Initial commit
Proof-of-concept implementation. Bugs will occur.
This commit is contained in:
279
vendor/github.com/hanwen/go-fuse/v2/fuse/mount_linux.go
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279
vendor/github.com/hanwen/go-fuse/v2/fuse/mount_linux.go
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// Copyright 2016 the Go-FUSE Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package fuse
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import (
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"bytes"
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"fmt"
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"os"
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"os/exec"
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"path"
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"strconv"
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"strings"
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"syscall"
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)
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func unixgramSocketpair() (l, r *os.File, err error) {
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fd, err := syscall.Socketpair(syscall.AF_UNIX, syscall.SOCK_SEQPACKET, 0)
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if err != nil {
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return nil, nil, os.NewSyscallError("socketpair",
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err.(syscall.Errno))
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}
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l = os.NewFile(uintptr(fd[0]), "socketpair-half1")
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r = os.NewFile(uintptr(fd[1]), "socketpair-half2")
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return
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}
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// Create a FUSE FS on the specified mount point without using
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// fusermount.
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func mountDirect(mountPoint string, opts *MountOptions, ready chan<- error) (fd int, err error) {
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fd, err = syscall.Open("/dev/fuse", os.O_RDWR, 0) // use syscall.Open since we want an int fd
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if err != nil {
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return
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}
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// managed to open dev/fuse, attempt to mount
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source := opts.FsName
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if source == "" {
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source = opts.Name
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}
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var flags uintptr = syscall.MS_NOSUID | syscall.MS_NODEV
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if opts.DirectMountFlags != 0 {
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flags = opts.DirectMountFlags
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}
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var st syscall.Stat_t
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err = syscall.Stat(mountPoint, &st)
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if err != nil {
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return
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}
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// some values we need to pass to mount - we do as fusermount does.
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// override possible since opts.Options comes after.
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//
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// Only the options listed below are understood by the kernel:
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// https://elixir.bootlin.com/linux/v6.14.2/source/fs/fuse/inode.c#L772
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// https://elixir.bootlin.com/linux/v6.14.2/source/fs/fs_context.c#L41
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// https://elixir.bootlin.com/linux/v6.14.2/source/fs/fs_context.c#L50
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// Everything else will cause an EINVAL error from syscall.Mount() and
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// a corresponding error message in the kernel logs.
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var r = []string{
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fmt.Sprintf("fd=%d", fd),
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fmt.Sprintf("rootmode=%o", st.Mode&syscall.S_IFMT),
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fmt.Sprintf("user_id=%d", os.Geteuid()),
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fmt.Sprintf("group_id=%d", os.Getegid()),
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// match what we do with fusermount
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fmt.Sprintf("max_read=%d", opts.MaxWrite),
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}
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// In syscall.Mount(), [no]dev/suid/exec must be
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// passed as bits in the flags parameter, not as strings.
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for _, o := range opts.Options {
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switch o {
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case "nodev":
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flags |= syscall.MS_NODEV
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case "dev":
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flags &^= syscall.MS_NODEV
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case "nosuid":
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flags |= syscall.MS_NOSUID
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case "suid":
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flags &^= syscall.MS_NOSUID
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case "noexec":
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flags |= syscall.MS_NOEXEC
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case "exec":
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flags &^= syscall.MS_NOEXEC
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default:
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r = append(r, o)
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}
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}
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if opts.AllowOther {
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r = append(r, "allow_other")
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}
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if opts.IDMappedMount && !opts.containsOption("default_permissions") {
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r = append(r, "default_permissions")
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}
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if opts.Debug {
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opts.Logger.Printf("mountDirect: calling syscall.Mount(%q, %q, %q, %#x, %q)",
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source, mountPoint, "fuse."+opts.Name, flags, strings.Join(r, ","))
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}
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err = syscall.Mount(source, mountPoint, "fuse."+opts.Name, flags, strings.Join(r, ","))
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if err != nil {
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syscall.Close(fd)
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return
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}
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// success
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close(ready)
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return
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}
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// callFusermount calls the `fusermount` suid helper with the right options so
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// that it:
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// * opens `/dev/fuse`
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// * mount()s this file descriptor to `mountPoint`
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// * passes this file descriptor back to us via a unix domain socket
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// This file descriptor is returned as `fd`.
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func callFusermount(mountPoint string, opts *MountOptions) (fd int, err error) {
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local, remote, err := unixgramSocketpair()
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if err != nil {
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return
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}
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defer local.Close()
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defer remote.Close()
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bin, err := fusermountBinary()
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if err != nil {
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return 0, err
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}
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cmd := []string{bin, mountPoint}
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if s := opts.optionsStrings(); len(s) > 0 {
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cmd = append(cmd, "-o", strings.Join(s, ","))
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}
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if opts.Debug {
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opts.Logger.Printf("callFusermount: executing %q", cmd)
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}
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proc, err := os.StartProcess(bin,
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cmd,
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&os.ProcAttr{
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Env: []string{"_FUSE_COMMFD=3"},
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Files: []*os.File{os.Stdin, os.Stdout, os.Stderr, remote}})
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if err != nil {
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return
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}
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w, err := proc.Wait()
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if err != nil {
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return
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}
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if !w.Success() {
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err = fmt.Errorf("fusermount exited with code %v\n", w.Sys())
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return
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}
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fd, err = getConnection(local)
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if err != nil {
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return -1, err
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}
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return
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}
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// Create a FUSE FS on the specified mount point. The returned
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// mount point is always absolute.
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func mount(mountPoint string, opts *MountOptions, ready chan<- error) (fd int, err error) {
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if opts.DirectMount || opts.DirectMountStrict {
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fd, err := mountDirect(mountPoint, opts, ready)
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if err == nil {
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return fd, nil
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} else if opts.Debug {
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opts.Logger.Printf("mount: failed to do direct mount: %s", err)
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}
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if opts.DirectMountStrict {
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return -1, err
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}
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}
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// Magic `/dev/fd/N` mountpoint. See the docs for NewServer() for how this
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// works.
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fd = parseFuseFd(mountPoint)
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if fd >= 0 {
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if opts.Debug {
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opts.Logger.Printf("mount: magic mountpoint %q, using fd %d", mountPoint, fd)
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}
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} else {
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// Usual case: mount via the `fusermount` suid helper
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fd, err = callFusermount(mountPoint, opts)
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if err != nil {
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return
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}
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}
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// golang sets CLOEXEC on file descriptors when they are
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// acquired through normal operations (e.g. open).
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// Buf for fd, we have to set CLOEXEC manually
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syscall.CloseOnExec(fd)
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close(ready)
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return fd, err
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}
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func unmount(mountPoint string, opts *MountOptions) (err error) {
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if opts.DirectMount || opts.DirectMountStrict {
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// Attempt to directly unmount, if fails fallback to fusermount method
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err := syscall.Unmount(mountPoint, 0)
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if err == nil {
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return nil
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}
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if opts.DirectMountStrict {
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return err
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}
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}
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bin, err := fusermountBinary()
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if err != nil {
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return err
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}
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errBuf := bytes.Buffer{}
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cmd := exec.Command(bin, "-u", mountPoint)
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cmd.Stderr = &errBuf
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if opts.Debug {
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opts.Logger.Printf("unmount: executing %q", cmd.Args)
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}
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err = cmd.Run()
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if errBuf.Len() > 0 {
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return fmt.Errorf("%s (code %v)\n",
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errBuf.String(), err)
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}
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return err
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}
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// lookPathFallback - search binary in PATH and, if that fails,
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// in fallbackDir. This is useful if PATH is possible empty.
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func lookPathFallback(file string, fallbackDir string) (string, error) {
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binPath, err := exec.LookPath(file)
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if err == nil {
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return binPath, nil
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}
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abs := path.Join(fallbackDir, file)
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return exec.LookPath(abs)
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}
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// fusermountBinary returns the path to the `fusermount3` binary, or, if not
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// found, the `fusermount` binary.
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func fusermountBinary() (string, error) {
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if path, err := lookPathFallback("fusermount3", "/bin"); err == nil {
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return path, nil
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}
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return lookPathFallback("fusermount", "/bin")
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}
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func umountBinary() (string, error) {
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return lookPathFallback("umount", "/bin")
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}
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func getMaxWrite() int {
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return maxPageLimit() * syscall.Getpagesize()
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}
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func maxPageLimit() (lim int) {
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lim = 256
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d, err := os.ReadFile("/proc/sys/fs/fuse/max_pages_limit")
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if err != nil {
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return lim
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}
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newLim, err := strconv.Atoi(string(d))
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if err != nil {
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return lim
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}
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return newLim
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}
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