Re: [PATCH blktests v2 2/2] blktests: add Ming Lei's scsi-stress-remove

[Omar Sandoval <osandov@osandov.com>]

On Thu, Dec 13, 2018 at 01:28:44PM -0500, Dennis Zhou wrote:
> This test exposed a race condition with shutting down a request_queue
> and the new blkg association. The issue ended up being that while the
> request_queue will just start failing requests, blkg destruction sets
> the q->root_blkg to %NULL. This caused a NPE when trying to reference
> it. So to help prevent this from happening again, integrate Ming's test
> into blktests so that it can more easily be ran.
> 
> Signed-off-by: Dennis Zhou <dennis@kernel.org>
> Cc: Ming Lei <ming.lei@redhat.com>
> ---
> v2:
> - Change scheduler retrieving logic based on Ming's comment
> 
>  tests/block/022     | 90 +++++++++++++++++++++++++++++++++++++++++++++
>  tests/block/022.out |  2 +
>  2 files changed, 92 insertions(+)
>  create mode 100755 tests/block/022
>  create mode 100644 tests/block/022.out
> 
> diff --git a/tests/block/022 b/tests/block/022
> new file mode 100755
> index 0000000..84336e0
> --- /dev/null
> +++ b/tests/block/022
> @@ -0,0 +1,90 @@
> +#!/bin/bash
> +# SPDX-License-Identifier: GPL-3.0+
> +# Copyright (C) 2018 Ming Lei
> +#
> +# Regression test for patch "blkcg: handle dying request_queue when associating
> +# a blkg"
> +#
> +# This tries to expose the race condition between blkg association and
> +# request_queue shutdown. When a request_queue is shutdown, the corresponding
> +# blkgs are destroyed. Any further associations should fail gracefully and not
> +# cause a kernel panic.
> +
> +. tests/block/rc
> +. common/scsi_debug
> +. common/cgroup
> +
> +DESCRIPTION="test graceful shutdown of scsi_debug devices with running fio jobs"
> +QUICK=1
> +
> +requires() {
> +	_have_cgroup2_controller io && _have_scsi_debug && _have_fio
> +}
> +
> +scsi_debug_stress_remove() {
> +	scsi_debug_path="/sys/bus/pseudo/drivers/scsi_debug"
> +	count=21
> +
> +	runtime=12
> +	nr_fio_jobs=8
> +	scsi_dbg_ndelay=10000
> +
> +	# set higher aio limit
> +	echo 524288 > /proc/sys/fs/aio-max-nr
> +
> +	#figure out the CAN_QUEUE
> +	can_queue=$(((count + 1) * (count / 2) / 2))
> +
> +	rmmod scsi_debug > /dev/null 2>&1
> +	modprobe scsi_debug virtual_gb=128 max_luns=$count \
> +		ndelay=$scsi_dbg_ndelay max_queue=$can_queue
> +
> +	# figure out scsi_debug disks
> +	hosts=$(ls -d /sys/bus/pseudo/drivers/scsi_debug/adapter0/host*)
> +	hostname=$(basename "$hosts")
> +	host=$(echo "$hostname" | grep -o -E '[0-9]+')
> +
> +	sdisks=$(ls -d $scsi_debug_path/adapter*/"$hostname"/target*/*/block/*)
> +	disks=""
> +	for sd in $sdisks; do
> +		disks+="/dev/"$(basename "$sd")
> +		disks+=" "
> +	done

blktests has _init_scsi_debug which does all of this for you. And,
block/001 is very similar to this test, just without the fio workload or
changing schedulers. Could you please rework this to be based on
block/001?