[PATCH v4 3/6] io_uring/napi: improve __io_napi_add

[Olivier Langlois <olivier@trillion01.com>]

1. move the sock->sk pointer validity test outside the function to
   avoid the function call overhead and to make the function more
   more reusable
2. change its name to __io_napi_add_id to be more precise about it is
   doing
3. return an error code to report errors

Signed-off-by: Olivier Langlois <olivier@trillion01.com>
---
 io_uring/napi.c | 19 ++++++-------------
 io_uring/napi.h |  6 +++---
 2 files changed, 9 insertions(+), 16 deletions(-)

diff --git a/io_uring/napi.c b/io_uring/napi.c
index 921de9de8d75..5e2299e7ff8e 100644
--- a/io_uring/napi.c
+++ b/io_uring/napi.c
@@ -38,22 +38,14 @@ static inline ktime_t net_to_ktime(unsigned long t)
 	return ns_to_ktime(t << 10);
 }
 
-void __io_napi_add(struct io_ring_ctx *ctx, struct socket *sock)
+int __io_napi_add_id(struct io_ring_ctx *ctx, unsigned int napi_id)
 {
 	struct hlist_head *hash_list;
-	unsigned int napi_id;
-	struct sock *sk;
 	struct io_napi_entry *e;
 
-	sk = sock->sk;
-	if (!sk)
-		return;
-
-	napi_id = READ_ONCE(sk->sk_napi_id);
-
 	/* Non-NAPI IDs can be rejected. */
 	if (napi_id < MIN_NAPI_ID)
-		return;
+		return -EINVAL;
 
 	hash_list = &ctx->napi_ht[hash_min(napi_id, HASH_BITS(ctx->napi_ht))];
 
@@ -62,13 +54,13 @@ void __io_napi_add(struct io_ring_ctx *ctx, struct socket *sock)
 	if (e) {
 		WRITE_ONCE(e->timeout, jiffies + NAPI_TIMEOUT);
 		rcu_read_unlock();
-		return;
+		return -EEXIST;
 	}
 	rcu_read_unlock();
 
 	e = kmalloc(sizeof(*e), GFP_NOWAIT);
 	if (!e)
-		return;
+		return -ENOMEM;
 
 	e->napi_id = napi_id;
 	e->timeout = jiffies + NAPI_TIMEOUT;
@@ -77,12 +69,13 @@ void __io_napi_add(struct io_ring_ctx *ctx, struct socket *sock)
 	if (unlikely(io_napi_hash_find(hash_list, napi_id))) {
 		spin_unlock(&ctx->napi_lock);
 		kfree(e);
-		return;
+		return -EEXIST;
 	}
 
 	hlist_add_tail_rcu(&e->node, hash_list);
 	list_add_tail_rcu(&e->list, &ctx->napi_list);
 	spin_unlock(&ctx->napi_lock);
+	return 0;
 }
 
 static void __io_napi_remove_stale(struct io_ring_ctx *ctx)
diff --git a/io_uring/napi.h b/io_uring/napi.h
index fd275ef0456d..4ae622f37b30 100644
--- a/io_uring/napi.h
+++ b/io_uring/napi.h
@@ -15,7 +15,7 @@ void io_napi_free(struct io_ring_ctx *ctx);
 int io_register_napi(struct io_ring_ctx *ctx, void __user *arg);
 int io_unregister_napi(struct io_ring_ctx *ctx, void __user *arg);
 
-void __io_napi_add(struct io_ring_ctx *ctx, struct socket *sock);
+int __io_napi_add_id(struct io_ring_ctx *ctx, unsigned int napi_id);
 
 void __io_napi_busy_loop(struct io_ring_ctx *ctx, struct io_wait_queue *iowq);
 int io_napi_sqpoll_busy_poll(struct io_ring_ctx *ctx);
@@ -48,8 +48,8 @@ static inline void io_napi_add(struct io_kiocb *req)
 		return;
 
 	sock = sock_from_file(req->file);
-	if (sock)
-		__io_napi_add(ctx, sock);
+	if (sock && sock->sk)
+		__io_napi_add_id(ctx, READ_ONCE(sock->sk->sk_napi_id));
 }
 
 #else
-- 
2.47.0