Add fast path for fsmagic supported drivers

For things that we can check if they are mounted by using their fsmagic
we should use that and for others do it the slow way.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

daemon/graphdriver/counter.go

@@ -1,10 +1,6 @@
 package graphdriver
 
-import (
-	"sync"
-
-	"github.com/docker/docker/pkg/mount"
-)
+import "sync"
 
 type minfo struct {
 	check bool
@@ -13,13 +9,20 @@ type minfo struct {
 
 // RefCounter is a generic counter for use by graphdriver Get/Put calls
 type RefCounter struct {
-	counts map[string]*minfo
-	mu     sync.Mutex
+	counts  map[string]*minfo
+	mu      sync.Mutex
+	checker Checker
 }
 
 // NewRefCounter returns a new RefCounter
-func NewRefCounter() *RefCounter {
-	return &RefCounter{counts: make(map[string]*minfo)}
+func NewRefCounter(c Checker) *RefCounter {
+	if c == nil {
+		c = &defaultChecker{}
+	}
+	return &RefCounter{
+		checker: c,
+		counts:  make(map[string]*minfo),
+	}
 }
 
 // Increment increaes the ref count for the given id and returns the current count
@@ -35,8 +38,7 @@ func (c *RefCounter) Increment(path string) int {
 	// count if it is mounted as it is in use.
 	if !m.check {
 		m.check = true
-		mntd, _ := mount.Mounted(path)
-		if mntd {
+		if c.checker.IsMounted(path) {
 			m.count++
 		}
 	}
@@ -58,8 +60,7 @@ func (c *RefCounter) Decrement(path string) int {
 	// count if it is mounted as it is in use.
 	if !m.check {
 		m.check = true
-		mntd, _ := mount.Mounted(path)
-		if mntd {
+		if c.checker.IsMounted(path) {
 			m.count++
 		}
 	}

daemon/graphdriver/devmapper/driver.go

@@ -47,7 +47,7 @@ func Init(home string, options []string, uidMaps, gidMaps []idtools.IDMap) (grap
 		home:      home,
 		uidMaps:   uidMaps,
 		gidMaps:   gidMaps,
-		ctr:       graphdriver.NewRefCounter(),
+		ctr:       graphdriver.NewRefCounter(nil),
 	}
 
 	return graphdriver.NewNaiveDiffDriver(d, uidMaps, gidMaps), nil

daemon/graphdriver/driver_linux.go

@@ -5,6 +5,8 @@ package graphdriver
 import (
 	"path/filepath"
 	"syscall"
+
+	"github.com/docker/docker/pkg/mount"
 )
 
 const (
@@ -89,6 +91,36 @@ func GetFSMagic(rootpath string) (FsMagic, error) {
 	return FsMagic(buf.Type), nil
 }
 
+// Checker makes checks on specified filesystems.
+type Checker interface {
+	// IsMounted returns true if the provided path is mounted for the specific checker
+	IsMounted(path string) bool
+}
+
+// NewFsChecker returns a checker configured for the provied FsMagic
+func NewFsChecker(t FsMagic) Checker {
+	return &fsChecker{
+		t: t,
+	}
+}
+
+type fsChecker struct {
+	t FsMagic
+}
+
+func (c *fsChecker) IsMounted(path string) bool {
+	m, _ := Mounted(c.t, path)
+	return m
+}
+
+type defaultChecker struct {
+}
+
+func (c *defaultChecker) IsMounted(path string) bool {
+	m, _ := mount.Mounted(path)
+	return m
+}
+
 // Mounted checks if the given path is mounted as the fs type
 func Mounted(fsType FsMagic, mountPath string) (bool, error) {
 	var buf syscall.Statfs_t

daemon/graphdriver/overlay/overlay.go

@@ -141,7 +141,7 @@ func Init(home string, options []string, uidMaps, gidMaps []idtools.IDMap) (grap
 		home:    home,
 		uidMaps: uidMaps,
 		gidMaps: gidMaps,
-		ctr:     graphdriver.NewRefCounter(),
+		ctr:     graphdriver.NewRefCounter(graphdriver.NewFsChecker(graphdriver.FsMagicOverlay)),
 	}
 
 	return NaiveDiffDriverWithApply(d, uidMaps, gidMaps), nil

daemon/graphdriver/zfs/zfs.go

@@ -105,7 +105,7 @@ func Init(base string, opt []string, uidMaps, gidMaps []idtools.IDMap) (graphdri
 		filesystemsCache: filesystemsCache,
 		uidMaps:          uidMaps,
 		gidMaps:          gidMaps,
-		ctr:              graphdriver.NewRefCounter(),
+		ctr:              graphdriver.NewRefCounter(graphdriver.NewFsChecker(graphdriver.FsMagicZfs)),
 	}
 	return graphdriver.NewNaiveDiffDriver(d, uidMaps, gidMaps), nil
 }