bpf: Factor out inc/dec of active flag into helpers.

Factor out local_inc/dec_return(&c->active) into helpers.
No functional changes.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/bpf/20230706033447.54696-6-alexei.starovoitov@gmail.com

Author: Alexei Starovoitov

kernel/bpf/memalloc.c

@@ -154,31 +154,41 @@ static struct mem_cgroup *get_memcg(const struct bpf_mem_cache *c)
 #endif
 }
 
-static void add_obj_to_free_list(struct bpf_mem_cache *c, void *obj)
+static void inc_active(struct bpf_mem_cache *c, unsigned long *flags)
 {
-	unsigned long flags;
-
 	if (IS_ENABLED(CONFIG_PREEMPT_RT))
 		/* In RT irq_work runs in per-cpu kthread, so disable
 		 * interrupts to avoid preemption and interrupts and
 		 * reduce the chance of bpf prog executing on this cpu
 		 * when active counter is busy.
 		 */
-		local_irq_save(flags);
+		local_irq_save(*flags);
 	/* alloc_bulk runs from irq_work which will not preempt a bpf
 	 * program that does unit_alloc/unit_free since IRQs are
 	 * disabled there. There is no race to increment 'active'
 	 * counter. It protects free_llist from corruption in case NMI
 	 * bpf prog preempted this loop.
 	 */
 	WARN_ON_ONCE(local_inc_return(&c->active) != 1);
-	__llist_add(obj, &c->free_llist);
-	c->free_cnt++;
+}
+
+static void dec_active(struct bpf_mem_cache *c, unsigned long flags)
+{
 	local_dec(&c->active);
 	if (IS_ENABLED(CONFIG_PREEMPT_RT))
 		local_irq_restore(flags);
 }
 
+static void add_obj_to_free_list(struct bpf_mem_cache *c, void *obj)
+{
+	unsigned long flags;
+
+	inc_active(c, &flags);
+	__llist_add(obj, &c->free_llist);
+	c->free_cnt++;
+	dec_active(c, flags);
+}
+
 /* Mostly runs from irq_work except __init phase. */
 static void alloc_bulk(struct bpf_mem_cache *c, int cnt, int node)
 {
@@ -300,17 +310,13 @@ static void free_bulk(struct bpf_mem_cache *c)
 	int cnt;
 
 	do {
-		if (IS_ENABLED(CONFIG_PREEMPT_RT))
-			local_irq_save(flags);
-		WARN_ON_ONCE(local_inc_return(&c->active) != 1);
+		inc_active(c, &flags);
 		llnode = __llist_del_first(&c->free_llist);
 		if (llnode)
 			cnt = --c->free_cnt;
 		else
 			cnt = 0;
-		local_dec(&c->active);
-		if (IS_ENABLED(CONFIG_PREEMPT_RT))
-			local_irq_restore(flags);
+		dec_active(c, flags);
 		if (llnode)
 			enque_to_free(c, llnode);
 	} while (cnt > (c->high_watermark + c->low_watermark) / 2);