syscallcompat: convert Getdents to fd input, add emulation

Now that we have Fstatat we can use it in Getdents to
get rid of the path name.

Also, add an emulated version of getdents for MacOS. This allows
to drop the !HaveGetdents special cases from fusefrontend.

Modify the getdents test to test both native getdents and the emulated
version.
libgocryptfs
Jakob Unterwurzacher 5 years ago
parent e33593d30d
commit 70bcf58a9b
  1. 22
      internal/fusefrontend/fs_dir.go
  2. 29
      internal/syscallcompat/getdents_linux.go
  3. 50
      internal/syscallcompat/getdents_other.go
  4. 22
      internal/syscallcompat/getdents_test.go
  5. 7
      internal/syscallcompat/sys_linux.go

@ -271,20 +271,14 @@ func (fs *FS) OpenDir(dirName string, context *fuse.Context) ([]fuse.DirEntry, f
cDirAbsPath := filepath.Join(fs.args.Cipherdir, cDirName)
var cipherEntries []fuse.DirEntry
var status fuse.Status
if syscallcompat.HaveGetdents {
// Getdents avoids calling Lstat on each file.
cipherEntries, err = syscallcompat.Getdents(cDirAbsPath)
if err != nil {
return nil, fuse.ToStatus(err)
}
} else {
haveGetdentsWarnOnce.Do(func() {
tlog.Warn.Printf("OpenDir: Getdents not available, falling back to OpenDir")
})
cipherEntries, status = fs.FileSystem.OpenDir(cDirName, context)
if !status.Ok() {
return nil, status
}
fd, err := syscall.Open(cDirAbsPath, syscall.O_RDONLY|syscall.O_NOFOLLOW, 0)
if err != nil {
return nil, fuse.ToStatus(err)
}
defer syscall.Close(fd)
cipherEntries, err = syscallcompat.Getdents(fd)
if err != nil {
return nil, fuse.ToStatus(err)
}
// Get DirIV (stays nil if PlaintextNames is used)
var cachedIV []byte

@ -12,26 +12,17 @@ import (
"syscall"
"unsafe"
"golang.org/x/sys/unix"
"github.com/hanwen/go-fuse/fuse"
"github.com/rfjakob/gocryptfs/internal/tlog"
)
// HaveGetdents is true if we have a working implementation of Getdents
const HaveGetdents = true
const sizeofDirent = int(unsafe.Sizeof(syscall.Dirent{}))
// Getdents wraps syscall.Getdents and converts the result to []fuse.DirEntry.
// The function takes a path instead of an fd because we need to be able to
// call Lstat on files. Fstatat is not yet available in Go as of v1.9:
// https://github.com/golang/go/issues/14216
func Getdents(dir string) ([]fuse.DirEntry, error) {
fd, err := syscall.Open(dir, syscall.O_RDONLY, 0)
if err != nil {
return nil, err
}
defer syscall.Close(fd)
// getdents wraps syscall.Getdents and converts the result to []fuse.DirEntry.
func getdents(fd int) ([]fuse.DirEntry, error) {
// Collect syscall result in smartBuf.
// "bytes.Buffer" is smart about expanding the capacity and avoids the
// exponential runtime of simple append().
@ -84,7 +75,7 @@ func Getdents(dir string) ([]fuse.DirEntry, error) {
// os.File.Readdir() drops "." and "..". Let's be compatible.
continue
}
mode, err := convertDType(s.Type, dir+"/"+name)
mode, err := convertDType(fd, name, s.Type)
if err != nil {
// The file may have been deleted in the meantime. Just skip it
// and go on.
@ -125,17 +116,17 @@ func getdentsName(s syscall.Dirent) (string, error) {
var dtUnknownWarnOnce sync.Once
// convertDType converts a Dirent.Type to at Stat_t.Mode value.
func convertDType(dtype uint8, file string) (uint32, error) {
func convertDType(dirfd int, name string, dtype uint8) (uint32, error) {
if dtype != syscall.DT_UNKNOWN {
// Shift up by four octal digits = 12 bits
return uint32(dtype) << 12, nil
}
// DT_UNKNOWN: we have to call Lstat()
// DT_UNKNOWN: we have to call stat()
dtUnknownWarnOnce.Do(func() {
tlog.Warn.Printf("Getdents: convertDType: received DT_UNKNOWN, falling back to Lstat")
tlog.Warn.Printf("Getdents: convertDType: received DT_UNKNOWN, falling back to stat")
})
var st syscall.Stat_t
err := syscall.Lstat(file, &st)
var st unix.Stat_t
err := Fstatat(dirfd, name, &st, unix.AT_SYMLINK_NOFOLLOW)
if err != nil {
return 0, err
}

@ -1,17 +1,49 @@
// +build !linux
package syscallcompat
import (
"log"
"os"
"syscall"
"golang.org/x/sys/unix"
"github.com/hanwen/go-fuse/fuse"
)
// HaveGetdents is true if we have a working implementation of Getdents
const HaveGetdents = false
func Getdents(dir string) ([]fuse.DirEntry, error) {
log.Panic("only implemented on Linux")
return nil, nil
// 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))
for _, name := range names {
var st unix.Stat_t
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.
continue
}
if err != nil {
return nil, err
}
newEntry := fuse.DirEntry{
Name: name,
Mode: uint32(st.Mode) & syscall.S_IFMT,
Ino: st.Ino,
}
out = append(out, newEntry)
}
return out, nil
}

@ -12,9 +12,19 @@ import (
"github.com/hanwen/go-fuse/fuse"
)
var getdentsUnderTest = getdents
func TestGetdents(t *testing.T) {
t.Logf("testing native getdents")
testGetdents(t)
t.Logf("testing emulateGetdents")
getdentsUnderTest = emulateGetdents
testGetdents(t)
}
func testGetdents(t *testing.T) {
// Fill a directory with filenames of length 1 ... 255
testDir, err := ioutil.TempDir("", "TestGetdents")
testDir, err := ioutil.TempDir(tmpDir, "TestGetdents")
if err != nil {
t.Fatal(err)
}
@ -35,17 +45,21 @@ func TestGetdents(t *testing.T) {
if err != nil {
t.Fatal(err)
}
defer fd.Close()
readdirEntries, err := fd.Readdir(0)
if err != nil {
t.Fatal(err)
}
fd.Close()
readdirMap := make(map[string]*syscall.Stat_t)
for _, v := range readdirEntries {
readdirMap[v.Name()] = fuse.ToStatT(v)
}
// Read using our Getdents()
getdentsEntries, err := Getdents(dir)
// Read using our Getdents() implementation
_, err = fd.Seek(0, 0) // Rewind directory
if err != nil {
t.Fatal(err)
}
getdentsEntries, err := getdentsUnderTest(int(fd.Fd()))
if err != nil {
t.Fatal(err)
}

@ -7,6 +7,8 @@ import (
"golang.org/x/sys/unix"
"github.com/hanwen/go-fuse/fuse"
"github.com/rfjakob/gocryptfs/internal/tlog"
)
@ -115,3 +117,8 @@ func Fstatat(dirfd int, path string, stat *unix.Stat_t, flags int) (err error) {
}
return unix.Fstatat(dirfd, path, stat, flags)
}
// Getdents syscall.
func Getdents(fd int) ([]fuse.DirEntry, error) {
return getdents(fd)
}

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