selftests: ublk: add stress test for per io daemons

Add a new test_stress_06 for the per io daemons feature. This is just a
copy of test_stress_01 with the per_io_tasks flag added, with varying
amounts of nthreads. This test is able to reproduce a panic which was
caught manually during development [1]; in the current version of this
patch set, it passes.

Note that this commit also makes all stress tests using the
run_io_and_remove helper more stressful by additionally exercising the
batch submit (queue_rqs) path.

[1] https://lore.kernel.org/linux-block/aDgwGoGCEpwd1mFY@fedora/

Suggested-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Uday Shankar <ushankar@purestorage.com>
Link: https://lore.kernel.org/r/20250529-ublk_task_per_io-v8-8-e9d3b119336a@purestorage.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: ps-ushankar

tools/testing/selftests/ublk/Makefile

@@ -38,6 +38,7 @@ TEST_PROGS += test_stress_02.sh
 TEST_PROGS += test_stress_03.sh
 TEST_PROGS += test_stress_04.sh
 TEST_PROGS += test_stress_05.sh
+TEST_PROGS += test_stress_06.sh
 
 TEST_GEN_PROGS_EXTENDED = kublk
 

tools/testing/selftests/ublk/test_common.sh

@@ -278,6 +278,11 @@ __run_io_and_remove()
 	fio --name=job1 --filename=/dev/ublkb"${dev_id}" --ioengine=libaio \
 		--rw=randrw --norandommap --iodepth=256 --size="${size}" --numjobs="$(nproc)" \
 		--runtime=20 --time_based > /dev/null 2>&1 &
+	fio --name=batchjob --filename=/dev/ublkb"${dev_id}" --ioengine=io_uring \
+		--rw=randrw --norandommap --iodepth=256 --size="${size}" \
+		--numjobs="$(nproc)" --runtime=20 --time_based \
+		--iodepth_batch_submit=32 --iodepth_batch_complete_min=32 \
+		--force_async=7 > /dev/null 2>&1 &
 	sleep 2
 	if [ "${kill_server}" = "yes" ]; then
 		local state

tools/testing/selftests/ublk/test_stress_06.sh

@@ -0,0 +1,36 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+. "$(cd "$(dirname "$0")" && pwd)"/test_common.sh
+TID="stress_06"
+ERR_CODE=0
+
+ublk_io_and_remove()
+{
+	run_io_and_remove "$@"
+	ERR_CODE=$?
+	if [ ${ERR_CODE} -ne 0 ]; then
+		echo "$TID failure: $*"
+		_show_result $TID $ERR_CODE
+	fi
+}
+
+if ! _have_program fio; then
+	exit "$UBLK_SKIP_CODE"
+fi
+
+_prep_test "stress" "run IO and remove device with per_io_tasks"
+
+_create_backfile 0 256M
+_create_backfile 1 128M
+_create_backfile 2 128M
+
+ublk_io_and_remove 8G -t null -q 4 --nthreads 5 --per_io_tasks &
+ublk_io_and_remove 256M -t loop -q 4 --nthreads 3 --per_io_tasks \
+        "${UBLK_BACKFILES[0]}" &
+ublk_io_and_remove 256M -t stripe -q 4 --nthreads 4 --per_io_tasks \
+        "${UBLK_BACKFILES[1]}" "${UBLK_BACKFILES[2]}" &
+wait
+
+_cleanup_test "stress"
+_show_result $TID $ERR_CODE