Re: [PATCH 2/2] nfsd: only set file_lock.fl_lmops in nfsd4_lockt if a stateowner is found

[Jeff Layton <jlayton@redhat.com>]

On Thu, 22 Jan 2009 13:52:32 -0500
"J. Bruce Fields" <bfields@fieldses.org> wrote:

> On Wed, Jan 21, 2009 at 11:34:51AM -0500, Jeff Layton wrote:
> > nfsd4_lockt does a search for a lockstateowner when building the lock
> > struct to test. If one is found, it'll set fl_owner to it. Regardless of
> > whether that happens, it'll also set fl_lmops.
> > 
> > If a lockstateowner is not found, then we'll have fl_owner set to NULL
> > and fl_lmops set pointing to nfsd_posix_mng_ops. Other parts of the
> > NFSv4 server code assume that fl_owner will point to a valid
> > nfs4_stateowner if fl_lmops is set this way.
> > 
> > This behavior exposed a bug in DLM's GETLK implementation where it
> > wasn't clearing out the fields in the file_lock before filling in
> > conflicting lock info. While we were able to fix this in DLM, it
> > still seems pointless and dangerous to set the fl_lmops this way
> > when we have a NULL lockstateowner.
> > 
> > Signed-off-by: Jeff Layton <jlayton@redhat.com>
> > ---
> >  fs/nfsd/nfs4state.c |    6 ++++--
> >  1 files changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> > index 88db7d3..07d196a 100644
> > --- a/fs/nfsd/nfs4state.c
> > +++ b/fs/nfsd/nfs4state.c
> > @@ -2867,11 +2867,13 @@ nfsd4_lockt(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
> >  
> >  	lockt->lt_stateowner = find_lockstateowner_str(inode,
> >  			&lockt->lt_clientid, &lockt->lt_owner);
> > -	if (lockt->lt_stateowner)
> > +	if (lockt->lt_stateowner) {
> >  		file_lock.fl_owner = (fl_owner_t)lockt->lt_stateowner;
> > +		file_lock.fl_lmops = &nfsd_posix_mng_ops;
> 
> So I think we just shouldn't need this second assignment at all.
> 
> --b.
> 

Do we even need to worry about the lockstateowner at all then? If
fl_lmops isn't set then I think the fl_owner will be basically ignored
by nfs4_set_lock_denied anyway.

> > +	}
> > +
> >  	file_lock.fl_pid = current->tgid;
> >  	file_lock.fl_flags = FL_POSIX;
> > -	file_lock.fl_lmops = &nfsd_posix_mng_ops;
> >  
> >  	file_lock.fl_start = lockt->lt_offset;
> >  	file_lock.fl_end = last_byte_offset(lockt->lt_offset, lockt->lt_length);
> > -- 
> > 1.5.5.6
> > 
> > _______________________________________________
> > NFSv4 mailing list
> > NFSv4@linux-nfs.org
> > http://linux-nfs.org/cgi-bin/mailman/listinfo/nfsv4


-- 
Jeff Layton <jlayton@redhat.com>