1 files changed, 65 insertions, 0 deletions
diff --git a/src/cmd/link/internal/ld/fallocate_test.go b/src/cmd/link/internal/ld/fallocate_test.go
new file mode 100644
index 0000000..1ed0eb2
--- /dev/null
+++ b/src/cmd/link/internal/ld/fallocate_test.go
@@ -0,0 +1,65 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build darwin || linux
+// +build darwin linux
+
+package ld
+
+import (
+	"os"
+	"path/filepath"
+	"syscall"
+	"testing"
+)
+
+func TestFallocate(t *testing.T) {
+	dir := t.TempDir()
+	filename := filepath.Join(dir, "a.out")
+	out := NewOutBuf(nil)
+	err := out.Open(filename)
+	if err != nil {
+		t.Fatalf("Open file failed: %v", err)
+	}
+	defer out.Close()
+
+	// Try fallocate first.
+	for {
+		err = out.fallocate(1 << 10)
+		if err == syscall.EOPNOTSUPP { // The underlying file system may not support fallocate
+			t.Skip("fallocate is not supported")
+		}
+		if err == syscall.EINTR {
+			continue // try again
+		}
+		if err != nil {
+			t.Fatalf("fallocate failed: %v", err)
+		}
+		break
+	}
+
+	// Mmap 1 MiB initially, and grow to 2 and 3 MiB.
+	// Check if the file size and disk usage is expected.
+	for _, sz := range []int64{1 << 20, 2 << 20, 3 << 20} {
+		err = out.Mmap(uint64(sz))
+		if err != nil {
+			t.Fatalf("Mmap failed: %v", err)
+		}
+		stat, err := os.Stat(filename)
+		if err != nil {
+			t.Fatalf("Stat failed: %v", err)
+		}
+		if got := stat.Size(); got != sz {
+			t.Errorf("unexpected file size: got %d, want %d", got, sz)
+		}
+		// The number of blocks must be enough for the requested size.
+		// We used to require an exact match, but it appears that
+		// some file systems allocate a few extra blocks in some cases.
+		// See issue #41127.
+		if got, want := stat.Sys().(*syscall.Stat_t).Blocks, (sz+511)/512; got < want {
+			t.Errorf("unexpected disk usage: got %d blocks, want at least %d", got, want)
+		}
+		out.munmap()
+	}
+}