rds: Fix non-atomic operation on shared flag variable

The bits in m_flags in struct rds_message are used for a plurality of
reasons, and from different contexts. To avoid any missing updates to
m_flags, use the atomic set_bit() instead of the non-atomic equivalent.

Signed-off-by: Håkon Bugge <haakon.bugge@oracle.com>
Reviewed-by: Knut Omang <knut.omang@oracle.com>
Reviewed-by: Wei Lin Guay <wei.lin.guay@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/rds/send.c

@@ -273,7 +273,7 @@ restart:
 			len = ntohl(rm->m_inc.i_hdr.h_len);
 			if (cp->cp_unacked_packets == 0 ||
 			    cp->cp_unacked_bytes < len) {
-				__set_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags);
+				set_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags);
 
 				cp->cp_unacked_packets =
 					rds_sysctl_max_unacked_packets;
@@ -829,7 +829,7 @@ static int rds_send_queue_rm(struct rds_sock *rs, struct rds_connection *conn,
 		 * throughput hits a certain threshold.
 		 */
 		if (rs->rs_snd_bytes >= rds_sk_sndbuf(rs) / 2)
-			__set_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags);
+			set_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags);
 
 		list_add_tail(&rm->m_sock_item, &rs->rs_send_queue);
 		set_bit(RDS_MSG_ON_SOCK, &rm->m_flags);