mirror of
https://github.com/ceph/ceph-csi.git
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533994daff
kubernetes/kubernetes#111083 has been merged and synced into k8s.io/mount-utils. This should remove any systemd log messages while calling NodeStageVolume and NodeGetVolumeStats. Signed-off-by: Niels de Vos <ndevos@redhat.com>
102 lines
3.0 KiB
Go
102 lines
3.0 KiB
Go
package mountinfo
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import (
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"os"
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"path/filepath"
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"golang.org/x/sys/unix"
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)
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// MountedFast is a method of detecting a mount point without reading
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// mountinfo from procfs. A caller can only trust the result if no error
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// and sure == true are returned. Otherwise, other methods (e.g. parsing
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// /proc/mounts) have to be used. If unsure, use Mounted instead (which
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// uses MountedFast, but falls back to parsing mountinfo if needed).
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//
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// If a non-existent path is specified, an appropriate error is returned.
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// In case the caller is not interested in this particular error, it should
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// be handled separately using e.g. errors.Is(err, os.ErrNotExist).
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//
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// This function is only available on Linux. When available (since kernel
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// v5.6), openat2(2) syscall is used to reliably detect all mounts. Otherwise,
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// the implementation falls back to using stat(2), which can reliably detect
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// normal (but not bind) mounts.
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func MountedFast(path string) (mounted, sure bool, err error) {
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// Root is always mounted.
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if path == string(os.PathSeparator) {
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return true, true, nil
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}
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path, err = normalizePath(path)
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if err != nil {
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return false, false, err
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}
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mounted, sure, err = mountedFast(path)
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return
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}
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// mountedByOpenat2 is a method of detecting a mount that works for all kinds
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// of mounts (incl. bind mounts), but requires a recent (v5.6+) linux kernel.
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func mountedByOpenat2(path string) (bool, error) {
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dir, last := filepath.Split(path)
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dirfd, err := unix.Openat2(unix.AT_FDCWD, dir, &unix.OpenHow{
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Flags: unix.O_PATH | unix.O_CLOEXEC,
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})
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if err != nil {
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return false, &os.PathError{Op: "openat2", Path: dir, Err: err}
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}
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fd, err := unix.Openat2(dirfd, last, &unix.OpenHow{
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Flags: unix.O_PATH | unix.O_CLOEXEC | unix.O_NOFOLLOW,
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Resolve: unix.RESOLVE_NO_XDEV,
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})
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_ = unix.Close(dirfd)
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switch err { //nolint:errorlint // unix errors are bare
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case nil: // definitely not a mount
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_ = unix.Close(fd)
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return false, nil
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case unix.EXDEV: // definitely a mount
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return true, nil
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}
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// not sure
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return false, &os.PathError{Op: "openat2", Path: path, Err: err}
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}
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// mountedFast is similar to MountedFast, except it expects a normalized path.
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func mountedFast(path string) (mounted, sure bool, err error) {
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// Root is always mounted.
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if path == string(os.PathSeparator) {
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return true, true, nil
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}
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// Try a fast path, using openat2() with RESOLVE_NO_XDEV.
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mounted, err = mountedByOpenat2(path)
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if err == nil {
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return mounted, true, nil
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}
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// Another fast path: compare st.st_dev fields.
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mounted, err = mountedByStat(path)
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// This does not work for bind mounts, so false negative
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// is possible, therefore only trust if return is true.
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if mounted && err == nil {
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return true, true, nil
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}
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return
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}
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func mounted(path string) (bool, error) {
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path, err := normalizePath(path)
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if err != nil {
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return false, err
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}
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mounted, sure, err := mountedFast(path)
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if sure && err == nil {
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return mounted, nil
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}
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// Fallback to parsing mountinfo.
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return mountedByMountinfo(path)
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}
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