Just a couple of questions though -- the semantics of reserved_lookup
are a little different, as you're no longer using dentry->d_mounts. Was
this the intent? Seems like dget(result->d_mounts) is still
appropriate.
The other question is in regards to d_move -- it appears to be possible
for the old dentry to no longer be hashed, as someone could have done a
d_drop on it after the original lookup. This would confuse your hash
swapping tricks, and it looks like both dentries would get put on the
new parent's hash chain. Perhaps it's safer to just do the slower
unhash/re-hash? d_move shouldn't be performance critical anyway.
Regards,
Bill