Re: [PATCH 3/3] net/ceph/messenger: add empty check to ceph_con_get_out_msg()

[Viacheslav Dubeyko]

On Wed, 2025-08-06 at 11:48 +0200, Max Kellermann wrote:
> This moves the list_empty() checks from the two callers (v1 and v2)
> into the base messenger.c library.  Now the v1/v2 specializations do
> not need to know about con->out_queue; that implementation detail is
> now hidden behind the ceph_con_get_out_msg() function.
> 
> Signed-off-by: Max Kellermann <max.kellermann@xxxxxxxxx>

Looks good.

Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@xxxxxxx>

Thanks,
Slava.

> ---
>  net/ceph/messenger.c    |  4 +++-
>  net/ceph/messenger_v1.c | 15 ++++++++++-----
>  net/ceph/messenger_v2.c |  4 ++--
>  3 files changed, 15 insertions(+), 8 deletions(-)
> 
> diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
> index 424fb2769b71..8886c38a55d2 100644
> --- a/net/ceph/messenger.c
> +++ b/net/ceph/messenger.c
> @@ -2113,7 +2113,9 @@ struct ceph_msg *ceph_con_get_out_msg(struct ceph_connection *con)
>  {
>  	struct ceph_msg *msg;
>  
> -	BUG_ON(list_empty(&con->out_queue));
> +	if (list_empty(&con->out_queue))
> +		return NULL;
> +
>  	msg = list_first_entry(&con->out_queue, struct ceph_msg, list_head);
>  	WARN_ON(msg->con != con);
>  
> diff --git a/net/ceph/messenger_v1.c b/net/ceph/messenger_v1.c
> index 516f2eeb122a..5eb6cfdbc494 100644
> --- a/net/ceph/messenger_v1.c
> +++ b/net/ceph/messenger_v1.c
> @@ -189,12 +189,18 @@ static void prepare_write_message_footer(struct ceph_connection *con, struct cep
>  
>  /*
>   * Prepare headers for the next outgoing message.
> + *
> + * @return false if there are no outgoing messages
>   */
> -static void prepare_write_message(struct ceph_connection *con)
> +static bool prepare_write_message(struct ceph_connection *con)
>  {
>  	struct ceph_msg *m;
>  	u32 crc;
>  
> +	m = ceph_con_get_out_msg(con);
> +	if (m == NULL)
> +		return false;
> +
>  	con_out_kvec_reset(con);
>  	con->v1.out_msg_done = false;
>  
> @@ -208,8 +214,6 @@ static void prepare_write_message(struct ceph_connection *con)
>  			&con->v1.out_temp_ack);
>  	}
>  
> -	m = ceph_con_get_out_msg(con);
> -
>  	dout("prepare_write_message %p seq %lld type %d len %d+%d+%zd\n",
>  	     m, con->out_seq, le16_to_cpu(m->hdr.type),
>  	     le32_to_cpu(m->hdr.front_len), le32_to_cpu(m->hdr.middle_len),
> @@ -256,6 +260,8 @@ static void prepare_write_message(struct ceph_connection *con)
>  	}
>  
>  	ceph_con_flag_set(con, CEPH_CON_F_WRITE_PENDING);
> +
> +	return true;
>  }
>  
>  /*
> @@ -1543,8 +1549,7 @@ int ceph_con_v1_try_write(struct ceph_connection *con)
>  			goto more;
>  		}
>  		/* is anything else pending? */
> -		if (!list_empty(&con->out_queue)) {
> -			prepare_write_message(con);
> +		if (prepare_write_message(con)) {
>  			goto more;
>  		}
>  		if (con->in_seq > con->in_seq_acked) {
> diff --git a/net/ceph/messenger_v2.c b/net/ceph/messenger_v2.c
> index 90109fa0fe60..e0b5f2e2582d 100644
> --- a/net/ceph/messenger_v2.c
> +++ b/net/ceph/messenger_v2.c
> @@ -3292,6 +3292,7 @@ static void finish_message(struct ceph_connection *con)
>  
>  static int populate_out_iter(struct ceph_connection *con)
>  {
> +	struct ceph_msg *msg;
>  	int ret;
>  
>  	dout("%s con %p state %d out_state %d\n", __func__, con, con->state,
> @@ -3337,8 +3338,7 @@ static int populate_out_iter(struct ceph_connection *con)
>  			pr_err("prepare_keepalive2 failed: %d\n", ret);
>  			return ret;
>  		}
> -	} else if (!list_empty(&con->out_queue)) {
> -		struct ceph_msg *msg = ceph_con_get_out_msg(con);
> +	} else if ((msg = ceph_con_get_out_msg(con)) != NULL) {
>  		ret = prepare_message(con, msg);
>  		if (ret) {
>  			pr_err("prepare_message failed: %d\n", ret);