On Thu, Jul 06, 2017 at 03:35:48PM +0800, Coly Li wrote: > Then gfs2 breaks the above rule ? in gfs2_metapath_ra() and > gfs2_dir_readahead(), only REQ_META is used in submit_bh(). It seems an > extra REQ_PRIO should be there. Or maybe not. E.g. XFS absolutely avoids using REQ_PRIO for any of the buffer writeback as it does not have priority. You'll need to ask gfs2 folks if they want this I/O to have priority or not.