diff --git a/qa/suites/krbd/wac/wac/tasks/wac.yaml b/qa/suites/krbd/wac/wac/tasks/wac.yaml
index 52dabc38bfc..524d29a431a 100644
--- a/qa/suites/krbd/wac/wac/tasks/wac.yaml
+++ b/qa/suites/krbd/wac/wac/tasks/wac.yaml
@@ -2,10 +2,7 @@ tasks:
 - exec:
     client.0:
     - "dmesg -C"
-- rbd:
-    all:
-      fs_type: ext4
 - workunit:
     clients:
       all:
-        - suites/wac.sh
+        - rbd/krbd_wac.sh
diff --git a/qa/workunits/rbd/krbd_wac.sh b/qa/workunits/rbd/krbd_wac.sh
new file mode 100755
index 00000000000..13446040940
--- /dev/null
+++ b/qa/workunits/rbd/krbd_wac.sh
@@ -0,0 +1,40 @@
+#!/usr/bin/env bash
+
+set -ex
+
+wget http://download.ceph.com/qa/wac.c
+gcc -o wac wac.c
+
+rbd create --size 300 img
+DEV=$(sudo rbd map img)
+
+sudo mkfs.ext4 $DEV
+sudo mount $DEV /mnt
+set +e
+sudo timeout 5m ./wac -l 65536 -n 64 -r /mnt/wac-test
+RET=$?
+set -e
+[[ $RET -eq 124 ]]
+sudo killall -w wac || true  # wac forks
+sudo umount /mnt
+
+sudo wipefs -a $DEV
+sudo vgcreate vg_img $DEV
+sudo lvcreate -L 256M -n lv_img vg_img
+udevadm settle
+sudo mkfs.ext4 /dev/mapper/vg_img-lv_img
+sudo mount /dev/mapper/vg_img-lv_img /mnt
+set +e
+sudo timeout 5m ./wac -l 65536 -n 64 -r /mnt/wac-test
+RET=$?
+set -e
+[[ $RET -eq 124 ]]
+sudo killall -w wac || true  # wac forks
+sudo umount /mnt
+sudo vgremove -f vg_img
+sudo pvremove $DEV
+
+sudo rbd unmap $DEV
+rbd rm img
+
+echo OK
diff --git a/qa/workunits/suites/wac.sh b/qa/workunits/suites/wac.sh
deleted file mode 100755
index a61148859a2..00000000000
--- a/qa/workunits/suites/wac.sh
+++ /dev/null
@@ -1,12 +0,0 @@
-#!/usr/bin/env bash
-
-set -ex
-
-wget http://download.ceph.com/qa/wac.c
-gcc -o wac wac.c
-set +e
-timeout 5m ./wac -l 65536 -n 64 -r wac-test
-RET=$?
-set -e
-[[ $RET -eq 124 ]]
-echo OK