tests: add a regression test for raid456 deadlock

The deadlock is described in [1], as the last patch described, it's
fixed first by [2], however this fix will be reverted and the deadlock
is supposed to be fixed by [3].

[1] https://lore.kernel.org/linux-raid/5ed54ffc-ce82-bf66-4eff-390cb23bc1ac@molgen.mpg.de/T/#t
[2] https://lore.kernel.org/linux-raid/20220621031129.24778-1-guoqing.jiang@linux.dev/
[3] https://lore.kernel.org/linux-raid/20230322064122.2384589-5-yukuai1@huaweicloud.com/

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Jes Sorensen <jes@trained-monkey.org>

diff --git a/tests/24raid456deadlock b/tests/24raid456deadlock
new file mode 100644 (file)
index 0000000..80e6e97
--- /dev/null
+++ b/tests/24raid456deadlock
@@ -0,0 +1,58 @@
+devs="$dev0 $dev1 $dev2 $dev3 $dev4 $dev5"
+runtime=120
+pid=""
+old=`cat /proc/sys/vm/dirty_background_ratio`
+
+test_write_action()
+{
+       while true; do
+               echo check > /sys/block/md0/md/sync_action &> /dev/null
+               sleep 0.1
+               echo idle > /sys/block/md0/md/sync_action &> /dev/null
+       done
+}
+
+test_write_back()
+{
+       fio -filename=$md0 -bs=4k -rw=write -numjobs=1 -name=test \
+               -time_based -runtime=$runtime &> /dev/null
+}
+
+set_up_test()
+{
+       fio -h &> /dev/null || die "fio not found"
+
+       # create a simple raid6
+       mdadm -Cv -R -n 6 -l6 $md0 $devs --assume-clean || die "create raid6 failed"
+
+       # trigger dirty pages write back
+       echo 0 > /proc/sys/vm/dirty_background_ratio
+}
+
+clean_up_test()
+{
+       echo $old > /proc/sys/vm/dirty_background_ratio
+
+       pkill -9 fio
+       kill -9 $pid
+
+       sleep 1
+
+       if ps $pid | tail -1 | awk '{print $3}' | grep D; then
+               die "thread that is writing sysfs is stuck in D state, deadlock is triggered"
+       fi
+       mdadm -S $md0
+}
+
+trap 'clean_up_test' EXIT
+
+set_up_test || die "set up test failed"
+
+test_write_back &
+
+test_write_action &
+pid="$!"
+
+sleep $runtime
+
+exit 0