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

[Max Kellermann <max.kellermann@ionos.com>]

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@ionos.com>
---
 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);
-- 
2.47.2