mirror of
https://gitea.com/Lydanne/buildx.git
synced 2025-11-04 10:03:42 +08:00
102 lines
3.0 KiB
Go
102 lines
3.0 KiB
Go
package mountinfo
|
|
|
|
import (
|
|
"os"
|
|
"path/filepath"
|
|
|
|
"golang.org/x/sys/unix"
|
|
)
|
|
|
|
// MountedFast is a method of detecting a mount point without reading
|
|
// mountinfo from procfs. A caller can only trust the result if no error
|
|
// and sure == true are returned. Otherwise, other methods (e.g. parsing
|
|
// /proc/mounts) have to be used. If unsure, use Mounted instead (which
|
|
// uses MountedFast, but falls back to parsing mountinfo if needed).
|
|
//
|
|
// If a non-existent path is specified, an appropriate error is returned.
|
|
// In case the caller is not interested in this particular error, it should
|
|
// be handled separately using e.g. errors.Is(err, fs.ErrNotExist).
|
|
//
|
|
// This function is only available on Linux. When available (since kernel
|
|
// v5.6), openat2(2) syscall is used to reliably detect all mounts. Otherwise,
|
|
// the implementation falls back to using stat(2), which can reliably detect
|
|
// normal (but not bind) mounts.
|
|
func MountedFast(path string) (mounted, sure bool, err error) {
|
|
// Root is always mounted.
|
|
if path == string(os.PathSeparator) {
|
|
return true, true, nil
|
|
}
|
|
|
|
path, err = normalizePath(path)
|
|
if err != nil {
|
|
return false, false, err
|
|
}
|
|
mounted, sure, err = mountedFast(path)
|
|
return
|
|
}
|
|
|
|
// mountedByOpenat2 is a method of detecting a mount that works for all kinds
|
|
// of mounts (incl. bind mounts), but requires a recent (v5.6+) linux kernel.
|
|
func mountedByOpenat2(path string) (bool, error) {
|
|
dir, last := filepath.Split(path)
|
|
|
|
dirfd, err := unix.Openat2(unix.AT_FDCWD, dir, &unix.OpenHow{
|
|
Flags: unix.O_PATH | unix.O_CLOEXEC,
|
|
})
|
|
if err != nil {
|
|
return false, &os.PathError{Op: "openat2", Path: dir, Err: err}
|
|
}
|
|
fd, err := unix.Openat2(dirfd, last, &unix.OpenHow{
|
|
Flags: unix.O_PATH | unix.O_CLOEXEC | unix.O_NOFOLLOW,
|
|
Resolve: unix.RESOLVE_NO_XDEV,
|
|
})
|
|
_ = unix.Close(dirfd)
|
|
switch err { //nolint:errorlint // unix errors are bare
|
|
case nil: // definitely not a mount
|
|
_ = unix.Close(fd)
|
|
return false, nil
|
|
case unix.EXDEV: // definitely a mount
|
|
return true, nil
|
|
}
|
|
// not sure
|
|
return false, &os.PathError{Op: "openat2", Path: path, Err: err}
|
|
}
|
|
|
|
// mountedFast is similar to MountedFast, except it expects a normalized path.
|
|
func mountedFast(path string) (mounted, sure bool, err error) {
|
|
// Root is always mounted.
|
|
if path == string(os.PathSeparator) {
|
|
return true, true, nil
|
|
}
|
|
|
|
// Try a fast path, using openat2() with RESOLVE_NO_XDEV.
|
|
mounted, err = mountedByOpenat2(path)
|
|
if err == nil {
|
|
return mounted, true, nil
|
|
}
|
|
|
|
// Another fast path: compare st.st_dev fields.
|
|
mounted, err = mountedByStat(path)
|
|
// This does not work for bind mounts, so false negative
|
|
// is possible, therefore only trust if return is true.
|
|
if mounted && err == nil {
|
|
return true, true, nil
|
|
}
|
|
|
|
return
|
|
}
|
|
|
|
func mounted(path string) (bool, error) {
|
|
path, err := normalizePath(path)
|
|
if err != nil {
|
|
return false, err
|
|
}
|
|
mounted, sure, err := mountedFast(path)
|
|
if sure && err == nil {
|
|
return mounted, nil
|
|
}
|
|
|
|
// Fallback to parsing mountinfo.
|
|
return mountedByMountinfo(path)
|
|
}
|