tools/getdelays: add backward compatibility for taskstats version

Add version checks to print_delayacct() to handle differences in struct
taskstats across kernel versions. Field availability depends on taskstats
version (t->version), corresponding to TASKSTATS_VERSION in kernel headers
(see include/uapi/linux/taskstats.h).

Version feature mapping:
- version >= 11 - supports COMPACT statistics
- version >= 13 - supports WPCOPY statistics
- version >= 14 - supports IRQ statistics
- version >= 16 - supports *_max and *_min delay statistics

This ensures the tool works correctly with both older and newer kernel
versions by conditionally printing fields based on the reported version.

eg.1
bash# grep -r "#define TASKSTATS_VERSION" /usr/include/linux/taskstats.h
"#define TASKSTATS_VERSION 10"
bash# ./getdelays -d -p 1
CPU count real total virtual total delay total delay average
7481 3786181709 3807098291 36393725 0.005ms
IO count delay total delay average
369 1116046035 3.025ms
SWAP count delay total delay average
0 0 0.000ms
RECLAIM count delay total delay average
0 0 0.000ms
THRASHING count delay total delay average
0 0 0.000ms

eg.2
bash# grep -r "#define TASKSTATS_VERSION" /usr/include/linux/taskstats.h
"#define TASKSTATS_VERSION 14"
bash# ./getdelays -d -p 1
CPU count real total virtual total delay total delay average
68862 163474790046 174584722267 19962496806 0.290ms
IO count delay total delay average
0 0 0.000ms
SWAP count delay total delay average
0 0 0.000ms
RECLAIM count delay total delay average
0 0 0.000ms
THRASHING count delay total delay average
0 0 0.000ms
COMPACT count delay total delay average
0 0 0.000ms
WPCOPY count delay total delay average
0 0 0.000ms
IRQ count delay total delay average
0 0 0.000ms

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Fan Yu <[e-mail]>
Cc: Fan Yu <[e-mail]>
Cc: Jonathan Corbet <[e-mail]>
Cc: Wang Yaxin <[e-mail]>
Cc: xu xin <[e-mail]>
Cc: Yang Yang <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

tools/accounting/getdelays.c

···
 #define average_ms(t, c) (t / 1000000ULL / (c ? c : 1))
 #define delay_ms(t) (t / 1000000ULL)
 
+/*
+ * Version compatibility note:
+ * Field availability depends on taskstats version (t->version),
+ * corresponding to TASKSTATS_VERSION in kernel headers
+ * see include/uapi/linux/taskstats.h
+ *
+ * Version feature mapping:
+ * version >= 11  - supports COMPACT statistics
+ * version >= 13  - supports WPCOPY statistics
+ * version >= 14  - supports IRQ statistics
+ * version >= 16  - supports *_max and *_min delay statistics
+ *
+ * Always verify version before accessing version-dependent fields
+ * to maintain backward compatibility.
+ */
+#define PRINT_CPU_DELAY(version, t) \
+	do { \
+		if (version >= 16) { \
+			printf("%-10s%15s%15s%15s%15s%15s%15s%15s\n", \
+				"CPU", "count", "real total", "virtual total", \
+				"delay total", "delay average", "delay max", "delay min"); \
+			printf("          %15llu%15llu%15llu%15llu%15.3fms%13.6fms%13.6fms\n", \
+				(unsigned long long)(t)->cpu_count, \
+				(unsigned long long)(t)->cpu_run_real_total, \
+				(unsigned long long)(t)->cpu_run_virtual_total, \
+				(unsigned long long)(t)->cpu_delay_total, \
+				average_ms((double)(t)->cpu_delay_total, (t)->cpu_count), \
+				delay_ms((double)(t)->cpu_delay_max), \
+				delay_ms((double)(t)->cpu_delay_min)); \
+		} else { \
+			printf("%-10s%15s%15s%15s%15s%15s\n", \
+				"CPU", "count", "real total", "virtual total", \
+				"delay total", "delay average"); \
+			printf("          %15llu%15llu%15llu%15llu%15.3fms\n", \
+				(unsigned long long)(t)->cpu_count, \
+				(unsigned long long)(t)->cpu_run_real_total, \
+				(unsigned long long)(t)->cpu_run_virtual_total, \
+				(unsigned long long)(t)->cpu_delay_total, \
+				average_ms((double)(t)->cpu_delay_total, (t)->cpu_count)); \
+		} \
+	} while (0)
+#define PRINT_FILED_DELAY(name, version, t, count, total, max, min) \
+	do { \
+		if (version >= 16) { \
+			printf("%-10s%15s%15s%15s%15s%15s\n", \
+				name, "count", "delay total", "delay average", \
+				"delay max", "delay min"); \
+			printf("          %15llu%15llu%15.3fms%13.6fms%13.6fms\n", \
+				(unsigned long long)(t)->count, \
+				(unsigned long long)(t)->total, \
+				average_ms((double)(t)->total, (t)->count), \
+				delay_ms((double)(t)->max), \
+				delay_ms((double)(t)->min)); \
+		} else { \
+			printf("%-10s%15s%15s%15s\n", \
+				name, "count", "delay total", "delay average"); \
+			printf("          %15llu%15llu%15.3fms\n", \
+				(unsigned long long)(t)->count, \
+				(unsigned long long)(t)->total, \
+				average_ms((double)(t)->total, (t)->count)); \
+		} \
+	} while (0)
+
 static void print_delayacct(struct taskstats *t)
 {
-	printf("\n\nCPU   %15s%15s%15s%15s%15s%15s%15s\n"
-	       "      %15llu%15llu%15llu%15llu%15.3fms%13.6fms%13.6fms\n"
-	       "IO    %15s%15s%15s%15s%15s\n"
-	       "      %15llu%15llu%15.3fms%13.6fms%13.6fms\n"
-	       "SWAP  %15s%15s%15s%15s%15s\n"
-	       "      %15llu%15llu%15.3fms%13.6fms%13.6fms\n"
-	       "RECLAIM  %12s%15s%15s%15s%15s\n"
-	       "      %15llu%15llu%15.3fms%13.6fms%13.6fms\n"
-	       "THRASHING%12s%15s%15s%15s%15s\n"
-	       "      %15llu%15llu%15.3fms%13.6fms%13.6fms\n"
-	       "COMPACT  %12s%15s%15s%15s%15s\n"
-	       "      %15llu%15llu%15.3fms%13.6fms%13.6fms\n"
-	       "WPCOPY   %12s%15s%15s%15s%15s\n"
-	       "      %15llu%15llu%15.3fms%13.6fms%13.6fms\n"
-	       "IRQ   %15s%15s%15s%15s%15s\n"
-	       "      %15llu%15llu%15.3fms%13.6fms%13.6fms\n",
-	       "count", "real total", "virtual total",
-	       "delay total", "delay average", "delay max", "delay min",
-	       (unsigned long long)t->cpu_count,
-	       (unsigned long long)t->cpu_run_real_total,
-	       (unsigned long long)t->cpu_run_virtual_total,
-	       (unsigned long long)t->cpu_delay_total,
-	       average_ms((double)t->cpu_delay_total, t->cpu_count),
-	       delay_ms((double)t->cpu_delay_max),
-	       delay_ms((double)t->cpu_delay_min),
-	       "count", "delay total", "delay average", "delay max", "delay min",
-	       (unsigned long long)t->blkio_count,
-	       (unsigned long long)t->blkio_delay_total,
-	       average_ms((double)t->blkio_delay_total, t->blkio_count),
-	       delay_ms((double)t->blkio_delay_max),
-	       delay_ms((double)t->blkio_delay_min),
-	       "count", "delay total", "delay average", "delay max", "delay min",
-	       (unsigned long long)t->swapin_count,
-	       (unsigned long long)t->swapin_delay_total,
-	       average_ms((double)t->swapin_delay_total, t->swapin_count),
-	       delay_ms((double)t->swapin_delay_max),
-	       delay_ms((double)t->swapin_delay_min),
-	       "count", "delay total", "delay average", "delay max", "delay min",
-	       (unsigned long long)t->freepages_count,
-	       (unsigned long long)t->freepages_delay_total,
-	       average_ms((double)t->freepages_delay_total, t->freepages_count),
-	       delay_ms((double)t->freepages_delay_max),
-	       delay_ms((double)t->freepages_delay_min),
-	       "count", "delay total", "delay average", "delay max", "delay min",
-	       (unsigned long long)t->thrashing_count,
-	       (unsigned long long)t->thrashing_delay_total,
-	       average_ms((double)t->thrashing_delay_total, t->thrashing_count),
-	       delay_ms((double)t->thrashing_delay_max),
-	       delay_ms((double)t->thrashing_delay_min),
-	       "count", "delay total", "delay average", "delay max", "delay min",
-	       (unsigned long long)t->compact_count,
-	       (unsigned long long)t->compact_delay_total,
-	       average_ms((double)t->compact_delay_total, t->compact_count),
-	       delay_ms((double)t->compact_delay_max),
-	       delay_ms((double)t->compact_delay_min),
-	       "count", "delay total", "delay average", "delay max", "delay min",
-	       (unsigned long long)t->wpcopy_count,
-	       (unsigned long long)t->wpcopy_delay_total,
-	       average_ms((double)t->wpcopy_delay_total, t->wpcopy_count),
-	       delay_ms((double)t->wpcopy_delay_max),
-	       delay_ms((double)t->wpcopy_delay_min),
-	       "count", "delay total", "delay average", "delay max", "delay min",
-	       (unsigned long long)t->irq_count,
-	       (unsigned long long)t->irq_delay_total,
-	       average_ms((double)t->irq_delay_total, t->irq_count),
-	       delay_ms((double)t->irq_delay_max),
-	       delay_ms((double)t->irq_delay_min));
+	printf("\n\n");
+
+	PRINT_CPU_DELAY(t->version, t);
+
+	PRINT_FILED_DELAY("IO", t->version, t,
+		blkio_count, blkio_delay_total,
+		blkio_delay_max, blkio_delay_min);
+
+	PRINT_FILED_DELAY("SWAP", t->version, t,
+		swapin_count, swapin_delay_total,
+		swapin_delay_max, swapin_delay_min);
+
+	PRINT_FILED_DELAY("RECLAIM", t->version, t,
+		freepages_count, freepages_delay_total,
+		freepages_delay_max, freepages_delay_min);
+
+	PRINT_FILED_DELAY("THRASHING", t->version, t,
+		thrashing_count, thrashing_delay_total,
+		thrashing_delay_max, thrashing_delay_min);
+
+	if (t->version >= 11) {
+		PRINT_FILED_DELAY("COMPACT", t->version, t,
+			compact_count, compact_delay_total,
+			compact_delay_max, compact_delay_min);
+	}
+
+	if (t->version >= 13) {
+		PRINT_FILED_DELAY("WPCOPY", t->version, t,
+			wpcopy_count, wpcopy_delay_total,
+			wpcopy_delay_max, wpcopy_delay_min);
+	}
+
+	if (t->version >= 14) {
+		PRINT_FILED_DELAY("IRQ", t->version, t,
+			irq_count, irq_delay_total,
+			irq_delay_max, irq_delay_min);
+	}
 }
 
 static void task_context_switch_counts(struct taskstats *t)