bpf: Convert bpf_cpumask to bpf_mem_cache_free_rcu.

Convert bpf_cpumask to bpf_mem_cache_free_rcu.
Note that migrate_disable() in bpf_cpumask_release() is still necessary, since
bpf_cpumask_release() is a dtor. bpf_obj_free_fields() can be converted to do
migrate_disable() there in a follow up.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/bpf/20230706033447.54696-14-alexei.starovoitov@gmail.com

diff --git a/kernel/bpf/cpumask.c b/kernel/bpf/cpumask.c
index 938a60f..6983af8 100644 (file)
--- a/kernel/bpf/cpumask.c
+++ b/kernel/bpf/cpumask.c
@@ -9,7 +9,6 @@
 /**
  * struct bpf_cpumask - refcounted BPF cpumask wrapper structure
  * @cpumask:   The actual cpumask embedded in the struct.
- * @rcu:       The RCU head used to free the cpumask with RCU safety.
  * @usage:     Object reference counter. When the refcount goes to 0, the
  *             memory is released back to the BPF allocator, which provides
  *             RCU safety.
@@ -25,7 +24,6 @@
  */
 struct bpf_cpumask {
        cpumask_t cpumask;
-       struct rcu_head rcu;
        refcount_t usage;
 };
 
@@ -82,16 +80,6 @@ __bpf_kfunc struct bpf_cpumask *bpf_cpumask_acquire(struct bpf_cpumask *cpumask)
        return cpumask;
 }
 
-static void cpumask_free_cb(struct rcu_head *head)
-{
-       struct bpf_cpumask *cpumask;
-
-       cpumask = container_of(head, struct bpf_cpumask, rcu);
-       migrate_disable();
-       bpf_mem_cache_free(&bpf_cpumask_ma, cpumask);
-       migrate_enable();
-}
-
 /**
  * bpf_cpumask_release() - Release a previously acquired BPF cpumask.
  * @cpumask: The cpumask being released.
@@ -102,8 +90,12 @@ static void cpumask_free_cb(struct rcu_head *head)
  */
 __bpf_kfunc void bpf_cpumask_release(struct bpf_cpumask *cpumask)
 {
-       if (refcount_dec_and_test(&cpumask->usage))
-               call_rcu(&cpumask->rcu, cpumask_free_cb);
+       if (!refcount_dec_and_test(&cpumask->usage))
+               return;
+
+       migrate_disable();
+       bpf_mem_cache_free_rcu(&bpf_cpumask_ma, cpumask);
+       migrate_enable();
 }
 
 /**