file.Lock/Unlock added mutex to avoid problems with concurrent calls

Signed-off-by: Máximo Cuadros <[email protected]>

Author: mcuadros

memfs/memory.go

@@ -297,11 +297,12 @@ func (f *file) Stat() (os.FileInfo, error) {
 	}, nil
 }
 
-// Lock protects file from access from other processes. Which is a no-op
-// for this memory only filesystem.
+// Lock is a no-op in memfs.
 func (f *file) Lock() error {
 	return nil
 }
+
+// Unlock is a no-op in memfs.
 func (f *file) Unlock() error {
 	return nil
 }

osfs/os.go

@@ -5,6 +5,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"sync"
 
 	"gopkg.in/src-d/go-billy.v3"
 	"gopkg.in/src-d/go-billy.v3/helper/chroot"
@@ -23,11 +24,6 @@ func New(baseDir string) billy.Filesystem {
 	return chroot.New(&OS{}, baseDir)
 }
 
-// file is a wrapper for an os.File which adds support for file locking.
-type file struct {
-	*os.File
-}
-
 func (fs *OS) Create(filename string) (billy.File, error) {
 	return fs.OpenFile(filename, os.O_RDWR|os.O_CREATE|os.O_TRUNC, defaultCreateMode)
 }
@@ -43,7 +39,7 @@ func (fs *OS) OpenFile(filename string, flag int, perm os.FileMode) (billy.File,
 	if err != nil {
 		return nil, err
 	}
-	return file{f}, err
+	return &file{File: f}, err
 }
 
 func (fs *OS) createDir(fullpath string) error {
@@ -100,7 +96,7 @@ func (fs *OS) TempFile(dir, prefix string) (billy.File, error) {
 	if err != nil {
 		return nil, err
 	}
-	return file{f}, nil
+	return &file{File: f}, nil
 }
 
 func (fs *OS) Join(elem ...string) string {
@@ -126,3 +122,9 @@ func (fs *OS) Symlink(target, link string) error {
 func (fs *OS) Readlink(link string) (string, error) {
 	return os.Readlink(link)
 }
+
+// file is a wrapper for an os.File which adds support for file locking.
+type file struct {
+	*os.File
+	m sync.Mutex
+}

osfs/os_posix.go

@@ -7,15 +7,20 @@ import (
 	"syscall"
 )
 
-// Stat returns the FileInfo structure describing file.
 func (fs *OS) Stat(filename string) (os.FileInfo, error) {
 	return os.Stat(filename)
 }
 
-// Lock protects file from access from other processes.
-func (f file) Lock() error {
+func (f *file) Lock() error {
+	f.m.Lock()
+	defer f.m.Unlock()
+
 	return syscall.Flock(int(f.File.Fd()), syscall.LOCK_EX)
 }
-func (f file) Unlock() error {
+
+func (f *file) Unlock() error {
+	f.m.Lock()
+	defer f.m.Unlock()
+
 	return syscall.Flock(int(f.File.Fd()), syscall.LOCK_UN)
 }

osfs/os_windows.go

@@ -54,8 +54,10 @@ const (
 	lockfileExclusiveLock = 0x2
 )
 
-// Lock protects file from access from other processes.
-func (f file) Lock() error {
+func (f *file) Lock() error {
+	f.m.Lock()
+	defer f.m.Unlock()
+
 	var overlapped windows.Overlapped
 	// err is always non-nil as per sys/windows semantics.
 	ret, _, err := lockFileExProc.Call(f.File.Fd(), lockfileExclusiveLock, 0, 0xFFFFFFFF, 0,
@@ -66,7 +68,11 @@ func (f file) Lock() error {
 	}
 	return nil
 }
-func (f file) Unlock() error {
+
+func (f *file) Unlock() error {
+	f.m.Lock()
+	defer f.m.Unlock()
+
 	// err is always non-nil as per sys/windows semantics.
 	ret, _, err := unlockFileProc.Call(f.File.Fd(), 0, 0, 0xFFFFFFFF, 0)
 	if ret == 0 {