xfs/260: Move and update xfs/260

1) Both ext4 and xfs have supported FS_XFLAG_DAX so move it to generic.
2) Modifying FS_XFLAG_DAX on flies does not take effect immediately so
   make files inherit the DAX state of parent directory.
3) Setting/clearing FS_XFLAG_DAX have no chance to change S_DAX flag if
   mount with dax option so remove the related subtest.
4) Setting/clearing FS_XFLAG_DAX doesn't change S_DAX flag on older xfs
   due to commit 742d84290739 ("xfs: disable per-inode DAX flag") so
   only do test when fs supports new dax=inode option.

Signed-off-by: Xiao Yang <yangx.jy@cn.fujitsu.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>
6 files changed