rds: rds_rm_zerocopy_callback() correct order for list_add_tail()

rds_rm_zerocopy_callback() uses list_add_tail() with swapped
arguments. This links the list head with the new entry, losing
the references to the remaining part of the list.

Fixes: 9426bbc6 ("rds: use list structure to track information for zerocopy completion notification")
Suggested-by: NPaolo Abeni <pabeni@redhat.com>
Signed-off-by: NPietro Borrello <borrello@diag.uniroma1.it>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/rds/message.c

@@ -118,7 +118,7 @@ static void rds_rm_zerocopy_callback(struct rds_sock *rs,
 	ck = &info->zcookies;
 	memset(ck, 0, sizeof(*ck));
 	WARN_ON(!rds_zcookie_add(info, cookie));
-	list_add_tail(&q->zcookie_head, &info->rs_zcookie_next);
+	list_add_tail(&info->rs_zcookie_next, &q->zcookie_head);
 
 	spin_unlock_irqrestore(&q->lock, flags);
 	/* caller invokes rds_wake_sk_sleep() */