iomap: Don't get an reference on ZERO_PAGE for direct I/O block zeroing

ZERO_PAGE can't go away, no need to hold an extra reference.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
cc: Al Viro <viro@zeniv.linux.org.uk>
cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christian Brauner <brauner@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230522205744.2825689-2-dhowells@redhat.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

fs/iomap/direct-io.c

@@ -203,7 +203,7 @@ static void iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio,
 	bio->bi_private = dio;
 	bio->bi_end_io = iomap_dio_bio_end_io;
 
-	get_page(page);
+	bio_set_flag(bio, BIO_NO_PAGE_REF);
 	__bio_add_page(bio, page, len, 0);
 	iomap_dio_submit_bio(iter, dio, bio, pos);
 }