vfs: re-use the File objects when re-reading the directory

Make it so that d.items is never nil to simplify the code

This should help with inconsistent reads when the source object changes.
This commit is contained in:
Nick Craig-Wood 2018-03-01 15:51:05 +00:00
parent 7fb53a031c
commit 5e334eedd2
2 changed files with 37 additions and 33 deletions

View File

@ -24,7 +24,7 @@ type Dir struct {
entry fs.Directory
mu sync.Mutex // protects the following
read time.Time // time directory entry last read
items map[string]Node // NB can be nil when directory not read yet
items map[string]Node // directory entries - can be empty but not nil
}
func newDir(vfs *VFS, f fs.Fs, parent *Dir, fsDir fs.Directory) *Dir {
@ -36,6 +36,7 @@ func newDir(vfs *VFS, f fs.Fs, parent *Dir, fsDir fs.Directory) *Dir {
path: fsDir.Remote(),
modTime: fsDir.ModTime(),
inode: newInode(),
items: make(map[string]Node),
}
}
@ -111,7 +112,7 @@ func (d *Dir) ForgetPath(relativePath string) {
d.walk(absPath, func(dir *Dir) {
fs.Debugf(dir.path, "forgetting directory cache")
dir.read = time.Time{}
dir.items = nil
dir.items = make(map[string]Node)
})
}
@ -122,13 +123,11 @@ func (d *Dir) ForgetPath(relativePath string) {
func (d *Dir) walk(absPath string, fun func(*Dir)) {
d.mu.Lock()
defer d.mu.Unlock()
if d.items != nil {
for _, node := range d.items {
if dir, ok := node.(*Dir); ok {
dir.walk(absPath, fun)
}
}
}
if d.path == absPath || absPath == "" || strings.HasPrefix(d.path, absPath+"/") {
fun(d)
@ -153,25 +152,21 @@ func (d *Dir) rename(newParent *Dir, fsDir fs.Directory) {
// note that we add new objects rather than updating old ones
func (d *Dir) addObject(node Node) {
d.mu.Lock()
if d.items != nil {
d.items[node.Name()] = node
}
d.mu.Unlock()
}
// delObject removes an object from the directory
func (d *Dir) delObject(leaf string) {
d.mu.Lock()
if d.items != nil {
delete(d.items, leaf)
}
d.mu.Unlock()
}
// read the directory and sets d.items - must be called with the lock held
func (d *Dir) _readDir() error {
when := time.Now()
if d.read.IsZero() || d.items == nil {
if d.read.IsZero() {
// fs.Debugf(d.path, "Reading directory")
} else {
age := when.Sub(d.read)
@ -187,39 +182,40 @@ func (d *Dir) _readDir() error {
} else if err != nil {
return err
}
// NB when we re-read a directory after its cache has expired
// we drop the old files which should lead to correct
// behaviour but may not be very efficient.
// Keep a note of the previous contents of the directory
oldItems := d.items
// Cache the items by name
d.items = make(map[string]Node, len(entries))
found := make(map[string]struct{})
for _, entry := range entries {
name := path.Base(entry.Remote())
node := d.items[name]
found[name] = struct{}{}
switch item := entry.(type) {
case fs.Object:
obj := item
name := path.Base(obj.Remote())
d.items[name] = newFile(d, obj, name)
// Reuse old file value if it exists
if file, ok := node.(*File); node != nil && ok {
file.setObjectNoUpdate(obj)
} else {
node = newFile(d, obj, name)
}
case fs.Directory:
dir := item
name := path.Base(dir.Remote())
// Use old dir value if it exists
if oldItems != nil {
if oldNode, ok := oldItems[name]; ok {
if oldNode.IsDir() {
d.items[name] = oldNode
continue
// Reuse old dir value if it exists
if node == nil || !node.IsDir() {
node = newDir(d.vfs, d.f, d, dir)
}
}
}
d.items[name] = newDir(d.vfs, d.f, d, dir)
default:
err = errors.Errorf("unknown type %T", item)
fs.Errorf(d, "readDir error: %v", err)
return err
}
d.items[name] = node
}
// delete unused entries
for name := range d.items {
if _, ok := found[name]; !ok {
delete(d.items, name)
}
}
d.read = when
return nil

View File

@ -252,6 +252,14 @@ func (f *File) setObject(o fs.Object) {
f.d.addObject(f)
}
// Update the object but don't update the directory cache - for use by
// the directory cache
func (f *File) setObjectNoUpdate(o fs.Object) {
f.mu.Lock()
defer f.mu.Unlock()
f.o = o
}
// Get the current fs.Object - may be nil
func (f *File) getObject() fs.Object {
f.mu.Lock()