Re: [PATCH RFC] NFSD: Fix possible sleep during nfsd4_release_lockowner()

[bfields@fieldses.org (J. Bruce Fields)]

On Mon, May 23, 2022 at 03:43:28PM -0400, Jeff Layton wrote:
> On Mon, 2022-05-23 at 19:35 +0000, Chuck Lever III wrote:
> > 
> > > On May 23, 2022, at 1:38 PM, Jeff Layton <jlayton@kernel.org> wrote:
> > > 
> > > On Mon, 2022-05-23 at 17:25 +0000, Chuck Lever III wrote:
> > > > 
> > > > > On May 23, 2022, at 12:37 PM, Jeff Layton <jlayton@kernel.org> wrote:
> > > > > 
> > > > > His suggestion was just to keep a counter in the lockowner of how many
> > > > > locks are associated with it. That seems like a good suggestion, though
> > > > > you'd probably need to add a parameter to lm_get_owner to indicate
> > > > > whether you were adding a new lock or just doing a conflock copy.
> > > > 
> > > > locks_copy_conflock() would need to take a boolean parameter
> > > > that callers would set when they actually manipulate a lock.
> > > > 
> > > 
> > > Yep. You'd also have to add a bool arg to lm_put_owner so that you know
> > > whether you need to decrement the counter.
> > 
> > It's the lm_put_owner() side that looks less than straightforward.
> > Suggestions and advice welcome there.
> > 
> 
> Maybe add a new fl_flags value that indicates that a particular lock is
> a conflock and not a lock record? Then locks_release_private could use
> that to pass the appropriate argument to lm_put_owner.
> 
> That's probably simpler overall than trying to audit all of the
> locks_free_lock callers.

Should conflock parameters really be represented by file_lock structures
at all?  It always seemed a little wrong to me.  But, that's a bit of
derail, apologies.

--b.