code: func (db *DB) meta() *meta {
  	// We have to return the meta with the highest txid which doesn't fail
  	// validation. Otherwise, we can cause errors when in fact the database is
  	// in a consistent state. metaA is the one with the higher txid.
  	metaA := db.meta0
  	metaB := db.meta1
  	if db.meta1.txid > db.meta0.txid {
  		metaA = db.meta1
  		metaB = db.meta0
  	}
  
  	// Use higher meta page if valid. Otherwise fallback to previous, if valid.
  	if err := metaA.validate(); err == nil {
  		return metaA
  	} else if err := metaB.validate(); err == nil {
  		return metaB
  	}
  
  	// This should never be reached, because both meta1 and meta0 were validated
  	// on mmap() and we do fsync() on every write.
  	panic("bolt.DB.meta(): invalid meta pages")
  }
docs: // meta retrieves the current meta page reference.