perf(vfs,mount2): remove redundant readdir sort

POSIX/FUSE do not require sorted readdir output. The mount2 sort
was a workaround for an Emby metadata refresh bug (now fixed).
ReadDirAll's sort duplicated list.DirSorted's earlier sort.

Signed-off-by: Anagh Kumar Baranwal <6824881+darthShadow@users.noreply.github.com>

Author: darthShadow

cmd/cmount/fs.go

@@ -221,7 +221,9 @@ func (fsys *FS) Readdir(dirPath string,
 		return -fuse.ESPIPE
 	}
 
-	nodes, err := dir.ReadDirAll()
+	// POSIX/FUSE readdir does not require sorted output, so use MapReadDir
+	// directly to avoid ReadDirAll sorting overhead in mount paths.
+	nodes, err := vfs.MapReadDir[vfs.Node](dir, func(n vfs.Node) (vfs.Node, error) { return n, nil }, 0)
 	if err != nil {
 		return translateError(err)
 	}

cmd/mount/dir.go

@@ -105,7 +105,9 @@ var _ fusefs.HandleReadDirAller = (*Dir)(nil)
 func (d *Dir) ReadDirAll(ctx context.Context) (dirents []fuse.Dirent, err error) {
 	itemsRead := -1
 	defer log.Trace(d, "")("item=%d, err=%v", &itemsRead, &err)
-	items, err := d.Dir.ReadDirAll()
+	// POSIX/FUSE readdir does not require sorted output, so use MapReadDir
+	// directly to avoid ReadDirAll sorting overhead in mount paths.
+	items, err := vfs.MapReadDir[vfs.Node](d.Dir, func(n vfs.Node) (vfs.Node, error) { return n, nil }, 0)
 	if err != nil {
 		return nil, translateError(err)
 	}

cmd/mount2/node.go

@@ -6,8 +6,6 @@ import (
 	"context"
 	"os"
 	"path"
-	"slices"
-	"strings"
 	"syscall"
 
 	fusefs "github.com/hanwen/go-fuse/v2/fs"
@@ -292,9 +290,13 @@ func (n *Node) Readdir(ctx context.Context) (ds fusefs.DirStream, errno syscall.
 		Name: "..",
 		Ino:  0, // FIXME
 	}
-	slices.SortFunc(items, func(a, b fuse.DirEntry) int {
-		return strings.Compare(a.Name, b.Name)
-	})
+	// Sort removed: Linux/POSIX readdir does not require sorted output.
+	// Previously needed to work around an Emby metadata refresh bug
+	// where unsorted listings caused spurious subtitle change detection.
+	// Fixed in Emby: https://emby.media/community/topic/136349
+	// slices.SortFunc(items, func(a, b fuse.DirEntry) int {
+	// 	return strings.Compare(a.Name, b.Name)
+	// })
 	return fusefs.NewListDirStream(items), 0
 }
 

vfs/dir.go

@@ -1163,14 +1163,16 @@ func (d *Dir) Stat(name string) (node Node, err error) {
 	return node, nil
 }
 
-// ReadDirAll reads the contents of the directory sorted
+// ReadDirAll reads the contents of the directory sorted by name.
 func (d *Dir) ReadDirAll() (items Nodes, err error) {
 	items, err = MapReadDir(d, func(n Node) (Node, error) { return n, nil }, 0)
 	if err != nil {
 		fs.Debugf(d.Path(), "Dir.ReadDirAll error: %v", err)
 		return nil, err
 	}
-	// Compare only the leaf strings of the nodes
+	// POSIX/FUSE readdir does not require sorted output, but ReadDirAll keeps
+	// deterministic ordering for general callers. Mount paths that need to skip
+	// this O(n log n) sort should call MapReadDir directly.
 	slices.SortFunc(items, func(a, b Node) int {
 		return strings.Compare(a.Name(), b.Name())
 	})

vfs/dir_handle_test.go

@@ -76,18 +76,17 @@ func TestDirHandleReaddir(t *testing.T) {
 	assert.False(t, fis[0].IsDir())
 	assert.False(t, fis[1].IsDir())
 
-	fis, err = fh.Readdir(2)
+	fis2, err := fh.Readdir(2)
 	require.NoError(t, err)
-	require.Equal(t, 1, len(fis))
-	assert.Equal(t, "subdir", fis[0].Name())
-	assert.True(t, fis[0].IsDir())
+	require.Equal(t, 1, len(fis2))
+	assert.Equal(t, "subdir", fis2[0].Name())
+	assert.True(t, fis2[0].IsDir())
 
-	fis, err = fh.Readdir(2)
+	fis3, err := fh.Readdir(2)
 	assert.Equal(t, io.EOF, err)
-	require.Equal(t, 0, len(fis))
+	require.Equal(t, 0, len(fis3))
 
 	require.NoError(t, fh.Close())
-
 }
 
 func TestDirHandleReaddirnames(t *testing.T) {