rds: don't let RDS shutdown a connection while senders are present

This is the first in a long line of patches that tries to fix races
between RDS connection shutdown and RDS traffic.

Here we are maintaining a count of active senders to make sure
the connection doesn't go away while they are using it.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 14 insertions, 3 deletions

diff --git a/net/rds/send.c b/net/rds/send.c
index 8e3fd9981c2e..d35c43ff792e 100644
--- a/net/rds/send.c
+++ b/net/rds/send.c
@@ -60,15 +60,23 @@ void rds_send_reset(struct rds_connection *conn)
         struct rds_message *rm, *tmp;
         unsigned long flags;
 
+        spin_lock_irqsave(&conn->c_send_lock, flags);
         if (conn->c_xmit_rm) {
+                rm = conn->c_xmit_rm;
+                conn->c_xmit_rm = NULL;
                 /* Tell the user the RDMA op is no longer mapped by the
                  * transport. This isn't entirely true (it's flushed out
                  * independently) but as the connection is down, there's
                  * no ongoing RDMA to/from that memory */
-                rds_message_unmapped(conn->c_xmit_rm);
-                rds_message_put(conn->c_xmit_rm);
-                conn->c_xmit_rm = NULL;
+printk(KERN_CRIT "send reset unmapping %p\n", rm);
+                rds_message_unmapped(rm);
+                spin_unlock_irqrestore(&conn->c_send_lock, flags);
+
+                rds_message_put(rm);
+        } else {
+                spin_unlock_irqrestore(&conn->c_send_lock, flags);
         }
+
         conn->c_xmit_sg = 0;
         conn->c_xmit_hdr_off = 0;
         conn->c_xmit_data_off = 0;
@@ -131,6 +139,7 @@ restart:
                 ret = -ENOMEM;
                 goto out;
         }
+        atomic_inc(&conn->c_senders);
 
         if (conn->c_trans->xmit_prepare)
                 conn->c_trans->xmit_prepare(conn);
@@ -350,6 +359,8 @@ restart:
                 rds_send_remove_from_sock(&to_be_dropped, RDS_RDMA_DROPPED);
         }
 
+        atomic_dec(&conn->c_senders);
+
         /*
          * Other senders will see we have c_send_lock and exit. We
          * need to recheck the send queue and race again for c_send_lock