A processing method includes: performing an I/O preparation process and an I/O request for a data block in an application program thread; activating, by the application program thread, a journaling thread; waiting for completion of an I/O for the data block and a commit of the journaling thread; preparing an I/O for the journal block and requesting the I/O for the journal block during the waiting for the completion of the I/O for the data block and the commit of the journaling thread, in the journaling thread; preparing an I/O for a journal commit block, before waiting for completion of the I/O for the journal block after the requesting of the I/O for the journal block; after waiting for the completion of the I/O for the journal block, requesting the I/O for the journal commit block; and waiting for completion of the I/O for the journal commit block.