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]>
diff --git a/MAINTAINERS b/MAINTAINERS
index 348f5c1..8670c22 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3151,6 +3151,12 @@
 S:	Maintained
 F:	drivers/i2c/busses/i2c-diolan-u2c.c
 
+DIRECT ACCESS (DAX)
+M:	Matthew Wilcox <[email protected]>
+L:	[email protected]
+S:	Supported
+F:	fs/dax.c
+
 DIRECTORY NOTIFICATION (DNOTIFY)
 M:	Eric Paris <[email protected]>
 S:	Maintained