os: consistently return ErrClosed for closed file

Catch all the cases where a file operation might return ErrFileClosing,
and convert to ErrClosed. Use a new method for the conversion, which
permits us to remove some KeepAlive calls.

Change-Id: I584178f297efe6cb86f3090b2341091b412f1041
Reviewed-on: https://go-review.googlesource.com/41793
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/os/file.go

@@ -101,17 +101,7 @@ func (f *File) Read(b []byte) (n int, err error) {
 		return 0, err
 	}
 	n, e := f.read(b)
-	if e != nil {
-		if e == poll.ErrFileClosing {
-			e = ErrClosed
-		}
-		if e == io.EOF {
-			err = e
-		} else {
-			err = &PathError{"read", f.name, e}
-		}
-	}
-	return n, err
+	return n, f.wrapErr("read", e)
 }
 
 // ReadAt reads len(b) bytes from the File starting at byte offset off.
@@ -130,11 +120,7 @@ func (f *File) ReadAt(b []byte, off int64) (n int, err error) {
 	for len(b) > 0 {
 		m, e := f.pread(b, off)
 		if e != nil {
-			if e == io.EOF {
-				err = e
-			} else {
-				err = &PathError{"read", f.name, e}
-			}
+			err = f.wrapErr("read", e)
 			break
 		}
 		n += m
@@ -161,10 +147,7 @@ func (f *File) Write(b []byte) (n int, err error) {
 
 	epipecheck(f, e)
 
-	if e != nil {
-		err = &PathError{"write", f.name, e}
-	}
-	return n, err
+	return n, f.wrapErr("write", e)
 }
 
 // WriteAt writes len(b) bytes to the File starting at byte offset off.
@@ -182,7 +165,7 @@ func (f *File) WriteAt(b []byte, off int64) (n int, err error) {
 	for len(b) > 0 {
 		m, e := f.pwrite(b, off)
 		if e != nil {
-			err = &PathError{"write", f.name, e}
+			err = f.wrapErr("write", e)
 			break
 		}
 		n += m
@@ -206,7 +189,7 @@ func (f *File) Seek(offset int64, whence int) (ret int64, err error) {
 		e = syscall.EISDIR
 	}
 	if e != nil {
-		return 0, &PathError{"seek", f.name, e}
+		return 0, f.wrapErr("seek", e)
 	}
 	return r, nil
 }
@@ -279,3 +262,16 @@ func fixCount(n int, err error) (int, error) {
 	}
 	return n, err
 }
+
+// wrapErr wraps an error that occurred during an operation on an open file.
+// It passes io.EOF through unchanged, otherwise converts
+// poll.ErrFileClosing to ErrClosed and wraps the error in a PathError.
+func (f *File) wrapErr(op string, err error) error {
+	if err == nil || err == io.EOF {
+		return err
+	}
+	if err == poll.ErrFileClosing {
+		err = ErrClosed
+	}
+	return &PathError{op, f.name, err}
+}

src/os/file_posix.go

@@ -7,7 +7,6 @@
 package os
 
 import (
-	"runtime"
 	"syscall"
 	"time"
 )
@@ -62,9 +61,8 @@ func (f *File) Chmod(mode FileMode) error {
 		return err
 	}
 	if e := f.pfd.Fchmod(syscallMode(mode)); e != nil {
-		return &PathError{"chmod", f.name, e}
+		return f.wrapErr("chmod", e)
 	}
-	runtime.KeepAlive(f)
 	return nil
 }
 
@@ -95,9 +93,8 @@ func (f *File) Chown(uid, gid int) error {
 		return err
 	}
 	if e := f.pfd.Fchown(uid, gid); e != nil {
-		return &PathError{"chown", f.name, e}
+		return f.wrapErr("chown", e)
 	}
-	runtime.KeepAlive(f)
 	return nil
 }
 
@@ -109,9 +106,8 @@ func (f *File) Truncate(size int64) error {
 		return err
 	}
 	if e := f.pfd.Ftruncate(size); e != nil {
-		return &PathError{"truncate", f.name, e}
+		return f.wrapErr("truncate", e)
 	}
-	runtime.KeepAlive(f)
 	return nil
 }
 
@@ -123,9 +119,8 @@ func (f *File) Sync() error {
 		return err
 	}
 	if e := f.pfd.Fsync(); e != nil {
-		return &PathError{"sync", f.name, e}
+		return f.wrapErr("sync", e)
 	}
-	runtime.KeepAlive(f)
 	return nil
 }
 
@@ -153,9 +148,8 @@ func (f *File) Chdir() error {
 		return err
 	}
 	if e := f.pfd.Fchdir(); e != nil {
-		return &PathError{"chdir", f.name, e}
+		return f.wrapErr("chdir", e)
 	}
-	runtime.KeepAlive(f)
 	return nil
 }
 

src/os/file_unix.go

@@ -186,6 +186,9 @@ func (file *file) close() error {
 	}
 	var err error
 	if e := file.pfd.Close(); e != nil {
+		if e == poll.ErrFileClosing {
+			e = ErrClosed
+		}
 		err = &PathError{"close", file.name, e}
 	}
 

src/os/file_windows.go

@@ -188,6 +188,9 @@ func (file *file) close() error {
 	}
 	var err error
 	if e := file.pfd.Close(); e != nil {
+		if e == poll.ErrFileClosing {
+			e = ErrClosed
+		}
 		err = &PathError{"close", file.name, e}
 	}
 

src/os/os_test.go

@@ -2178,3 +2178,23 @@ func TestPipeThreads(t *testing.T) {
 		}
 	}
 }
+
+func TestDoubleCloseError(t *testing.T) {
+	path := sfdir + "/" + sfname
+	file, err := Open(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := file.Close(); err != nil {
+		t.Fatalf("unexpected error from Close: %v", err)
+	}
+	if err := file.Close(); err == nil {
+		t.Error("second Close did not fail")
+	} else if pe, ok := err.(*PathError); !ok {
+		t.Errorf("second Close returned unexpected error type %T; expected os.PathError", pe)
+	} else if pe.Err != ErrClosed {
+		t.Errorf("second Close returned %q, wanted %q", err, ErrClosed)
+	} else {
+		t.Logf("second close returned expected error %q", err)
+	}
+}

src/os/pipe_test.go

@@ -114,7 +114,7 @@ func TestStdPipeHelper(t *testing.T) {
 	os.Exit(0)
 }
 
-func TestClosedPipeRace(t *testing.T) {
+func testClosedPipeRace(t *testing.T, read bool) {
 	switch runtime.GOOS {
 	case "freebsd":
 		t.Skip("FreeBSD does not use the poller; issue 19093")
@@ -128,25 +128,46 @@ func TestClosedPipeRace(t *testing.T) {
 	defer w.Close()
 
 	// Close the read end of the pipe in a goroutine while we are
-	// writing to the write end.
+	// writing to the write end, or vice-versa.
 	go func() {
-		// Give the main goroutine a chance to enter the Read call.
-		// This is sloppy but the test will pass even if we close
-		// before the read.
+		// Give the main goroutine a chance to enter the Read or
+		// Write call. This is sloppy but the test will pass even
+		// if we close before the read/write.
 		time.Sleep(20 * time.Millisecond)
 
-		if err := r.Close(); err != nil {
+		var err error
+		if read {
+			err = r.Close()
+		} else {
+			err = w.Close()
+		}
+		if err != nil {
 			t.Error(err)
 		}
 	}()
 
-	if _, err := r.Read(make([]byte, 1)); err == nil {
-		t.Error("Read of closed pipe unexpectedly succeeded")
+	// A slice larger than PIPE_BUF.
+	var b [65537]byte
+	if read {
+		_, err = r.Read(b[:])
+	} else {
+		_, err = w.Write(b[:])
+	}
+	if err == nil {
+		t.Error("I/O on closed pipe unexpectedly succeeded")
 	} else if pe, ok := err.(*os.PathError); !ok {
-		t.Errorf("Read of closed pipe returned unexpected error type %T; expected os.PathError", pe)
+		t.Errorf("I/O on closed pipe returned unexpected error type %T; expected os.PathError", pe)
 	} else if pe.Err != os.ErrClosed {
 		t.Errorf("got error %q but expected %q", pe.Err, os.ErrClosed)
 	} else {
-		t.Logf("Read returned expected error %q", err)
+		t.Logf("I/O returned expected error %q", err)
 	}
 }
+
+func TestClosedPipeRaceRead(t *testing.T) {
+	testClosedPipeRace(t, true)
+}
+
+func TestClosedPipeRaceWrite(t *testing.T) {
+	testClosedPipeRace(t, false)
+}