[Virtio-fs] 'FORGET' ordering semantics (vs unlink & NFS)

[Dr. David Alan Gilbert]

Hi,
  On virtio-fs we're hitting a problem with NFS, where
unlinking a file in a directory and then rmdir'ing that
directory fails complaining about the directory not being empty.

The problem here is that if a file has an open fd, NFS doesn't
actually delete the file on unlink, it just renames it to
a hidden file (e.g. .nfs*******).  That open file is there because
the 'FORGET' hasn't completed yet by the time the rmdir is issued.

Question:
  a) In the FUSE protocol, are requests assumed to complete in order;
i.e.  unlink, forget, rmdir   is it required that 'forget' completes
before the rmdir is processed?
     (In virtiofs we've been processing requests, in parallel, and
have sent forgets down a separate queue to keep them out of the way).

  b) 'forget' doesn't send a reply - so the kernel can't wait for the
client to have finished it;  do we need a synchronous forget here?

  c) Has this problem been hit by any other fuse users (with NFS or otherwise)?

Dave

-- 
Dr. David Alan Gilbert / dgilbert at redhat.com / Manchester, UK