Merge pull request #47530 from vvoland/flaky-liverestore

volume: Don't decrement refcount below 0

volume/local/local.go

@@ -9,6 +9,7 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
+	"runtime/debug"
 	"strings"
 	"sync"
 
@@ -334,8 +335,15 @@ func (v *localVolume) Unmount(id string) error {
 	// ultimately there's nothing that can be done. If we don't decrement the count
 	// this volume can never be removed until a daemon restart occurs.
 	if v.needsMount() {
-		v.active.count--
-		logger.WithField("active mounts", v.active).Debug("Decremented active mount count")
+		// TODO: Remove once the real bug is fixed: https://github.com/moby/moby/issues/46508
+		if v.active.count > 0 {
+			v.active.count--
+			logger.WithField("active mounts", v.active).Debug("Decremented active mount count")
+		} else {
+			logger.Error("An attempt to decrement a zero mount count")
+			logger.Error(string(debug.Stack()))
+			return nil
+		}
 	}
 
 	if v.active.count > 0 {

volume/mounts/mounts.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"runtime/debug"
 	"syscall"
 
 	"github.com/containerd/log"
@@ -88,6 +89,15 @@ func (m *MountPoint) Cleanup(ctx context.Context) error {
 		return nil
 	}
 
+	logger := log.G(ctx).WithFields(log.Fields{"active": m.active, "id": m.ID})
+
+	// TODO: Remove once the real bug is fixed: https://github.com/moby/moby/issues/46508
+	if m.active == 0 {
+		logger.Error("An attempt to decrement a zero mount count")
+		logger.Error(string(debug.Stack()))
+		return nil
+	}
+
 	for _, p := range m.safePaths {
 		if !p.IsValid() {
 			continue
@@ -108,6 +118,8 @@ func (m *MountPoint) Cleanup(ctx context.Context) error {
 	}
 
 	m.active--
+	logger.Debug("MountPoint.Cleanup Decrement active count")
+
 	if m.active == 0 {
 		m.ID = ""
 	}