smc-tools: Display sndbuf/RMB stats only if supported by the kernel

Recent smc-tools commits introduced the display of ring buffer usage
statistics:

845ab35 smcd/smcr: Add statistics on ringbufs being used by smc conns
089d42e smcr/smcd: Add statistics of linkgroup ringbuf usage

These features rely on kernel support added in the following commits:

e0d103542b06 net/smc: Add statistics for ring buffer usage per network
namespace
d386d59b7c1a net/smc: Add statistics for allocated ring buffers within a
link group

On systems running kernels without these commits, smc-tools may report zero
values for ring buffer usage and allocation. While zero is a valid
statistic, in this context it may misleadingly suggest that no buffers are
in use, rather than indicating a lack of kernel support.

This patch ensures that sndbuf/RMB statistics are displayed only when the
kernel provides explicit support for these metrics, thereby avoiding
confusion on unsupported systems.

Reviewed-by: Mahanta Jambigi <mjambigi@linux.ibm.com>
Reviewed-by: Wenjia Zhang <wenjia@linux.ibm.com>
Reviewed-by: Sidraya Jayagond <sidraya@linux.ibm.com>
Signed-off-by: Nagamani PV <nagamani@linux.ibm.com>

Author: Nagamani PV

linkgroup.c

@@ -321,8 +321,12 @@ static int fill_lgr_struct(struct smc_diag_lgr *lgr, struct nlattr **attrs)
 			 nla_get_string(lgr_attrs[SMC_NLA_LGR_R_PNETID]));
 	if (lgr_attrs[SMC_NLA_LGR_R_SNDBUF_ALLOC])
 		lgr->sndbuf_alloc = nl_attr_get_uint(lgr_attrs[SMC_NLA_LGR_R_SNDBUF_ALLOC]);
+	else
+		lgr->sndbuf_alloc = SMC_BUFF_STATS_KERNEL_SUPPORT_ABSENT;
 	if (lgr_attrs[SMC_NLA_LGR_R_RMB_ALLOC])
 		lgr->rmb_alloc = nl_attr_get_uint(lgr_attrs[SMC_NLA_LGR_R_RMB_ALLOC]);
+	else
+		lgr->rmb_alloc = SMC_BUFF_STATS_KERNEL_SUPPORT_ABSENT;
 	if (lgr_attrs[SMC_NLA_LGR_R_V2_COMMON]) {
 		struct nlattr *v2_lgr_attrs[SMC_NLA_LGR_V2_MAX + 1];
 
@@ -371,8 +375,12 @@ static int fill_lgr_smcd_struct(struct smcd_diag_dmbinfo_v2 *lgr, struct nlattr
 			 nla_get_string(lgr_attrs[SMC_NLA_LGR_D_PNETID]));
 	if (lgr_attrs[SMC_NLA_LGR_D_SNDBUF_ALLOC])
 		lgr->sndbuf_alloc = nl_attr_get_uint(lgr_attrs[SMC_NLA_LGR_D_SNDBUF_ALLOC]);
+	else
+		lgr->sndbuf_alloc = SMC_BUFF_STATS_KERNEL_SUPPORT_ABSENT;
 	if (lgr_attrs[SMC_NLA_LGR_D_DMB_ALLOC])
 		lgr->dmb_alloc = nl_attr_get_uint(lgr_attrs[SMC_NLA_LGR_D_DMB_ALLOC]);
+	else
+		lgr->dmb_alloc = SMC_BUFF_STATS_KERNEL_SUPPORT_ABSENT;
 	if (lgr_attrs[SMC_NLA_LGR_D_V2_COMMON]) {
 		struct nlattr *v2_lgr_attrs[SMC_NLA_LGR_V2_MAX + 1];
 
@@ -410,8 +418,10 @@ static void show_lgr_smcr_info_lgr_details(struct smc_diag_lgr *lgr)
 		printf("EID      : %s\n", lgr->v2_lgr_info.negotiated_eid);
 	}
 	printf("#Conns   : %d\n", lgr->conns_num);
-	printf("Sndbuf   : %lld B\n", lgr->sndbuf_alloc);
-	printf("RMB      : %lld B\n", lgr->rmb_alloc);
+	if (lgr->sndbuf_alloc != SMC_BUFF_STATS_KERNEL_SUPPORT_ABSENT)
+		printf("Sndbuf   : %lld B\n", lgr->sndbuf_alloc);
+	if (lgr->rmb_alloc != SMC_BUFF_STATS_KERNEL_SUPPORT_ABSENT)
+		printf("RMB      : %lld B\n", lgr->rmb_alloc);
 }
 
 static int show_lgr_smcr_info(struct nlattr **attr)
@@ -492,8 +502,10 @@ static void show_lgr_smcd_info_lgr_details(struct smcd_diag_dmbinfo_v2 *lgr)
 		printf("EID      : %s\n", lgr->v2_lgr_info.negotiated_eid);
 	}
 	printf("#Conns   : %d\n", lgr->conns_num);
-	printf("Sndbuf   : %lld B\n", lgr->sndbuf_alloc);
-	printf("DMB      : %lld B\n", lgr->dmb_alloc);
+	if (lgr->sndbuf_alloc != SMC_BUFF_STATS_KERNEL_SUPPORT_ABSENT)
+		printf("Sndbuf   : %lld B\n", lgr->sndbuf_alloc);
+	if (lgr->dmb_alloc != SMC_BUFF_STATS_KERNEL_SUPPORT_ABSENT)
+		printf("DMB      : %lld B\n", lgr->dmb_alloc);
 }
 
 static int show_lgr_smcd_info(struct nlattr **attr)

stats.c

@@ -399,8 +399,10 @@ static void print_as_text()
 	printf("  Data transmitted (Bytes) %14llu (%s)\n",
 		smc_stat.smc[tech_type].rx_bytes, temp_str);
 	printf("  Total requests             %12llu\n", tech->rx_cnt);
-	get_abbreviated(smc_stat.smc[tech_type].rx_rmbuse, 6, temp_str);
-	printf("  Buffer usage (Bytes)       %12llu (%s)\n", tech->rx_rmbuse, temp_str);
+	if (smc_stat.smc[tech_type].rx_rmbuse != SMC_BUFF_STATS_KERNEL_SUPPORT_ABSENT) {
+		get_abbreviated(smc_stat.smc[tech_type].rx_rmbuse, 6, temp_str);
+		printf("  Buffer usage (Bytes)       %12llu (%s)\n", tech->rx_rmbuse, temp_str);
+	}
 	printf("  Buffer full                %12llu (%.2f%%)\n", tech->rmb_rx.buf_full_cnt,
 			buf_rx_full);
 	if (d_level) {
@@ -422,8 +424,10 @@ static void print_as_text()
 	printf("  Data transmitted (Bytes) %14llu (%s)\n",
 		smc_stat.smc[tech_type].tx_bytes, temp_str);
 	printf("  Total requests             %12llu\n", tech->tx_cnt);
-	get_abbreviated(smc_stat.smc[tech_type].tx_rmbuse, 6, temp_str);
-	printf("  Buffer usage (Bytes)       %12llu (%s)\n", tech->tx_rmbuse, temp_str);
+	if (smc_stat.smc[tech_type].tx_rmbuse != SMC_BUFF_STATS_KERNEL_SUPPORT_ABSENT) {
+		get_abbreviated(smc_stat.smc[tech_type].tx_rmbuse, 6, temp_str);
+		printf("  Buffer usage (Bytes)       %12llu (%s)\n", tech->tx_rmbuse, temp_str);
+	}
 	printf("  Buffer full                %12llu (%.2f%%)\n", tech->rmb_tx.buf_full_cnt,
 			buf_full);
 	printf("  Buffer full (remote)       %12llu (%.2f%%)\n", tech->rmb_tx.buf_full_peer_cnt,
@@ -629,11 +633,13 @@ static int fill_tech_info(struct nlattr **attr, int type)
 	if (tech_attrs[SMC_NLA_STATS_T_RX_RMB_USAGE]) {
 		trgt = nl_attr_get_uint(tech_attrs[SMC_NLA_STATS_T_RX_RMB_USAGE]);
 		smc_stat.smc[tech_type].rx_rmbuse = trgt;
-	}
+	} else
+		smc_stat.smc[tech_type].rx_rmbuse = SMC_BUFF_STATS_KERNEL_SUPPORT_ABSENT;
 	if (tech_attrs[SMC_NLA_STATS_T_TX_RMB_USAGE]) {
 		trgt = nl_attr_get_uint(tech_attrs[SMC_NLA_STATS_T_TX_RMB_USAGE]);
 		smc_stat.smc[tech_type].tx_rmbuse = trgt;
-	}
+	} else
+		smc_stat.smc[tech_type].tx_rmbuse = SMC_BUFF_STATS_KERNEL_SUPPORT_ABSENT;
 	if (tech_attrs[SMC_NLA_STATS_T_RX_CNT]) {
 		trgt = nla_get_u64(tech_attrs[SMC_NLA_STATS_T_RX_CNT]);
 		smc_stat.smc[tech_type].rx_cnt = trgt;

util.h

@@ -21,7 +21,7 @@
 #define SMC_OPTION_ABS -1
 #define SMC_OPTION_DETAIL_ABS -2
 #define SMC_TYPE_STR_MAX 5
-
+#define SMC_BUFF_STATS_KERNEL_SUPPORT_ABSENT ((__u64) -1)
 
 #define NEXT_ARG() do { argv++; argc--; } while(0)
 #define NEXT_ARG_OK() (argc - 1 > 0)