fs/dax: Reject IOCB_ATOMIC in dax_iomap_rw()

The DAX write path does not support IOCB_ATOMIC, so reject it when set.

Suggested-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>

Author: johnpgarry

fs/dax.c

@@ -1743,6 +1743,9 @@ dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 	loff_t done = 0;
 	int ret;
 
+	if (WARN_ON_ONCE(iocb->ki_flags & IOCB_ATOMIC))
+		return -EIO;
+
 	if (!iomi.len)
 		return 0;