dax,ext2: replace the XIP page fault handler with the DAX page fault handler

dax,ext2: replace the XIP page fault handler with the DAX page fault handler

Instead of calling aops->get_xip_mem from the fault handler, the
filesystem passes a get_block_t that is used to find the appropriate
blocks.

This requires that all architectures implement copy_user_page().  At the
time of writing, mips and arm do not.  Patches exist and are in progress.

[[email protected]: remap_file_pages went away]
Signed-off-by: Matthew Wilcox <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Cc: Andreas Dilger <[email protected]>
Cc: Boaz Harrosh <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Dave Chinner <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Randy Dunlap <[email protected]>
Cc: Ross Zwisler <[email protected]>
Cc: Theodore Ts'o <[email protected]>
Cc: Russell King <[email protected]>
Cc: Ralf Baechle <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>