Re: [RFC v4 5/9] qemu-iotests: test new zone operations.

[Stefan Hajnoczi <stefanha@gmail.com>]

On Wed, 27 Jul 2022 at 11:00, Ming Lei <ming.lei@redhat.com> wrote:
>
> On Wed, Jul 27, 2022 at 10:34:56AM -0400, Stefan Hajnoczi wrote:
> > On Mon, 11 Jul 2022 at 22:21, Sam Li <faithilikerun@gmail.com> wrote:
> > >
> > > We have added new block layer APIs of zoned block devices. Test it with:
> > > (1) Create a null_blk device, run each zone operation on it and see
> > > whether reporting right zone information.
> > >
> > > Signed-off-by: Sam Li <faithilikerun@gmail.com>
> > > ---
> > >  tests/qemu-iotests/tests/zoned.sh | 69 +++++++++++++++++++++++++++++++
> > >  1 file changed, 69 insertions(+)
> > >  create mode 100755 tests/qemu-iotests/tests/zoned.sh
> > >
> > > diff --git a/tests/qemu-iotests/tests/zoned.sh b/tests/qemu-iotests/tests/zoned.sh
> > > new file mode 100755
> > > index 0000000000..e14a3a420e
> > > --- /dev/null
> > > +++ b/tests/qemu-iotests/tests/zoned.sh
> > > @@ -0,0 +1,69 @@
> > > +#!/usr/bin/env bash
> > > +#
> > > +# Test zone management operations.
> > > +#
> > > +
> > > +seq="$(basename $0)"
> > > +echo "QA output created by $seq"
> > > +status=1 # failure is the default!
> > > +
> > > +_cleanup()
> > > +{
> > > +  _cleanup_test_img
> > > +  sudo rmmod null_blk
> > > +}
> > > +trap "_cleanup; exit \$status" 0 1 2 3 15
> > > +
> > > +# get standard environment, filters and checks
> > > +. ./common.rc
> > > +. ./common.filter
> > > +. ./common.qemu
> > > +
> > > +# This test only runs on Linux hosts with raw image files.
> > > +_supported_fmt raw
> > > +_supported_proto file
> > > +_supported_os Linux
> > > +
> > > +QEMU_IO="build/qemu-io"
> > > +IMG="--image-opts driver=zoned_host_device,filename=/dev/nullb0"
> > > +QEMU_IO_OPTIONS=$QEMU_IO_OPTIONS_NO_FMT
> > > +
> > > +echo "Testing a null_blk device"
> > > +echo "Simple cases: if the operations work"
> > > +sudo modprobe null_blk nr_devices=1 zoned=1
> >
> > Jens & Ming Lei:
> >
> > null_blk is not ideal for automated test cases because it requires
> > root and is global. If two tests are run at the same time they will
> > interfere with each other. There is no way to have independent
> > instances of the null_blk kernel module and the /dev/nullb0 device on
> > a single Linux system. I think this test case can be merged for now
> > but if there's time I suggest investigating alternatives.
> >
> > Maybe the new Linux ublk_drv driver is a better choice if it supports
> > unprivileged operation with multiple independent block devices (plus
>
> This can be one big topic, and IMO, the io path needs to be reviewed
> wrt. security risk. Also if one block device is stuck, it shouldn't
> affect others, so far it can be one problem at least in sync/writeback,
> if one device is hang, writeback on all block device may not move on.
>
> > zoned storage!). It would be necessary to write a userspace null block
> > device that supports zoned storage if that doesn't exist already. I
> > have CCed Ming Lei and Jens Axboe for thoughts.
>
> IMO, it shouldn't be hard to simulate zoned from userspace, the
> patches[1] for setting device parameters are just sent out, then zoned
> parameter could be sent to driver with the added commands easily.
>
> Even ublk can be used to implement zoned target, such as, ublk is
> exposed as one normal disk, but the backing disk could be one real
> zoned/zns device.
>
> [1] https://lore.kernel.org/linux-block/20220727141628.985429-1-ming.lei@redhat.com/T/#mb5518cf418b63fb6ca649f0df199137e50907a29

Thanks for replying!

For QEMU testing purposes a null block driver with zone emulation is
ideal. It does not need to persist data or zone metadata. It shouldn't
require a backing device so that testing can be performed even without
real zoned storage devices.

It should also be possible to extend Linux null_blk to make it more
friendly for parallel tests that are run without knowledge of each
other/cooperation. But I was thinking ublk may have that
infrastructure already.

Stefan