RDMA/rtrs: server: statistics functions

This introduces set of functions used on server side to account statistics
of RDMA data sent/received.

Link: https://lore.kernel.org/r/20200511135131.27580-12-danil.kipnis@cloud.ionos.comSigned-off-by: NDanil Kipnis <danil.kipnis@cloud.ionos.com>
Signed-off-by: NJack Wang <jinpu.wang@cloud.ionos.com>
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/ulp/rtrs/rtrs-srv-stats.c

+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * RDMA Transport Layer
+ *
+ * Copyright (c) 2014 - 2018 ProfitBricks GmbH. All rights reserved.
+ * Copyright (c) 2018 - 2019 1&1 IONOS Cloud GmbH. All rights reserved.
+ * Copyright (c) 2019 - 2020 1&1 IONOS SE. All rights reserved.
+ */
+#undef pr_fmt
+#define pr_fmt(fmt) KBUILD_MODNAME " L" __stringify(__LINE__) ": " fmt
+
+#include "rtrs-srv.h"
+
+int rtrs_srv_reset_rdma_stats(struct rtrs_srv_stats *stats, bool enable)
+{
+	if (enable) {
+		struct rtrs_srv_stats_rdma_stats *r = &stats->rdma_stats;
+
+		memset(r, 0, sizeof(*r));
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
+ssize_t rtrs_srv_stats_rdma_to_str(struct rtrs_srv_stats *stats,
+				    char *page, size_t len)
+{
+	struct rtrs_srv_stats_rdma_stats *r = &stats->rdma_stats;
+	struct rtrs_srv_sess *sess = stats->sess;
+
+	return scnprintf(page, len, "%lld %lld %lld %lld %u\n",
+			 (s64)atomic64_read(&r->dir[READ].cnt),
+			 (s64)atomic64_read(&r->dir[READ].size_total),
+			 (s64)atomic64_read(&r->dir[WRITE].cnt),
+			 (s64)atomic64_read(&r->dir[WRITE].size_total),
+			 atomic_read(&sess->ids_inflight));
+}