Revert "os: employ sendfile(2) for file-to-file copying on Linux when needed"

This reverts CL 603295.

Reason for revert: can cause child exit_group to hang.

This is not a clean revert. CL 603098 did a major refactoring of the
tests. That refactor is kept, just the sendfile-specific tests are
dropped from the linux tests.

Fixes #71375.

Change-Id: Ic4d6535759667c69a44bd9281bbb33d5b559f591
Reviewed-on: https://go-review.googlesource.com/c/go/+/644895
Auto-Submit: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Andy Pan <panjf2000@gmail.com>

1 files changed, 2 insertions, 50 deletions

diff --git a/src/os/readfrom_linux_test.go b/src/os/readfrom_linux_test.go
index cc0322882b..d33f9cf9c9 100644
--- a/src/os/readfrom_linux_test.go
+++ b/src/os/readfrom_linux_test.go
@@ -242,13 +242,12 @@ func testSpliceToTTY(t *testing.T, proto string, size int64) {
 }
 
 var (
-	copyFileTests = []copyFileTestFunc{newCopyFileRangeTest, newSendfileOverCopyFileRangeTest}
-	copyFileHooks = []copyFileTestHook{hookCopyFileRange, hookSendFileOverCopyFileRange}
+	copyFileTests = []copyFileTestFunc{newCopyFileRangeTest}
+	copyFileHooks = []copyFileTestHook{hookCopyFileRange}
 )
 
 func testCopyFiles(t *testing.T, size, limit int64) {
 	testCopyFileRange(t, size, limit)
-	testSendfileOverCopyFileRange(t, size, limit)
 }
 
 func testCopyFileRange(t *testing.T, size int64, limit int64) {
@@ -256,11 +255,6 @@ func testCopyFileRange(t *testing.T, size int64, limit int64) {
 	testCopyFile(t, dst, src, data, hook, limit, name)
 }
 
-func testSendfileOverCopyFileRange(t *testing.T, size int64, limit int64) {
-	dst, src, data, hook, name := newSendfileOverCopyFileRangeTest(t, size)
-	testCopyFile(t, dst, src, data, hook, limit, name)
-}
-
 // newCopyFileRangeTest initializes a new test for copy_file_range.
 //
 // It hooks package os' call to poll.CopyFileRange and returns the hook,
@@ -276,20 +270,6 @@ func newCopyFileRangeTest(t *testing.T, size int64) (dst, src *File, data []byte
 	return
 }
 
-// newSendfileOverCopyFileRangeTest initializes a new test for sendfile over copy_file_range.
-// It hooks package os' call to poll.SendFile and returns the hook,
-// so it can be inspected.
-func newSendfileOverCopyFileRangeTest(t *testing.T, size int64) (dst, src *File, data []byte, hook *copyFileHook, name string) {
-	t.Helper()
-
-	name = "newSendfileOverCopyFileRangeTest"
-
-	dst, src, data = newCopyFileTest(t, size)
-	hook, _ = hookSendFileOverCopyFileRange(t)
-
-	return
-}
-
 // newSpliceFileTest initializes a new test for splice.
 //
 // It creates source sockets and destination file, and populates the source sockets
@@ -342,34 +322,6 @@ func hookCopyFileRange(t *testing.T) (hook *copyFileHook, name string) {
 	return
 }
 
-func hookSendFileOverCopyFileRange(t *testing.T) (*copyFileHook, string) {
-	return hookSendFileTB(t), "hookSendFileOverCopyFileRange"
-}
-
-func hookSendFileTB(tb testing.TB) *copyFileHook {
-	// Disable poll.CopyFileRange to force the fallback to poll.SendFile.
-	originalCopyFileRange := *PollCopyFileRangeP
-	*PollCopyFileRangeP = func(dst, src *poll.FD, remain int64) (written int64, handled bool, err error) {
-		return 0, false, nil
-	}
-
-	hook := new(copyFileHook)
-	orig := poll.TestHookDidSendFile
-	tb.Cleanup(func() {
-		*PollCopyFileRangeP = originalCopyFileRange
-		poll.TestHookDidSendFile = orig
-	})
-	poll.TestHookDidSendFile = func(dstFD *poll.FD, src int, written int64, err error, handled bool) {
-		hook.called = true
-		hook.dstfd = dstFD.Sysfd
-		hook.srcfd = src
-		hook.written = written
-		hook.err = err
-		hook.handled = handled
-	}
-	return hook
-}
-
 func hookSpliceFile(t *testing.T) *spliceFileHook {
 	h := new(spliceFileHook)
 	h.install()