Re: CIFS VFS

["Petr Vandrovec" <VANDROVE@vc.cvut.cz>]

On  1 Oct 02 at 19:42, Matthew Wilcox wrote:
> 
> On Tue, Oct 01, 2002 at 12:30:28PM -0500, Steven French wrote:
> > 8) Byte Range and File locks
> 
> there's some changes in progress around file locking in 2.5... let
> me know your requirements.

If I can place ncpfs's requirements here... 

For ncpfs easiest interface would be one which:

(1) does not merge locks; Netware does not do that, you must release
    exact records you locked, otherwise unlock will fail.
    
(2) first resolve locks locally, and then, if you succesfully obtained 
    lock locally, consult filesystem's lock method; ncpfs must do it 
    that way because of there is only one server filehandle for each 
    opened file, and so from server's view there is only one entity on 
    connection.

I would be also satisfied with interface F_GETLK uses: call default
posix_test_lock only if filesystem returned LOCK_USE_CLNT: in such
case filesystem can return < 0 on failure, LOCK_USE_CLNT when
lock succeeded, but kernel should do local bookkeeping itself,
or 0 when lock succeeded, and inode's i_flock was already updated.

If current method (first call filesystem, then obtain lock locally) is 
going to stay, then I believe that we should call F_UNLOCK when 
filesystem's lock succeeded, but local posix_lock_file failed (either 
due to EAGAIN or EINTR or ...). Otherwise server is never notified
that lock was not acquired by workstation, and will be never released.

                                                    Petr Vandrovec
                                                    vandrove@vc.cvut.cz