cmd/link: fix size calculation for file space preallocation on darwin
On darwin, we preallocate file storage space with fcntl
F_ALLOCATEALL in F_PEOFPOSMODE mode. This is specified as
allocating from the physical end of the file. So the size we give
it should be the increment, instead of the total size.
Fixes #39044.
Change-Id: I10c7ee8d51f237b4a7604233ac7abc6f91dcd602
Reviewed-on: https://go-review.googlesource.com/c/go/+/234481
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Jeremy Faller <jeremy@golang.org>
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..a064bea
--- /dev/null
+++ b/src/cmd/link/internal/ld/fallocate_test.go
@@ -0,0 +1,50 @@
+// 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.
+
+// +build darwin linux
+
+package ld
+
+import (
+ "io/ioutil"
+ "os"
+ "path/filepath"
+ "syscall"
+ "testing"
+)
+
+func TestFallocate(t *testing.T) {
+ dir, err := ioutil.TempDir("", "TestFallocate")
+ if err != nil {
+ t.Fatal(err)
+ }
+ defer os.RemoveAll(dir)
+ 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()
+
+ // 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)
+ }
+ if got, want := stat.Sys().(*syscall.Stat_t).Blocks, (sz+511)/512; got != want {
+ t.Errorf("unexpected disk usage: got %d blocks, want %d", got, want)
+ }
+ out.munmap()
+ }
+}
diff --git a/src/cmd/link/internal/ld/outbuf_darwin.go b/src/cmd/link/internal/ld/outbuf_darwin.go
index 299902e..9a74ba8 100644
--- a/src/cmd/link/internal/ld/outbuf_darwin.go
+++ b/src/cmd/link/internal/ld/outbuf_darwin.go
@@ -10,16 +10,25 @@
)
func (out *OutBuf) fallocate(size uint64) error {
+ stat, err := out.f.Stat()
+ if err != nil {
+ return err
+ }
+ cursize := uint64(stat.Size())
+ if size <= cursize {
+ return nil
+ }
+
store := &syscall.Fstore_t{
Flags: syscall.F_ALLOCATEALL,
Posmode: syscall.F_PEOFPOSMODE,
Offset: 0,
- Length: int64(size),
+ Length: int64(size - cursize), // F_PEOFPOSMODE allocates from the end of the file, so we want the size difference here
}
- _, _, err := syscall.Syscall(syscall.SYS_FCNTL, uintptr(out.f.Fd()), syscall.F_PREALLOCATE, uintptr(unsafe.Pointer(store)))
- if err != 0 {
- return err
+ _, _, errno := syscall.Syscall(syscall.SYS_FCNTL, uintptr(out.f.Fd()), syscall.F_PREALLOCATE, uintptr(unsafe.Pointer(store)))
+ if errno != 0 {
+ return errno
}
return nil
