diff --git a/staging/src/k8s.io/mount-utils/mount_linux.go b/staging/src/k8s.io/mount-utils/mount_linux.go index 7d18072304766..07ce76de1986a 100644 --- a/staging/src/k8s.io/mount-utils/mount_linux.go +++ b/staging/src/k8s.io/mount-utils/mount_linux.go @@ -33,6 +33,7 @@ import ( "time" "github.com/moby/sys/mountinfo" + "golang.org/x/sys/unix" "k8s.io/klog/v2" utilexec "k8s.io/utils/exec" @@ -55,6 +56,11 @@ const ( errNotMounted = "not mounted" ) +var ( + // Error statx support since Linux 4.11, https://man7.org/linux/man-pages/man2/statx.2.html + errStatxNotSupport = errors.New("the statx syscall is not supported. At least Linux kernel 4.11 is needed") +) + // Mounter provides the default implementation of mount.Interface // for the linux platform. This implementation assumes that the // kubelet is running in the host's root mount namespace. @@ -385,14 +391,20 @@ func (*Mounter) List() ([]MountPoint, error) { return ListProcMounts(procMountsPath) } -// IsLikelyNotMountPoint determines if a directory is not a mountpoint. -// It is fast but not necessarily ALWAYS correct. If the path is in fact -// a bind mount from one part of a mount to another it will not be detected. -// It also can not distinguish between mountpoints and symbolic links. -// mkdir /tmp/a /tmp/b; mount --bind /tmp/a /tmp/b; IsLikelyNotMountPoint("/tmp/b") -// will return true. When in fact /tmp/b is a mount point. If this situation -// is of interest to you, don't use this function... -func (mounter *Mounter) IsLikelyNotMountPoint(file string) (bool, error) { +func statx(file string) (unix.Statx_t, error) { + var stat unix.Statx_t + if err := unix.Statx(0, file, unix.AT_STATX_DONT_SYNC, 0, &stat); err != nil { + if err == unix.ENOSYS { + return stat, errStatxNotSupport + } + + return stat, err + } + + return stat, nil +} + +func (mounter *Mounter) isLikelyNotMountPointStat(file string) (bool, error) { stat, err := os.Stat(file) if err != nil { return true, err @@ -409,6 +421,51 @@ func (mounter *Mounter) IsLikelyNotMountPoint(file string) (bool, error) { return true, nil } +func (mounter *Mounter) isLikelyNotMountPointStatx(file string) (bool, error) { + var stat, rootStat unix.Statx_t + var err error + + if stat, err = statx(file); err != nil { + return true, err + } + + if stat.Attributes_mask != 0 { + if stat.Attributes_mask&unix.STATX_ATTR_MOUNT_ROOT != 0 { + if stat.Attributes&unix.STATX_ATTR_MOUNT_ROOT != 0 { + // file is a mountpoint + return false, nil + } else { + // no need to check rootStat if unix.STATX_ATTR_MOUNT_ROOT supported + return true, nil + } + } + } + + root := filepath.Dir(strings.TrimSuffix(file, "/")) + if rootStat, err = statx(root); err != nil { + return true, err + } + + return (stat.Dev_major == rootStat.Dev_major && stat.Dev_minor == rootStat.Dev_minor), nil +} + +// IsLikelyNotMountPoint determines if a directory is not a mountpoint. +// It is fast but not necessarily ALWAYS correct. If the path is in fact +// a bind mount from one part of a mount to another it will not be detected. +// It also can not distinguish between mountpoints and symbolic links. +// mkdir /tmp/a /tmp/b; mount --bind /tmp/a /tmp/b; IsLikelyNotMountPoint("/tmp/b") +// will return true. When in fact /tmp/b is a mount point. If this situation +// is of interest to you, don't use this function... +func (mounter *Mounter) IsLikelyNotMountPoint(file string) (bool, error) { + notMountPoint, err := mounter.isLikelyNotMountPointStatx(file) + if errors.Is(err, errStatxNotSupport) { + // fall back to isLikelyNotMountPointStat + return mounter.isLikelyNotMountPointStat(file) + } + + return notMountPoint, err +} + // CanSafelySkipMountPointCheck relies on the detected behavior of umount when given a target that is not a mount point. func (mounter *Mounter) CanSafelySkipMountPointCheck() bool { return mounter.withSafeNotMountedBehavior