dax: Introduce IOMAP_FAULT flag

Introduce a flag telling iomap operations whether they are handling a
fault or other IO. That may influence behavior wrt inode size and
similar things.

Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>

diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index e63e288..b9e7b8e 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -44,6 +44,7 @@
  */
 #define IOMAP_WRITE		(1 << 0)
 #define IOMAP_ZERO		(1 << 1)
+#define IOMAP_FAULT		(1 << 3) /* mapping for page fault */
 
 struct iomap_ops {
 	/*