incusd/instance: Add support for creating qcow2 snapshots while instance is running

Signed-off-by: Piotr Resztak <piotr.resztak@futurfusion.io>

Author: presztak

internal/server/instance/drivers/driver_lxc.go

@@ -9379,3 +9379,8 @@ func (d *lxc) setupCredentials(update bool) error {
 func (d *lxc) GuestOS() string {
 	return "linux"
 }
+
+// CreateQcow2Snapshot creates a qcow2 snapshot for a running instance. Not supported by containers.
+func (d *lxc) CreateQcow2Snapshot(snapName string, backingFilename string) error {
+	return nil
+}

internal/server/instance/drivers/driver_qemu.go

@@ -24,6 +24,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"regexp"
 	"slices"
 	"sort"
 	"strconv"
@@ -10455,9 +10456,6 @@ func (d *qemu) GuestOS() string {
 	return "unknown"
 }
 
-<<<<<<< Updated upstream
-func (b *qemu) isQCOW2(devPath string) (bool, error) {
-=======
 // CreateQcow2Snapshot creates a qcow2 snapshot for a running instance.
 func (d *qemu) CreateQcow2Snapshot(snapshotName string, backingFilename string) error {
 	monitor, err := d.qmpConnect()
@@ -10518,12 +10516,12 @@ func (d *qemu) CreateQcow2Snapshot(snapshotName string, backingFilename string)
 	}
 
 	blockDev := map[string]any{
-		"driver": "qcow2",
+		"driver":    "qcow2",
 		"discard":   "unmap", // Forward as an unmap request. This is the same as `discard=on` in the qemu config file.
 		"node-name": nextOverlayName,
 		"read-only": false,
 		"file": map[string]any{
-			"driver":    "host_device",
+			"driver":   "host_device",
 			"filename": fmt.Sprintf("/dev/fdset/%d", info.ID),
 		},
 	}
@@ -10550,7 +10548,6 @@ func (d *qemu) CreateQcow2Snapshot(snapshotName string, backingFilename string)
 }
 
 func (d *qemu) isQCOW2(devPath string) (bool, error) {
->>>>>>> Stashed changes
 	imgInfo, err := storageDrivers.Qcow2Info(devPath)
 	if err != nil {
 		return false, err
@@ -10603,3 +10600,22 @@ func (d *qemu) qcow2BlockDev(m *qmp.Monitor, nodeName string, aioMode string, di
 
 	return blockDev, nil
 }
+
+// currentQcow2OverlayIndex returns the current maximum overlay index.
+func currentQcow2OverlayIndex(names []string, prefix string) int {
+	re := regexp.MustCompile(fmt.Sprintf(`^%s_overlay(\d+)$`, prefix))
+
+	maxIndex := -1
+
+	for _, name := range names {
+		m := re.FindStringSubmatch(name)
+		if len(m) == 2 {
+			n, err := strconv.Atoi(m[1])
+			if err == nil && n > maxIndex {
+				maxIndex = n
+			}
+		}
+	}
+
+	return maxIndex
+}

internal/server/instance/instance_interface.go

@@ -98,6 +98,7 @@ type Instance interface {
 	Backups() ([]backup.InstanceBackup, error)
 	UpdateBackupFile() error
 	CanLiveMigrate() bool
+	CreateQcow2Snapshot(snapshotName string, backingFilename string) error
 
 	// Config handling.
 	Rename(newName string, applyTemplateTrigger bool) error