[PATCH] unbindable mounts

An unbindable mount does not forward or receive propagation.  Also
unbindable mount disallows bind mounts.  The semantics is as follows.

Bind semantics:
  It is invalid to bind mount an unbindable mount.

Move semantics:
  It is invalid to move an unbindable mount under shared mount.

Clone-namespace semantics:
  If a mount is unbindable in the parent namespace, the corresponding
  cloned mount in the child namespace becomes unbindable too.  Note:
  there is subtle difference, unbindable mounts cannot be bind mounted
  but can be cloned during clone-namespace.

Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/pnode.h b/fs/pnode.h
index b59f0e9fe6b1..020e1bb60fdb 100644
--- a/fs/pnode.h
+++ b/fs/pnode.h
@@ -15,6 +15,7 @@
 #define IS_MNT_SLAVE(mnt) (mnt->mnt_master)
 #define IS_MNT_NEW(mnt)  (!mnt->mnt_namespace)
 #define CLEAR_MNT_SHARED(mnt) (mnt->mnt_flags &= ~MNT_SHARED)
+#define IS_MNT_UNBINDABLE(mnt) (mnt->mnt_flags & MNT_UNBINDABLE)
 
 #define CL_EXPIRE               0x01
 #define CL_SLAVE                0x02