linux.git/tools/testing/selftests/filesystems/move_mount, branch master Linux kernel source tree selftests/filesystems: add MOVE_MOUNT_BENEATH rootfs tests 2026-03-12T12:34:59+00:00 Christian Brauner brauner@kernel.org 2026-02-24T00:40:28+00:00 bb5c17bc863d1ac9ee0d51d300d5399d632fe69f Add tests for mounting beneath the rootfs using MOVE_MOUNT_BENEATH: - beneath_rootfs_success: mount beneath /, fchdir, chroot, umount2 MNT_DETACH -- verify root changed - beneath_rootfs_old_root_stacked: after mount-beneath, verify old root parent is clone via statmount - beneath_rootfs_in_chroot_fail: chroot into subdir of same mount, mount-beneath fails (dentry != mnt_root) - beneath_rootfs_in_chroot_success: chroot into separate tmpfs mount, mount-beneath succeeds - beneath_rootfs_locked_transfer: in user+mount ns: mount-beneath rootfs succeeds, MNT_LOCKED transfers, old root unmountable - beneath_rootfs_locked_containment: in user+mount ns: after full root-switch workflow, new root is MNT_LOCKED (containment preserved) - beneath_non_rootfs_locked_transfer: mounts created before unshare(CLONE_NEWUSER | CLONE_NEWNS) become locked; mount-beneath transfers MNT_LOCKED, displaced mount can be unmounted - beneath_non_rootfs_locked_containment: same setup, verify new mount is MNT_LOCKED (containment preserved) Link: https://patch.msgid.link/20260224-work-mount-beneath-rootfs-v1-3-8c58bf08488f@kernel.org Signed-off-by: Christian Brauner <brauner@kernel.org> 
Add tests for mounting beneath the rootfs using MOVE_MOUNT_BENEATH:

- beneath_rootfs_success: mount beneath /, fchdir, chroot, umount2
  MNT_DETACH -- verify root changed
- beneath_rootfs_old_root_stacked: after mount-beneath, verify old root
  parent is clone via statmount
- beneath_rootfs_in_chroot_fail: chroot into subdir of same mount,
  mount-beneath fails (dentry != mnt_root)
- beneath_rootfs_in_chroot_success: chroot into separate tmpfs mount,
  mount-beneath succeeds
- beneath_rootfs_locked_transfer: in user+mount ns: mount-beneath
  rootfs succeeds, MNT_LOCKED transfers, old root unmountable
- beneath_rootfs_locked_containment: in user+mount ns: after full
  root-switch workflow, new root is MNT_LOCKED (containment preserved)
- beneath_non_rootfs_locked_transfer: mounts created before
  unshare(CLONE_NEWUSER | CLONE_NEWNS) become locked; mount-beneath
  transfers MNT_LOCKED, displaced mount can be unmounted
- beneath_non_rootfs_locked_containment: same setup, verify new mount
  is MNT_LOCKED (containment preserved)

Link: https://patch.msgid.link/20260224-work-mount-beneath-rootfs-v1-3-8c58bf08488f@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>