jbd2_journal_add_journal_head
jh = jbd2_journal_add_journal_head(bh);
struct journal_head *jh = jbd2_journal_add_journal_head(bh);
jh = jbd2_journal_add_journal_head(bh);
struct journal_head *jbd2_journal_add_journal_head(struct buffer_head *bh);