[PATCH 0/4] xfs: fixes for XFS_DIFLAG2_DAX support

[Dave Chinner]

Hi folks,

This is a series to add the correct constraints to using the on-disk
inode flag to enable DAX on per-file basis. The same constraints are
placed on setting the flag on directories for inheritance purposes.

These constraints are:
	- the inode flag is limited to regular files or directory
	  inodes.
	- the S_DAX flag is only ever set on regular files
	- the flag can only ever be set on filesystems which have
	  blocksize == PAGE_SIZE (for now)
	- When the flag is set or cleared, the current mapping
	  contents are flushed and then invalidated so that the new
	  access mode starts with an empty mapping.
	- Setting or clearing the flag is atomic w.r.t. IO and
	  page faults.

I've tested these manually with xfs_io (patchset for supporting
chattr +x/-x to be sent soon), and it all appears to work as
expected. I'd like to push these for 4.5-rc6 so the initial kernel
with support for this flag doesn't do silly things, so comments,
testing and review woul dbe appreciated.

Cheers,

Dave.