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>

5 files changed, 26 insertions, 16 deletions

diff --git a/net/rds/connection.c b/net/rds/connection.c
index 7e4e9dfdbc0b..9c249f394f29 100644
--- a/net/rds/connection.c
+++ b/net/rds/connection.c
@@ -148,6 +148,7 @@ static struct rds_connection *__rds_conn_create(__be32 laddr, __be32 faddr,
 
         spin_lock_init(&conn->c_send_lock);
         atomic_set(&conn->c_send_generation, 1);
+        atomic_set(&conn->c_senders, 0);
         INIT_LIST_HEAD(&conn->c_send_queue);
         INIT_LIST_HEAD(&conn->c_retrans);
 
@@ -276,6 +277,12 @@ void rds_conn_shutdown(struct rds_connection *conn)
                 spin_lock_irq(&conn->c_send_lock);
                 spin_unlock_irq(&conn->c_send_lock);
 
+                while(atomic_read(&conn->c_senders)) {
+                        schedule_timeout(1);
+                        spin_lock_irq(&conn->c_send_lock);
+                        spin_unlock_irq(&conn->c_send_lock);
+                }
+
                 conn->c_trans->conn_shutdown(conn);
                 rds_conn_reset(conn);
 
diff --git a/net/rds/ib_recv.c b/net/rds/ib_recv.c
index 8f041f7954a2..24d14615f41a 100644
--- a/net/rds/ib_recv.c
+++ b/net/rds/ib_recv.c
@@ -863,18 +863,6 @@ int rds_ib_recv(struct rds_connection *conn)
         int ret = 0;
 
         rdsdebug("conn %p\n", conn);
-
-        /*
-         * If we get a temporary posting failure in this context then
-         * we're really low and we want the caller to back off for a bit.
-         */
-        mutex_lock(&ic->i_recv_mutex);
-        if (rds_ib_recv_refill(conn, 0))
-                ret = -ENOMEM;
-        else
-                rds_ib_stats_inc(s_ib_rx_refill_from_thread);
-        mutex_unlock(&ic->i_recv_mutex);
-
         if (rds_conn_up(conn))
                 rds_ib_attempt_ack(ic);
 
diff --git a/net/rds/message.c b/net/rds/message.c
index 96e2bf7dc77e..84f937f11d47 100644
--- a/net/rds/message.c
+++ b/net/rds/message.c
@@ -81,7 +81,10 @@ static void rds_message_purge(struct rds_message *rm)
 void rds_message_put(struct rds_message *rm)
 {
         rdsdebug("put rm %p ref %d\n", rm, atomic_read(&rm->m_refcount));
-
+        if (atomic_read(&rm->m_refcount) == 0) {
+printk(KERN_CRIT "danger refcount zero on %p\n", rm);
+WARN_ON(1);
+        }
         if (atomic_dec_and_test(&rm->m_refcount)) {
                 BUG_ON(!list_empty(&rm->m_sock_item));
                 BUG_ON(!list_empty(&rm->m_conn_item));
diff --git a/net/rds/rds.h b/net/rds/rds.h
index 241a0859d16e..4ab3d1aa0237 100644
--- a/net/rds/rds.h
+++ b/net/rds/rds.h
@@ -93,6 +93,7 @@ struct rds_connection {
 
         spinlock_t              c_send_lock;    /* protect send ring */
         atomic_t                c_send_generation;
+        atomic_t                c_senders;
         struct rds_message      *c_xmit_rm;
         unsigned long           c_xmit_sg;
         unsigned int            c_xmit_hdr_off;
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