Add a test that repeatedly rescans nvme controllers while doing IO
on an nvme namespace connected to these controllers. The purpose
of the test is to make sure that no I/O errors or data corruption
occurs because of the rescan operations. The test uses sub-second
sleeps, which can't be easily accomplished in bash because of
missing floating-point arithmetic (and because usleep(1) isn't
portable). Therefore an awk program is used to trigger the
device rescans.

Signed-off-by: Martin Wilck <redacted>
---
v2: - don't use usleep (Nilay Shroff). Use an awk program to do floating
      point arithmetic and achieve more accurate sub-second sleep times.
    - add 053.out (Nilay Shroff).
---
 tests/nvme/053     | 70 ++++++++++++++++++++++++++++++++++++++++++++++
 tests/nvme/053.out |  2 ++
 tests/nvme/rc      | 18 ++++++++++++
 3 files changed, 90 insertions(+)
 create mode 100755 tests/nvme/053
 create mode 100644 tests/nvme/053.out

diff --git a/tests/nvme/053 b/tests/nvme/053
new file mode 100755
index 0000000..d32484c
--- /dev/null
+++ b/tests/nvme/053

@@ -0,0 +1,70 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-3.0+
+# Copyright (C) 2024 Martin Wilck, SUSE LLC
+
+. tests/nvme/rc
+
+DESCRIPTION="test controller rescan under I/O load"
+TIMED=1
+: "${TIMEOUT:=60}"
+
+rescan_controller() {
+	local path
+	path="$1/rescan_controller"
+
+	[[ -f "$path" ]] || {
+		echo "cannot rescan $1"
+		return 1
+	}
+
+	awk -f "$TMPDIR/rescan.awk" \
+	    -v path="$path" -v timeout="$TIMEOUT" -v seed="$2" &
+}
+
+create_rescan_script() {
+	cat >"$TMPDIR/rescan.awk" <<EOF
+@load "time"
+
+BEGIN {
+    srand(seed);
+    finish = gettimeofday() + strtonum(timeout);
+    while (gettimeofday() < finish) {
+	sleep(0.1 + 5 * rand());
+	printf("1\n") > path;
+	close(path);
+    }
+}
+EOF
+}