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

Jeff Layton
2024-03-15T16:53:13Z

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);
};

struct lock_manager {

--
2.44.0