[PATCH net-next v2 8/9] net/rds: drop rds_conn_count in favor of t_conn_count

[Allison Henderson <achender@kernel.org>]

The previous patch gave each transport its own connection count in
t_conn_count, incremented and decremented at exactly the points where
the global rds_conn_count is.  That leaves rds_conn_count with a
single remaining consumer: the seed of the per-path workqueue names
in __rds_conn_create().

Switch the name seed to t_conn_count, as UEK does, and remove
rds_conn_count.  The numbering becomes per-transport instead of
global, so connections of different transports can now receive the
same seed; workqueue names carry no uniqueness requirement, and the
seed was already reused as the count rose and fell.  Removing the
counter also removes the rds_conn_lock round-trip that
rds_conn_destroy_fini() took solely to decrement it, leaving the
free path lock-free.

Based on the Oracle UEK commit "net/rds: Each RDS transport
should keep its own connection count".

Assisted-by: Claude-Code:claude-fable-5
Signed-off-by: Allison Henderson <achender@kernel.org>
---
 net/rds/connection.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/net/rds/connection.c b/net/rds/connection.c
index 1ec141d6faa3..11813f93961d 100644
--- a/net/rds/connection.c
+++ b/net/rds/connection.c
@@ -47,7 +47,6 @@
 
 /* converting this to RCU is a chore for another day.. */
 static DEFINE_SPINLOCK(rds_conn_lock);
-static unsigned long rds_conn_count;
 /* woken whenever a transport's t_conn_count drops to zero */
 static DECLARE_WAIT_QUEUE_HEAD(rds_conn_freed_waitq);
 static struct hlist_head rds_conn_hash[RDS_CONNECTION_HASH_ENTRIES];
@@ -316,12 +315,13 @@ static struct rds_connection *__rds_conn_create(struct net *net,
 
 	init_waitqueue_head(&conn->c_hs_waitq);
 	for (i = 0; i < npaths; i++) {
+		int seq = atomic_read(&trans->t_conn_count);
+
 		__rds_conn_path_init(conn, &conn->c_path[i],
 				     is_outgoing);
 		conn->c_path[i].cp_index = i;
 		conn->c_path[i].cp_wq =
-			alloc_ordered_workqueue("krds_cp_wq#%lu/%d", 0,
-						rds_conn_count, i);
+			alloc_ordered_workqueue("krds_cp_wq#%d/%d", 0, seq, i);
 		if (!conn->c_path[i].cp_wq)
 			conn->c_path[i].cp_wq = rds_wq;
 	}
@@ -392,7 +392,6 @@ static struct rds_connection *__rds_conn_create(struct net *net,
 			rds_conn_get(conn);	/* caller */
 			rcu_assign_pointer(parent->c_passive, conn);
 			rds_cong_add_conn(conn);
-			rds_conn_count++;
 			atomic_inc(&conn->c_trans->t_conn_count);
 		}
 	} else {
@@ -426,7 +425,6 @@ static struct rds_connection *__rds_conn_create(struct net *net,
 			rds_conn_get(conn);
 			hlist_add_head_rcu(&conn->c_hash_node, head);
 			rds_cong_add_conn(conn);
-			rds_conn_count++;
 			atomic_inc(&conn->c_trans->t_conn_count);
 		}
 	}
@@ -656,7 +654,6 @@ static void rds_conn_destroy_fini(struct kref *kref)
 						   c_refcount);
 	int npaths = (conn->c_trans->t_mp_capable ? RDS_MPATH_WORKERS : 1);
 	struct rds_transport *trans = conn->c_trans;
-	unsigned long flags;
 	int i;
 
 	for (i = 0; i < npaths; i++)
@@ -665,10 +662,6 @@ static void rds_conn_destroy_fini(struct kref *kref)
 	kfree(conn->c_path);
 	kmem_cache_free(rds_conn_slab, conn);
 
-	spin_lock_irqsave(&rds_conn_lock, flags);
-	rds_conn_count--;
-	spin_unlock_irqrestore(&rds_conn_lock, flags);
-
 	/* only after everything the transport module owns has been
 	 * freed above may its unload proceed
 	 */
-- 
2.25.1