devmapper: add pool metadata

Signed-off-by: Maksym Pavlenko <makpav@amazon.com>

snapshots/devmapper/device_info.go

@@ -0,0 +1,104 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package devmapper
+
+import (
+	"fmt"
+)
+
+const (
+	maxDeviceID = 0xffffff // Device IDs are 24-bit numbers
+)
+
+// DeviceState represents current devmapper device state reflected in meta store
+type DeviceState int
+
+const (
+	// Unknown means that device just allocated and no operations were performed
+	Unknown DeviceState = iota
+	// Creating means that device is going to be created
+	Creating
+	// Created means that devices successfully created
+	Created
+	// Activating means that device is going to be activated
+	Activating
+	// Activated means that device successfully activated
+	Activated
+	// Suspending means that device is going to be suspended
+	Suspending
+	// Suspended means that device successfully suspended
+	Suspended
+	// Resuming means that device is going to be resumed from suspended state
+	Resuming
+	// Resumed means that device successfully resumed
+	Resumed
+	// Deactivating means that device is going to be deactivated
+	Deactivating
+	// Deactivated means that device successfully deactivated
+	Deactivated
+	// Removing means that device is going to be removed
+	Removing
+	// Removed means that device successfully removed but not yet deleted from meta store
+	Removed
+)
+
+func (s DeviceState) String() string {
+	switch s {
+	case Creating:
+		return "Creating"
+	case Created:
+		return "Created"
+	case Activating:
+		return "Activating"
+	case Activated:
+		return "Activated"
+	case Suspending:
+		return "Suspending"
+	case Suspended:
+		return "Suspended"
+	case Resuming:
+		return "Resuming"
+	case Resumed:
+		return "Resumed"
+	case Deactivating:
+		return "Deactivating"
+	case Deactivated:
+		return "Deactivated"
+	case Removing:
+		return "Removing"
+	case Removed:
+		return "Removed"
+	default:
+		return fmt.Sprintf("unknown %d", s)
+	}
+}
+
+// DeviceInfo represents metadata for thin device within thin-pool
+type DeviceInfo struct {
+	// DeviceID is a 24-bit number assigned to a device within thin-pool device
+	DeviceID uint32 `json:"device_id"`
+	// Size is a thin device size
+	Size uint64 `json:"size"`
+	// Name is a device name to be used in /dev/mapper/
+	Name string `json:"name"`
+	// ParentName is a name of parent device (if snapshot)
+	ParentName string `json:"parent_name"`
+	// State represents current device state
+	State DeviceState `json:"state"`
+	// Error details if device state change failed
+	Error string `json:"error"`
+}