blktrace: add blktrace zone management regression test

Create a new blktrace test group and add a regression test for a
blktrace false positive WARNING that occurs when zone management
commands are traced with blktrace on V1 version.

Bug: https://syzkaller.appspot.com/bug?extid=153e64c0aa875d7e4c37
Location: kernel/trace/blktrace.c:367-368

The test:
1. Creates a zoned null_blk device (8 zones, 1GB, no conventional zones)
2. Starts blktrace on the device
3. Issues zone open command for all zones
4. Checks dmesg for the false positive WARNING

Device configuration:
- Total size: 1GB
- Zone size: 128MB
- Number of zones: 8
- Conventional zones: 0

If the WARNING is found, the bug is present and logged to the full
output. If no WARNING appears, the bug is fixed.

Note: The bug uses WARN_ON_ONCE, so it triggers only once per boot.
Subsequent runs after the first trigger will not show the WARNING:
commit 4a0940bdcac260be1e3460e99464fa63d317c6a2
Author: Chaitanya Kulkarni <[email protected]>
Date:   Mon Oct 27 19:46:19 2025 -0700

    blktrace: use debug print to report dropped events

https://lore.kernel.org/linux-block/[email protected]/

Signed-off-by: Chaitanya Kulkarni <[email protected]>
Reviewed-by: Johannes Thumshirn <[email protected]>
Signed-off-by: Shin'ichiro Kawasaki <[email protected]>

Author: ChaitanayaKulkarni

tests/blktrace/001

@@ -0,0 +1,90 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-3.0+
+# Copyright (C) 2025 Chaitanya Kulkarni <[email protected]>
+#
+# Regression test for blktrace false positive WARNING on zone management
+# commands.
+#
+# Bug: https://syzkaller.appspot.com/bug?extid=153e64c0aa875d7e4c37
+# Location: kernel/trace/blktrace.c:367-368
+#
+# The bug triggers a WARNING when zone management commands (zone open/close/
+# finish/reset) are traced with blktrace on V1 version. This is a false
+# positive that should be fixed.
+
+. tests/blktrace/rc
+. common/null_blk
+
+DESCRIPTION="blktrace zone management command tracing"
+QUICK=1
+
+requires() {
+	_have_program blkzone
+	_have_null_blk
+	_have_module_param null_blk zoned
+}
+
+test() {
+	echo "Running ${TEST_NAME}"
+
+	local blktrace_pid
+	local warning_count
+	local device
+
+	# Create zoned null_blk device via configfs
+	# 8 zones, 1GB total, 128MB per zone, no conventional zones
+	if ! _configure_null_blk nullb1 \
+		memory_backed=1 \
+		zone_size=128 \
+		zone_nr_conv=0 \
+		size=1024 \
+		zoned=1 \
+		power=1; then
+		return 1
+	fi
+
+	device=/dev/nullb1
+
+	# Verify it's a zoned device
+	local zoned_mode
+	zoned_mode=$(cat /sys/block/nullb1/queue/zoned)
+	if [[ "$zoned_mode" != "host-managed" ]]; then
+		echo "Device is not zoned (mode: $zoned_mode)"
+		_exit_null_blk
+		return 1
+	fi
+
+	# Start blktrace
+	blktrace --dev="${device}" --output=trace --output-dir="$TMPDIR" \
+		>> "$FULL" 2>&1 &
+	blktrace_pid=$!
+	sleep 2
+
+	# Verify blktrace started
+	if ! ps -p $blktrace_pid > /dev/null 2>&1; then
+		echo "blktrace failed to start"
+		_exit_null_blk
+		return 1
+	fi
+
+	# Issue zone open command for all zones (triggers bug if present)
+	blkzone open "${device}" >> "$FULL" 2>&1
+
+	sleep 1
+
+	# Stop blktrace
+	kill $blktrace_pid 2>/dev/null
+	wait $blktrace_pid 2>/dev/null
+
+	# Check for WARNING (bug present if WARNING found)
+	warning_count=$(_dmesg_since_test_start | grep -c "WARNING.*blktrace.c:367" || true)
+
+	if [[ $warning_count -gt 0 ]]; then
+		echo "WARNING: blktrace bug detected at blktrace.c:367"
+		_dmesg_since_test_start | grep -A 10 "WARNING.*blktrace.c:367" >> "$FULL"
+	fi
+
+	_exit_null_blk
+
+	echo "Test complete"
+}

tests/blktrace/001.out

@@ -0,0 +1,2 @@
+Running blktrace/001
+Test complete

tests/blktrace/rc

@@ -0,0 +1,13 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-3.0+
+# Copyright (C) 2025 Chaitanya Kulkarni <[email protected]>
+#
+# Tests for blktrace infrastructure
+
+. common/rc
+
+group_requires() {
+	_have_root
+	_have_blktrace
+	_have_program blkparse
+}