Patch from Shyam attached (tentatively merged into cifs-2.6.git
for-next). See his description below:

The num_remote_opens counter keeps track of the number of open files
which must be maintained by the server at any point. This is a
per-tree-connect counter, and the value of this counter gets displayed
in the /proc/fs/cifs/Stats output as a following...

    Open files: 0 total (local), 1 open on server
                                 ^^^^^^^^^^^^^^^^
    As a thumb-rule, we want to increment this counter for each
open/create that we successfully execute on the server. Similarly, we
should decrement the counter when we successfully execute a close.

    In this case, an increment was being missed in case of smb2_query_dir_first,
    in case of successful open. As a result, we would underflow the
counter and we could even see the counter go to negative after
sufficient smb2_query_dir_first calls.

    I tested the stats counter for a bunch of filesystem operations
with the fix.
    And it looks like the counter looks correct to me.

    I also check if we missed the increments and decrements elsewhere.
It does not seem so. Few other cases where an open is done and we
don't increment the counter are
    the compound calls where the corresponding close is also sent in
the request.

-- 
Thanks,

Steve