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

Christian Brauner
2024-03-20T13:13:58Z

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.
> + */
> + bool (*lm_set_conflict)(struct file_lease *new, struct file_lease *old);

Minor, but it seems a bit misnamed to me. I'd recommend calling this
lm_may_set_lease() or lm_may_lease().