Merge pull request #2390 from mheon/update_cstorage

Update c/storage vendor to v1.10 release

13 files changed, 203 insertions, 89 deletions

diff --git a/vendor.conf b/vendor.conf
index 309189c05..9488bb644 100644
--- a/vendor.conf
+++ b/vendor.conf
@@ -16,7 +16,7 @@ github.com/containerd/continuity 004b46473808b3e7a4a3049c20e4376c91eb966d
 github.com/containernetworking/cni v0.7.0-alpha1
 github.com/containernetworking/plugins v0.7.4
 github.com/containers/image 93bced01015eb94bec4821df1876314be8197680
-github.com/containers/storage 06b6c2e4cf254f5922a79da058c94ac2a65bb92f
+github.com/containers/storage v1.10
 github.com/containers/psgo v1.1
 github.com/coreos/go-systemd v14
 github.com/cri-o/ocicni 2d2983e40c242322a56c22a903785e7f83eb378c
diff --git a/vendor/github.com/containers/storage/containers.go b/vendor/github.com/containers/storage/containers.go
index beaf41f39..10d628dbe 100644
--- a/vendor/github.com/containers/storage/containers.go
+++ b/vendor/github.com/containers/storage/containers.go
@@ -568,6 +568,9 @@ func (r *containerStore) Lock() {
 	r.lockfile.Lock()
 }
 
+func (r *containerStore) RLock() {
+	r.lockfile.RLock()
+}
 func (r *containerStore) Unlock() {
 	r.lockfile.Unlock()
 }
diff --git a/vendor/github.com/containers/storage/containers_ffjson.go b/vendor/github.com/containers/storage/containers_ffjson.go
index 40b912bb3..aef6becfe 100644
--- a/vendor/github.com/containers/storage/containers_ffjson.go
+++ b/vendor/github.com/containers/storage/containers_ffjson.go
@@ -1,5 +1,5 @@
 // Code generated by ffjson <https://github.com/pquerna/ffjson>. DO NOT EDIT.
-// source: ./containers.go
+// source: containers.go
 
 package storage
 
diff --git a/vendor/github.com/containers/storage/drivers/overlay/overlay.go b/vendor/github.com/containers/storage/drivers/overlay/overlay.go
index 57d6dd63a..657d9b3ce 100644
--- a/vendor/github.com/containers/storage/drivers/overlay/overlay.go
+++ b/vendor/github.com/containers/storage/drivers/overlay/overlay.go
@@ -239,6 +239,8 @@ func parseOptions(options []string) (*overlayOptions, error) {
 		}
 		key = strings.ToLower(key)
 		switch key {
+		case ".override_kernel_check", "overlay.override_kernel_check", "overlay2.override_kernel_check":
+			logrus.Warnf("overlay: override_kernel_check option was specified, but is no longer necessary")
 		case ".mountopt", "overlay.mountopt", "overlay2.mountopt":
 			o.mountOptions = val
 		case ".size", "overlay.size", "overlay2.size":
diff --git a/vendor/github.com/containers/storage/errors.go b/vendor/github.com/containers/storage/errors.go
index 562415c09..63cb9ab74 100644
--- a/vendor/github.com/containers/storage/errors.go
+++ b/vendor/github.com/containers/storage/errors.go
@@ -43,8 +43,6 @@ var (
 	ErrSizeUnknown = errors.New("size is not known")
 	// ErrStoreIsReadOnly is returned when the caller makes a call to a read-only store that would require modifying its contents.
 	ErrStoreIsReadOnly = errors.New("called a write method on a read-only store")
-	// ErrLockReadOnly indicates that the caller only took a read-only lock, and is not allowed to write.
-	ErrLockReadOnly = errors.New("lock is not a read-write lock")
 	// ErrDuplicateImageNames indicates that the read-only store uses the same name for multiple images.
 	ErrDuplicateImageNames = errors.New("read-only image store assigns the same name to multiple images")
 	// ErrDuplicateLayerNames indicates that the read-only store uses the same name for multiple layers.
diff --git a/vendor/github.com/containers/storage/images.go b/vendor/github.com/containers/storage/images.go
index fa4a7c43b..93505f5fb 100644
--- a/vendor/github.com/containers/storage/images.go
+++ b/vendor/github.com/containers/storage/images.go
@@ -756,6 +756,10 @@ func (r *imageStore) Lock() {
 	r.lockfile.Lock()
 }
 
+func (r *imageStore) RLock() {
+	r.lockfile.RLock()
+}
+
 func (r *imageStore) Unlock() {
 	r.lockfile.Unlock()
 }
diff --git a/vendor/github.com/containers/storage/layers.go b/vendor/github.com/containers/storage/layers.go
index cdc3cbba9..d612f0459 100644
--- a/vendor/github.com/containers/storage/layers.go
+++ b/vendor/github.com/containers/storage/layers.go
@@ -1222,6 +1222,10 @@ func (r *layerStore) Lock() {
 	r.lockfile.Lock()
 }
 
+func (r *layerStore) RLock() {
+	r.lockfile.RLock()
+}
+
 func (r *layerStore) Unlock() {
 	r.lockfile.Unlock()
 }
diff --git a/vendor/github.com/containers/storage/layers_ffjson.go b/vendor/github.com/containers/storage/layers_ffjson.go
index 09b5d0f33..125b5d8c9 100644
--- a/vendor/github.com/containers/storage/layers_ffjson.go
+++ b/vendor/github.com/containers/storage/layers_ffjson.go
@@ -1,5 +1,5 @@
 // Code generated by ffjson <https://github.com/pquerna/ffjson>. DO NOT EDIT.
-// source: ./layers.go
+// source: layers.go
 
 package storage
 
diff --git a/vendor/github.com/containers/storage/lockfile.go b/vendor/github.com/containers/storage/lockfile.go
index 9f6a18144..7f07b9ac5 100644
--- a/vendor/github.com/containers/storage/lockfile.go
+++ b/vendor/github.com/containers/storage/lockfile.go
@@ -1,7 +1,6 @@
 package storage
 
 import (
-	"fmt"
 	"path/filepath"
 	"sync"
 	"time"
@@ -13,7 +12,14 @@ import (
 // identifier of the last party that made changes to whatever's being protected
 // by the lock.
 type Locker interface {
-	sync.Locker
+	// Acquire a writer lock.
+	Lock()
+
+	// Unlock the lock.
+	Unlock()
+
+	// Acquire a reader lock.
+	RLock()
 
 	// Touch records, for others sharing the lock, that the caller was the
 	// last writer.  It should only be called with the lock held.
@@ -39,31 +45,22 @@ var (
 )
 
 // GetLockfile opens a read-write lock file, creating it if necessary.  The
-// Locker object it returns will be returned unlocked.
+// Locker object may already be locked if the path has already been requested
+// by the current process.
 func GetLockfile(path string) (Locker, error) {
-	lockfilesLock.Lock()
-	defer lockfilesLock.Unlock()
-	if lockfiles == nil {
-		lockfiles = make(map[string]Locker)
-	}
-	cleanPath := filepath.Clean(path)
-	if locker, ok := lockfiles[cleanPath]; ok {
-		if !locker.IsReadWrite() {
-			return nil, errors.Wrapf(ErrLockReadOnly, "lock %q is a read-only lock", cleanPath)
-		}
-		return locker, nil
-	}
-	locker, err := getLockFile(path, false) // platform dependent locker
-	if err != nil {
-		return nil, err
-	}
-	lockfiles[filepath.Clean(path)] = locker
-	return locker, nil
+	return getLockfile(path, false)
 }
 
-// GetROLockfile opens a read-only lock file.  The Locker object it returns
-// will be returned unlocked.
+// GetROLockfile opens a read-only lock file, creating it if necessary.  The
+// Locker object may already be locked if the path has already been requested
+// by the current process.
 func GetROLockfile(path string) (Locker, error) {
+	return getLockfile(path, true)
+}
+
+// getLockfile is a helper for GetLockfile and GetROLockfile and returns Locker
+// based on the path and read-only property.
+func getLockfile(path string, ro bool) (Locker, error) {
 	lockfilesLock.Lock()
 	defer lockfilesLock.Unlock()
 	if lockfiles == nil {
@@ -71,12 +68,15 @@ func GetROLockfile(path string) (Locker, error) {
 	}
 	cleanPath := filepath.Clean(path)
 	if locker, ok := lockfiles[cleanPath]; ok {
-		if locker.IsReadWrite() {
-			return nil, fmt.Errorf("lock %q is a read-write lock", cleanPath)
+		if ro && locker.IsReadWrite() {
+			return nil, errors.Errorf("lock %q is not a read-only lock", cleanPath)
+		}
+		if !ro && !locker.IsReadWrite() {
+			return nil, errors.Errorf("lock %q is not a read-write lock", cleanPath)
 		}
 		return locker, nil
 	}
-	locker, err := getLockFile(path, true) // platform dependent locker
+	locker, err := getLockFile(path, ro) // platform dependent locker
 	if err != nil {
 		return nil, err
 	}
diff --git a/vendor/github.com/containers/storage/lockfile_unix.go b/vendor/github.com/containers/storage/lockfile_unix.go
index 31e39c02e..0adbc49a5 100644
--- a/vendor/github.com/containers/storage/lockfile_unix.go
+++ b/vendor/github.com/containers/storage/lockfile_unix.go
@@ -3,6 +3,7 @@
 package storage
 
 import (
+	"fmt"
 	"os"
 	"sync"
 	"time"
@@ -24,38 +25,84 @@ func getLockFile(path string, ro bool) (Locker, error) {
 		return nil, errors.Wrapf(err, "error opening %q", path)
 	}
 	unix.CloseOnExec(fd)
+
+	locktype := unix.F_WRLCK
 	if ro {
-		return &lockfile{file: path, fd: uintptr(fd), lw: stringid.GenerateRandomID(), locktype: unix.F_RDLCK, locked: false}, nil
+		locktype = unix.F_RDLCK
 	}
-	return &lockfile{file: path, fd: uintptr(fd), lw: stringid.GenerateRandomID(), locktype: unix.F_WRLCK, locked: false}, nil
+	return &lockfile{
+		stateMutex: &sync.Mutex{},
+		writeMutex: &sync.Mutex{},
+		file:       path,
+		fd:         uintptr(fd),
+		lw:         stringid.GenerateRandomID(),
+		locktype:   int16(locktype),
+		locked:     false,
+		ro:         ro}, nil
 }
 
 type lockfile struct {
-	mu       sync.Mutex
-	file     string
-	fd       uintptr
-	lw       string
-	locktype int16
-	locked   bool
+	// stateMutex is used to synchronize concurrent accesses
+	stateMutex *sync.Mutex
+	// writeMutex is used to serialize and avoid recursive writer locks
+	writeMutex *sync.Mutex
+	counter    int64
+	file       string
+	fd         uintptr
+	lw         string
+	locktype   int16
+	locked     bool
+	ro         bool
 }
 
-// Lock locks the lock file
-func (l *lockfile) Lock() {
+// lock locks the lockfile via FCTNL(2) based on the specified type and
+// command.
+func (l *lockfile) lock(l_type int16) {
 	lk := unix.Flock_t{
-		Type:   l.locktype,
+		Type:   l_type,
 		Whence: int16(os.SEEK_SET),
 		Start:  0,
 		Len:    0,
 		Pid:    int32(os.Getpid()),
 	}
-	l.mu.Lock()
+	if l_type == unix.F_WRLCK {
+		// If we try to lock as a writer, lock the writerMutex first to
+		// avoid multiple writer acquisitions of the same process.
+		// Note: it's important to lock it prior to the stateMutex to
+		// avoid a deadlock.
+		l.writeMutex.Lock()
+	}
+	l.stateMutex.Lock()
+	l.locktype = l_type
+	if l.counter == 0 {
+		// Optimization: only use the (expensive) fcntl syscall when
+		// the counter is 0.  If it's greater than that, we're owning
+		// the lock already and can only be a reader.
+		for unix.FcntlFlock(l.fd, unix.F_SETLKW, &lk) != nil {
+			time.Sleep(10 * time.Millisecond)
+		}
+	}
 	l.locked = true
-	for unix.FcntlFlock(l.fd, unix.F_SETLKW, &lk) != nil {
-		time.Sleep(10 * time.Millisecond)
+	l.counter++
+	l.stateMutex.Unlock()
+}
+
+// Lock locks the lockfile as a writer.  Note that RLock() will be called if
+// the lock is a read-only one.
+func (l *lockfile) Lock() {
+	if l.ro {
+		l.RLock()
+	} else {
+		l.lock(unix.F_WRLCK)
 	}
 }
 
-// Unlock unlocks the lock file
+// LockRead locks the lockfile as a reader.
+func (l *lockfile) RLock() {
+	l.lock(unix.F_RDLCK)
+}
+
+// Unlock unlocks the lockfile.
 func (l *lockfile) Unlock() {
 	lk := unix.Flock_t{
 		Type:   unix.F_UNLCK,
@@ -64,19 +111,40 @@ func (l *lockfile) Unlock() {
 		Len:    0,
 		Pid:    int32(os.Getpid()),
 	}
-	for unix.FcntlFlock(l.fd, unix.F_SETLKW, &lk) != nil {
-		time.Sleep(10 * time.Millisecond)
+	l.stateMutex.Lock()
+	if l.locked == false {
+		// Panic when unlocking an unlocked lock.  That's a violation
+		// of the lock semantics and will reveal such.
+		panic("calling Unlock on unlocked lock")
+	}
+	l.counter--
+	if l.counter < 0 {
+		// Panic when the counter is negative.  There is no way we can
+		// recover from a corrupted lock and we need to protect the
+		// storage from corruption.
+		panic(fmt.Sprintf("lock %q has been unlocked too often", l.file))
+	}
+	if l.counter == 0 {
+		// We should only release the lock when the counter is 0 to
+		// avoid releasing read-locks too early; a given process may
+		// acquire a read lock multiple times.
+		l.locked = false
+		for unix.FcntlFlock(l.fd, unix.F_SETLKW, &lk) != nil {
+			time.Sleep(10 * time.Millisecond)
+		}
+	}
+	if l.locktype == unix.F_WRLCK {
+		l.writeMutex.Unlock()
 	}
-	l.locked = false
-	l.mu.Unlock()
+	l.stateMutex.Unlock()
 }
 
-// Check if lock is locked
+// Locked checks if lockfile is locked.
 func (l *lockfile) Locked() bool {
 	return l.locked
 }
 
-// Touch updates the lock file with the UID of the user
+// Touch updates the lock file with the UID of the user.
 func (l *lockfile) Touch() error {
 	l.lw = stringid.GenerateRandomID()
 	id := []byte(l.lw)
@@ -98,7 +166,8 @@ func (l *lockfile) Touch() error {
 	return nil
 }
 
-// Modified indicates if the lock file has been updated since the last time it was loaded
+// Modified indicates if the lockfile has been updated since the last time it
+// was loaded.
 func (l *lockfile) Modified() (bool, error) {
 	id := []byte(l.lw)
 	_, err := unix.Seek(int(l.fd), 0, os.SEEK_SET)
@@ -117,7 +186,7 @@ func (l *lockfile) Modified() (bool, error) {
 	return l.lw != lw, nil
 }
 
-// IsRWLock indicates if the lock file is a read-write lock
+// IsReadWriteLock indicates if the lock file is a read-write lock.
 func (l *lockfile) IsReadWrite() bool {
-	return (l.locktype == unix.F_WRLCK)
+	return !l.ro
 }
diff --git a/vendor/github.com/containers/storage/lockfile_windows.go b/vendor/github.com/containers/storage/lockfile_windows.go
index 77490b851..a3821bfeb 100644
--- a/vendor/github.com/containers/storage/lockfile_windows.go
+++ b/vendor/github.com/containers/storage/lockfile_windows.go
@@ -23,6 +23,11 @@ func (l *lockfile) Lock() {
 	l.locked = true
 }
 
+func (l *lockfile) RLock() {
+	l.mu.Lock()
+	l.locked = true
+}
+
 func (l *lockfile) Unlock() {
 	l.locked = false
 	l.mu.Unlock()
diff --git a/vendor/github.com/containers/storage/pkg/archive/archive_ffjson.go b/vendor/github.com/containers/storage/pkg/archive/archive_ffjson.go
index 2ba44b85d..9b8103e4d 100644
--- a/vendor/github.com/containers/storage/pkg/archive/archive_ffjson.go
+++ b/vendor/github.com/containers/storage/pkg/archive/archive_ffjson.go
@@ -1,5 +1,5 @@
 // Code generated by ffjson <https://github.com/pquerna/ffjson>. DO NOT EDIT.
-// source: ./pkg/archive/archive.go
+// source: pkg/archive/archive.go
 
 package archive
 
diff --git a/vendor/github.com/containers/storage/store.go b/vendor/github.com/containers/storage/store.go
index 856c73e51..d53703d6b 100644
--- a/vendor/github.com/containers/storage/store.go
+++ b/vendor/github.com/containers/storage/store.go
@@ -566,10 +566,10 @@ func GetStore(options StoreOptions) (Store, error) {
 	}
 
 	if options.GraphRoot == "" {
-		return nil, ErrIncompleteOptions
+		return nil, errors.Wrap(ErrIncompleteOptions, "no storage root specified")
 	}
 	if options.RunRoot == "" {
-		return nil, ErrIncompleteOptions
+		return nil, errors.Wrap(ErrIncompleteOptions, "no storage runroot specified")
 	}
 
 	if err := os.MkdirAll(options.RunRoot, 0700); err != nil && !os.IsExist(err) {
@@ -870,7 +870,8 @@ func (s *store) PutLayer(id, parent string, names []string, mountLabel string, w
 	gidMap := options.GIDMap
 	if parent != "" {
 		var ilayer *Layer
-		for _, lstore := range append([]ROLayerStore{rlstore}, rlstores...) {
+		for _, l := range append([]ROLayerStore{rlstore}, rlstores...) {
+			lstore := l
 			if lstore != rlstore {
 				lstore.Lock()
 				defer lstore.Unlock()
@@ -949,7 +950,8 @@ func (s *store) CreateImage(id string, names []string, layer, metadata string, o
 			return nil, err
 		}
 		var ilayer *Layer
-		for _, store := range append([]ROLayerStore{lstore}, lstores...) {
+		for _, s := range append([]ROLayerStore{lstore}, lstores...) {
+			store := s
 			store.Lock()
 			defer store.Unlock()
 			if modified, err := store.Modified(); modified || err != nil {
@@ -1010,7 +1012,8 @@ func (s *store) imageTopLayerForMapping(image *Image, ristore ROImageStore, crea
 	}
 	var layer, parentLayer *Layer
 	// Locate the image's top layer and its parent, if it has one.
-	for _, store := range append([]ROLayerStore{rlstore}, lstores...) {
+	for _, s := range append([]ROLayerStore{rlstore}, lstores...) {
+		store := s
 		if store != rlstore {
 			store.Lock()
 			defer store.Unlock()
@@ -1143,7 +1146,8 @@ func (s *store) CreateContainer(id string, names []string, image, layer, metadat
 			}
 		}
 		var cimage *Image
-		for _, store := range append([]ROImageStore{istore}, istores...) {
+		for _, s := range append([]ROImageStore{istore}, istores...) {
+			store := s
 			store.Lock()
 			defer store.Unlock()
 			if modified, err := store.Modified(); modified || err != nil {
@@ -1315,7 +1319,8 @@ func (s *store) Metadata(id string) (string, error) {
 	if err != nil {
 		return "", err
 	}
-	for _, store := range append([]ROLayerStore{lstore}, lstores...) {
+	for _, s := range append([]ROLayerStore{lstore}, lstores...) {
+		store := s
 		store.Lock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {
@@ -1336,7 +1341,8 @@ func (s *store) Metadata(id string) (string, error) {
 	if err != nil {
 		return "", err
 	}
-	for _, store := range append([]ROImageStore{istore}, istores...) {
+	for _, s := range append([]ROImageStore{istore}, istores...) {
+		store := s
 		store.Lock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {
@@ -1375,7 +1381,8 @@ func (s *store) ListImageBigData(id string) ([]string, error) {
 	if err != nil {
 		return nil, err
 	}
-	for _, store := range append([]ROImageStore{istore}, istores...) {
+	for _, s := range append([]ROImageStore{istore}, istores...) {
+		store := s
 		store.Lock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {
@@ -1400,7 +1407,8 @@ func (s *store) ImageBigDataSize(id, key string) (int64, error) {
 	if err != nil {
 		return -1, err
 	}
-	for _, store := range append([]ROImageStore{istore}, istores...) {
+	for _, s := range append([]ROImageStore{istore}, istores...) {
+		store := s
 		store.Lock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {
@@ -1426,7 +1434,8 @@ func (s *store) ImageBigDataDigest(id, key string) (digest.Digest, error) {
 		return "", err
 	}
 	stores = append([]ROImageStore{ristore}, stores...)
-	for _, ristore := range stores {
+	for _, r := range stores {
+		ristore := r
 		ristore.Lock()
 		defer ristore.Unlock()
 		if modified, err := ristore.Modified(); modified || err != nil {
@@ -1451,8 +1460,9 @@ func (s *store) ImageBigData(id, key string) ([]byte, error) {
 	if err != nil {
 		return nil, err
 	}
-	for _, store := range append([]ROImageStore{istore}, istores...) {
-		store.Lock()
+	for _, s := range append([]ROImageStore{istore}, istores...) {
+		store := s
+		store.RLock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {
 			if err = store.Load(); err != nil {
@@ -1495,7 +1505,8 @@ func (s *store) ImageSize(id string) (int64, error) {
 	if err != nil {
 		return -1, errors.Wrapf(err, "error loading additional layer stores")
 	}
-	for _, store := range append([]ROLayerStore{lstore}, lstores...) {
+	for _, s := range append([]ROLayerStore{lstore}, lstores...) {
+		store := s
 		store.Lock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {
@@ -1516,7 +1527,8 @@ func (s *store) ImageSize(id string) (int64, error) {
 	}
 
 	// Look for the image's record.
-	for _, store := range append([]ROImageStore{istore}, istores...) {
+	for _, s := range append([]ROImageStore{istore}, istores...) {
+		store := s
 		store.Lock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {
@@ -1603,7 +1615,8 @@ func (s *store) ContainerSize(id string) (int64, error) {
 	if err != nil {
 		return -1, err
 	}
-	for _, store := range append([]ROLayerStore{lstore}, lstores...) {
+	for _, s := range append([]ROLayerStore{lstore}, lstores...) {
+		store := s
 		store.Lock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {
@@ -1772,7 +1785,8 @@ func (s *store) Exists(id string) bool {
 	if err != nil {
 		return false
 	}
-	for _, store := range append([]ROLayerStore{lstore}, lstores...) {
+	for _, s := range append([]ROLayerStore{lstore}, lstores...) {
+		store := s
 		store.Lock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {
@@ -1793,7 +1807,8 @@ func (s *store) Exists(id string) bool {
 	if err != nil {
 		return false
 	}
-	for _, store := range append([]ROImageStore{istore}, istores...) {
+	for _, s := range append([]ROImageStore{istore}, istores...) {
+		store := s
 		store.Lock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {
@@ -1895,7 +1910,8 @@ func (s *store) Names(id string) ([]string, error) {
 	if err != nil {
 		return nil, err
 	}
-	for _, store := range append([]ROLayerStore{lstore}, lstores...) {
+	for _, s := range append([]ROLayerStore{lstore}, lstores...) {
+		store := s
 		store.Lock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {
@@ -1916,7 +1932,8 @@ func (s *store) Names(id string) ([]string, error) {
 	if err != nil {
 		return nil, err
 	}
-	for _, store := range append([]ROImageStore{istore}, istores...) {
+	for _, s := range append([]ROImageStore{istore}, istores...) {
+		store := s
 		store.Lock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {
@@ -1955,7 +1972,8 @@ func (s *store) Lookup(name string) (string, error) {
 	if err != nil {
 		return "", err
 	}
-	for _, store := range append([]ROLayerStore{lstore}, lstores...) {
+	for _, s := range append([]ROLayerStore{lstore}, lstores...) {
+		store := s
 		store.Lock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {
@@ -1976,7 +1994,8 @@ func (s *store) Lookup(name string) (string, error) {
 	if err != nil {
 		return "", err
 	}
-	for _, store := range append([]ROImageStore{istore}, istores...) {
+	for _, s := range append([]ROImageStore{istore}, istores...) {
+		store := s
 		store.Lock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {
@@ -2486,7 +2505,8 @@ func (s *store) Changes(from, to string) ([]archive.Change, error) {
 	if err != nil {
 		return nil, err
 	}
-	for _, store := range append([]ROLayerStore{lstore}, lstores...) {
+	for _, s := range append([]ROLayerStore{lstore}, lstores...) {
+		store := s
 		store.Lock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {
@@ -2510,7 +2530,8 @@ func (s *store) DiffSize(from, to string) (int64, error) {
 	if err != nil {
 		return -1, err
 	}
-	for _, store := range append([]ROLayerStore{lstore}, lstores...) {
+	for _, s := range append([]ROLayerStore{lstore}, lstores...) {
+		store := s
 		store.Lock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {
@@ -2534,8 +2555,9 @@ func (s *store) Diff(from, to string, options *DiffOptions) (io.ReadCloser, erro
 	if err != nil {
 		return nil, err
 	}
-	for _, store := range append([]ROLayerStore{lstore}, lstores...) {
-		store.Lock()
+	for _, s := range append([]ROLayerStore{lstore}, lstores...) {
+		store := s
+		store.RLock()
 		if modified, err := store.Modified(); modified || err != nil {
 			if err = store.Load(); err != nil {
 				return nil, err
@@ -2588,7 +2610,8 @@ func (s *store) layersByMappedDigest(m func(ROLayerStore, digest.Digest) ([]Laye
 	if err != nil {
 		return nil, err
 	}
-	for _, store := range append([]ROLayerStore{lstore}, lstores...) {
+	for _, s := range append([]ROLayerStore{lstore}, lstores...) {
+		store := s
 		store.Lock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {
@@ -2634,7 +2657,8 @@ func (s *store) LayerSize(id string) (int64, error) {
 	if err != nil {
 		return -1, err
 	}
-	for _, store := range append([]ROLayerStore{lstore}, lstores...) {
+	for _, s := range append([]ROLayerStore{lstore}, lstores...) {
+		store := s
 		store.Lock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {
@@ -2712,7 +2736,8 @@ func (s *store) Layers() ([]Layer, error) {
 		return nil, err
 	}
 
-	for _, store := range append([]ROLayerStore{lstore}, lstores...) {
+	for _, s := range append([]ROLayerStore{lstore}, lstores...) {
+		store := s
 		store.Lock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {
@@ -2740,7 +2765,8 @@ func (s *store) Images() ([]Image, error) {
 	if err != nil {
 		return nil, err
 	}
-	for _, store := range append([]ROImageStore{istore}, istores...) {
+	for _, s := range append([]ROImageStore{istore}, istores...) {
+		store := s
 		store.Lock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {
@@ -2783,7 +2809,8 @@ func (s *store) Layer(id string) (*Layer, error) {
 	if err != nil {
 		return nil, err
 	}
-	for _, store := range append([]ROLayerStore{lstore}, lstores...) {
+	for _, s := range append([]ROLayerStore{lstore}, lstores...) {
+		store := s
 		store.Lock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {
@@ -2808,7 +2835,8 @@ func (s *store) Image(id string) (*Image, error) {
 	if err != nil {
 		return nil, err
 	}
-	for _, store := range append([]ROImageStore{istore}, istores...) {
+	for _, s := range append([]ROImageStore{istore}, istores...) {
+		store := s
 		store.Lock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {
@@ -2840,7 +2868,8 @@ func (s *store) ImagesByTopLayer(id string) ([]*Image, error) {
 	if err != nil {
 		return nil, err
 	}
-	for _, store := range append([]ROImageStore{istore}, istores...) {
+	for _, s := range append([]ROImageStore{istore}, istores...) {
+		store := s
 		store.Lock()
 		defer store.Unlock()
 		if modified, err := store.Modified(); modified || err != nil {