[RFC v5 0/1] ns: introduce binfmt_misc namespace

v5: Use READ_ONCE()/WRITE_ONCE() move mount pointer struct init to bm_fill_super() and add smp_wmb() remove useless NULL value init add WARN_ON_ONCE() v4: first user namespace is initialized with _binfmt_ns, all new user namespaces are initialized with a NULL and use the one

[RFC v5 0/1] ns: introduce binfmt_misc namespace

v5: Use READ_ONCE()/WRITE_ONCE() move mount pointer struct init to bm_fill_super() and add smp_wmb() remove useless NULL value init add WARN_ON_ONCE() v4: first user namespace is initialized with _binfmt_ns, all new user namespaces are initialized with a NULL and use the one