dm: allocate buffer for messages with small number of arguments using GFP_NOIO

/*

 * Used to dynamically allocate the arg array.

 *

 * We do first allocation with GFP_NOIO because dm-mpath and dm-thin must

 * process messages even if some device is suspended. These messages have a

 * small fixed number of arguments.

 *

 * On the other hand, dm-switch needs to process bulk data using messages and

 * excessive use of GFP_NOIO could cause trouble.

 */

static char **realloc_argv(unsigned *array_size, char **old_argv)

{

	char **argv;

	unsigned new_size;

	gfp_t gfp;

	new_size = *array_size ? *array_size * 2 : 64;

	argv = kmalloc(new_size * sizeof(*argv), GFP_KERNEL);

	if (*array_size) {

		new_size = *array_size * 2;

		gfp = GFP_KERNEL;

	} else {

		new_size = 8;

		gfp = GFP_NOIO;

	}

	argv = kmalloc(new_size * sizeof(*argv), gfp);

	if (argv) {

		memcpy(argv, old_argv, *array_size * sizeof(*argv));

		*array_size = new_size;