This function arms a flag (MNT_SPECIAL) on the vfs, to avoid
refcounting on permanent system vfs.
Use this function for sockets, pipes, anonymous fds.

(socket8 bench result : from 2.94s to 2.23s)

Signed-off-by: Eric Dumazet <redacted>
---
 fs/anon_inodes.c      |    2 +-
 fs/pipe.c             |    2 +-
 fs/super.c            |    9 +++++++++
 include/linux/fs.h    |    1 +
 include/linux/mount.h |    5 +++--
 net/socket.c          |    2 +-
 6 files changed, 16 insertions(+), 5 deletions(-)