Here's a first stab at a patchset to close a potential race when setting
a delegation on a file. Between the point where we open the file and
where we set the delegation, another task or client could unlink or
rename the dentry. If that occurs, we shouldn't hand out a delegation
in the open response, but we don't prevent that today.

The basic idea here is to re-do the lookup after setting the delegation.
If the resulting dentry is not the one we have in the open, then we can
reject handing out a delegation.

Only lightly tested, so this is an RFC for now.

Jeff Layton (3):
  nfsd: drop fh argument from alloc_init_deleg
  nfsd: rework arguments to nfs4_set_delegation
  nfsd: vet the opened dentry after setting a delegation

 fs/nfsd/nfs4state.c | 65 ++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 55 insertions(+), 10 deletions(-)

-- 
2.36.1