scftorture: Count single_rpc offline failures in statistics outputgrafted

scf_torture_stats_print() aggregates each invoker thread's counters
into a local scf_statistics structure before printing, but the
n_single_rpc_ofl field is missing from the aggregation loop.  As a
result, the "single_rpc_ofl" value printed in the statistics line is
always zero, even when smp_call_function_single() invocations for the
RPC test have failed due to offline CPUs and been counted by the
invoker threads.

Add the missing accumulation so that the printed value reflects the
actual counts.

Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

1 files changed, 81 insertions, 0 deletions

diff --git a/drivers/md/dm-zero.c b/drivers/md/dm-zero.c
new file mode 100644
index 000000000..9a0bb623e
--- /dev/null
+++ b/drivers/md/dm-zero.c
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2003 Jana Saout <jana@saout.de>
+ *
+ * This file is released under the GPL.
+ */
+
+#include <linux/device-mapper.h>
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/bio.h>
+
+#define DM_MSG_PREFIX "zero"
+
+/*
+ * Construct a dummy mapping that only returns zeros
+ */
+static int zero_ctr(struct dm_target *ti, unsigned int argc, char **argv)
+{
+	if (argc != 0) {
+		ti->error = "No arguments required";
+		return -EINVAL;
+	}
+
+	/*
+	 * Silently drop discards, avoiding -EOPNOTSUPP.
+	 */
+	ti->num_discard_bios = 1;
+	ti->discards_supported = true;
+
+	return 0;
+}
+
+/*
+ * Return zeros only on reads
+ */
+static int zero_map(struct dm_target *ti, struct bio *bio)
+{
+	switch (bio_op(bio)) {
+	case REQ_OP_READ:
+		if (bio->bi_opf & REQ_RAHEAD) {
+			/* readahead of null bytes only wastes buffer cache */
+			return DM_MAPIO_KILL;
+		}
+		zero_fill_bio(bio);
+		break;
+	case REQ_OP_WRITE:
+	case REQ_OP_DISCARD:
+		/* writes get silently dropped */
+		break;
+	default:
+		return DM_MAPIO_KILL;
+	}
+
+	bio_endio(bio);
+
+	/* accepted bio, don't make new request */
+	return DM_MAPIO_SUBMITTED;
+}
+
+static void zero_io_hints(struct dm_target *ti, struct queue_limits *limits)
+{
+	limits->max_hw_discard_sectors = UINT_MAX;
+	limits->discard_granularity = 512;
+}
+
+static struct target_type zero_target = {
+	.name   = "zero",
+	.version = {1, 2, 0},
+	.features = DM_TARGET_NOWAIT,
+	.module = THIS_MODULE,
+	.ctr    = zero_ctr,
+	.map    = zero_map,
+	.io_hints = zero_io_hints,
+};
+module_dm(zero);
+
+MODULE_AUTHOR("Jana Saout <jana@saout.de>");
+MODULE_DESCRIPTION(DM_NAME " dummy target returning zeros");
+MODULE_LICENSE("GPL");