Re: [PATCH 4/4] iotests: add tests for FUSE-over-io_uring

[Stefan Hajnoczi <stefanha@redhat.com>]

[-- Attachment #1: Type: text/plain, Size: 5652 bytes --]

On Tue, Sep 09, 2025 at 04:51:12PM -0400, Brian Song wrote:
> 
> 
> On 9/9/25 3:38 PM, Stefan Hajnoczi wrote:
> > On Fri, Aug 29, 2025 at 10:50:25PM -0400, Brian Song wrote:
> > > To test FUSE-over-io_uring, set the environment variable
> > > FUSE_OVER_IO_URING=1. This applies only when using the
> > > 'fuse' protocol.
> > > 
> > > $ FUSE_OVER_IO_URING=1 ./check -fuse
> > > 
> > > Suggested-by: Kevin Wolf <kwolf@redhat.com>
> > > Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
> > > Signed-off-by: Brian Song <hibriansong@gmail.com>
> > > ---
> > >   tests/qemu-iotests/check     |  2 ++
> > >   tests/qemu-iotests/common.rc | 45 +++++++++++++++++++++++++++---------
> > >   2 files changed, 36 insertions(+), 11 deletions(-)
> > > 
> > > diff --git a/tests/qemu-iotests/check b/tests/qemu-iotests/check
> > > index 545f9ec7bd..c6fa0f9e3d 100755
> > > --- a/tests/qemu-iotests/check
> > > +++ b/tests/qemu-iotests/check
> > > @@ -94,6 +94,8 @@ def make_argparser() -> argparse.ArgumentParser:
> > >           mg.add_argument('-' + fmt, dest='imgfmt', action='store_const',
> > >                           const=fmt, help=f'test {fmt}')
> > > +    # To test FUSE-over-io_uring, set the environment variable
> > > +    # FUSE_OVER_IO_URING=1. This applies only when using the 'fuse' protocol
> > >       protocol_list = ['file', 'rbd', 'nbd', 'ssh', 'nfs', 'fuse']
> > >       g_prt = p.add_argument_group(
> > >           '  image protocol options',
> > > diff --git a/tests/qemu-iotests/common.rc b/tests/qemu-iotests/common.rc
> > > index e977cb4eb6..f8b79c3810 100644
> > > --- a/tests/qemu-iotests/common.rc
> > > +++ b/tests/qemu-iotests/common.rc
> > > @@ -539,17 +539,38 @@ _make_test_img()
> > >           touch "$export_mp"
> > >           rm -f "$SOCK_DIR/fuse-output"
> > > -        # Usually, users would export formatted nodes.  But we present fuse as a
> > > -        # protocol-level driver here, so we have to leave the format to the
> > > -        # client.
> > > -        # Switch off allow-other, because in general we do not need it for
> > > -        # iotests.  The default allow-other=auto has the downside of printing a
> > > -        # fusermount error on its first attempt if allow_other is not
> > > -        # permissible, which we would need to filter.
> > 
> > This comment applies to both branches of the if statement. I think
> > keeping it here is slightly better.
> > 
> > > -        QSD_NEED_PID=y $QSD \
> > > -              --blockdev file,node-name=export-node,filename=$img_name,discard=unmap \
> > > -              --export fuse,id=fuse-export,node-name=export-node,mountpoint="$export_mp",writable=on,growable=on,allow-other=off \
> > > -              &
> > > +        if [ -n "$FUSE_OVER_IO_URING" ]; then
> > > +            nr_cpu=$(nproc 2>/dev/null || echo 1)
> > > +            nr_iothreads=$((nr_cpu / 2))
> > > +            if [ $nr_iothreads -lt 1 ]; then
> > > +                nr_iothreads=1
> > > +            fi
> > 
> > Please add a comment explaining that the purpose of this configuration
> > based on the number of CPUs is to test multiple IOThreads when the host
> > allows it, since that is a more interesting case then just 1 IOThread.
> > Many other configurations are possible as well, but not all of them can
> > be tested because the test matrix would be large.
> > 
> > > +
> > > +            iothread_args=""
> > > +            iothread_export_args=""
> > > +            for ((i=0; i<$nr_iothreads; i++)); do
> > > +                iothread_args="$iothread_args --object iothread,id=iothread$i"
> > > +                iothread_export_args="$iothread_export_args,iothread.$i=iothread$i"
> > > +            done
> > > +
> > > +            QSD_NEED_PID=y $QSD \
> > > +                    $iothread_args \
> > > +                    --blockdev file,node-name=export-node,filename=$img_name,discard=unmap \
> > > +                    --export fuse,id=fuse-export,node-name=export-node,mountpoint="$export_mp",writable=on,growable=on,allow-other=off,io-uring=on$iothread_export_args \
> > > +                &
> > > +        else
> > > +            # Usually, users would export formatted nodes.  But we present fuse as a
> > > +            # protocol-level driver here, so we have to leave the format to the
> > > +            # client.
> > > +            # Switch off allow-other, because in general we do not need it for
> > > +            # iotests.  The default allow-other=auto has the downside of printing a
> > > +            # fusermount error on its first attempt if allow_other is not
> > > +            # permissible, which we would need to filter.
> > > +            QSD_NEED_PID=y $QSD \
> > > +                --blockdev file,node-name=export-node,filename=$img_name,discard=unmap \
> > > +                --export fuse,id=fuse-export,node-name=export-node,mountpoint="$export_mp",writable=on,growable=on,allow-other=off \
> > > +                &
> > > +        fi
> > >           pidfile="$QEMU_TEST_DIR/qemu-storage-daemon.pid"
> > > @@ -592,6 +613,8 @@ _rm_test_img()
> > >           kill "${FUSE_PIDS[index]}"
> > > +        sleep 1
> > > +
> > 
> > What is the purpose of this sleep command?
> > 
> 
> I don’t exactly remember why. It might get stuck if there’s no sleep here. I
> remember we discussed this problem in earlier emails.

The purpose needs to be understood. Otherwise there is a good chance
that the test will fail randomly in a continuous integration environment
where things sometimes take a long time due to CPU contention.

Stefan

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]