Implemet docker update command

It's used for updating properties of one or more containers, we only
support resource configs for now. It can be extended in the future.

Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>

daemon/update.go

@@ -0,0 +1,58 @@
+package daemon
+
+import (
+	"fmt"
+
+	"github.com/docker/docker/api/types/container"
+)
+
+// ContainerUpdate updates resources of the container
+func (daemon *Daemon) ContainerUpdate(name string, hostConfig *container.HostConfig) ([]string, error) {
+	var warnings []string
+
+	warnings, err := daemon.verifyContainerSettings(hostConfig, nil)
+	if err != nil {
+		return warnings, err
+	}
+
+	if err := daemon.update(name, hostConfig); err != nil {
+		return warnings, err
+	}
+
+	return warnings, nil
+}
+
+func (daemon *Daemon) update(name string, hostConfig *container.HostConfig) error {
+	if hostConfig == nil {
+		return nil
+	}
+
+	container, err := daemon.GetContainer(name)
+	if err != nil {
+		return err
+	}
+
+	if container.RemovalInProgress || container.Dead {
+		return fmt.Errorf("Container is marked for removal and cannot be \"update\".")
+	}
+
+	if container.IsRunning() && hostConfig.KernelMemory != 0 {
+		return fmt.Errorf("Can not update kernel memory to a running container, please stop it first.")
+	}
+
+	if err := container.UpdateContainer(hostConfig); err != nil {
+		return err
+	}
+
+	// If container is not running, update hostConfig struct is enough,
+	// resources will be updated when the container is started again.
+	// If container is running (including paused), we need to update configs
+	// to the real world.
+	if container.IsRunning() {
+		if err := daemon.execDriver.Update(container.Command); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}