fusefrontend: Rework the Utimens handling on macOS.

For Linux, everything effectively stays the same. For both path-based and
fd-based Utimens() calls, we use unix.UtimesNanoAt(). To avoid introducing
a separate syscall wrapper for futimens() (as done in go-fuse, for example),
we instead use the /proc/self/fd - trick.

On macOS, this changes quite a lot:

* Path-based Utimens() calls were previously completely broken, since
  unix.UtimensNanoAt() ignores the passed file descriptor. Note that this
  cannot be fixed easily since there IS no appropriate syscall available on
  macOS prior to High Sierra (10.13). We emulate this case by using
  Fchdir() + setattrlist().

* Fd-based Utimens() calls were previously translated to f.GetAttr() (to
  fill any empty parameters) and syscall.Futimes(), which does not does
  support nanosecond precision. Both issues can be fixed by switching to
  fsetattrlist().

Fixes https://github.com/rfjakob/gocryptfs/issues/350
This commit is contained in:
Sebastian Lackner 2019-01-16 15:38:32 +01:00 committed by Jakob Unterwurzacher
parent 1d2ce9c213
commit 682e642cfa
4 changed files with 113 additions and 8 deletions

View File

@ -44,8 +44,6 @@ type File struct {
qIno openfiletable.QIno
// Entry in the open file table
fileTableEntry *openfiletable.Entry
// go-fuse nodefs.loopbackFile
loopbackFile nodefs.File
// Store where the last byte was written
lastWrittenOffset int64
// The opCount is used to judge whether "lastWrittenOffset" is still
@ -75,7 +73,6 @@ func NewFile(fd *os.File, fs *FS) (*File, fuse.Status) {
contentEnc: fs.contentEnc,
qIno: qi,
fileTableEntry: e,
loopbackFile: nodefs.NewLoopbackFile(fd),
fs: fs,
File: nodefs.NewDefaultFile(),
}, fuse.OK
@ -474,5 +471,6 @@ func (f *File) GetAttr(a *fuse.Attr) fuse.Status {
func (f *File) Utimens(a *time.Time, m *time.Time) fuse.Status {
f.fdLock.RLock()
defer f.fdLock.RUnlock()
return f.loopbackFile.Utimens(a, m)
err := syscallcompat.FutimesNano(f.intFd(), a, m)
return fuse.ToStatus(err)
}

View File

@ -372,10 +372,7 @@ func (fs *FS) Utimens(path string, a *time.Time, m *time.Time, context *fuse.Con
return fuse.ToStatus(err)
}
defer syscall.Close(dirfd)
ts := make([]unix.Timespec, 2)
ts[0] = unix.Timespec(fuse.UtimeToTimespec(a))
ts[1] = unix.Timespec(fuse.UtimeToTimespec(m))
err = unix.UtimesNanoAt(dirfd, cName, ts, unix.AT_SYMLINK_NOFOLLOW)
err = syscallcompat.UtimesNanoAtNofollow(dirfd, cName, a, m)
return fuse.ToStatus(err)
}

View File

@ -2,8 +2,11 @@ package syscallcompat
import (
"log"
"path/filepath"
"runtime"
"syscall"
"time"
"unsafe"
"golang.org/x/sys/unix"
@ -33,6 +36,24 @@ func pthread_setugid_np(uid uint32, gid uint32) (err error) {
return
}
// Unfortunately fsetattrlist does not have a syscall wrapper yet.
func fsetattrlist(fd int, list unsafe.Pointer, buf unsafe.Pointer, size uintptr, options int) (err error) {
_, _, e1 := syscall.Syscall6(syscall.SYS_FSETATTRLIST, uintptr(fd), uintptr(list), uintptr(buf), uintptr(size), uintptr(options), 0)
if e1 != 0 {
err = e1
}
return
}
// Setattrlist already has a syscall wrapper, but it is not exported.
func setattrlist(path *byte, list unsafe.Pointer, buf unsafe.Pointer, size uintptr, options int) (err error) {
_, _, e1 := syscall.Syscall6(syscall.SYS_SETATTRLIST, uintptr(unsafe.Pointer(path)), uintptr(list), uintptr(buf), uintptr(size), uintptr(options), 0)
if e1 != 0 {
err = e1
}
return
}
// Sorry, fallocate is not available on OSX at all and
// fcntl F_PREALLOCATE is not accessible from Go.
// See https://github.com/rfjakob/gocryptfs/issues/18 if you want to help.
@ -125,6 +146,72 @@ func MkdiratUser(dirfd int, path string, mode uint32, context *fuse.Context) (er
return Mkdirat(dirfd, path, mode)
}
type attrList struct {
bitmapCount uint16
_ uint16
CommonAttr uint32
VolAttr uint32
DirAttr uint32
FileAttr uint32
Forkattr uint32
}
func timesToAttrList(a *time.Time, m *time.Time) (attrList attrList, attributes [2]unix.Timespec) {
attrList.bitmapCount = unix.ATTR_BIT_MAP_COUNT
attrList.CommonAttr = 0
i := 0
if m != nil {
attributes[i] = unix.Timespec(fuse.UtimeToTimespec(m))
attrList.CommonAttr |= unix.ATTR_CMN_MODTIME
i += 1
}
if a != nil {
attributes[i] = unix.Timespec(fuse.UtimeToTimespec(a))
attrList.CommonAttr |= unix.ATTR_CMN_ACCTIME
i += 1
}
return attrList, attributes
}
// FutimesNano syscall.
func FutimesNano(fd int, a *time.Time, m *time.Time) (err error) {
attrList, attributes := timesToAttrList(a, m)
return fsetattrlist(fd, unsafe.Pointer(&attrList), unsafe.Pointer(&attributes),
unsafe.Sizeof(attributes), 0)
}
// UtimesNanoAtNofollow is like UtimesNanoAt but never follows symlinks.
//
// Unfortunately we cannot use unix.UtimesNanoAt since it is broken and just
// ignores the provided 'dirfd'. In addition, it also lacks handling of 'nil'
// pointers (used to preserve one of both timestamps).
func UtimesNanoAtNofollow(dirfd int, path string, a *time.Time, m *time.Time) (err error) {
if !filepath.IsAbs(path) {
chdirMutex.Lock()
defer chdirMutex.Unlock()
var cwd int
cwd, err = syscall.Open(".", syscall.O_RDONLY, 0)
if err != nil {
return err
}
defer syscall.Close(cwd)
err = syscall.Fchdir(dirfd)
if err != nil {
return err
}
defer syscall.Fchdir(cwd)
}
_p0, err := syscall.BytePtrFromString(path)
if err != nil {
return err
}
attrList, attributes := timesToAttrList(a, m)
return setattrlist(_p0, unsafe.Pointer(&attrList), unsafe.Pointer(&attributes),
unsafe.Sizeof(attributes), unix.FSOPT_NOFOLLOW)
}
func Getdents(fd int) ([]fuse.DirEntry, error) {
return emulateGetdents(fd)
}

View File

@ -6,6 +6,7 @@ import (
"runtime"
"sync"
"syscall"
"time"
"golang.org/x/sys/unix"
@ -191,6 +192,28 @@ func MkdiratUser(dirfd int, path string, mode uint32, context *fuse.Context) (er
return Mkdirat(dirfd, path, mode)
}
func timesToTimespec(a *time.Time, m *time.Time) []unix.Timespec {
ts := make([]unix.Timespec, 2)
ts[0] = unix.Timespec(fuse.UtimeToTimespec(a))
ts[1] = unix.Timespec(fuse.UtimeToTimespec(m))
return ts
}
// FutimesNano syscall.
func FutimesNano(fd int, a *time.Time, m *time.Time) (err error) {
ts := timesToTimespec(a, m)
// To avoid introducing a separate syscall wrapper for futimens()
// (as done in go-fuse, for example), we instead use the /proc/self/fd trick.
procPath := fmt.Sprintf("/proc/self/fd/%d", fd)
return unix.UtimesNanoAt(unix.AT_FDCWD, procPath, ts, 0)
}
// UtimesNanoAtNofollow is like UtimesNanoAt but never follows symlinks.
func UtimesNanoAtNofollow(dirfd int, path string, a *time.Time, m *time.Time) (err error) {
ts := timesToTimespec(a, m)
return unix.UtimesNanoAt(dirfd, path, ts, unix.AT_SYMLINK_NOFOLLOW)
}
// Getdents syscall.
func Getdents(fd int) ([]fuse.DirEntry, error) {
return getdents(fd)