crimson/os/seastore/../fixed_kv_node: add comment to copy-from-source

Signed-off-by: Yingxin Cheng <yingxin.cheng@intel.com>

diff --git a/src/crimson/os/seastore/btree/fixed_kv_node.h b/src/crimson/os/seastore/btree/fixed_kv_node.h
index 6ad55e3b9b32f98813ea7740c9d0b7be5be12be6..544727f30aac82aa017a50e48192dd4f0e19540f 100644 (file)
--- a/src/crimson/os/seastore/btree/fixed_kv_node.h
+++ b/src/crimson/os/seastore/btree/fixed_kv_node.h
@@ -430,6 +430,8 @@ struct FixedKVNode : ChildableCachedExtent {
        // the foreign key is preserved
        if (!child) {
          child = source.children[foreign_it.get_offset()];
+         // child can be either valid if present, nullptr if absent,
+         // or RESERVATION_PTR.
        }
        foreign_it++;
        local_it++;