fs: dlm: update comments about recovery and membership handling

Make clear that a particular recovery iteration must not be aborted
before membership changes are applied to the members list (ls_nodes)
and midcomms layer.  Interrupting recovery before this can result
in missing node-specific changes in midcomms or through lsops.
Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>

fs/dlm/member.c

@@ -534,7 +534,11 @@ int dlm_recover_members(struct dlm_ls *ls, struct dlm_recover *rv, int *neg_out)
 	int i, error, neg = 0, low = -1;
 
 	/* previously removed members that we've not finished removing need to
-	   count as a negative change so the "neg" recovery steps will happen */
+	 * count as a negative change so the "neg" recovery steps will happen
+	 *
+	 * This functionality must report all member changes to lsops or
+	 * midcomms layer and must never return before.
+	 */
 
 	list_for_each_entry(memb, &ls->ls_nodes_gone, list) {
 		log_rinfo(ls, "prev removed member %d", memb->nodeid);

fs/dlm/recoverd.c

@@ -70,6 +70,10 @@ static int ls_recover(struct dlm_ls *ls, struct dlm_recover *rv)
 
 	/*
 	 * Add or remove nodes from the lockspace's ls_nodes list.
+	 *
+	 * Due to the fact that we must report all membership changes to lsops
+	 * or midcomms layer, it is not permitted to abort ls_recover() until
+	 * this is done.
 	 */
 
 	error = dlm_recover_members(ls, rv, &neg);