rgw: disable RGWDataChangesLog::add_entry() when log_data is off

this restores a check for RGWZone::log_data in add_entry(). with
per-bucket replication, this check was replaced by a call to
`RGWBucketSyncPolicyHandler::bucket_exports_data()`

this call has to consult two rados objects,
`bucket.sync-source-hints.<bucketname>` and
`bucket.sync-target-hints.<bucketname>`

but if the zone is not configured for multisite, we should avoid these
extra object reads and return early

Fixes: https://tracker.ceph.com/issues/61300

Signed-off-by: Casey Bodley <[email protected]>

Author: cbodley

src/rgw/driver/rados/rgw_datalog.cc

@@ -640,6 +640,10 @@ int RGWDataChangesLog::add_entry(const DoutPrefixProvider *dpp,
 				 const rgw::bucket_log_layout_generation& gen,
 				 int shard_id, optional_yield y)
 {
+  if (!zone->log_data) {
+    return 0;
+  }
+
   auto& bucket = bucket_info.bucket;
 
   if (!filter_bucket(dpp, bucket, y)) {