489 lines
13 KiB
Go
489 lines
13 KiB
Go
package fusefrontend
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import (
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"context"
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"syscall"
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"golang.org/x/sys/unix"
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"github.com/hanwen/go-fuse/v2/fs"
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"github.com/hanwen/go-fuse/v2/fuse"
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"github.com/rfjakob/gocryptfs/v2/internal/nametransform"
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"github.com/rfjakob/gocryptfs/v2/internal/syscallcompat"
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"github.com/rfjakob/gocryptfs/v2/internal/tlog"
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)
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// Node is a file or directory in the filesystem tree
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// in a gocryptfs mount.
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type Node struct {
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fs.Inode
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}
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// Lookup - FUSE call for discovering a file.
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func (n *Node) Lookup(ctx context.Context, name string, out *fuse.EntryOut) (ch *fs.Inode, errno syscall.Errno) {
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dirfd, cName, errno := n.prepareAtSyscall(name)
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if errno != 0 {
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return
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}
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defer syscall.Close(dirfd)
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// Get device number and inode number into `st`
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st, err := syscallcompat.Fstatat2(dirfd, cName, unix.AT_SYMLINK_NOFOLLOW)
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if err != nil {
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return nil, fs.ToErrno(err)
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}
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// Create new inode and fill `out`
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ch = n.newChild(ctx, st, out)
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// Translate ciphertext size in `out.Attr.Size` to plaintext size
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n.translateSize(dirfd, cName, &out.Attr)
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rn := n.rootNode()
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if rn.args.SharedStorage {
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// If we already have a child node that matches what we found on disk*
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// (as reflected in `ch`), return it here.
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//
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// This keeps the Node ID for each directory entry stable
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// (until forgotten).
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//
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// *We compare `name`, `Ino`, `Mode` (but not `Gen`!)
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old := n.Inode.GetChild(name)
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if old != nil &&
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old.StableAttr().Ino == ch.StableAttr().Ino &&
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// `Mode` has already been masked with syscall.S_IFMT by n.newChild()
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old.StableAttr().Mode == ch.StableAttr().Mode {
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return old, 0
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}
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}
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return ch, 0
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}
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// GetAttr - FUSE call for stat()ing a file.
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//
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// GetAttr is symlink-safe through use of openBackingDir() and Fstatat().
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func (n *Node) Getattr(ctx context.Context, f fs.FileHandle, out *fuse.AttrOut) (errno syscall.Errno) {
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// If the kernel gives us a file handle, use it.
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if f != nil {
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return f.(fs.FileGetattrer).Getattr(ctx, out)
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}
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dirfd, cName, errno := n.prepareAtSyscallMyself()
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if errno != 0 {
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return
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}
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defer syscall.Close(dirfd)
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st, err := syscallcompat.Fstatat2(dirfd, cName, unix.AT_SYMLINK_NOFOLLOW)
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if err != nil {
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return fs.ToErrno(err)
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}
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// Fix inode number
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rn := n.rootNode()
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rn.inoMap.TranslateStat(st)
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out.Attr.FromStat(st)
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// Translate ciphertext size in `out.Attr.Size` to plaintext size
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n.translateSize(dirfd, cName, &out.Attr)
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if rn.args.ForceOwner != nil {
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out.Owner = *rn.args.ForceOwner
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}
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return 0
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}
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// Unlink - FUSE call. Delete a file.
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//
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// Symlink-safe through use of Unlinkat().
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func (n *Node) Unlink(ctx context.Context, name string) (errno syscall.Errno) {
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dirfd, cName, errno := n.prepareAtSyscall(name)
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if errno != 0 {
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return
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}
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defer syscall.Close(dirfd)
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// Delete content
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err := syscallcompat.Unlinkat(dirfd, cName, 0)
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if err != nil {
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return fs.ToErrno(err)
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}
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// Delete ".name" file
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if !n.rootNode().args.PlaintextNames && nametransform.IsLongContent(cName) {
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err = nametransform.DeleteLongNameAt(dirfd, cName)
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if err != nil {
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tlog.Warn.Printf("Unlink: could not delete .name file: %v", err)
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}
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}
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return fs.ToErrno(err)
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}
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// Readlink - FUSE call.
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//
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// Symlink-safe through openBackingDir() + Readlinkat().
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func (n *Node) Readlink(ctx context.Context) (out []byte, errno syscall.Errno) {
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dirfd, cName, errno := n.prepareAtSyscallMyself()
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if errno != 0 {
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return
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}
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defer syscall.Close(dirfd)
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return n.readlink(dirfd, cName)
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}
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// Setattr - FUSE call. Called for chmod, truncate, utimens, ...
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func (n *Node) Setattr(ctx context.Context, f fs.FileHandle, in *fuse.SetAttrIn, out *fuse.AttrOut) (errno syscall.Errno) {
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// Use the fd if the kernel gave us one
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if f != nil {
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f2 := f.(*File)
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return f2.Setattr(ctx, in, out)
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}
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dirfd, cName, errno := n.prepareAtSyscallMyself()
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if errno != 0 {
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return
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}
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defer syscall.Close(dirfd)
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// chmod(2)
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//
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// gocryptfs.diriv & gocryptfs.longname.[sha256].name files do NOT get chmod'ed
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// or chown'ed with their parent file/dir for simplicity.
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// See nametransform/perms.go for details.
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if mode, ok := in.GetMode(); ok {
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errno = fs.ToErrno(syscallcompat.FchmodatNofollow(dirfd, cName, mode))
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if errno != 0 {
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return errno
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}
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}
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// chown(2)
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uid32, uOk := in.GetUID()
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gid32, gOk := in.GetGID()
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if uOk || gOk {
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uid := -1
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gid := -1
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if uOk {
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uid = int(uid32)
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}
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if gOk {
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gid = int(gid32)
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}
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errno = fs.ToErrno(syscallcompat.Fchownat(dirfd, cName, uid, gid, unix.AT_SYMLINK_NOFOLLOW))
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if errno != 0 {
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return errno
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}
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}
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// utimens(2)
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mtime, mok := in.GetMTime()
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atime, aok := in.GetATime()
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if mok || aok {
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ap := &atime
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mp := &mtime
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if !aok {
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ap = nil
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}
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if !mok {
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mp = nil
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}
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errno = fs.ToErrno(syscallcompat.UtimesNanoAtNofollow(dirfd, cName, ap, mp))
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if errno != 0 {
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return errno
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}
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}
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// For truncate, the user has to have write permissions. That means we can
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// depend on opening a RDWR fd and letting the File handle truncate.
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if sz, ok := in.GetSize(); ok {
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f, _, errno := n.Open(ctx, syscall.O_RDWR)
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if errno != 0 {
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return errno
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}
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f2 := f.(*File)
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defer f2.Release(ctx)
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errno = syscall.Errno(f2.truncate(sz))
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if errno != 0 {
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return errno
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}
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return f2.Getattr(ctx, out)
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}
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return n.Getattr(ctx, nil, out)
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}
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// StatFs - FUSE call. Returns information about the filesystem.
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//
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// Symlink-safe because the path is ignored.
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func (n *Node) Statfs(ctx context.Context, out *fuse.StatfsOut) syscall.Errno {
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p := n.rootNode().args.Cipherdir
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var st syscall.Statfs_t
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err := syscall.Statfs(p, &st)
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if err != nil {
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return fs.ToErrno(err)
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}
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out.FromStatfsT(&st)
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return 0
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}
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// Mknod - FUSE call. Create a device file.
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//
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// Symlink-safe through use of Mknodat().
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func (n *Node) Mknod(ctx context.Context, name string, mode, rdev uint32, out *fuse.EntryOut) (inode *fs.Inode, errno syscall.Errno) {
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dirfd, cName, errno := n.prepareAtSyscall(name)
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if errno != 0 {
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return
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}
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defer syscall.Close(dirfd)
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// Make sure context is nil if we don't want to preserve the owner
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rn := n.rootNode()
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if !rn.args.PreserveOwner {
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ctx = nil
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}
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// Create ".name" file to store long file name (except in PlaintextNames mode)
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var err error
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ctx2 := toFuseCtx(ctx)
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if !rn.args.PlaintextNames && nametransform.IsLongContent(cName) {
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err := rn.nameTransform.WriteLongNameAt(dirfd, cName, name)
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if err != nil {
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errno = fs.ToErrno(err)
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return
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}
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// Create "gocryptfs.longfile." device node
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err = syscallcompat.MknodatUser(dirfd, cName, mode, int(rdev), ctx2)
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if err != nil {
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nametransform.DeleteLongNameAt(dirfd, cName)
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}
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} else {
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// Create regular device node
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err = syscallcompat.MknodatUser(dirfd, cName, mode, int(rdev), ctx2)
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}
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if err != nil {
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errno = fs.ToErrno(err)
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return
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}
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st, err := syscallcompat.Fstatat2(dirfd, cName, unix.AT_SYMLINK_NOFOLLOW)
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if err != nil {
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errno = fs.ToErrno(err)
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return
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}
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inode = n.newChild(ctx, st, out)
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return inode, 0
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}
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// Link - FUSE call. Creates a hard link at "newPath" pointing to file
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// "oldPath".
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//
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// Symlink-safe through use of Linkat().
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func (n *Node) Link(ctx context.Context, target fs.InodeEmbedder, name string, out *fuse.EntryOut) (inode *fs.Inode, errno syscall.Errno) {
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dirfd, cName, errno := n.prepareAtSyscall(name)
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if errno != 0 {
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return
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}
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defer syscall.Close(dirfd)
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n2 := toNode(target)
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dirfd2, cName2, errno := n2.prepareAtSyscallMyself()
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if errno != 0 {
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return
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}
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defer syscall.Close(dirfd2)
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// Handle long file name (except in PlaintextNames mode)
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rn := n.rootNode()
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var err error
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if !rn.args.PlaintextNames && nametransform.IsLongContent(cName) {
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err = rn.nameTransform.WriteLongNameAt(dirfd, cName, name)
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if err != nil {
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errno = fs.ToErrno(err)
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return
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}
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// Create "gocryptfs.longfile." link
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err = unix.Linkat(dirfd2, cName2, dirfd, cName, 0)
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if err != nil {
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nametransform.DeleteLongNameAt(dirfd, cName)
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}
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} else {
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// Create regular link
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err = unix.Linkat(dirfd2, cName2, dirfd, cName, 0)
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}
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if err != nil {
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errno = fs.ToErrno(err)
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return
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}
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st, err := syscallcompat.Fstatat2(dirfd, cName, unix.AT_SYMLINK_NOFOLLOW)
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if err != nil {
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errno = fs.ToErrno(err)
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return
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}
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inode = n.newChild(ctx, st, out)
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return inode, 0
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}
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// Symlink - FUSE call. Create a symlink.
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//
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// Symlink-safe through use of Symlinkat.
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func (n *Node) Symlink(ctx context.Context, target, name string, out *fuse.EntryOut) (inode *fs.Inode, errno syscall.Errno) {
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dirfd, cName, errno := n.prepareAtSyscall(name)
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if errno != 0 {
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return
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}
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defer syscall.Close(dirfd)
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// Make sure context is nil if we don't want to preserve the owner
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rn := n.rootNode()
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if !rn.args.PreserveOwner {
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ctx = nil
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}
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cTarget := target
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if !rn.args.PlaintextNames {
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// Symlinks are encrypted like file contents (GCM) and base64-encoded
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cTarget = rn.encryptSymlinkTarget(target)
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}
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// Create ".name" file to store long file name (except in PlaintextNames mode)
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var err error
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ctx2 := toFuseCtx(ctx)
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if !rn.args.PlaintextNames && nametransform.IsLongContent(cName) {
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err = rn.nameTransform.WriteLongNameAt(dirfd, cName, name)
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if err != nil {
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return nil, fs.ToErrno(err)
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}
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// Create "gocryptfs.longfile." symlink
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err = syscallcompat.SymlinkatUser(cTarget, dirfd, cName, ctx2)
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if err != nil {
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nametransform.DeleteLongNameAt(dirfd, cName)
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return nil, fs.ToErrno(err)
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}
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} else {
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// Create symlink
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err = syscallcompat.SymlinkatUser(cTarget, dirfd, cName, ctx2)
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if err != nil {
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return nil, fs.ToErrno(err)
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}
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}
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st, err := syscallcompat.Fstatat2(dirfd, cName, unix.AT_SYMLINK_NOFOLLOW)
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if err != nil {
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return nil, fs.ToErrno(err)
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}
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// Report the plaintext size, not the encrypted blob size
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st.Size = int64(len(target))
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inode = n.newChild(ctx, st, out)
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return inode, 0
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}
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// xfstests generic/013 now also exercises RENAME_EXCHANGE and RENAME_WHITEOUT,
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// uncovering lots of problems with longnames
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//
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// Reject those flags with syscall.EINVAL.
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// If we can handle the flags, this function returns 0.
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func rejectRenameFlags(flags uint32) syscall.Errno {
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// Normal rename, we can handle that
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if flags == 0 {
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return 0
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}
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// We also can handle RENAME_NOREPLACE
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if flags == syscallcompat.RENAME_NOREPLACE {
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return 0
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}
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// We cannot handle RENAME_EXCHANGE and RENAME_WHITEOUT yet.
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// Needs extra code for .name files.
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return syscall.EINVAL
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}
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// Rename - FUSE call.
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// This function is called on the PARENT DIRECTORY of `name`.
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//
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// Symlink-safe through Renameat().
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func (n *Node) Rename(ctx context.Context, name string, newParent fs.InodeEmbedder, newName string, flags uint32) (errno syscall.Errno) {
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if errno = rejectRenameFlags(flags); errno != 0 {
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return errno
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}
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dirfd, cName, errno := n.prepareAtSyscall(name)
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if errno != 0 {
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return
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}
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defer syscall.Close(dirfd)
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n2 := toNode(newParent)
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dirfd2, cName2, errno := n2.prepareAtSyscall(newName)
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if errno != 0 {
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return
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}
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defer syscall.Close(dirfd2)
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// Easy case.
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rn := n.rootNode()
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if rn.args.PlaintextNames {
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return fs.ToErrno(syscallcompat.Renameat2(dirfd, cName, dirfd2, cName2, uint(flags)))
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}
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// Long destination file name: create .name file
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nameFileAlreadyThere := false
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var err error
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if nametransform.IsLongContent(cName2) {
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err = rn.nameTransform.WriteLongNameAt(dirfd2, cName2, newName)
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// Failure to write the .name file is expected when the target path already
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// exists. Since hashes are pretty unique, there is no need to modify the
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// .name file in this case, and we ignore the error.
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if err == syscall.EEXIST {
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nameFileAlreadyThere = true
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} else if err != nil {
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return fs.ToErrno(err)
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}
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}
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// Actual rename
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tlog.Debug.Printf("Renameat %d/%s -> %d/%s\n", dirfd, cName, dirfd2, cName2)
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err = syscallcompat.Renameat2(dirfd, cName, dirfd2, cName2, uint(flags))
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if (flags&syscallcompat.RENAME_NOREPLACE == 0) && (err == syscall.ENOTEMPTY || err == syscall.EEXIST) {
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// If an empty directory is overwritten we will always get an error as
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// the "empty" directory will still contain gocryptfs.diriv.
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// Interestingly, ext4 returns ENOTEMPTY while xfs returns EEXIST.
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// We handle that by trying to fs.Rmdir() the target directory and trying
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// again.
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tlog.Debug.Printf("Rename: Handling ENOTEMPTY")
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if n2.Rmdir(ctx, newName) == 0 {
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err = syscallcompat.Renameat2(dirfd, cName, dirfd2, cName2, uint(flags))
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}
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}
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if err != nil {
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if nametransform.IsLongContent(cName2) && !nameFileAlreadyThere {
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// Roll back .name creation unless the .name file was already there
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nametransform.DeleteLongNameAt(dirfd2, cName2)
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}
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return fs.ToErrno(err)
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}
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if nametransform.IsLongContent(cName) {
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nametransform.DeleteLongNameAt(dirfd, cName)
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}
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return 0
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}
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// Fsync: handles FUSE opcodes FSYNC & FDIRSYNC
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//
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// Note: f is always set to nil by go-fuse
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func (n *Node) Fsync(ctx context.Context, f fs.FileHandle, flags uint32) syscall.Errno {
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dirfd, cName, errno := n.prepareAtSyscallMyself()
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if errno != 0 {
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return errno
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}
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defer syscall.Close(dirfd)
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fd, err := syscallcompat.Openat(dirfd, cName, syscall.O_RDONLY|syscall.O_NOFOLLOW, 0)
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if err != nil {
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return fs.ToErrno(err)
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}
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defer syscall.Close(fd)
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return fs.ToErrno(syscall.Fsync(fd))
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}
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