[RFC PATCH bpf-next 08/17] bpf: Factor bpf_trampoline_lookup function

[Jiri Olsa <jolsa@kernel.org>]

Factoring bpf_trampoline_lookup function and adding to new
functions which will be needed in following changes:

  struct bpf_trampoline *__bpf_trampoline_lookup(u64 key)
  - returns trampoline without locking trampoline_mutex

  static struct bpf_trampoline *bpf_trampoline_alloc(void)
  - alocates trampoline object

The bpf_trampoline_lookup logic stays the same.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 kernel/bpf/trampoline.c | 45 ++++++++++++++++++++++++++++++-----------
 1 file changed, 33 insertions(+), 12 deletions(-)

diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index e926692ded85..15801f6c5071 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -188,38 +188,59 @@ void bpf_tramp_id_put(struct bpf_tramp_id *id)
 	kfree(id);
 }
 
-static struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
+static struct bpf_trampoline *__bpf_trampoline_lookup(u64 key)
 {
 	struct bpf_trampoline *tr;
 	struct hlist_head *head;
 
-	mutex_lock(&trampoline_mutex);
 	head = &trampoline_table[hash_64(key, TRAMPOLINE_HASH_BITS)];
 	hlist_for_each_entry(tr, head, hlist) {
-		if (tr->key == key) {
-			refcount_inc(&tr->refcnt);
-			goto out;
-		}
+		if (tr->key == key)
+			return tr;
 	}
+	return NULL;
+}
+
+static struct bpf_trampoline *bpf_trampoline_alloc(void)
+{
+	struct bpf_trampoline *tr;
+
 	tr = kzalloc(sizeof(*tr), GFP_KERNEL);
 	if (!tr)
-		goto out;
+		return NULL;
+
+	INIT_HLIST_NODE(&tr->hlist);
+	refcount_set(&tr->refcnt, 1);
+	mutex_init(&tr->mutex);
 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
 	tr->fops = kzalloc(sizeof(struct ftrace_ops), GFP_KERNEL);
 	if (!tr->fops) {
 		kfree(tr);
-		tr = NULL;
-		goto out;
+		return NULL;
 	}
 	tr->fops->private = tr;
 	tr->fops->ops_func = bpf_tramp_ftrace_ops_func;
 #endif
+	return tr;
+}
+
+static struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
+{
+	struct bpf_trampoline *tr;
+	struct hlist_head *head;
 
+	mutex_lock(&trampoline_mutex);
+	tr = __bpf_trampoline_lookup(key);
+	if (tr) {
+		refcount_inc(&tr->refcnt);
+		goto out;
+	}
+	tr = bpf_trampoline_alloc();
+	if (!tr)
+		goto out;
 	tr->key = key;
-	INIT_HLIST_NODE(&tr->hlist);
+	head = &trampoline_table[hash_64(key, TRAMPOLINE_HASH_BITS)];
 	hlist_add_head(&tr->hlist, head);
-	refcount_set(&tr->refcnt, 1);
-	mutex_init(&tr->mutex);
 out:
 	mutex_unlock(&trampoline_mutex);
 	return tr;
-- 
2.37.1