vfs: stop change notify polling clearing so much of the directory cache

Before this change, change notify polls would clear the directory
cache recursively. So uploading a file to the root would clear the
entire directory cache.

After this change we just invalidate the directory cache of the parent
directory of the item and if the item was a directory we invalidate it
too.

vfs/dir.go

@@ -13,6 +13,7 @@ import (
 	"github.com/rclone/rclone/fs"
 	"github.com/rclone/rclone/fs/dirtree"
 	"github.com/rclone/rclone/fs/list"
+	"github.com/rclone/rclone/fs/log"
 	"github.com/rclone/rclone/fs/operations"
 	"github.com/rclone/rclone/fs/walk"
 )
@@ -119,6 +120,32 @@ func (d *Dir) ForgetAll() {
 	d.forgetDirPath("")
 }
 
+// invalidateDir invalidates the directory cache for absPath relative to this dir
+func (d *Dir) invalidateDir(absPath string) {
+	node := d.vfs.root.cachedNode(absPath)
+	if dir, ok := node.(*Dir); ok {
+		dir.mu.Lock()
+		if !dir.read.IsZero() {
+			fs.Debugf(dir.path, "invalidating directory cache")
+			dir.read = time.Time{}
+		}
+		dir.mu.Unlock()
+	}
+}
+
+// changeNotify invalidates the directory cache for the relativePath
+// passed in.
+//
+// if entryType is a directory it invalidates the parent of the directory too.
+func (d *Dir) changeNotify(relativePath string, entryType fs.EntryType) {
+	defer log.Trace(d.path, "relativePath=%q, type=%v", relativePath, entryType)("")
+	absPath := path.Join(d.path, relativePath)
+	d.invalidateDir(findParent(absPath))
+	if entryType == fs.EntryDirectory {
+		d.invalidateDir(absPath)
+	}
+}
+
 // ForgetPath clears the cache for itself and all subdirectories if
 // they match the given path. The path is specified relative from the
 // directory it is called from. The cache of the parent directory is
@@ -126,22 +153,10 @@ func (d *Dir) ForgetAll() {
 // It is not possible to traverse the directory tree upwards, i.e.
 // you cannot clear the cache for the Dir's ancestors or siblings.
 func (d *Dir) ForgetPath(relativePath string, entryType fs.EntryType) {
+	defer log.Trace(d.path, "relativePath=%q, type=%v", relativePath, entryType)("")
 	if absPath := path.Join(d.path, relativePath); absPath != "" {
-		parent := path.Dir(absPath)
-		if parent == "." || parent == "/" {
-			parent = ""
-		}
-		parentNode := d.vfs.root.cachedNode(parent)
-		if dir, ok := parentNode.(*Dir); ok {
-			dir.mu.Lock()
-			if !dir.read.IsZero() {
-				fs.Debugf(dir.path, "invalidating directory cache")
-				dir.read = time.Time{}
-			}
-			dir.mu.Unlock()
-		}
+		d.invalidateDir(findParent(absPath))
 	}
-
 	if entryType == fs.EntryDirectory {
 		d.forgetDirPath(relativePath)
 	}

vfs/vfs.go

@@ -232,7 +232,7 @@ func New(f fs.Fs, opt *Options) *VFS {
 	// Start polling function
 	if do := vfs.f.Features().ChangeNotify; do != nil {
 		vfs.pollChan = make(chan time.Duration)
-		do(context.TODO(), vfs.root.ForgetPath, vfs.pollChan)
+		do(context.TODO(), vfs.root.changeNotify, vfs.pollChan)
 		vfs.pollChan <- vfs.Opt.PollInterval
 	} else {
 		fs.Infof(f, "poll-interval is not supported by this remote")