zbd/013: Test stacked drivers and queue freezing

Since there is no test yet in the blktests repository for a device mapper
driver stacked on top of a zoned block device, add such a test. This test
triggers the following deadlock in kernel versions 6.10..6.14:

Call Trace:
 <TASK>
 __schedule+0x43f/0x12f0
 schedule+0x27/0xf0
 __bio_queue_enter+0x10e/0x230
 __submit_bio+0xf0/0x280
 submit_bio_noacct_nocheck+0x185/0x3d0
 blk_zone_wplug_bio_work+0x1ad/0x1f0
 process_one_work+0x17b/0x330
 worker_thread+0x2ce/0x3f0
 kthread+0xec/0x220
 ret_from_fork+0x31/0x50
 ret_from_fork_asm+0x1a/0x30
 </TASK>
Call Trace:
 <TASK>
 __schedule+0x43f/0x12f0
 schedule+0x27/0xf0
 blk_mq_freeze_queue_wait+0x6f/0xa0
 queue_attr_store+0x14f/0x1b0
 kernfs_fop_write_iter+0x13b/0x1f0
 vfs_write+0x253/0x420
 ksys_write+0x64/0xe0
 do_syscall_64+0x82/0x160
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
 </TASK>

Signed-off-by: Bart Van Assche <bvanassche@acm.org>

Author: bvanassche

tests/zbd/013

@@ -0,0 +1,110 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-3.0+
+# Copyright (C) 2025 Google LLC
+
+. tests/zbd/rc
+. common/null_blk
+
+DESCRIPTION="test stacked drivers and queue freezing"
+QUICK=1
+
+requires() {
+	_have_driver dm-crypt
+	_have_fio
+	_have_module null_blk
+	_have_program cryptsetup
+}
+
+# Trigger blk_mq_freeze_queue() repeatedly because there is a bug in the
+# Linux kernel 6.10..6.14 zoned block device code that triggers a deadlock
+# between zoned writes and queue freezing.
+queue_freeze_loop() {
+	while true; do
+		echo 4 >"$1"
+		sleep .1
+		echo 8 >"$1"
+		sleep .1
+	done
+}
+
+test() {
+	set -e
+
+	echo "Running ${TEST_NAME}"
+
+	_init_null_blk nr_devices=0 queue_mode=2
+
+	# A small conventional block device for the LUKS header.
+	local null_blk_params=(
+		blocksize=4096
+		completion_nsec=0
+		memory_backed=1
+		size=4            # MiB
+		submit_queues=1
+		power=1
+	)
+	_configure_null_blk nullb0 "${null_blk_params[@]}"
+	local hdev=/dev/nullb0
+
+	# A larger zoned block device for the data.
+	local null_blk_params=(
+		blocksize=4096
+		completion_nsec=0
+		memory_backed=1
+		size=1024         # MiB
+		submit_queues=1
+		zoned=1
+		power=1
+	)
+	_configure_null_blk nullb1 "${null_blk_params[@]}"
+	local zdev=/dev/nullb1
+
+	local luks_passphrase=this-passphrase-is-not-secret
+	{ echo "${luks_passphrase}" |
+		  cryptsetup luksFormat --batch-mode ${zdev} \
+			     --header ${hdev}; }
+	local luks_vol_name=zbd-013
+	{ echo "${luks_passphrase}" |
+		  cryptsetup luksOpen \
+			     --batch-mode "${zdev}" "${luks_vol_name}" \
+			     --header ${hdev}; }
+	local luksdev="/dev/mapper/${luks_vol_name}"
+	local dmdev
+	dmdev="$(basename "$(readlink "${luksdev}")")"
+	ls -ld "${hdev}" "${zdev}" "${luksdev}" "/dev/${dmdev}" >>"${FULL}"
+	local zdev_basename
+	zdev_basename=$(basename "$zdev")
+	local max_sectors_zdev
+	max_sectors_zdev=/sys/block/"${zdev_basename}"/queue/max_sectors_kb
+	echo 4 > "${max_sectors_zdev}"
+	echo "${zdev_basename}: max_sectors_kb=$(<"${max_sectors_zdev}")" >>"${FULL}"
+	local max_sectors_dm
+	max_sectors_dm=/sys/block/"${dmdev}"/queue/max_sectors_kb
+	echo "${dmdev}: max_sectors_kb=$(<"${max_sectors_dm}")" >>"${FULL}"
+	queue_freeze_loop /sys/block/"$dmdev"/queue/read_ahead_kb &
+	local loop_pid=$!
+	local fio_args=(
+		--bs=64M
+		--direct=1
+		--filename="${luksdev}"
+		--runtime="$TIMEOUT"
+		--time_based
+		--zonemode=zbd
+	)
+	if ! _run_fio_verify_io "${fio_args[@]}" >>"${FULL}" 2>&1; then
+		fail=true
+	fi
+
+	set +e
+
+	kill "${loop_pid}"
+	cryptsetup luksClose "${luks_vol_name}"
+	_exit_null_blk
+
+	if [ -z "$fail" ]; then
+		echo "Test complete"
+	else
+		echo "Test failed"
+		return 1
+	fi
+}

tests/zbd/013.out

@@ -0,0 +1,2 @@
+Running zbd/013
+Test complete