Re: [PATCH RFC 02/24] filelock: add a lm_set_conflict lease_manager callback

Jeff Layton
2024-03-18T11:07:13Z

On Sun, 2024-03-17 at 10:56 -0400, Chuck Lever wrote:
> On Fri, Mar 15, 2024 at 12:52:53PM -0400, Jeff Layton wrote:
> > The NFSv4.1 protocol adds support for directory delegations, but it
> > specifies that if you already have a delegation and try to request a new
> > one on the same filehandle, the server must reply that the delegation is
> > unavailable.
> >
> > Add a new lease_manager callback to allow the lease manager (nfsd in
> > this case) to impose extra checks when performing a setlease.
> >
> > Signed-off-by: Jeff Layton <jlayton@kernel.org>
> > ---
> > fs/locks.c | 5 +++++
> > include/linux/filelock.h | 10 ++++++++++
> > 2 files changed, 15 insertions(+)
> >
> > diff --git a/fs/locks.c b/fs/locks.c
> > index cb4b35d26162..415cca8e9565 100644
> > --- a/fs/locks.c
> > +++ b/fs/locks.c
> > @@ -1822,6 +1822,11 @@ generic_add_lease(struct file *filp, int arg, struct file_lease **flp, void **pr
> > continue;
> > }
> >
> > + /* Allow the lease manager to veto the setlease */
> > + if (lease->fl_lmops->lm_set_conflict &&
> > + lease->fl_lmops->lm_set_conflict(lease, fl))
> > + goto out;
> > +
> > /*
> > * No exclusive leases if someone else has a lease on
> > * this file:
> > diff --git a/include/linux/filelock.h b/include/linux/filelock.h
> > index daee999d05f3..c5fc768087df 100644
> > --- a/include/linux/filelock.h
> > +++ b/include/linux/filelock.h
> > @@ -49,6 +49,16 @@ struct lease_manager_operations {
> > int (*lm_change)(struct file_lease *, int, struct list_head *);
> > void (*lm_setup)(struct file_lease *, void **);
> > bool (*lm_breaker_owns_lease)(struct file_lease *);
> > +
> > + /**
> > + * lm_set_conflict - extra conditions for setlease
> > + * @new: new file_lease being set
> > + * @old: old (extant) file_lease
> > + *
> > + * This allows the lease manager to add extra conditions when
> > + * setting a lease.
>
> To make it clear which return value causes add_lease() to abort, I'd
> rather see API contract-style descriptions of the meaning of the
> return values instead of this design note. Something like:
>
> * Return values:
> * %true: @new and @old conflict
> * %false: No conflict detected
>
>

Thanks. I added this to the patch in my tree.

> > + */
> > + bool (*lm_set_conflict)(struct file_lease *new, struct file_lease *old);
> > };
> >
> > struct lock_manager {
> >
> > --
> > 2.44.0
> >
>

--
Jeff Layton <jlayton@kernel.org>