Merge tag 'vfs-7.4-rc1.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull mount updates from Christian Brauner:
 "This adds OPEN_TREE_DROP_MNTNS_MOUNTS.

  crun started using OPEN_TREE_NAMESPACE to set up the container's mount
  namespace and open_tree(OPEN_TREE_CLONE) for the sources of its bind
  mounts. That fails on any host with a mount namespace pinned below
  such a source. The recursive clone picks the pinned namespace up and
  move_mount() refuses to attach the tree with ELOOP. Only a younger
  mount namespace may ever be bound into an older one or mount namespace
  references could form a loop. A namespace created with
  OPEN_TREE_NAMESPACE is younger than everything else on the system so
  from inside it every pinned namespace is older. By the time this fails
  setns() has run and the host tree is out of reach, so the runtime has
  to predict the situation beforehand and lose the optimization. snapd
  pins mount namespaces under /run/snapd/ns so on Ubuntu that is any
  container bind mounting the host root.

  Every other path crossing a mount namespace boundary already leaves
  these mounts behind, copy_mnt_ns() and create_new_namespace() both do.
  Only get_detached_copy() asks for them.

  The new flag lets a caller get a clone without them. It stays opt-in
  because open_tree(OPEN_TREE_CLONE) plus move_mount() is mount --rbind
  through a file descriptor and dropping them by default would silently
  lose /run/snapd/ns/*.mnt on a live system. It requires AT_RECURSIVE,
  is a no-op with OPEN_TREE_NAMESPACE and skips locked nsfs mounts the
  way copy_mnt_ns() does, so nothing new is exposed. Selftests are
  included"

* tag 'vfs-7.4-rc1.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  selftests/filesystems: test OPEN_TREE_DROP_MNTNS_MOUNTS
  mount: add OPEN_TREE_DROP_MNTNS_MOUNTS

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