From 5b6b8df0c1b5a54ae9a717810eedf9fc971e1321 Mon Sep 17 00:00:00 2001
From: Michael Crosby <crosbymichael@gmail.com>
Date: Fri, 6 May 2016 13:09:45 -0700
Subject: [PATCH] Add reference counting to aufs

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>
---
 daemon/graphdriver/aufs/aufs.go        |  8 ++++++++
 daemon/graphdriver/counter.go          |  3 ---
 daemon/graphdriver/devmapper/driver.go |  2 +-
 daemon/graphdriver/driver.go           |  6 ++++++
 daemon/graphdriver/driver_linux.go     | 12 ++++++------
 5 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/daemon/graphdriver/aufs/aufs.go b/daemon/graphdriver/aufs/aufs.go
index 83380e1143..044351b7ee 100644
--- a/daemon/graphdriver/aufs/aufs.go
+++ b/daemon/graphdriver/aufs/aufs.go
@@ -70,6 +70,7 @@ type Driver struct {
 	root          string
 	uidMaps       []idtools.IDMap
 	gidMaps       []idtools.IDMap
+	ctr           *graphdriver.RefCounter
 	pathCacheLock sync.Mutex
 	pathCache     map[string]string
 }
@@ -108,6 +109,7 @@ func Init(root string, options []string, uidMaps, gidMaps []idtools.IDMap) (grap
 		uidMaps:   uidMaps,
 		gidMaps:   gidMaps,
 		pathCache: make(map[string]string),
+		ctr:       graphdriver.NewRefCounter(graphdriver.NewFsChecker(graphdriver.FsMagicAufs)),
 	}
 
 	rootUID, rootGID, err := idtools.GetRootUIDGID(uidMaps, gidMaps)
@@ -320,6 +322,9 @@ func (a *Driver) Get(id, mountLabel string) (string, error) {
 			m = a.getMountpoint(id)
 		}
 	}
+	if count := a.ctr.Increment(m); count > 1 {
+		return m, nil
+	}
 
 	// If a dir does not have a parent ( no layers )do not try to mount
 	// just return the diff path to the data
@@ -344,6 +349,9 @@ func (a *Driver) Put(id string) error {
 		a.pathCache[id] = m
 	}
 	a.pathCacheLock.Unlock()
+	if count := a.ctr.Decrement(m); count > 0 {
+		return nil
+	}
 
 	err := a.unmount(m)
 	if err != nil {
diff --git a/daemon/graphdriver/counter.go b/daemon/graphdriver/counter.go
index 2de80b7e1e..5ea604f5b6 100644
--- a/daemon/graphdriver/counter.go
+++ b/daemon/graphdriver/counter.go
@@ -16,9 +16,6 @@ type RefCounter struct {
 
 // NewRefCounter returns a new RefCounter
 func NewRefCounter(c Checker) *RefCounter {
-	if c == nil {
-		c = &defaultChecker{}
-	}
 	return &RefCounter{
 		checker: c,
 		counts:  make(map[string]*minfo),
diff --git a/daemon/graphdriver/devmapper/driver.go b/daemon/graphdriver/devmapper/driver.go
index 9b58dba66d..38fa3ece70 100644
--- a/daemon/graphdriver/devmapper/driver.go
+++ b/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(nil),
+		ctr:       graphdriver.NewRefCounter(graphdriver.NewDefaultChecker()),
 	}
 
 	return graphdriver.NewNaiveDiffDriver(d, uidMaps, gidMaps), nil
diff --git a/daemon/graphdriver/driver.go b/daemon/graphdriver/driver.go
index 495bac2cf5..79f6789f99 100644
--- a/daemon/graphdriver/driver.go
+++ b/daemon/graphdriver/driver.go
@@ -113,6 +113,12 @@ type FileGetCloser interface {
 	Close() error
 }
 
+// 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
+}
+
 func init() {
 	drivers = make(map[string]InitFunc)
 }
diff --git a/daemon/graphdriver/driver_linux.go b/daemon/graphdriver/driver_linux.go
index 10a1abcf0d..70b2ce22f1 100644
--- a/daemon/graphdriver/driver_linux.go
+++ b/daemon/graphdriver/driver_linux.go
@@ -91,12 +91,6 @@ 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{
@@ -113,6 +107,12 @@ func (c *fsChecker) IsMounted(path string) bool {
 	return m
 }
 
+// NewDefaultChecker returns a check that parses /proc/mountinfo to check
+// if the specified path is mounted.
+func NewDefaultChecker() Checker {
+	return &defaultChecker{}
+}
+
 type defaultChecker struct {
 }