dm vdo: fix sparse 'warning: Using plain integer as NULL pointer'

Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Susan LeGendre-McGhee <slegendr@redhat.com>
Signed-off-by: Matthew Sakai <msakai@redhat.com>

drivers/md/dm-vdo/index.c

@@ -732,18 +732,18 @@ static void close_chapters(void *arg)
 
 static void stop_chapter_writer(struct chapter_writer *writer)
 {
-	struct thread *writer_thread = 0;
+	struct thread *writer_thread = NULL;
 
 	uds_lock_mutex(&writer->mutex);
-	if (writer->thread != 0) {
+	if (writer->thread != NULL) {
 		writer_thread = writer->thread;
-		writer->thread = 0;
+		writer->thread = NULL;
 		writer->stop = true;
 		uds_broadcast_cond(&writer->cond);
 	}
 	uds_unlock_mutex(&writer->mutex);
 
-	if (writer_thread != 0)
+	if (writer_thread != NULL)
 		uds_join_threads(writer_thread);
 }
 

drivers/md/dm-vdo/vdo.c

@@ -889,7 +889,8 @@ int vdo_synchronous_flush(struct vdo *vdo)
 	int result;
 	struct bio bio;
 
-	bio_init(&bio, vdo_get_backing_device(vdo), 0, 0, REQ_OP_WRITE | REQ_PREFLUSH);
+	bio_init(&bio, vdo_get_backing_device(vdo), NULL, 0,
+		 REQ_OP_WRITE | REQ_PREFLUSH);
 	submit_bio_wait(&bio);
 	result = blk_status_to_errno(bio.bi_status);