[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>
diff --git a/include/linux/mount.h b/include/linux/mount.h
index 7e133ae..dd4e83e 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -21,6 +21,7 @@
#define MNT_NODEV 0x02
#define MNT_NOEXEC 0x04
#define MNT_SHARED 0x10 /* if the vfsmount is a shared mount */
+#define MNT_UNBINDABLE 0x20 /* if the vfsmount is a unbindable mount */
#define MNT_PNODE_MASK 0x30 /* propogation flag mask */
struct vfsmount {