syscallcompat: add GetdentsSpecial()

GetdentsSpecial calls then Getdents syscall,
with normal entries and "." / ".." split into two slices.

internal/syscallcompat/getdents_linux.go

@@ -27,7 +27,7 @@ const sizeofDirent = int(unsafe.Sizeof(unix.Dirent{}))
 const maxReclen = 280
 
 // getdents wraps unix.Getdents and converts the result to []fuse.DirEntry.
-func getdents(fd int) ([]fuse.DirEntry, error) {
+func getdents(fd int) (entries []fuse.DirEntry, entriesSpecial []fuse.DirEntry, err error) {
 	// Collect syscall result in smartBuf.
 	// "bytes.Buffer" is smart about expanding the capacity and avoids the
 	// exponential runtime of simple append().
@@ -44,9 +44,9 @@ func getdents(fd int) ([]fuse.DirEntry, error) {
 		} else if err != nil {
 			if smartBuf.Len() > 0 {
 				tlog.Warn.Printf("warning: unix.Getdents returned errno %d in the middle of data ( https://github.com/rfjakob/gocryptfs/issues/483 )", err.(syscall.Errno))
-				return nil, syscall.EIO
+				return nil, nil, syscall.EIO
 			}
-			return nil, err
+			return nil, nil, err
 		}
 		if n == 0 {
 			break
@@ -66,12 +66,12 @@ func getdents(fd int) ([]fuse.DirEntry, error) {
 			tlog.Warn.Printf("Getdents: corrupt entry #%d: Reclen=0 at offset=%d. Returning EBADR",
 				numEntries, offset)
 			// EBADR = Invalid request descriptor
-			return nil, syscall.EBADR
+			return nil, nil, syscall.EBADR
 		}
 		if int(s.Reclen) > maxReclen {
 			tlog.Warn.Printf("Getdents: corrupt entry #%d: Reclen=%d > %d. Returning EBADR",
 				numEntries, s.Reclen, maxReclen)
-			return nil, syscall.EBADR
+			return nil, nil, syscall.EBADR
 		}
 		offset += int(s.Reclen)
 		numEntries++
@@ -80,17 +80,22 @@ func getdents(fd int) ([]fuse.DirEntry, error) {
 	// Note: syscall.ParseDirent() only returns the names,
 	// we want all the data, so we have to implement
 	// it on our own.
-	entries := make([]fuse.DirEntry, 0, numEntries)
+	entries = make([]fuse.DirEntry, 0, numEntries)
 	offset = 0
 	for offset < len(buf) {
 		s := *(*unix.Dirent)(unsafe.Pointer(&buf[offset]))
 		name, err := getdentsName(s)
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
 		offset += int(s.Reclen)
 		if name == "." || name == ".." {
-			// os.File.Readdir() drops "." and "..". Let's be compatible.
+			// These are always directories, no need to call convertDType.
+			entriesSpecial = append(entriesSpecial, fuse.DirEntry{
+				Ino:  s.Ino,
+				Mode: syscall.S_IFDIR,
+				Name: name,
+			})
 			continue
 		}
 		mode, err := convertDType(fd, name, s.Type)
@@ -105,7 +110,7 @@ func getdents(fd int) ([]fuse.DirEntry, error) {
 			Name: name,
 		})
 	}
-	return entries, nil
+	return entries, entriesSpecial, nil
 }
 
 // getdentsName extracts the filename from a Dirent struct and returns it as

internal/syscallcompat/getdents_other.go

@@ -9,27 +9,11 @@ import (
 	"github.com/hanwen/go-fuse/v2/fuse"
 )
 
-// emulateGetdents reads all directory entries from the open directory "fd"
-// and returns them in a fuse.DirEntry slice.
-func emulateGetdents(fd int) (out []fuse.DirEntry, err error) {
-	// os.File closes the fd in its finalizer. Duplicate the fd to not affect
-	// the original fd.
-	newFd, err := syscall.Dup(fd)
-	if err != nil {
-		return nil, err
-	}
-	f := os.NewFile(uintptr(newFd), "")
-	defer f.Close()
-	// Get all file names in the directory
-	names, err := f.Readdirnames(0)
-	if err != nil {
-		return nil, err
-	}
-	// Stat all of them and convert to fuse.DirEntry
-	out = make([]fuse.DirEntry, 0, len(names))
+func fillDirEntries(fd int, names []string) ([]fuse.DirEntry, error) {
+	out := make([]fuse.DirEntry, 0, len(names))
 	for _, name := range names {
 		var st unix.Stat_t
-		err = Fstatat(fd, name, &st, unix.AT_SYMLINK_NOFOLLOW)
+		err := Fstatat(fd, name, &st, unix.AT_SYMLINK_NOFOLLOW)
 		if err == syscall.ENOENT {
 			// File disappeared between readdir and stat. Pretend we did not
 			// see it.
@@ -47,3 +31,31 @@ func emulateGetdents(fd int) (out []fuse.DirEntry, err error) {
 	}
 	return out, nil
 }
+
+// emulateGetdents reads all directory entries from the open directory "fd"
+// and returns normal entries and "." / ".." split into two slices.
+func emulateGetdents(fd int) (out []fuse.DirEntry, outSpecial []fuse.DirEntry, err error) {
+	// os.File closes the fd in its finalizer. Duplicate the fd to not affect
+	// the original fd.
+	newFd, err := syscall.Dup(fd)
+	if err != nil {
+		return nil, nil, err
+	}
+	f := os.NewFile(uintptr(newFd), "")
+	defer f.Close()
+	// Get all file names in the directory
+	names, err := f.Readdirnames(0)
+	if err != nil {
+		return nil, nil, err
+	}
+	// Stat all the names and convert to fuse.DirEntry
+	out, err = fillDirEntries(fd, names)
+	if err != nil {
+		return nil, nil, err
+	}
+	outSpecial, err = fillDirEntries(fd, []string{".", ".."})
+	if err != nil {
+		return nil, nil, err
+	}
+	return out, outSpecial, nil
+}

internal/syscallcompat/getdents_test.go

@@ -83,7 +83,7 @@ func testGetdents(t *testing.T) {
 		if err != nil {
 			t.Fatal(err)
 		}
-		getdentsEntries, err := getdentsUnderTest(int(fd.Fd()))
+		getdentsEntries, special, err := getdentsUnderTest(int(fd.Fd()))
 		if err != nil {
 			t.Log(err)
 			skipOnGccGo(t)
@@ -114,5 +114,20 @@ func testGetdents(t *testing.T) {
 				}
 			}
 		}
+		if len(special) != 2 {
+			t.Error(special)
+		}
+		if !(special[0].Name == "." && special[1].Name == ".." ||
+			special[1].Name == "." && special[0].Name == "..") {
+			t.Error(special)
+		}
+		for _, v := range special {
+			if v.Ino == 0 {
+				t.Error(v)
+			}
+			if v.Mode != syscall.S_IFDIR {
+				t.Error(v)
+			}
+		}
 	}
 }

internal/syscallcompat/sys_darwin.go

@@ -216,6 +216,11 @@ func UtimesNanoAtNofollow(dirfd int, path string, a *time.Time, m *time.Time) (e
 }
 
 func Getdents(fd int) ([]fuse.DirEntry, error) {
+	entries, _, err := emulateGetdents(fd)
+	return entries, err
+}
+
+func GetdentsSpecial(fd int) (entries []fuse.DirEntry, entriesSpecial []fuse.DirEntry, err error) {
 	return emulateGetdents(fd)
 }
 

internal/syscallcompat/sys_linux.go

@@ -244,8 +244,15 @@ func UtimesNanoAtNofollow(dirfd int, path string, a *time.Time, m *time.Time) (e
 	return err
 }
 
-// Getdents syscall.
+// Getdents syscall with "." and ".." filtered out.
 func Getdents(fd int) ([]fuse.DirEntry, error) {
+	entries, _, err := getdents(fd)
+	return entries, err
+}
+
+// GetdentsSpecial calls the Getdents syscall,
+// with normal entries and "." / ".." split into two slices.
+func GetdentsSpecial(fd int) (entries []fuse.DirEntry, entriesSpecial []fuse.DirEntry, err error) {
 	return getdents(fd)
 }