offset>> disk_log_impl::do_gc(gc_config cfg) {
     vassert(!_closed, "gc on closed log - {}", *this);
+    vassert(
+      !config().is_tiered_cloud(),
+      "[{}] gc on tiered_cloud partition",
+      config().ntp());
 
     cfg = apply_overrides(cfg);