fs: set Blksize and Blocks automatically based on Size

Change-Id: I272909148667e1f0246914ef7fdd1052bf3b5bc3

fs/api.go

@@ -222,7 +222,8 @@ type NodeAccesser interface {
 // FOPEN_DIRECTIO, Size should be set so it can be read correctly.  If
 // returning zeroed permissions, the default behavior is to change the
 // mode of 0755 (directory) or 0644 (files). This can be switched off
-// with the Options.NullPermissions setting.
+// with the Options.NullPermissions setting. If blksize is unset, 4096
+// is assumed, and the 'blocks' field is set accordingly.
 type NodeGetattrer interface {
 	Getattr(ctx context.Context, f FileHandle, out *fuse.AttrOut) syscall.Errno
 }

fs/bridge.go

@@ -159,6 +159,7 @@ func (b *rawBridge) setAttr(out *fuse.Attr) {
 	if b.options.GID != 0 && out.Gid == 0 {
 		out.Gid = b.options.GID
 	}
+	setBlocks(out)
 }
 
 func (b *rawBridge) setAttrTimeout(out *fuse.AttrOut) {
@@ -244,7 +245,6 @@ func (b *rawBridge) Lookup(cancel <-chan struct{}, header *fuse.InHeader, name s
 	child.setEntryOut(out)
 	b.addNewChild(parent, name, child, nil, 0, out)
 	b.setEntryOutTimeout(out)
-
 	return fuse.OK
 }
 

fs/files_darwin.go

+// Copyright 2019 the Go-FUSE Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fs
+
+import "github.com/hanwen/go-fuse/v2/fuse"
+
+func setBlocks(out *fuse.Attr) {
+}

fs/files_linux.go

@@ -30,3 +30,13 @@ func (f *loopbackFile) utimens(a *time.Time, m *time.Time) syscall.Errno {
 	err := futimens(int(f.fd), &ts)
 	return ToErrno(err)
 }
+
+func setBlocks(out *fuse.Attr) {
+	if out.Blksize > 0 {
+		return
+	}
+
+	out.Blksize = 4096
+	pages := (out.Size + 4095) / 4096
+	out.Blocks = pages * 8
+}

fs/loopback.go

@@ -56,7 +56,6 @@ func (n *loopbackNode) Statfs(ctx context.Context, out *fuse.StatfsOut) syscall.
 }
 
 func (n *loopbackRoot) Getattr(ctx context.Context, f FileHandle, out *fuse.AttrOut) syscall.Errno {
-
 	st := syscall.Stat_t{}
 	err := syscall.Stat(n.rootPath, &st)
 	if err != nil {

fs/mem_test.go

@@ -96,6 +96,10 @@ func TestDataFile(t *testing.T) {
 		t.Errorf("got mode %o, want %o", st.Mode, want)
 	}
 
+	if st.Size != int64(len(want)) || st.Blocks != 8 || st.Blksize != 4096 {
+		t.Errorf("got %#v, want sz = %d, 8 blocks, 4096 blocksize", st, len(want))
+	}
+
 	fd, err := syscall.Open(mntDir+"/file", syscall.O_RDONLY, 0)
 	if err != nil {
 		t.Fatalf("Open: %v", err)