io context: fix ref counting

Commit d9c7d394a8ebacb60097b192939ae9f15235225e
("block: prevent possible io_context->refcount overflow") mistakenly
changed atomic_inc(&ioc->nr_tasks) to atomic_long_inc(&ioc->refcount).

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Nikanth Karthikesan <knikanth@suse.de>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h
index dd05434..4da4a75 100644
--- a/include/linux/iocontext.h
+++ b/include/linux/iocontext.h
@@ -92,7 +92,7 @@
 	 * a race).
 	 */
 	if (ioc && atomic_long_inc_not_zero(&ioc->refcount)) {
-		atomic_long_inc(&ioc->refcount);
+		atomic_inc(&ioc->nr_tasks);
 		return ioc;
 	}