unix: fix IoctlFileDedupeRange test

The test introduced in CL 284352 breaks on several builders, either
with IoctlFileDedupeRange returning ENOTTY (as already seen for android
in the TryBot run) or returning EINVAL in the FileDedupeRange.Status
field. Both seem to indicate that the underlying filesystem doesn't
support deduplication, so skip the test in these cases.

Also rename the test to indicate the func it is testing.

Change-Id: I29553a5fc95f98335cb233f05d4c2dfb5640dc4c
Reviewed-on: https://go-review.googlesource.com/c/sys/+/295911
Trust: Tobias Klauser <[email protected]>
Run-TryBot: Tobias Klauser <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Matt Layher <[email protected]>

Author: tklauser

unix/syscall_linux_test.go

@@ -797,13 +797,7 @@ func TestOpenat2(t *testing.T) {
 	}
 }
 
-func TestFideduperange(t *testing.T) {
-	if runtime.GOOS == "android" {
-		// The ioctl in the build robot android-amd64 returned ENOTTY,
-		// an error not documented for that syscall.
-		t.Skip("FIDEDUPERANGE ioctl doesn't work on android, skipping test")
-	}
-
+func TestIoctlFileDedupeRange(t *testing.T) {
 	f1, err := ioutil.TempFile("", t.Name())
 	if err != nil {
 		t.Fatal(err)
@@ -855,17 +849,19 @@ func TestFideduperange(t *testing.T) {
 		}}
 
 	err = unix.IoctlFileDedupeRange(int(f1.Fd()), &dedupe)
-	if err == unix.EOPNOTSUPP || err == unix.EINVAL {
+	if err == unix.EOPNOTSUPP || err == unix.EINVAL || err == unix.ENOTTY {
 		t.Skip("deduplication not supported on this filesystem")
 	} else if err != nil {
 		t.Fatal(err)
 	}
 
 	// The first Info should be equal
 	if dedupe.Info[0].Status < 0 {
-		// We expect status to be a negated errno
-		t.Errorf("Unexpected error in FileDedupeRange: %s",
-			unix.ErrnoName(unix.Errno(-dedupe.Info[0].Status)))
+		errno := unix.Errno(-dedupe.Info[0].Status)
+		if errno == unix.EINVAL {
+			t.Skip("deduplication not supported on this filesystem")
+		}
+		t.Errorf("Unexpected error in FileDedupeRange: %s", unix.ErrnoName(errno))
 	} else if dedupe.Info[0].Status == unix.FILE_DEDUPE_RANGE_DIFFERS {
 		t.Errorf("Unexpected different bytes in FileDedupeRange")
 	}
@@ -876,9 +872,11 @@ func TestFideduperange(t *testing.T) {
 
 	// The second Info should be different
 	if dedupe.Info[1].Status < 0 {
-		// We expect status to be a negated errno
-		t.Errorf("Unexpected error in FileDedupeRange: %s",
-			unix.ErrnoName(unix.Errno(-dedupe.Info[1].Status)))
+		errno := unix.Errno(-dedupe.Info[1].Status)
+		if errno == unix.EINVAL {
+			t.Skip("deduplication not supported on this filesystem")
+		}
+		t.Errorf("Unexpected error in FileDedupeRange: %s", unix.ErrnoName(errno))
 	} else if dedupe.Info[1].Status == unix.FILE_DEDUPE_RANGE_SAME {
 		t.Errorf("Unexpected equal bytes in FileDedupeRange")
 	}