rbd: use GFP_NOIO in rbd_obj_request_create()

rbd_obj_request_create() is called on the main I/O path, so we need to
use GFP_NOIO to make sure allocation doesn't blow back on us.  Not all
callers need this, but I'm still hardcoding the flag inside rather than
making it a parameter because a) this is going to stable, and b) those
callers shouldn't really use rbd_obj_request_create() and will be fixed
in the future.

More memory allocation fixes will follow.

Cc: stable@vger.kernel.org # 3.10+
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Alex Elder <elder@linaro.org>

drivers/block/rbd.c

@@ -2022,11 +2022,11 @@ static struct rbd_obj_request *rbd_obj_request_create(const char *object_name,
 	rbd_assert(obj_request_type_valid(type));
 
 	size = strlen(object_name) + 1;
-	name = kmalloc(size, GFP_KERNEL);
+	name = kmalloc(size, GFP_NOIO);
 	if (!name)
 		return NULL;
 
-	obj_request = kmem_cache_zalloc(rbd_obj_request_cache, GFP_KERNEL);
+	obj_request = kmem_cache_zalloc(rbd_obj_request_cache, GFP_NOIO);
 	if (!obj_request) {
 		kfree(name);
 		return NULL;