FWIW, I've folded that pile into vfs.git#work.autofs.
Problems:
* (fixed) __path_is_mountpoint() should _not_ treat NULL from
__lookup_mnt() as "nothing's mounted there" until it has checked
that mount_lock hadn't been touched - mount --move on something unrelated
can race with lockless hash lookup and lead to false negatives.
* linux/mount.h might be the wrong place for path_is_mountpoint().
Or it shouldn't be inlined. I don't like the includes you've added there.
* path_has_submounts() is broken. At the very least, it's
AB-BA between mount_lock and rename_lock. I would suggest trying to
put read_seqlock_excl(&mount_lock) around the call of d_walk() in there,
and using __lookup_mnt() in the callback (without retries on the mount_lock,
of course - read_seqlock_excl done on the outside is enough). I'm not sure
if it won't cause trouble with contention, though; that needs testing. As
it is, that function is broken in #work.autofs, same as it is in -mm and
-next.
* the last one (propagation-related) is too ugly to live - at the
very least, its pieces should live in fs/pnode.c; exposing propagate_next()
is simply wrong. I hadn't picked that one at all, and I would suggest
coordinating anything in that area with ebiederman - he has some work
around fs/pnode.c and you risk stepping on his toes.
