Introduce an abritrary 128MiB cap to avoid malloc failures when using a larger block device. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: WeiXiong Liao <gmpy.liaowx@gmail.com> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20201016132047.3068029-2-hch@lst.de