[PATCH v2 0/9] nfs: prepare for VFS locking changes.

[NeilBrown]

sashiko reported some problem with the previous posting.  A lot
were false positives as it used the wrong base.  However:
3/9 had inverted the return code from nfs_neg_need_reval() - it returns
    1 for "must revalidate" unlike d_revalidate which returns 0.
8/9 didn't handle and error from nfs_lookup() correctly - it
    should be fatal rather than triggering a retry.

Original intro below.
Thanks,
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.

 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.  Various techiniques are used to avoid the
    need for d_drop(), particularly that d_splice_alias() is now able to
    splice a hashed alias.

Further, the first two patches here fixes bugs that I found while
developing and reviewing these changes.

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 NFS
maintainers.

Thanks,
NeilBrown

 [PATCH v2 1/9] nfs: fix open-blocking with d_fsdata
 [PATCH v2 2/9] nfs: fix nfs_call_unlink()
 [PATCH v2 3/9] nfs: remove d_drop()/d_alloc_parallel() from
 [PATCH v2 4/9] nfs: use d_splice_alias() in nfs_link()
 [PATCH v2 5/9] nfs: don't d_drop() before d_splice_alias()
 [PATCH v2 6/9] nfs: don't d_drop() before d_splice_alias() in
 [PATCH v2 7/9] nfs: Use d_alloc_trylock() in nfs_prime_dcache()
 [PATCH v2 8/9] nfs: use d_alloc_trylock() in silly-rename
 [PATCH v2 9/9] nfs: use d_duplicate()