internal/poll, net, os: remove poll.Splice syscall name return value

The sc return value of internal/poll.Splice is always set to the same
value "splice" in the error case and then passed to wrapSyscallError.
Move that value to the wrapSyscallError calls to simplify the code a
bit.

Change-Id: I98104d755da68ff9f301fabc43c2618fda21a175
Reviewed-on: https://go-review.googlesource.com/c/go/+/575655
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>

src/internal/poll/splice_linux.go

@@ -31,12 +31,10 @@ const (
 //
 // Splice gets a pipe buffer from the pool or creates a new one if needed, to serve as a buffer for the data transfer.
 // src and dst must both be stream-oriented sockets.
-//
+func Splice(dst, src *FD, remain int64) (written int64, handled bool, err error) {
-// If err != nil, sc is the system call which caused the error.
+	p, err := getPipe()
-func Splice(dst, src *FD, remain int64) (written int64, handled bool, sc string, err error) {
-	p, sc, err := getPipe()
 	if err != nil {
-		return 0, false, sc, err
+		return 0, false, err
 	}
 	defer putPipe(p)
 	var inPipe, n int
@@ -71,9 +69,9 @@ func Splice(dst, src *FD, remain int64) (written int64, handled bool, sc string,
 		}
 	}
 	if err != nil {
-		return written, handled, "splice", err
+		return written, handled, err
 	}
-	return written, true, "", nil
+	return written, true, nil
 }
 
 // spliceDrain moves data from a socket to a pipe.
@@ -204,15 +202,12 @@ func newPoolPipe() any {
 }
 
 // getPipe tries to acquire a pipe buffer from the pool or create a new one with newPipe() if it gets nil from the cache.
-//
+func getPipe() (*splicePipe, error) {
-// Note that it may fail to create a new pipe buffer by newPipe(), in which case getPipe() will return a generic error
-// and system call name splice in a string as the indication.
-func getPipe() (*splicePipe, string, error) {
 	v := splicePipePool.Get()
 	if v == nil {
-		return nil, "splice", syscall.EINVAL
+		return nil, syscall.EINVAL
 	}
-	return v.(*splicePipe), "", nil
+	return v.(*splicePipe), nil
 }
 
 func putPipe(p *splicePipe) {

src/internal/poll/splice_linux_test.go

@@ -41,7 +41,7 @@ func TestSplicePipePool(t *testing.T) {
 	t.Cleanup(func() { closeHook.Store((func(int))(nil)) })
 
 	for i := 0; i < N; i++ {
-		p, _, err = poll.GetPipe()
+		p, err = poll.GetPipe()
 		if err != nil {
 			t.Skipf("failed to create pipe due to error(%v), skip this test", err)
 		}
@@ -93,7 +93,7 @@ func TestSplicePipePool(t *testing.T) {
 func BenchmarkSplicePipe(b *testing.B) {
 	b.Run("SplicePipeWithPool", func(b *testing.B) {
 		for i := 0; i < b.N; i++ {
-			p, _, err := poll.GetPipe()
+			p, err := poll.GetPipe()
 			if err != nil {
 				continue
 			}
@@ -114,7 +114,7 @@ func BenchmarkSplicePipe(b *testing.B) {
 func BenchmarkSplicePipePoolParallel(b *testing.B) {
 	b.RunParallel(func(pb *testing.PB) {
 		for pb.Next() {
-			p, _, err := poll.GetPipe()
+			p, err := poll.GetPipe()
 			if err != nil {
 				continue
 			}

src/net/splice_linux.go

@@ -41,11 +41,11 @@ func spliceFrom(c *netFD, r io.Reader) (written int64, err error, handled bool)
 		return 0, nil, false
 	}
 
-	written, handled, sc, err := pollSplice(&c.pfd, &s.pfd, remain)
+	written, handled, err = pollSplice(&c.pfd, &s.pfd, remain)
 	if lr != nil {
 		lr.N -= written
 	}
-	return written, wrapSyscallError(sc, err), handled
+	return written, wrapSyscallError("splice", err), handled
 }
 
 // spliceTo transfers data from c to w using the splice system call to minimize
@@ -59,6 +59,6 @@ func spliceTo(w io.Writer, c *netFD) (written int64, err error, handled bool) {
 		return
 	}
 
-	written, handled, sc, err := pollSplice(&uc.fd.pfd, &c.pfd, 1<<63-1)
+	written, handled, err = pollSplice(&uc.fd.pfd, &c.pfd, 1<<63-1)
-	return written, wrapSyscallError(sc, err), handled
+	return written, wrapSyscallError("splice", err), handled
 }

src/net/splice_linux_test.go

@@ -519,21 +519,20 @@ type spliceHook struct {
 
 	written int64
 	handled bool
-	sc      string
 	err     error
 
-	original func(dst, src *poll.FD, remain int64) (int64, bool, string, error)
+	original func(dst, src *poll.FD, remain int64) (int64, bool, error)
 }
 
 func (h *spliceHook) install() {
 	h.original = pollSplice
-	pollSplice = func(dst, src *poll.FD, remain int64) (int64, bool, string, error) {
+	pollSplice = func(dst, src *poll.FD, remain int64) (int64, bool, error) {
 		h.called = true
 		h.dstfd = dst.Sysfd
 		h.srcfd = src.Sysfd
 		h.remain = remain
-		h.written, h.handled, h.sc, h.err = h.original(dst, src, remain)
+		h.written, h.handled, h.err = h.original(dst, src, remain)
-		return h.written, h.handled, h.sc, h.err
+		return h.written, h.handled, h.err
 	}
 }
 

src/os/readfrom_linux_test.go

@@ -693,21 +693,20 @@ type spliceFileHook struct {
 
 	written int64
 	handled bool
-	sc      string
 	err     error
 
-	original func(dst, src *poll.FD, remain int64) (int64, bool, string, error)
+	original func(dst, src *poll.FD, remain int64) (int64, bool, error)
 }
 
 func (h *spliceFileHook) install() {
 	h.original = *PollSpliceFile
-	*PollSpliceFile = func(dst, src *poll.FD, remain int64) (int64, bool, string, error) {
+	*PollSpliceFile = func(dst, src *poll.FD, remain int64) (int64, bool, error) {
 		h.called = true
 		h.dstfd = dst.Sysfd
 		h.srcfd = src.Sysfd
 		h.remain = remain
-		h.written, h.handled, h.sc, h.err = h.original(dst, src, remain)
+		h.written, h.handled, h.err = h.original(dst, src, remain)
-		return h.written, h.handled, h.sc, h.err
+		return h.written, h.handled, h.err
 	}
 }
 

src/os/zero_copy_linux.go

@@ -87,14 +87,13 @@ func (f *File) spliceToFile(r io.Reader) (written int64, handled bool, err error
 		return
 	}
 
-	var syscallName string
+	written, handled, err = pollSplice(&f.pfd, pfd, remain)
-	written, handled, syscallName, err = pollSplice(&f.pfd, pfd, remain)
 
 	if lr != nil {
 		lr.N = remain - written
 	}
 
-	return written, handled, wrapSyscallError(syscallName, err)
+	return written, handled, wrapSyscallError("splice", err)
 }
 
 func (f *File) copyFileRange(r io.Reader) (written int64, handled bool, err error) {