[PATCH blktests v5 2/3] bcache: add bcache/002

Add test case from Stephen Zhang [1][2], which is

1. Wait for fio to complete (wait $fio_pid)
2. Wait a few seconds for I/O to drain
3. Then check the utilization

If utilization is still > 0% after I/O completes, then there's a real
accounting leak.

[1] https://lore.kernel.org/linux-bcache/CANubcdX7eNbH_bo4-f94DUbdiEbt04Vxy1MPyhm+CZyXB01FuQ@mail.gmail.com/
[2] https://lore.kernel.org/all/CANubcdU92Uv7wNdZH357LLTnfwPouekXNTPSjHnzYzK99-eZ9w@mail.gmail.com

Signed-off-by: Daniel Wagner <[email protected]>
---
 tests/bcache/002     | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 tests/bcache/002.out |  2 ++
 2 files changed, 80 insertions(+)

diff --git a/tests/bcache/002 b/tests/bcache/002
new file mode 100755
index 000000000000..a50722ff9e0e
--- /dev/null
+++ b/tests/bcache/002
@@ -0,0 +1,78 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-3.0+
+# Copyright (C) 2026 Daniel Wagner, SUSE Labs
+#
+# Test based on Stephen Zhang <[email protected]> test case
+# https://lore.kernel.org/linux-bcache/CANubcdX7eNbH_bo4-f94DUbdiEbt04Vxy1MPyhm+CZyXB01FuQ@mail.gmail.com/#t
+#
+# Test bcache for bio leaks in clone
+
+. tests/bcache/rc
+
+DESCRIPTION="test bcache for bio leaks in clone"
+
+requires() {
+	_have_fio
+}
+
+read_ticks() {
+	local bdev_name="$1"
+	local stat_file
+
+	stat_file="/sys/block/${bdev_name}/stat"
+	awk '{print $10}' "$stat_file"
+}
+
+get_utilization() {
+	local bdev_name="$1"
+	local t1 t2
+
+	t1="$(read_ticks ${bdev_name})"
+	sleep 1
+	t2="$(read_ticks ${bdev_name})"
+
+	# (t2 - t1) is the ms busy. Over 1000ms, (delta/10) gives percentage.
+	echo "scale=2; ($t2 - $t1) / 10" | bc
+}
+
+test_device_array() {
+	echo "Running ${TEST_NAME}"
+
+	if [[ ${#TEST_DEV_ARRAY[@]} -lt 2 ]]; then
+		SKIP_REASONS+=("requires at least 2 devices")
+		return 1
+	fi
+
+	_setup_bcache "${TEST_DEV_ARRAY[@]}"
+
+	local -a bcache_nodes
+	local bcache_dev bdev_name fio_pid state
+
+	mapfile -t bcache_nodes < <(_create_bcache \
+				--cache "${TEST_DEV_ARRAY[0]##*/}" \
+				--bdev "${TEST_DEV_ARRAY[1]##*/}" \
+				--writeback)
+
+	bcache_dev="${bcache_nodes[0]}"
+	bdev_name="$(basename "${bcache_dev}")"
+	echo 1 > /sys/block/"${bdev_name}"/bcache/detach
+
+	state="$(cat /sys/block/"${bdev_name}"/bcache/state)"
+	echo "Device state: ${state}"
+
+	_run_fio_rand_io --filename="${bcache_dev}" --time_base \
+			--runtime=10 >> "$FULL" 2>&1 
+	
+	sleep 5
+
+	local util
+	util="$(get_utilization "${bdev_name}")"
+
+	if (( $(echo "${util} > 1.0" | bc --mathlib) )); then
+		echo "ERROR: Accounting leak detected! Current utilization: ${util}%"
+	fi
+
+	_remove_bcache --bcache "${bcache_nodes[@]}" \
+			--cache "${TEST_DEV_ARRAY[0]##*/}" \
+			--bdev "${TEST_DEV_ARRAY[1]##*/}"
+}
diff --git a/tests/bcache/002.out b/tests/bcache/002.out
new file mode 100644
index 000000000000..529c1a90b135
--- /dev/null
+++ b/tests/bcache/002.out
@@ -0,0 +1,2 @@
+Running bcache/002
+Device state: no cache

-- 
2.53.0