NFS: Fix a reference leak in nfs_wb_cancel_page()

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@kernel.org
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfs/write.c

@@ -1541,6 +1541,7 @@ int nfs_wb_page_cancel(struct inode *inode, struct page *page)
 			break;
 		}
 		ret = nfs_wait_on_request(req);
+		nfs_release_request(req);
 		if (ret < 0)
 			goto out;
 	}