[PATCH 0/9] afs: 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/ the d_alloc_parallel() not be called while i_rwsem is held.  NFS does
    this in a few places. New interfaces d_alloc_trylock() and d_duplicate()
    are now available and can be used instead.  In one case we must drop
    and reclaim the lock and LOOKUP_SHARED helps with that.

 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 affect 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 AFS
maintainers.

Thanks,
NeilBrown

 [PATCH 1/5] afs: don't unhash/rehash dentries during unlink/rename
 [PATCH 2/5] afs: use d_splice_alias() in afs_vnode_new_inode()
 [PATCH 3/5] afs: use d_alloc_trylock in afs_sillyrename()
 [PATCH 4/5] afs: lookup_atsys to drop and reclaim lock.
 [PATCH 5/5] afs: use d_duplicate()