removing comment I meant to remove during flusher threads work

    }

}

// FIXME started_at_root does not exist anymore. this is out of date.

//

// The parameter "started_at_root" is needed to resolve #4147 and #4160,

// which are subtle interactions of background flushing (cleaner and

// flusher threads) and MSN logic.

//

// When we rebalance basement nodes to write out a leaf, we can't have two

// basement nodes with different max_msn_applieds.  When we flush to a

// basement node, it may have stale ancestors' messages applied already.

//

// If we've flushed everything down from the root recursively, then there

// is no problem.  Anything that was applied to the leaf node by a query

// already must be in the batch of stuff we're flushing, so it's okay to

// do whatever we want, the MSNs will be consistent.

//

// But if we started somewhere in the middle (as a cleaner thread does),

// then we might not have all the messages that were applied to the leaf,

// and some basement nodes may be in a different state than others.  So

// before we flush to it, we have to destroy and re-read (off disk) the

// basement nodes which have messages applied.  Similarly, if a flush

// started in the middle wants to merge two leaf nodes, we can't do that

// because we might create a leaf node in a bad state.

//

// We use "started_at_root" to decide what to do about this problem in

// code further down.  For now, anything started by the cleaner thread

// will have started_at_root==false and anything started by the flusher

// thread will have started_at_root==true, but future mechanisms need to

// be mindful of this issue.

void

flush_some_child(

    struct brt_header *h,