+
+/*
+ * Write the index while holding an already-taken lock. The flags may
+ * contain at most one of `COMMIT_LOCK` and `CLOSE_LOCK`.
+ *
+ * Unless a split index is in use, write the index into the lockfile.
+ *
+ * With a split index, write the shared index to a temporary file,
+ * adjust its permissions and rename it into place, then write the
+ * split index to the lockfile. If the temporary file for the shared
+ * index cannot be created, fall back to the behavior described in
+ * the previous paragraph.
+ */