RDS: Use spinlock to protect 64b value update on 32b archs

We have a 64bit value that needs to be set atomically.
This is easy and quick on all 64bit archs, and can also be done
on x86/32 with set_64bit() (uses cmpxchg8b). However other
32b archs don't have this.

I actually changed this to the current state in preparation for
mainline because the old way (using a spinlock on 32b) resulted in
unsightly #ifdefs in the code. But obviously, being correct takes
precedence.

Signed-off-by: Andy Grover <andy.grover@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 1 deletions

diff --git a/net/rds/ib_cm.c b/net/rds/ib_cm.c
index 889ab0441359..f8e40e1a6038 100644
--- a/net/rds/ib_cm.c
+++ b/net/rds/ib_cm.c
@@ -636,7 +636,11 @@ void rds_ib_conn_shutdown(struct rds_connection *conn)
 
         /* Clear the ACK state */
         clear_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags);
-        rds_ib_set_64bit(&ic->i_ack_next, 0);
+#ifdef KERNEL_HAS_ATOMIC64
+        atomic64_set(&ic->i_ack_next, 0);
+#else
+        ic->i_ack_next = 0;
+#endif
         ic->i_ack_recv = 0;
 
         /* Clear flow control state */
@@ -669,6 +673,9 @@ int rds_ib_conn_alloc(struct rds_connection *conn, gfp_t gfp)
 
         INIT_LIST_HEAD(&ic->ib_node);
         mutex_init(&ic->i_recv_mutex);
+#ifndef KERNEL_HAS_ATOMIC64
+        spin_lock_init(&ic->i_ack_lock);
+#endif
 
         /*
          * rds_ib_conn_shutdown() waits for these to be emptied so they