Ira Weiny <ira.weiny@xxxxxxxxx> writes: > [disclaimer: the following assumes the underlying 'device' (superblock) > supports DAX] > > ... which results in S_DAX == false when the file is opened without the mount > option. The key would be that all directories/files created under a root with > XFS_DIFLAG2_DAX == true would inherit their flag and be XFS_DIFLAG2_DAX == true > all the way down the tree. Any file not wanting DAX would need to set > XFS_DIFLAG2_DAX == false. And setting false could be used on a directory to > allow a user or group to not use dax on files in that sub-tree. > > Then without '-o dax' (XFS_MOUNT_DAX == false) all files when opened set S_DAX > equal to XFS_DIFLAG2_DAX value. (Directories, as of V4, never get S_DAX set.) > > If '-o dax' (XFS_MOUNT_DAX == true) then S_DAX is set on all files. One more clarifying question. Let's say I set XFS_DIFLAG2_DAX on an inode. I then open the file, and perform mmap/load/store/etc. I close the file, and I unset XFS_DIFLAG2_DAX. Will the next open treat the file as S_DAX or not? My guess is the inode won't be evicted, and so S_DAX will remain set. The reason I ask is I've had requests from application developers to do just this. They want to be able to switch back and forth between dax modes. Thanks, Jeff > [1] I'm beginning to think that if I type dax one more time I'm going to go > crazy... :-P dax dax dax!
