bpf: Refactor alloc_bulk().

Factor out inner body of alloc_bulk into separate helper.
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/20230706033447.54696-5-alexei.starovoitov@gmail.com

Author: Alexei Starovoitov

kernel/bpf/memalloc.c

@@ -154,11 +154,35 @@ 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)
+{
+	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);
+	/* 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++;
+	local_dec(&c->active);
+	if (IS_ENABLED(CONFIG_PREEMPT_RT))
+		local_irq_restore(flags);
+}
+
 /* Mostly runs from irq_work except __init phase. */
 static void alloc_bulk(struct bpf_mem_cache *c, int cnt, int node)
 {
 	struct mem_cgroup *memcg = NULL, *old_memcg;
-	unsigned long flags;
 	void *obj;
 	int i;
 
@@ -188,25 +212,7 @@ static void alloc_bulk(struct bpf_mem_cache *c, int cnt, int node)
 			if (!obj)
 				break;
 		}
-		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);
-		/* 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++;
-		local_dec(&c->active);
-		if (IS_ENABLED(CONFIG_PREEMPT_RT))
-			local_irq_restore(flags);
+		add_obj_to_free_list(c, obj);
 	}
 	set_active_memcg(old_memcg);
 	mem_cgroup_put(memcg);