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

[Brian Song <hibriansong@gmail.com>]

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.
-        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 [ $nr_iothreads -lt 1 ]; then
+                nr_iothreads=1
+            fi
+
+            iothread_args=""
+            iothread_export_args=""
+            for ((i=0; i<$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
+
         # Wait until the mount is gone
         timeout=10 # *0.5 s
         while true; do
-- 
2.45.2