dax,ext2: replace XIP read and write with DAX I/O

Use the generic AIO infrastructure instead of custom read and write
methods.  In addition to giving us support for AIO, this adds the missing
locking between read() and truncate().

Signed-off-by: Matthew Wilcox <[email protected]>
Reviewed-by: Ross Zwisler <[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: Theodore Ts'o <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
8 files changed