[PATCH 0/3] smb/client(cifs): prepare for locking changes.

[NeilBrown]

I am working on changes to directory locking.  The medium term goal is
to lift d_alloc_parallel() locking above i_rwsem, so d_alloc_paralle()
can be run unlocked, and consequently cannot be called when ->i_rwsem is
held.

The requires:
 1/ that d_alloc_parallel() not be called while i_rwsem is held.  cifs
    does this in a couple of places.  A new interface d_alloc_trylock()
    is now available and can be used instead.

 2/ a dentry must not be d_drop()ed while an operation is ongoing, as an
    unlocked d_alloc_parallel() would then be able to create a new
    dentry with the same name.  In particular d_rehash() must be phased
    out as it won't be safe.  This particularly affects the mechanism to
    block lookups/revalidates while an unlink/rename is happening.  The
    mechanism is changed to use one similar to how NFS addresses this
    needed, though using the new LOOKUP_PRIVATE flag.

The patches depend on patches recently added to the vfs tree.  I would
prefer these land in that tree too with an Acked-by or similar from cifs
maintainers.

Thanks,
NeilBrown

 [PATCH 1/3] smb/client: don't unhash and rehash to prevent new opens.
 [PATCH 2/3] smb/client: use d_alloc_trylock in cifs_silly_fullpath()
 [PATCH 3/3] smb/client: Use d_alloc_trylock() in cifs_prime_dcache()