Remove hard coded device paths

This is prep work for the virtio-blk backend changes

Signed-off-by: Daniel Hill <daniel@gluo.nz>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Co-developed-by: Kent Overstreet <kent.overstreet@linux.dev>

10 files changed, 602 insertions, 570 deletions

diff --git a/tests/bcachefs/ec.ktest b/tests/bcachefs/ec.ktest
index 442fd2d..9914284 100755
--- a/tests/bcachefs/ec.ktest
+++ b/tests/bcachefs/ec.ktest
@@ -22,8 +22,8 @@ test_ec_small()
 	--errors=panic				\
 	--erasure_code				\
 	--replicas=2				\
-	/dev/sd[bcdef]
-    devs=/dev/sdb:/dev/sdc:/dev/sdd:/dev/sde:/dev/sdf
+	"${ktest_scratch_dev[@]}"
+    devs="$(join_by : "${ktest_scratch_dev[@]}")"
 
     mount -t bcachefs $devs /mnt
 
@@ -36,16 +36,16 @@ test_ec_small()
     df -h /mnt
     umount /mnt
 
-    bcachefs fsck -n /dev/sd[bcdef]
+    bcachefs fsck -n "${ktest_scratch_dev[@]}"
 
     # test remount:
     echo "Testing remount"
     mount -t bcachefs -o fsck $devs /mnt
     umount /mnt
 
-    bcachefs fsck /dev/sd[bcdef]
+    bcachefs fsck -n "${ktest_scratch_dev[@]}"
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_ec_umount()
@@ -56,8 +56,8 @@ test_ec_umount()
 	--errors=panic				\
 	--erasure_code				\
 	--replicas=2				\
-	/dev/sd[bcdef]
-    devs=/dev/sdb:/dev/sdc:/dev/sdd:/dev/sde:/dev/sdf
+	"${ktest_scratch_dev[@]}"
+    devs="$(join_by : "${ktest_scratch_dev[@]}")"
 
     for i in $(seq 1 10); do
 	mount -t bcachefs $devs /mnt
@@ -66,7 +66,7 @@ test_ec_umount()
 	umount /mnt
     done
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 do_ec_test()
@@ -80,8 +80,8 @@ do_ec_test()
 	--erasure_code				\
 	"$@"					\
 	--replicas=2				\
-	/dev/sd[bcdef]
-    devs=/dev/sdb:/dev/sdc:/dev/sdd:/dev/sde:/dev/sdf
+	"${ktest_scratch_dev[@]}"
+    devs="$(join_by : "${ktest_scratch_dev[@]}")"
 
     mount -t bcachefs $devs /mnt
 
@@ -93,7 +93,7 @@ do_ec_test()
 
     bcachefs fs usage -h /mnt
     umount /mnt
-    bcachefs fsck -n /dev/sd[bcdef]
+    bcachefs fsck -n "${ktest_scratch_dev[@]}"
 
     # test remount:
     echo "Testing remount"
@@ -101,7 +101,7 @@ do_ec_test()
     cat /mnt/fiotest > /dev/null
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_ec()
@@ -133,13 +133,18 @@ test_ec_mixed_tiers()
 	--erasure_code				\
 	--compression=lz4			\
 	--replicas=2				\
-	--label dup /dev/sd[bc] 		\
-	--label tri /dev/sd[def] 		\
+	--label dup				\
+	${ktest_scratch_dev[0]}			\
+	${ktest_scratch_dev[1]}			\
+	--label tri				\
+	${ktest_scratch_dev[2]}			\
+	${ktest_scratch_dev[3]}			\
+	${ktest_scratch_dev[4]}			\
 	--foreground_target=dup			\
 	--promote_target=dup			\
 	--background_target=tri
-    devs=/dev/sdb:/dev/sdc:/dev/sdd:/dev/sde:/dev/sdf
 
+    devs="$(join_by : "${ktest_scratch_dev[@]}")"
     mount -t bcachefs $devs /mnt
 
     #enable_memory_faults
@@ -155,9 +160,9 @@ test_ec_mixed_tiers()
     mount -t bcachefs -o fsck $devs /mnt
     umount /mnt
 
-    bcachefs fsck /dev/sd[bcdef]
+    bcachefs fsck -n "${ktest_scratch_dev[@]}"
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_ec_gc()
@@ -169,9 +174,9 @@ test_ec_gc()
     run_quiet "" bcachefs format -f		\
 	--errors=continue			\
 	--replicas=2				\
-	/dev/sd[bcdef]
-    devs=/dev/sdb:/dev/sdc:/dev/sdd:/dev/sde:/dev/sdf
+	"${ktest_scratch_dev[@]}"
 
+    devs="$(join_by : "${ktest_scratch_dev[@]}")"
     mount -t bcachefs -o erasure_code $devs /mnt
 
     fill_device /mnt/fiotest
@@ -205,9 +210,9 @@ test_ec_gc()
     mount -t bcachefs -o fix_errors,erasure_code $devs /mnt
     umount /mnt
 
-    bcachefs fsck /dev/sd[bcdef]
+    bcachefs fsck "${ktest_scratch_dev[@]}"
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 do_remove_test()
@@ -221,9 +226,9 @@ do_remove_test()
 	--errors=panic				\
 	--erasure_code				\
 	--replicas=2				\
-	/dev/sd[bcdef]
+	"${ktest_scratch_dev[@]}"
 
-    mount -t bcachefs /dev/sdb:/dev/sdc:/dev/sdd:/dev/sde:/dev/sdf /mnt
+    mount -t bcachefs "$(join_by : "${ktest_scratch_dev[@]}")" /mnt
 
     local fioout="$ktest_out/fio-out"
     run_fio_randrw >"$fioout" 2>&1 &
@@ -232,22 +237,22 @@ do_remove_test()
     sleep 1
 
     if [[ $offline = 1 ]]; then
-	echo -n "offlining /dev/sdb... "
-	bcachefs device offline --force	/dev/sdb
+	echo -n "offlining ${ktest_scratch_dev[0]}... "
+	bcachefs device offline --force	${ktest_scratch_dev[0]}
 	echo "done"
     fi
 
     if [[ $evacuate = 1 ]]; then
-	echo -n "evacuating /dev/sdb... "
-	bcachefs device evacuate	/dev/sdb
+	echo -n "evacuating ${ktest_scratch_dev[0]}... "
+	bcachefs device evacuate	${ktest_scratch_dev[0]}
 	echo "done"
     fi
 
-    echo -n "removing /dev/sdb... "
+    echo -n "removing ${ktest_scratch_dev[0]}... "
     if [[ $evacuate = 1 ]]; then
-	bcachefs device remove		/dev/sdb
+	bcachefs device remove		${ktest_scratch_dev[0]}
     else
-	bcachefs device remove --force	/dev/sdb
+	bcachefs device remove --force	${ktest_scratch_dev[0]}
     fi
     echo "done"
 
@@ -258,10 +263,10 @@ do_remove_test()
 
     umount /mnt
 
-    mount -t bcachefs /dev/sdb:/dev/sdc:/dev/sdd:/dev/sde:/dev/sdf /mnt
+    mount -t bcachefs "$(join_by : "${ktest_scratch_dev[@]}")" /mnt
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 d_test_device_remove_offline()
diff --git a/tests/bcachefs/nas_apps.ktest b/tests/bcachefs/nas_apps.ktest
index b567a77..97b0a3a 100755
--- a/tests/bcachefs/nas_apps.ktest
+++ b/tests/bcachefs/nas_apps.ktest
@@ -40,9 +40,9 @@ array_setup()
 	--errors=panic				\
 	--erasure_code				\
 	--replicas=3				\
-	/dev/sd[bcdefghijk]
-    devs=/dev/sdb:/dev/sdc:/dev/sdd:/dev/sde:/dev/sdf:/dev/sdg:/dev/sdh:/dev/sdi:/dev/sdj:/dev/sdk
-    mount -t bcachefs $devs /mnt
+	${ktest_scratch_dev[@]}
+
+    mount -t bcachefs "$(join_by : "${ktest_scratch_dev[@]}")" /mnt
 }
 
 array_teardown()
@@ -67,7 +67,7 @@ test_iscsi()
     run_quiet "" iscsiadm -m discovery -t sendtargets -p 127.0.0.1
     run_quiet "" iscsiadm -m node --login
 
-    run_fio_randrw --filename=/dev/sdl
+    run_fio_randrw --filename=${ktest_scratch_dev[10]}
 
     run_quiet "" iscsiadm -m node --logout
     run_quiet "" targetcli /iscsi delete iqn.2018-05.world.srv:dlp.target01
diff --git a/tests/bcachefs/nfs.ktest b/tests/bcachefs/nfs.ktest
index 234d227..411debd 100755
--- a/tests/bcachefs/nfs.ktest
+++ b/tests/bcachefs/nfs.ktest
@@ -18,8 +18,8 @@ test_nfs()
 
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
-	/dev/sdb
-    mount -t bcachefs /dev/sdb /export2
+	${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /export2
 
     echo "/export1  *(rw,insecure,no_root_squash,no_subtree_check)" >> /etc/exports
     echo "/export2  *(rw,insecure,no_root_squash,no_subtree_check)" >> /etc/exports
diff --git a/tests/bcachefs/perf.ktest b/tests/bcachefs/perf.ktest
index da775cf..4f0f0d1 100755
--- a/tests/bcachefs/perf.ktest
+++ b/tests/bcachefs/perf.ktest
@@ -28,15 +28,15 @@ perf_mkfs()
 	--btree_node_size=$btree_node_size	\
 	--no_initialize				\
 	--version=11				\
-	/dev/sdb
-    mount -t bcachefs -o version_upgrade /dev/sdb /mnt
-    bcachefs device resize-journal /dev/sdb 1G
+	${ktest_scratch_dev[0]}
+    mount -t bcachefs -o version_upgrade ${ktest_scratch_dev[0]} /mnt
+    bcachefs device resize-journal ${ktest_scratch_dev[0]} 1G
     sleep 1
-    bcachefs device resize-journal /dev/sdb 2G
+    bcachefs device resize-journal ${ktest_scratch_dev[0]} 2G
     sleep 1
-    bcachefs device resize-journal /dev/sdb 3G
+    bcachefs device resize-journal ${ktest_scratch_dev[0]} 3G
     sleep 1
-    bcachefs device resize-journal /dev/sdb 4G
+    bcachefs device resize-journal ${ktest_scratch_dev[0]} 4G
     ln -sf /sys/fs/bcachefs/*/perf_test p
 }
 
diff --git a/tests/bcachefs/quota.ktest b/tests/bcachefs/quota.ktest
index e6535c2..3704822 100755
--- a/tests/bcachefs/quota.ktest
+++ b/tests/bcachefs/quota.ktest
@@ -13,11 +13,11 @@ require-make linuxquota
 
 test_usrquota_twodevices()
 {
-    bcachefs format				\
-	--errors=panic		\
-	/dev/sd[bc] >/dev/null
+    run_quiet "" bcachefs format		\
+	--errors=panic				\
+	${ktest_scratch_dev[@]}
 
-    mount -t bcachefs -o usrquota,grpquota,prjquota /dev/sdc:/dev/sdb /mnt
+    mount -t bcachefs -o usrquota,grpquota,prjquota ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]} /mnt
 
     repquota -s /mnt
 
@@ -44,14 +44,14 @@ test_usrquota_twodevices()
 test_usrquota()
 {
     if false; then
-	mkfs.xfs /dev/sdb
+	mkfs.xfs ${ktest_scratch_dev[0]}
     else
 	bcachefs format				\
-	    --errors=panic		\
-	    /dev/sdb >/dev/null
+	    --errors=panic			\
+	    ${ktest_scratch_dev[0]} >/dev/null
     fi
 
-    mount -t bcachefs -o usrquota,grpquota,prjquota /dev/sdb /mnt
+    mount -t bcachefs -o usrquota,grpquota,prjquota ${ktest_scratch_dev[0]} /mnt
 
     repquota -s /mnt
 
@@ -78,14 +78,14 @@ test_usrquota()
 test_grpquota()
 {
     if false; then
-	mkfs.xfs /dev/sdb
+	mkfs.xfs ${ktest_scratch_dev[0]}
     else
-	bcachefs format				\
-	    --errors=panic		\
-	    /dev/sdb /dev/sdc >/dev/null
+	run_quiet "" bcachefs format		\
+	    --errors=panic			\
+	    ${ktest_scratch_dev[0]} ${ktest_scratch_dev[1]} >/dev/null
     fi
 
-    mount -t bcachefs -o usrquota,grpquota,prjquota /dev/sdb:/dev/sdc /mnt
+    mount -t bcachefs -o usrquota,grpquota,prjquota ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]} /mnt
 
     setquota -g root 256M 512M 64 128 /mnt
     #setquota -t 60 60 /mnt
@@ -101,11 +101,11 @@ test_grpquota()
 
 test_prjquota()
 {
-    bcachefs format		\
-	--errors=panic		\
-	/dev/sdb >/dev/null
+   run_quiet ""  bcachefs format	\
+	--errors=panic			\
+	${ktest_scratch_dev[0]} >/dev/null
 
-    mount -t bcachefs -o usrquota,grpquota,prjquota /dev/sdb /mnt
+    mount -t bcachefs -o usrquota,grpquota,prjquota ${ktest_scratch_dev[0]} /mnt
 
     repquota -vP  /mnt
     mkdir /mnt/q1
@@ -135,11 +135,11 @@ test_prjquota()
 
 test_prjquota_multidevices()
 {
-    bcachefs format			\
-	--errors=panic		\
-	/dev/sd[bc] >/dev/null
+    run_quiet "" bcachefs format	\
+	--errors=panic			\
+	${ktest_scratch_dev[@]}
 
-    mount -t bcachefs -o usrquota,grpquota,prjquota /dev/sdb:/dev/sdc /mnt
+    mount -t bcachefs -o usrquota,grpquota,prjquota ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]} /mnt
 
     repquota -vP  /mnt
     mkdir /mnt/q1
diff --git a/tests/bcachefs/replication.ktest b/tests/bcachefs/replication.ktest
index 8c54580..47c09da 100755
--- a/tests/bcachefs/replication.ktest
+++ b/tests/bcachefs/replication.ktest
@@ -22,10 +22,12 @@ test_recovery()
 	--discard				\
 	--bucket=64k				\
 	--block_size=4k				\
-	/dev/sd[bcd]
+	${ktest_scratch_dev[0]}			\
+	${ktest_scratch_dev[1]}			\
+	${ktest_scratch_dev[2]}
 
     for i in `seq 0 20`; do
-	mount -t bcachefs /dev/sdb:/dev/sdc:/dev/sdd /mnt
+	mount -t bcachefs ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]}:${ktest_scratch_dev[2]} /mnt
 
 	#run_fio_randrw
 	fio --eta=always			\
@@ -48,48 +50,53 @@ test_recovery()
 	umount /mnt
     done
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_multimount()
 {
     set_watchdog 10
     bcachefs format				\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 
     mkdir -p /mnt/1 /mnt/2
-    mount -t bcachefs /dev/sdb /mnt/1
-    mount -t bcachefs /dev/sdb /mnt/2
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt/1
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt/2
 
     umount /mnt/1
     umount /mnt/2
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_twodevices()
 {
     run_basic_fio_test				\
-	/dev/sdb /dev/sdc /dev/sdd
+	${ktest_scratch_dev[0]} ${ktest_scratch_dev[1]} ${ktest_scratch_dev[2]}
 }
 
 test_largebuckets()
 {
     set_watchdog 30
-    run_quiet "" bcachefs format -f --bucket=8M /dev/sd[bcd]
+    run_quiet "" bcachefs format -f --bucket=8M	\
+	${ktest_scratch_dev[0]}			\
+	${ktest_scratch_dev[1]}			\
+	${ktest_scratch_dev[2]}
 
-    mount -t bcachefs /dev/sdb:/dev/sdc:/dev/sdd /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]}:${ktest_scratch_dev[2]} /mnt
     dd if=/dev/zero of=/mnt/foo bs=8M count=1024 oflag=direct
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_replicas()
 {
     run_basic_fio_test				\
 	--replicas=2				\
-	/dev/sd[bcd]
+	${ktest_scratch_dev[0]}			\
+	${ktest_scratch_dev[1]}			\
+	${ktest_scratch_dev[2]}
 }
 
 test_replicas_variable_buckets()
@@ -97,18 +104,18 @@ test_replicas_variable_buckets()
     set_watchdog 1200
     run_quiet "" bcachefs format -f			\
 	--replicas=2					\
-	--bucket=32k	/dev/sdb			\
-	--bucket=64k	/dev/sdc			\
-	--bucket=128k	/dev/sdd			\
-	--bucket=128k	/dev/sde			\
-	--bucket=128k	/dev/sdf
+	--bucket=32k	${ktest_scratch_dev[0]}		\
+	--bucket=64k	${ktest_scratch_dev[1]}		\
+	--bucket=128k	${ktest_scratch_dev[2]}		\
+	--bucket=128k	${ktest_scratch_dev[3]}		\
+	--bucket=128k	${ktest_scratch_dev[4]}
 
-    mount -t bcachefs /dev/sdb:/dev/sdc:/dev/sdd:/dev/sde:/dev/sdf /mnt
+    mount -t bcachefs "$(join_by : "${ktest_scratch_dev[@]}")" /mnt
     fs_mark -v -n 20000 -s 4096 -k -S 0 -D 1000 -N 100000 -d /mnt -t 60
     df -h /mnt
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 d_test_copygc_torture()
@@ -118,10 +125,12 @@ d_test_copygc_torture()
     bcachefs_antagonist
     set_watchdog 600
 
-    run_quiet "" bcachefs format -f		\
-	"$@" /dev/sd[bcd]
+    run_quiet "" bcachefs format -f "$@"	\
+	${ktest_scratch_dev[0]}			\
+	${ktest_scratch_dev[1]}			\
+	${ktest_scratch_dev[2]}
 
-    mount -t bcachefs /dev/sdb:/dev/sdc:/dev/sdd /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]}:${ktest_scratch_dev[2]} /mnt
     #enable_memory_faults
 
     fio						\
@@ -161,7 +170,7 @@ d_test_copygc_torture()
     #disable_memory_faults
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 do_remove_test()
@@ -172,9 +181,11 @@ do_remove_test()
 
     run_quiet "" bcachefs format		\
 	--replicas=2				\
-	/dev/sd[bcd]
+	${ktest_scratch_dev[0]}			\
+	${ktest_scratch_dev[1]}			\
+	${ktest_scratch_dev[2]}
 
-    mount -t bcachefs /dev/sdb:/dev/sdc:/dev/sdd /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]}:${ktest_scratch_dev[2]} /mnt
 
     local fioout="$ktest_out/fio-out"
     run_fio_randrw >"$fioout" 2>&1 &
@@ -183,25 +194,25 @@ do_remove_test()
     sleep 1
 
     if [[ $offline = 1 ]]; then
-	echo -n "offlining /dev/sdb... "
-	bcachefs device offline --force	/dev/sdb
+	echo -n "offlining ${ktest_scratch_dev[0]}... "
+	bcachefs device offline --force	${ktest_scratch_dev[0]}
 	echo "done"
     fi
 
     if [[ $evacuate = 1 ]]; then
-	echo -n "evacuating /dev/sdb... "
-	bcachefs device evacuate	/dev/sdb
+	echo -n "evacuating ${ktest_scratch_dev[0]}... "
+	bcachefs device evacuate	${ktest_scratch_dev[0]}
 	echo "done"
     fi
 
     bcachefs fs usage -h /mnt
 
-    echo -n "removing /dev/sdb... "
+    echo -n "removing ${ktest_scratch_dev[0]}... "
     if [[ $evacuate = 1 ]]; then
-	#bcachefs device remove		/dev/sdb
+	#bcachefs device remove		${ktest_scratch_dev[0]}
 	bcachefs device remove		0 /mnt
     else
-	#bcachefs device remove --force	/dev/sdb
+	#bcachefs device remove --force	${ktest_scratch_dev[0]}
 	bcachefs device remove --force	0 /mnt
     fi
     echo "done"
@@ -214,10 +225,10 @@ do_remove_test()
     bcachefs fs usage -h /mnt
     umount /mnt
 
-    mount -t bcachefs /dev/sdb:/dev/sdc:/dev/sdd /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]}:${ktest_scratch_dev[2]} /mnt
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_device_remove_offline()
@@ -248,17 +259,17 @@ test_device_add()
     run_quiet "" bcachefs format		\
 	--block_size=4k				\
 	--no_initialize				\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     run_fio_randrw >"$ktest_out/fio-out" 2>&1 &
     local fiopid=$!
 
     sleep 1
 
-    echo -n "adding /dev/sdc... "
-    bcachefs device add /mnt /dev/sdc
+    echo -n "adding ${ktest_scratch_dev[1]}... "
+    bcachefs device add /mnt ${ktest_scratch_dev[1]}
     echo "done"
 
     if ! wait $fiopid; then
@@ -267,12 +278,12 @@ test_device_add()
     fi
 
     umount /mnt
-    bcachefs fsck -n /dev/sdb /dev/sdc
+    bcachefs fsck -n ${ktest_scratch_dev[0]} ${ktest_scratch_dev[1]}
 
-    mount -t bcachefs /dev/sdb:/dev/sdc /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]} /mnt
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_device_add_label()
@@ -281,13 +292,13 @@ test_device_add_label()
     # Caught bugs:
     #   - label was not set correctly; set to dev-0 label instead of new one.
 
-    bcachefs format -L test_add_label --label=foo /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
-    bcachefs device add --label=bar /mnt /dev/sdc
+    bcachefs format -L test_add_label --label=foo ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
+    bcachefs device add --label=bar /mnt ${ktest_scratch_dev[1]}
     expect_sysfs dev-1 label bar
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_device_add_label_compound()
@@ -299,13 +310,13 @@ test_device_add_label_compound()
 
     set_watchdog 30
 
-    bcachefs format -L test_add_compound_label --label=hdd /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
-    bcachefs device add --label=foo.bar /mnt /dev/sdc
+    bcachefs format -L test_add_compound_label --label=hdd ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
+    bcachefs device add --label=foo.bar /mnt ${ktest_scratch_dev[1]}
     expect_sysfs dev-1 label foo.bar
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_device_set_state()
@@ -314,9 +325,11 @@ test_device_set_state()
 
     run_quiet "" bcachefs format		\
 	--replicas=2				\
-	/dev/sd[bcd]
+	${ktest_scratch_dev[0]}			\
+	${ktest_scratch_dev[1]}			\
+	${ktest_scratch_dev[2]}
 
-    mount -t bcachefs /dev/sdb:/dev/sdc:/dev/sdd /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]}:${ktest_scratch_dev[2]} /mnt
 
     run_fio_randrw >"$ktest_out/fio-out" 2>&1 &
     local fiopid=$!
@@ -325,10 +338,10 @@ test_device_set_state()
 
     for state in ro failed spare; do
 	echo "setting state $state"
-	bcachefs device set-state --force $state    /dev/sdc
+	bcachefs device set-state --force $state    ${ktest_scratch_dev[1]}
 
 	echo "setting state rw"
-	#bcachefs device set-state	  rw /dev/sdc
+	#bcachefs device set-state	  rw ${ktest_scratch_dev[1]}
 	bcachefs device set-state	  rw 1 /mnt
     done
 
@@ -339,7 +352,7 @@ test_device_set_state()
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_device_ro()
@@ -348,9 +361,11 @@ test_device_ro()
 
     run_quiet "" bcachefs format		\
 	--btree_node_size=128k			\
-	/dev/sd[bcd]
+	${ktest_scratch_dev[0]}			\
+	${ktest_scratch_dev[1]}			\
+	${ktest_scratch_dev[2]}
 
-    mount -t bcachefs /dev/sdb:/dev/sdc:/dev/sdd /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]}:${ktest_scratch_dev[2]} /mnt
 
     local fioout="$ktest_out/fio-out"
     run_fio_randrw >"$fioout" 2>&1 &
@@ -358,7 +373,7 @@ test_device_ro()
 
     sleep 4
 
-    bcachefs device set-state ro /dev/sdc
+    bcachefs device set-state ro ${ktest_scratch_dev[1]}
 
     if ! wait $fiopid; then
 	cat "$fioout"
@@ -367,10 +382,10 @@ test_device_ro()
 
     umount /mnt
 
-    mount -t bcachefs /dev/sdb:/dev/sdc:/dev/sdd /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]}:${ktest_scratch_dev[2]} /mnt
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_device_set_state_offline()
@@ -378,9 +393,11 @@ test_device_set_state_offline()
     set_watchdog 120
     run_quiet "" bcachefs format		\
 	--replicas=2				\
-	/dev/sd[bcd]
+	${ktest_scratch_dev[0]}			\
+	${ktest_scratch_dev[1]}			\
+	${ktest_scratch_dev[2]}
 
-    mount -t bcachefs /dev/sdb:/dev/sdc:/dev/sdd /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]}:${ktest_scratch_dev[2]} /mnt
 
     local fioout="$ktest_out/fio-out"
     run_fio_randrw >"$fioout" 2>&1 &
@@ -388,7 +405,7 @@ test_device_set_state_offline()
 
     sleep 1
 
-    bcachefs device set-state --force	    ro /dev/sdc
+    bcachefs device set-state --force	    ro ${ktest_scratch_dev[1]}
 
     if ! wait $fiopid; then
 	cat "$fioout"
@@ -397,13 +414,13 @@ test_device_set_state_offline()
 
     umount /mnt
 
-    bcachefs device set-state --offline	    rw /dev/sdc
+    bcachefs device set-state --offline	    rw ${ktest_scratch_dev[1]}
 
-    mount -t bcachefs /dev/sdb:/dev/sdc:/dev/sdd /mnt
-    cat /sys/block/sdc/bcachefs/state
+    mount -t bcachefs ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]}:${ktest_scratch_dev[2]} /mnt
+    cat /sys/block/[sv]dc/bcachefs/state
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_device_readd()
@@ -411,9 +428,10 @@ test_device_readd()
     set_watchdog 120
     run_quiet "" bcachefs format		\
 	--replicas=2				\
-	/dev/sd[bc]
+	${ktest_scratch_dev[0]}			\
+	${ktest_scratch_dev[1]}	
 
-    mount -t bcachefs /dev/sdb:/dev/sdc /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]} /mnt
 
     local fioout="$ktest_out/fio-out"
     run_fio_randrw >"$fioout" 2>&1 &
@@ -421,12 +439,12 @@ test_device_readd()
 
     sleep 1
 
-    echo -n "offlining /dev/sdb... "
-    bcachefs device offline --force	/dev/sdb
+    echo -n "offlining ${ktest_scratch_dev[0]}... "
+    bcachefs device offline --force	${ktest_scratch_dev[0]}
     echo "done"
 
-    echo -n "onlining /dev/sdb... "
-    bcachefs device online /dev/sdb
+    echo -n "onlining ${ktest_scratch_dev[0]}... "
+    bcachefs device online ${ktest_scratch_dev[0]}
     echo "done"
 
     if ! wait $fiopid; then
@@ -436,10 +454,10 @@ test_device_readd()
 
     umount /mnt
 
-    mount -t bcachefs /dev/sdb:/dev/sdc /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]} /mnt
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_device_repeated_add_remove()
@@ -450,22 +468,22 @@ test_device_repeated_add_remove()
 
     set_watchdog 120
 
-    bcachefs format -L test_device_repeated_add_remove --label=hdd /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    bcachefs format -L test_device_repeated_add_remove --label=hdd ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     for ii in {1..10}; do
         echo "add-remove run #$ii ----------------------------------------------------"
         echo "bcachefs device add"
-        bcachefs device add /mnt /dev/sdc
+        bcachefs device add /mnt ${ktest_scratch_dev[1]}
         echo "bcachefs device evacuate"
-        bcachefs device evacuate /dev/sdc
+        bcachefs device evacuate ${ktest_scratch_dev[1]}
         echo "bcachefs device remove"
-        bcachefs device remove /dev/sdc
+        bcachefs device remove ${ktest_scratch_dev[1]}
     done
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 do_replicas_errors_test()
@@ -476,13 +494,13 @@ do_replicas_errors_test()
     echo 1 > /sys/module/bcachefs/parameters/verify_all_btree_replicas
     #bcachefs_antagonist
 
-    mdadm -B /dev/md0 -lfaulty -n1 /dev/sdc
+    mdadm -B /dev/md0 -lfaulty -n1 ${ktest_scratch_dev[1]}
 
     run_quiet "" bcachefs format		\
 	--replicas=2				\
-	/dev/md0 /dev/sdb
+	/dev/md0 ${ktest_scratch_dev[0]}
 
-    mount -t bcachefs -o degraded /dev/sdb:/dev/md0 /mnt
+    mount -t bcachefs -o degraded ${ktest_scratch_dev[0]}:/dev/md0 /mnt
 
     mdadm -G /dev/md0 -p$error_type
 
@@ -495,12 +513,12 @@ do_replicas_errors_test()
     umount /mnt
     mdadm --stop /dev/md0
 
-    #bcachefs fsck -n /dev/sdb /dev/sdc
+    #bcachefs fsck -n ${ktest_scratch_dev[0]} ${ktest_scratch_dev[1]}
 
-    mount -t bcachefs -o fsck /dev/sdb:/dev/sdc /mnt
+    mount -t bcachefs -o fsck ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]} /mnt
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_replicas_write_errors()
@@ -520,10 +538,12 @@ test_cmd_fs_usage()
     run_quiet "" bcachefs format		\
 	--replicas=2				\
 	--bucket=128k				\
-	/dev/sd[bcd]
+	${ktest_scratch_dev[0]}			\
+	${ktest_scratch_dev[1]}			\
+	${ktest_scratch_dev[2]}
 
     echo -n "mounting... "
-    mount -t bcachefs -o verbose /dev/sdb:/dev/sdc:/dev/sdd /mnt
+    mount -t bcachefs -o verbose ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]}:${ktest_scratch_dev[2]} /mnt
     echo done
 
     echo "Before writing:"
@@ -542,20 +562,22 @@ test_cmd_fs_usage()
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_rereplicate()
 {
     set_watchdog 60
     run_quiet "" bcachefs format		\
-	/dev/sd[bcd]
-    mount -t bcachefs /dev/sdb:/dev/sdc:/dev/sdd /mnt
+	${ktest_scratch_dev[0]}			\
+	${ktest_scratch_dev[1]}			\
+	${ktest_scratch_dev[2]}
+    mount -t bcachefs ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]}:${ktest_scratch_dev[2]} /mnt
 
     dd if=/dev/zero of=/mnt/test bs=1M count=1024 oflag=direct
 
     umount /mnt
-    mount -t bcachefs -o metadata_replicas=2,data_replicas=2 /dev/sdb:/dev/sdc:/dev/sdd /mnt
+    mount -t bcachefs -o metadata_replicas=2,data_replicas=2 ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]}:${ktest_scratch_dev[2]} /mnt
 
     #echo 2 > /sys/fs/bcachefs/*/options/data_replicas
     #echo 2 > /sys/fs/bcachefs/*/options/metadata_replicas
@@ -565,10 +587,10 @@ test_rereplicate()
     bcachefs fs usage -h /mnt
     umount /mnt
 
-    mount -t bcachefs -o degraded /dev/sdb:/dev/sdc /mnt
+    mount -t bcachefs -o degraded ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]} /mnt
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 disabled_test_device_add_faults()
@@ -577,13 +599,13 @@ disabled_test_device_add_faults()
 
     run_quiet "" bcachefs format		\
 	--errors=remount-ro			\
-	/dev/sdb
-    mount /dev/sdb /mnt
+	${ktest_scratch_dev[0]}
+    mount ${ktest_scratch_dev[0]} /mnt
 
     device_add_fault_fn()
     {
 	set_faults "$1 enable"
-	! bcachefs device add /mnt /dev/sdc
+	! bcachefs device add /mnt ${ktest_scratch_dev[1]}
     }
 
     run_fault_injection_test bcachefs:add			device_add_fault_fn
@@ -591,7 +613,7 @@ disabled_test_device_add_faults()
     run_fault_injection_test bcachefs:bch_fs_init:alloc_start	device_add_fault_fn
     run_fault_injection_test bcachefs:bch_fs_init:read_super	device_add_fault_fn
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_striping()
@@ -602,14 +624,15 @@ test_striping()
     if false; then
 	run_quiet "" bcachefs format		\
 	    --replicas=2			\
-	    /dev/sd[bc]
+	    ${ktest_scratch_dev[0]}		\
+	    ${ktest_scratch_dev[1]}
 
-	mount -t bcachefs /dev/sdb:/dev/sdc /mnt
+	mount -t bcachefs ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]} /mnt
 
 	dd if=/dev/zero of=/mnt/test0 bs=1M count=1024 oflag=direct
 	bcachefs fs usage -h /mnt
 
-	bcachefs device add /mnt /dev/sdd
+	bcachefs device add /mnt ${ktest_scratch_dev[2]}
 
 	dd if=/dev/zero of=/mnt/test1 bs=1M count=1024 oflag=direct
     else
@@ -618,15 +641,17 @@ test_striping()
 	    --replicas=2			\
 	    --label cache			\
 	    --durability=1			\
-	    --bucket=8M /dev/sd[b]		\
+	    --bucket=8M				\
+	    ${ktest_scratch_dev[0]}		\
 	    --label hdd				\
 	    --durability=2			\
-	    --bucket=8M /dev/sd[cd]		\
+	    ${ktest_scratch_dev[1]}		\
+	    ${ktest_scratch_dev[2]}		\
 	    --foreground_target=cache		\
 	    --background_target=hdd		\
 	    --promote_target=cache
 
-	mount -t bcachefs /dev/sdb:/dev/sdc:/dev/sdd /mnt
+	mount -t bcachefs ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]}:${ktest_scratch_dev[2]} /mnt
 
 	dd if=/dev/zero of=/mnt/test0 bs=1M count=1024 oflag=direct
     fi
@@ -635,16 +660,17 @@ test_striping()
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 disabled_change_replicas()
 {
     run_quiet "" bcachefs format		\
 	--replicas=2				\
-	/dev/sd[bc]
+	${ktest_scratch_dev[0]}			\
+	${ktest_scratch_dev[1]}
 
-    mount -t bcachefs /dev/sdb:/dev/sdc /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]} /mnt
 
     (
 	cd /sys/fs/bcachefs/*
@@ -667,16 +693,17 @@ disabled_change_replicas()
     kill %1
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 disabled_change_replicas2()
 {
     run_quiet "" bcachefs format		\
 	--replicas=2				\
-	/dev/sd[bc]
+	${ktest_scratch_dev[0]}			\
+	${ktest_scratch_dev[1]}
 
-    mount -t bcachefs /dev/sdb:/dev/sdc /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]} /mnt
 
     local opt=/sys/fs/bcachefs/*/options/data_replicas
     while true; do
@@ -689,7 +716,7 @@ disabled_change_replicas2()
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_replicas_gc()
@@ -701,8 +728,8 @@ test_replicas_gc()
 
     run_quiet "" bcachefs format -f		\
 	--replicas=2				\
-	/dev/sd[bcdef]
-    devs=/dev/sdb:/dev/sdc:/dev/sdd:/dev/sde:/dev/sdf
+	${ktest_scratch_dev[@]}	
+    devs="$(join_by : "${ktest_scratch_dev[@]}")"
 
     mount -t bcachefs $devs /mnt
 
@@ -716,58 +743,58 @@ test_replicas_gc()
     mount -t bcachefs -o fix_errors,erasure_code $devs /mnt
     umount /mnt
 
-    bcachefs fsck /dev/sd[bcdef]
+    bcachefs fsck ${ktest_scratch_dev[@]}
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_replace_replica()
 {
     set_watchdog 60
 
-    bcachefs format --replicas=2 /dev/sd[bc]
-    mount -t bcachefs -o degraded /dev/sdb /mnt
+    bcachefs format --replicas=2 ${ktest_scratch_dev[0]} ${ktest_scratch_dev[1]}
+    mount -t bcachefs -o degraded ${ktest_scratch_dev[0]} /mnt
 
-    bcachefs device add -f /mnt /dev/sdd
+    bcachefs device add -f /mnt ${ktest_scratch_dev[2]}
 
-    bcachefs device set-state --force failed /dev/sdc
+    bcachefs device set-state --force failed ${ktest_scratch_dev[1]}
 
     bcachefs data rereplicate /mnt
 
     umount /mnt
 
-    mount -t bcachefs -o degraded /dev/sdd /mnt
+    mount -t bcachefs -o degraded ${ktest_scratch_dev[2]} /mnt
     umount /mnt
 
     # We expect more btree_path_upgrade_fail events than usual in this test,
     # due to the way the btree node rewrite path works and the fact that we're
     # rewriting every btree node
-    check_counters /dev/sdb 4
+    check_counters ${ktest_scratch_dev[0]} 4
 }
 
 test_key_type_error()
 {
     set_watchdog 20
 
-    bcachefs format --replicas=2 /dev/sd[bc]
+    bcachefs format --replicas=2 ${ktest_scratch_dev[0]} ${ktest_scratch_dev[1]}
 
-    mount -t bcachefs /dev/sdb:/dev/sdc /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]} /mnt
     bcachefs setattr --data_replicas=1 /mnt
-    bcachefs setattr --foreground_target=sdc /mnt
+    bcachefs setattr --foreground_target=$(basename ${ktest_scratch_dev[1]}) /mnt
 
     dd if=/dev/zero of=/mnt/foo bs=64k count=8 oflag=direct
 
     umount /mnt
-    mount -t bcachefs -o very_degraded /dev/sdb /mnt
+    mount -t bcachefs -o very_degraded ${ktest_scratch_dev[0]} /mnt
 
-    bcachefs device remove --force /dev/sdc
+    bcachefs device remove --force ${ktest_scratch_dev[1]}
 
     # should fail:
     ! dd if=/mnt/foo of=/dev/null bs=64k count=1 iflag=direct
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 main "$@"
diff --git a/tests/bcachefs/single_device.ktest b/tests/bcachefs/single_device.ktest
index 113e614..f8aa41b 100755
--- a/tests/bcachefs/single_device.ktest
+++ b/tests/bcachefs/single_device.ktest
@@ -17,23 +17,23 @@ test_stress_ng()
     set_watchdog 300
     setup_tracing 'bcachefs:*'
 
-    run_quiet "" bcachefs format --no_initialize --version=11 -f /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format --no_initialize --version=11 -f ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     cd /mnt
     stress-ng  -v -t 60 --class filesystem --all 1 || true
     stress-ng  -v -t 60 --class filesystem --all 2 || true
     cd /root
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_punch()
 {
     set_watchdog 10
 
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     xfs_io -f /mnt/foo -c "pwrite -S 0x55 0 16384"
     xfs_io -f /mnt/foo -c "fsync"
@@ -42,26 +42,26 @@ test_punch()
     md5sum /mnt/foo
     umount /mnt
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     md5sum /mnt/foo
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_remount_ro_rw()
 {
     set_watchdog 10
 
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     mount -o remount,ro /mnt
     mount -o remount,rw /mnt
     touch /mnt/foo
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_extent_merge2()
@@ -69,25 +69,25 @@ test_extent_merge2()
     set_watchdog 10
     echo 1 > /sys/module/bcachefs/parameters/debug_check_iterators
 
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     fallocate -o    0 -l 4096 /mnt/foo
     fallocate -o 4096 -l 4096 /mnt/foo
 
     umount /mnt
-    bcachefs fsck -n /dev/sdb
+    bcachefs fsck -n ${ktest_scratch_dev[0]}
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_reflink2()
 {
     set_watchdog 10
     bcachefs_antagonist
-    run_quiet "" bcachefs format /dev/sdb
+    run_quiet "" bcachefs format ${ktest_scratch_dev[0]}
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     dd if=/dev/urandom of=/mnt/foo bs=16k count=1 oflag=direct
     cp --reflink /mnt/foo /mnt/foo2
@@ -114,14 +114,14 @@ test_reflink2()
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_reflink()
 {
     set_watchdog 10
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     run_fio_randrw --filesize=1000M &
 
@@ -146,7 +146,7 @@ test_reflink()
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_fio_raw()
@@ -160,7 +160,7 @@ test_fio_raw()
 	--iodepth_batch=16			\
 	--direct=1				\
 	--numjobs=1				\
-	--filename=/dev/sdb		    	\
+	--filename=${ktest_scratch_dev[0]}		    	\
 	--name=randread				\
 	--rw=randread				\
 	--size=40G				\
@@ -170,29 +170,29 @@ test_fio_raw()
 test_rewrite_old_nodes()
 {
     set_watchdog 60
-    run_quiet "" bcachefs format -f --no_initialize --version=10 /dev/sdb
+    run_quiet "" bcachefs format -f --no_initialize --version=10 ${ktest_scratch_dev[0]}
 
-    bcachefs show-super /dev/sdb
+    bcachefs show-super ${ktest_scratch_dev[0]}
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     dd if=/dev/zero of=/mnt/foo bs=4k count=65536 oflag=direct
     umount /mnt
 
-    bcachefs show-super /dev/sdb
+    bcachefs show-super ${ktest_scratch_dev[0]}
 
-    bcachefs fsck /dev/sdb
+    bcachefs fsck ${ktest_scratch_dev[0]}
 
-    bcachefs show-super /dev/sdb
+    bcachefs show-super ${ktest_scratch_dev[0]}
 
-    mount -t bcachefs -o version_upgrade /dev/sdb /mnt
+    mount -t bcachefs -o version_upgrade ${ktest_scratch_dev[0]} /mnt
     bcachefs data job rewrite_old_nodes /mnt
     umount /mnt
 
-    bcachefs fsck /dev/sdb
+    bcachefs fsck ${ktest_scratch_dev[0]}
 
-    bcachefs show-super /dev/sdb
+    bcachefs show-super ${ktest_scratch_dev[0]}
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_merge_torture_flakey()
@@ -201,7 +201,7 @@ test_merge_torture_flakey()
     local loops=$((($ktest_priority + 1) * 3))
     local n=40M
 
-    mdadm -B /dev/md0 -lfaulty -n1 /dev/sdb
+    mdadm -B /dev/md0 -lfaulty -n1 ${ktest_scratch_dev[0]}
 
     run_quiet "" bcachefs format -f --btree_node_size=32k --errors=panic /dev/md0
 
@@ -236,7 +236,7 @@ test_merge_torture_flakey()
 
     mdadm --stop /dev/md0
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 # Disabled, because currently OOMs
@@ -247,10 +247,10 @@ d_test_merge_torture()
     local loops=$((($ktest_priority + 1) * 3))
     local n=10M
 
-    run_quiet "" bcachefs format -f --errors=panic --btree_node_size=8k --no_initialize /dev/sdb
+    run_quiet "" bcachefs format -f --errors=panic --btree_node_size=8k --no_initialize ${ktest_scratch_dev[0]}
 
     for i in `seq 0 $loops`; do
-	mount -t bcachefs -o fsck /dev/sdb /mnt
+	mount -t bcachefs -o fsck ${ktest_scratch_dev[0]} /mnt
 
 	echo "loop: $i"
 	echo rand_insert	$n 1	> /sys/fs/bcachefs/*/perf_test
@@ -268,8 +268,8 @@ d_test_merge_torture()
 test_make_files()
 {
     set_watchdog 30
-    run_quiet "" bcachefs format -f /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     echo 3 > /proc/sys/vm/drop_caches
     free -m
@@ -283,48 +283,48 @@ test_make_files()
     free -m
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_journal_resize()
 {
     set_watchdog 30
-    run_quiet "" bcachefs format -f /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     run_fio_randrw --filesize=2G &
 
     sleep 4
-    bcachefs device resize-journal /dev/sdb 1G
+    bcachefs device resize-journal ${ktest_scratch_dev[0]} 1G
 
     wait
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_drop_alloc()
 {
     set_watchdog 120
-    run_quiet "" bcachefs format -f /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     run_fio_randrw --filesize=2G
     umount /mnt
 
-    mount -t bcachefs -o reconstruct_alloc,fsck,fix_errors /dev/sdb /mnt
+    mount -t bcachefs -o reconstruct_alloc,fsck,fix_errors ${ktest_scratch_dev[0]} /mnt
     umount /mnt
 
-    bcachefs fsck -n /dev/sdb
+    bcachefs fsck -n ${ktest_scratch_dev[0]}
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_reflink_inline_data()
 {
     set_watchdog 30
-    run_quiet "" bcachefs format -f /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     dd if=/dev/urandom of=/root/foo bs=256 count=1
     cp		    /root/foo /mnt/foo1
@@ -334,21 +334,21 @@ test_reflink_inline_data()
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_split_compressed()
 {
     set_watchdog 30
-    run_quiet "" bcachefs format --compression=zstd /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format --compression=zstd ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     # Test that splitting of compressed extents is working correctly:
     dd if=/dev/zero of=/mnt/foo bs=128k	    count=1 oflag=direct
     dd if=/dev/urandom of=/mnt/foo bs=4k    count=1 seek=1 oflag=direct conv=notrunc
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_fcollapse()
@@ -356,8 +356,8 @@ test_fcollapse()
     set_watchdog 30
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
-	/dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+	${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     dd if=/dev/zero of=/mnt/foo bs=4k count=4 oflag=direct
 
@@ -375,14 +375,14 @@ test_fcollapse()
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_finsert()
 {
     set_watchdog 30
-    run_quiet "" bcachefs format /dev/sdb
-    mount -t bcachefs -o fsck /dev/sdb /mnt
+    run_quiet "" bcachefs format ${ktest_scratch_dev[0]}
+    mount -t bcachefs -o fsck ${ktest_scratch_dev[0]} /mnt
 
     dd if=/dev/zero of=/mnt/foo bs=64k count=1 oflag=direct
 
@@ -391,15 +391,15 @@ test_finsert()
     xfs_io -c "finsert 1024 1024" /mnt/foo
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_key_merge()
 {
     set_watchdog 30
-    run_quiet "" bcachefs format --data_checksum=none /dev/sdb
+    run_quiet "" bcachefs format --data_checksum=none ${ktest_scratch_dev[0]}
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     dd if=/dev/zero of=/mnt/foo bs=8k count=128 oflag=direct
 
@@ -409,15 +409,15 @@ test_key_merge()
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_key_merge_csum()
 {
     set_watchdog 30
-    run_quiet "" bcachefs format --data_checksum=crc32c /dev/sdb
+    run_quiet "" bcachefs format --data_checksum=crc32c ${ktest_scratch_dev[0]}
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     dd if=/dev/urandom of=/mnt/foo bs=8k count=128 oflag=direct
 
@@ -429,39 +429,39 @@ test_key_merge_csum()
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_reconstruct_alloc()
 {
     set_watchdog 120
-    run_quiet "" bcachefs format --btree_node_size=16k /dev/sdb
+    run_quiet "" bcachefs format --btree_node_size=16k ${ktest_scratch_dev[0]}
 
-    mount -t bcachefs -o reconstruct_alloc,fix_errors,fsck /dev/sdb /mnt
+    mount -t bcachefs -o reconstruct_alloc,fix_errors,fsck ${ktest_scratch_dev[0]} /mnt
 
     umount /mnt
-    bcachefs fsck -n /dev/sdb
+    bcachefs fsck -n ${ktest_scratch_dev[0]}
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     run_fio_randrw
     umount /mnt
 
     echo "Running fsck --reconstruct_alloc"
-    fsck.bcachefs -ny --reconstruct_alloc /dev/sdb  && rc=$? || rc=$? 
+    fsck.bcachefs -ny --reconstruct_alloc ${ktest_scratch_dev[0]}  && rc=$? || rc=$? 
     if (( $rc != 0 && $rc != 1 )); then
 	echo "Bad exit status from fsck: $rc"
 	exit 1
     fi
 
     echo "Mounting with -o reconstruct_alloc"
-    mount -t bcachefs -o reconstruct_alloc,fix_errors,fsck /dev/sdb /mnt
+    mount -t bcachefs -o reconstruct_alloc,fix_errors,fsck ${ktest_scratch_dev[0]} /mnt
     umount /mnt
 
-    bcachefs fsck -n /dev/sdb
-    mount -t bcachefs -o fsck /dev/sdb /mnt
+    bcachefs fsck -n ${ktest_scratch_dev[0]}
+    mount -t bcachefs -o fsck ${ktest_scratch_dev[0]} /mnt
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_recovery()
@@ -471,10 +471,10 @@ test_recovery()
 	--errors=panic				\
 	--encrypted --no_passphrase		\
 	--bucket=8k				\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 
     for i in `seq 0 1`; do
-	mount -t bcachefs /dev/sdb /mnt
+	mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
 	dd if=/dev/zero of=/mnt/foo bs=4k count=8 oflag=direct
 
@@ -501,39 +501,39 @@ test_recovery()
 	umount /mnt
     done
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_lz4_zeros()
 {
     set_watchdog 30
-    run_quiet "" bcachefs format -f --errors=panic --compression=lz4 --data_checksum=none --bucket=2M /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic --compression=lz4 --data_checksum=none --bucket=2M ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     dd if=/dev/zero of=/mnt/foo bs=1M count=10
     # XXX check disk space used
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_lz4_incompressible()
 {
     set_watchdog 120
-    run_quiet "" bcachefs format -f --errors=panic --compression=lz4 --data_checksum=none --bucket=2M /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic --compression=lz4 --data_checksum=none --bucket=2M ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     dd if=/dev/urandom of=/mnt/foo || true
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_lz4()
 {
     run_basic_fio_test				\
 	--compression=lz4			\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 }
 
 test_lz4_buffered()
@@ -544,8 +544,8 @@ test_lz4_buffered()
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
 	--compression=lz4			\
-	/dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+	${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     echo starting copy
     cp -rx / /mnt/foo
@@ -558,21 +558,21 @@ test_lz4_buffered()
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_gzip()
 {
     run_basic_fio_test				\
 	--compression=gzip			\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 }
 
 test_zstd()
 {
     run_basic_fio_test				\
 	--compression=zstd			\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 }
 
 disabled_test_background_compression()
@@ -580,12 +580,12 @@ disabled_test_background_compression()
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
 	--background_compression=zstd	    	\
-	/dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+	${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     echo zstd > /sys/fs/bcachefs/*/options/background_compression
     run_fio_randrw
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_compress_no_checksum()
@@ -594,7 +594,7 @@ test_compress_no_checksum()
 	--compression=lz4			\
 	--metadata_checksum=none	    	\
 	--data_checksum=none			\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 }
 
 test_no_checksum()
@@ -602,7 +602,7 @@ test_no_checksum()
     run_basic_fio_test				\
 	--metadata_checksum=none		\
 	--data_checksum=none			\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 }
 
 test_crc32c()
@@ -610,7 +610,7 @@ test_crc32c()
     run_basic_fio_test				\
 	--metadata_checksum=crc32c		\
 	--data_checksum=crc32c			\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 }
 
 test_crc64()
@@ -618,31 +618,31 @@ test_crc64()
     run_basic_fio_test				\
 	--metadata_checksum=crc64		\
 	--data_checksum=crc64			\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 }
 
 test_crypto_locked_mnt()
 {
-    echo foo|bcachefs format --encrypted /dev/sdb
-    echo foo|bcachefs unlock -k session /dev/sdb
-    mount -t bcachefs -o verbose /dev/sdb /mnt
+    echo foo|bcachefs format --encrypted ${ktest_scratch_dev[0]}
+    echo foo|bcachefs unlock -k session ${ktest_scratch_dev[0]}
+    mount -t bcachefs -o verbose ${ktest_scratch_dev[0]} /mnt
     umount /mnt
-    bcachefs fsck /dev/sdb
+    bcachefs fsck ${ktest_scratch_dev[0]}
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_crypto()
 {
     run_basic_fio_test				\
 	--encrypted --no_passphrase		\
-	/dev/sdb
-    mount -t bcachefs -o fsck /dev/sdb /mnt
+	${ktest_scratch_dev[0]}
+    mount -t bcachefs -o fsck ${ktest_scratch_dev[0]} /mnt
     umount /mnt
     bcachefs fsck				\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_crypto_lz4()
@@ -650,7 +650,7 @@ test_crypto_lz4()
     run_basic_fio_test				\
 	--encrypted --no_passphrase		\
 	--compression=lz4			\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 }
 
 run_copygc_torture()
@@ -664,9 +664,9 @@ run_copygc_torture()
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
 	--data_checksum=none			\
-	"$@" /dev/sdb
+	"$@" ${ktest_scratch_dev[0]}
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     fill_device /mnt/fiotest
 
@@ -695,9 +695,9 @@ run_copygc_torture()
     expect_sysfs cache cached_data	0
 
     umount /mnt
-    bcachefs fsck -n /dev/sdb
+    bcachefs fsck -n ${ktest_scratch_dev[0]}
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_copygc_torture()
@@ -720,7 +720,7 @@ test_small_buckets()
 {
     run_basic_fio_test				\
 	--bucket=32k				\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 }
 
 # Gets stuck due to only having 512 buckets
@@ -729,7 +729,7 @@ test_large_buckets()
     run_basic_fio_test				\
 	--bucket=8M				\
 	--data_checksum=none			\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 }
 
 test_small_nodes()
@@ -737,19 +737,19 @@ test_small_nodes()
     run_basic_fio_test				\
 	--bucket=256k				\
 	--btree_node_size=4k			\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 }
 
 d_test_crypto_passphrase()
 {
     bcachefs_antagonist
 
-    echo ""|bcachefs format -f --encrypted /dev/sdb
-    echo ""|bcachefs unlock /dev/sdb
+    echo ""|bcachefs format -f --encrypted ${ktest_scratch_dev[0]}
+    echo ""|bcachefs unlock ${ktest_scratch_dev[0]}
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     umount /mnt
-    bcachefs fsck /dev/sdb
+    bcachefs fsck ${ktest_scratch_dev[0]}
 }
 
 test_partial_overwritten_extents()
@@ -759,8 +759,8 @@ test_partial_overwritten_extents()
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
 	--encrypted --no_passphrase		\
-	/dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+	${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     dd if=/dev/urandom	of=/mnt/foo  bs=32k  count=1 skip=0 oflag=direct
     dd if=/mnt/foo	of=/dev/null bs=4k   count=8 skip=0 iflag=direct
@@ -779,7 +779,7 @@ test_partial_overwritten_extents()
     dd if=/mnt/baz	of=/dev/null bs=4k   count=8 skip=0 iflag=direct > /dev/null
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 # test the xattr interface for per-inode IO options:
@@ -788,8 +788,8 @@ test_xattr()
     set_watchdog 10
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
-	/dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+	${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     mkdir /mnt/foo
     setfattr -n bcachefs.compression -v lz4 /mnt/foo
@@ -809,7 +809,7 @@ test_xattr()
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_quota()
@@ -819,8 +819,8 @@ test_quota()
 
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
-	/dev/sdb
-    mount -t bcachefs -o usrquota,grpquota,prjquota /dev/sdb /mnt
+	${ktest_scratch_dev[0]}
+    mount -t bcachefs -o usrquota,grpquota,prjquota ${ktest_scratch_dev[0]} /mnt
 
     loops=$((($ktest_priority + 1) * 4))
 
@@ -829,7 +829,7 @@ test_quota()
     rm /mnt/fiotest
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 # test nfs exports:
@@ -843,8 +843,8 @@ test_nfs()
 
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
-	/dev/sdb
-    mount -t bcachefs /dev/sdb /export2
+	${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /export2
 
     echo "/export1  *(ro,insecure,all_squash,no_subtree_check)" >> /etc/exports
     echo "/export2  *(ro,insecure,all_squash,no_subtree_check)" >> /etc/exports
@@ -853,7 +853,7 @@ test_nfs()
 
     umount /export2
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 # We should get this working at some point:
@@ -876,8 +876,8 @@ d_test_suspend()
 
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
-	/dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+	${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     if false; then
 	run_dbench
@@ -886,7 +886,7 @@ d_test_suspend()
 	run_stress
     fi
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_journal_torture()
@@ -896,9 +896,9 @@ test_journal_torture()
 
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     #enable_memory_faults
 
     echo 1 > /sys/fs/bcachefs/*/options/journal_flush_delay
@@ -908,7 +908,7 @@ test_journal_torture()
     #disable_memory_faults
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_online_resize()
@@ -919,17 +919,17 @@ test_online_resize()
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
 	--fs_size=1G				\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     df -h /mnt
-    bcachefs device resize /dev/sdb
+    bcachefs device resize ${ktest_scratch_dev[0]}
     df -h /mnt
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_offline_resize()
@@ -940,21 +940,21 @@ test_offline_resize()
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
 	--fs_size=1G				\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     df -h /mnt
     cat /proc/mounts
 
     umount /mnt
 
-    bcachefs device resize /dev/sdb
+    bcachefs device resize ${ktest_scratch_dev[0]}
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     df -h /mnt
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 require-kernel-config BLK_DEV_DM
@@ -962,8 +962,8 @@ require-kernel-config BLK_DEV_DM
 test_offline_resize_lv()
 {
     set_watchdog 60
-    pvcreate /dev/sdb
-    vgcreate vg /dev/sdb
+    pvcreate ${ktest_scratch_dev[0]}
+    vgcreate vg ${ktest_scratch_dev[0]}
     lvcreate -L 1G -n foo  vg
     dev=/dev/vg/foo
 
@@ -992,14 +992,14 @@ test_sysfs()
     set_watchdog 10
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
-	/dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+	${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     find -H /sys/fs/bcachefs/ -type f -perm -0400 -exec cat {} \; > /dev/null
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_debugfs()
@@ -1007,8 +1007,8 @@ test_debugfs()
     set_watchdog 30
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
-	/dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+	${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     dd if=/dev/zero of=/mnt/test1 bs=1k count=10240 oflag=direct
     dd if=/dev/zero of=/mnt/test2 bs=1k count=10240 oflag=direct
@@ -1017,7 +1017,7 @@ test_debugfs()
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_set_option()
@@ -1025,28 +1025,28 @@ test_set_option()
     set_watchdog 10
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 
-    mount -t bcachefs /dev/sdb /mnt
-    bcachefs set-option --compression=zstd /dev/sdb
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
+    bcachefs set-option --compression=zstd ${ktest_scratch_dev[0]}
     cat /sys/fs/bcachefs/*/options/compression
     umount /mnt
 
-    bcachefs set-option --compression=lz4 /dev/sdb
+    bcachefs set-option --compression=lz4 ${ktest_scratch_dev[0]}
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     cat /sys/fs/bcachefs/*/options/compression
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 disabled_test_swapfile()
 {
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
-	/dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+	${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     fallocate -l 1G /mnt/swapfile
     mkswap  /mnt/swapfile
@@ -1064,11 +1064,11 @@ migrate_from_fs()
     local fstype=$1
 
     if [[ $fstype = ext4 ]]; then
-	run_quiet "" mkfs.$fstype -F /dev/sdb
-	mount -t $fstype -o user_xattr /dev/sdb /mnt
+	run_quiet "" mkfs.$fstype -F ${ktest_scratch_dev[0]}
+	mount -t $fstype -o user_xattr ${ktest_scratch_dev[0]} /mnt
     else
-	run_quiet "" mkfs.$fstype -f /dev/sdb
-	mount -t $fstype /dev/sdb /mnt
+	run_quiet "" mkfs.$fstype -f ${ktest_scratch_dev[0]}
+	mount -t $fstype ${ktest_scratch_dev[0]} /mnt
     fi
 
     cp -a /usr /mnt
@@ -1088,7 +1088,7 @@ migrate_from_fs()
 
     if true; then
 	mkdir -p /mnt2
-	mount -t bcachefs -o noexcl,nochanges,sb=$offset /dev/sdb /mnt2
+	mount -t bcachefs -o noexcl,nochanges,sb=$offset ${ktest_scratch_dev[0]} /mnt2
 
 	rsync	--archive			\
 	    --acls				\
@@ -1104,19 +1104,19 @@ migrate_from_fs()
     fi
 
     umount /mnt
-    fsck.$fstype -n /dev/sdb
+    fsck.$fstype -n ${ktest_scratch_dev[0]}
 
-    mount -t bcachefs -o sb=$offset /dev/sdb /mnt
+    mount -t bcachefs -o sb=$offset ${ktest_scratch_dev[0]} /mnt
     umount /mnt
 
     echo "Creating default superblock"
-    bcachefs migrate-superblock -d /dev/sdb -o $offset
+    bcachefs migrate-superblock -d ${ktest_scratch_dev[0]} -o $offset
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     rm /mnt/old_migrated_filesystem
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_migrate_from_ext4()
@@ -1148,10 +1148,10 @@ d_test_init_faults()
 
     run_quiet "" bcachefs format -f		\
 	--errors=remount-ro			\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 
     # put some data on the filesystem
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     run_fio_randrw
     # dbench would be better, create a directory structure
@@ -1163,7 +1163,7 @@ d_test_init_faults()
     {
 	set_faults "$1 enable"
 	# should fail:
-	! mount -t bcachefs -o verbose /dev/sdb /mnt
+	! mount -t bcachefs -o verbose ${ktest_scratch_dev[0]} /mnt
     }
 
     run_fault_injection_test bcachefs:bch_fs_init   init_fault_fn
@@ -1177,11 +1177,11 @@ d_test_meta_write_faults()
 
     run_quiet "" bcachefs format -f		\
 	--errors=remount-ro			\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 
     meta_write_fault_fn()
     {
-	mount -t bcachefs /dev/sdb /mnt
+	mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 	(sleep 2; set_faults "$1 enable") &
 
 	# Should fail due to read only cache set
@@ -1199,8 +1199,8 @@ test_long_name()
     set_watchdog 20
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
-	/dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+	${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     local i=1
     local n="1"
@@ -1212,7 +1212,7 @@ test_long_name()
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_many_files()
@@ -1220,8 +1220,8 @@ test_many_files()
     set_watchdog 60
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
-	/dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+	${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     for i in {1..1000}; do
 	touch /mnt/$i
@@ -1229,10 +1229,10 @@ test_many_files()
 
     umount /mnt
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 disabled_test_invalid_keys()
@@ -1241,8 +1241,8 @@ disabled_test_invalid_keys()
 
     run_quiet "" bcachefs format -f		\
 	--errors=continue			\
-	/dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+	${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     for i in {1..1000}; do
 	touch /mnt/$i
@@ -1250,7 +1250,7 @@ disabled_test_invalid_keys()
 
     umount /mnt
 
-    mount -t bcachefs -o fix_errors /dev/sdb /mnt
+    mount -t bcachefs -o fix_errors ${ktest_scratch_dev[0]} /mnt
     umount /mnt
 
     echo 0 > /sys/module/bcachefs/parameters/inject_invalid_keys
@@ -1263,16 +1263,16 @@ test_buffered_reads()
 	--errors=panic				\
 	--bucket=8M				\
 	--data_checksum=none			\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     dd if=/dev/zero of=/mnt/foo bs=1M oflag=direct 2>/dev/null || true
 
     time dd if=/mnt/foo of=/dev/null bs=1M count=1024
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_small_fs()
@@ -1282,9 +1282,9 @@ test_small_fs()
 	--errors=panic				\
 	--bucket=4k				\
 	--fs_size=512k				\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     df -h /mnt
 
     dd if=/dev/zero of=/mnt/foo bs=4k oflag=direct 2>/dev/null || true
@@ -1292,7 +1292,7 @@ test_small_fs()
     df -h /mnt
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_small_torture()
@@ -1306,10 +1306,10 @@ test_small_fsck()
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
 	--fs_size=1M				\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 
     for i in {1..100}; do
-	bcachefs fsck /dev/sdb
+	bcachefs fsck ${ktest_scratch_dev[0]}
     done
 }
 
@@ -1319,19 +1319,19 @@ test_gc()
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
 	--compression=lz4			\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     antagonist_trigger_gc &
     run_fio_randrw
 
     umount /mnt
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_attr_inherit()
@@ -1339,9 +1339,9 @@ test_attr_inherit()
     set_watchdog 60
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     mkdir /mnt/foo
     mkdir /mnt/bar
@@ -1365,7 +1365,7 @@ test_attr_inherit()
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_setattr()
@@ -1373,9 +1373,9 @@ test_setattr()
     set_watchdog 60
     run_quiet "" bcachefs format -f		\
 	--errors=panic				\
-	/dev/sdb
+	${ktest_scratch_dev[0]}
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     mkdir /mnt/foo
     touch /mnt/foo/bar
@@ -1386,17 +1386,17 @@ test_setattr()
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_mount_twice()
 {
     set_watchdog 60
     mkdir -p /mnt/1 /mnt/2
-    #run_quiet "" bcachefs format -f /dev/sdb
-    mkfs.ext2 /dev/sdb
-    mount -t ext2 /dev/sdb /mnt/1
-    mount -t ext2 /dev/sdb /mnt/2
+    #run_quiet "" bcachefs format -f ${ktest_scratch_dev[0]}
+    mkfs.ext2 ${ktest_scratch_dev[0]}
+    mount -t ext2 ${ktest_scratch_dev[0]} /mnt/1
+    mount -t ext2 ${ktest_scratch_dev[0]} /mnt/2
 
     umount /mnt/1
     umount /mnt/2
@@ -1405,22 +1405,22 @@ test_mount_twice()
 test_dump()
 {
     set_watchdog 60
-    run_quiet "" bcachefs format /dev/sdb
+    run_quiet "" bcachefs format ${ktest_scratch_dev[0]}
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     touch /mnt/a
     touch /mnt/b
     umount /mnt
-    bcachefs dump -o /tmp/sdb.qcow2 /dev/sdb
+    bcachefs dump -o /tmp/sdb.qcow2 ${ktest_scratch_dev[0]}
 }
 
 test_kill_btree_node()
 {
     set_watchdog 240
-    run_quiet "" bcachefs format --errors=panic /dev/sdb
+    run_quiet "" bcachefs format --errors=panic ${ktest_scratch_dev[0]}
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     cp -a /usr /mnt
     umount /mnt
 
@@ -1431,20 +1431,20 @@ test_kill_btree_node()
 
 	[[ $btree = freespace ]] && index=0
 
-	bcachefs kill_btree_node -b $btree -i $index /dev/sdb
+	bcachefs kill_btree_node -b $btree -i $index ${ktest_scratch_dev[0]}
 
 	echo "Running fsck"
 	# How to assert exit status equals something specific with -o errexit?
-	mount -t bcachefs -o fsck,fix_errors,verbose /dev/sdb /mnt
+	mount -t bcachefs -o fsck,fix_errors,verbose ${ktest_scratch_dev[0]} /mnt
 	umount /mnt
-	#bcachefs fsck -y /dev/sdb || true
+	#bcachefs fsck -y ${ktest_scratch_dev[0]} || true
 
 	echo
 	echo "Running fsck again; should be clean"
-	bcachefs fsck -y /dev/sdb || true
+	bcachefs fsck -y ${ktest_scratch_dev[0]} || true
     done
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 main "$@"
diff --git a/tests/bcachefs/subvol.ktest b/tests/bcachefs/subvol.ktest
index e3f3d05..18f734c 100755
--- a/tests/bcachefs/subvol.ktest
+++ b/tests/bcachefs/subvol.ktest
@@ -11,8 +11,8 @@ test_snapshots_simple()
 
     bcachefs_antagonist
 
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     pushd /mnt
     for i in `seq 0 $NR_SNAPS`; do
@@ -23,14 +23,14 @@ test_snapshots_simple()
 
     umount /mnt
     sleep 0.2
-    bcachefs fsck -n /dev/sdb
+    bcachefs fsck -n ${ktest_scratch_dev[0]}
     exit
 
     for i in `seq 0 $NR_SNAPS|sort -r`; do
 	umount /mnt
 	sleep 0.2
-	bcachefs fsck -n /dev/sdb
-	mount -t bcachefs /dev/sdb /mnt
+	bcachefs fsck -n ${ktest_scratch_dev[0]}
+	mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
 	echo "deleting snap-$i"
 	bcachefs subvolume delete /mnt/snap-$i
@@ -39,18 +39,18 @@ test_snapshots_simple()
 
     umount /mnt
     sleep 0.2
-    mount -t bcachefs -o fsck /dev/sdb /mnt
+    mount -t bcachefs -o fsck ${ktest_scratch_dev[0]} /mnt
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_files_many()
 {
     #bcachefs_antagonist
 
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     for i in $(seq 0 1000001); do
        	echo $i > /mnt/$i 
@@ -58,18 +58,18 @@ test_files_many()
 
     umount /mnt
     sleep 0.2
-    time mount -t bcachefs -o fsck /dev/sdb /mnt
+    time mount -t bcachefs -o fsck ${ktest_scratch_dev[0]} /mnt
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 d_test_snapshots_many()
 {
     #bcachefs_antagonist
 
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     cd /mnt
 
@@ -80,10 +80,10 @@ d_test_snapshots_many()
 
     umount /mnt
     sleep 0.2
-    mount -t bcachefs -o fsck /dev/sdb /mnt
+    mount -t bcachefs -o fsck ${ktest_scratch_dev[0]} /mnt
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_dbench()
@@ -93,8 +93,8 @@ test_dbench()
 
     NR_SNAPS=10
 
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     (
 	cd /mnt
@@ -117,18 +117,18 @@ test_dbench()
 
     umount /mnt
     sleep 0.2
-    #bcachefs fsck -n /dev/sdb
-    mount -t bcachefs -o fsck /dev/sdb /mnt
+    #bcachefs fsck -n ${ktest_scratch_dev[0]}
+    mount -t bcachefs -o fsck ${ktest_scratch_dev[0]} /mnt
     df -h /mnt
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_reflink()
 {
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     pushd /mnt
     cp -a /usr .
@@ -138,13 +138,13 @@ test_reflink()
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 d_test_finsert()
 {
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     pushd /mnt
     dd if=/dev/zero of=foo bs=1M count=8 oflag=direct
@@ -154,7 +154,7 @@ d_test_finsert()
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 d_test_snapshots_fio()
@@ -162,8 +162,8 @@ d_test_snapshots_fio()
     # so wait doesn't hang
     [[ $(jobs -p) != "" ]] && kill $(jobs -p)
 
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     fallocate -l500M /mnt/fiotest
 
@@ -222,7 +222,7 @@ d_test_snapshots_fio()
     for i in `seq 0 10|sort -r`; do
 	umount /mnt
 	sleep 0.1
-	mount -t bcachefs -o fsck /dev/sdb /mnt
+	mount -t bcachefs -o fsck ${ktest_scratch_dev[0]} /mnt
 
 	echo "deleting snap-$i"
 	cd /mnt
@@ -234,17 +234,17 @@ d_test_snapshots_fio()
     umount /mnt
 
     sleep 0.1
-    mount -t bcachefs -o fsck /dev/sdb /mnt
+    mount -t bcachefs -o fsck ${ktest_scratch_dev[0]} /mnt
     df -h /mnt
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_subvol_create()
 {
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     bcachefs subvolume create /mnt/subvolume_1
 
     touch /mnt/foo
@@ -252,43 +252,43 @@ test_subvol_create()
 
     umount /mnt
 
-    bcachefs fsck -n /dev/sdb
+    bcachefs fsck -n ${ktest_scratch_dev[0]}
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_subvol_delete()
 {
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     bcachefs subvolume create /mnt/subvolume_1
     rm -rf /mnt/subvolume_1
 
     umount /mnt
 
-    bcachefs fsck -n /dev/sdb
+    bcachefs fsck -n ${ktest_scratch_dev[0]}
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_subvol_snapshot_create()
 {
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     bcachefs subvolume create /mnt/subvolume_1
     bcachefs subvolume snapshot /mnt/subvolume_1 /mnt/snapshot_1
 
     umount /mnt
 
-    bcachefs fsck -n /dev/sdb
+    bcachefs fsck -n ${ktest_scratch_dev[0]}
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_subvol_snapshot_create_ro()
 {
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     bcachefs subvolume create /mnt/subvolume_1
     bcachefs subvolume snapshot -r /mnt/subvolume_1 /mnt/snapshot_1
 
@@ -296,30 +296,30 @@ test_subvol_snapshot_create_ro()
 
     umount /mnt
 
-    bcachefs fsck -n /dev/sdb
+    bcachefs fsck -n ${ktest_scratch_dev[0]}
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_subvol_snapshot_delete()
 {
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     bcachefs subvolume create /mnt/subvolume_1
     bcachefs subvolume snapshot /mnt/subvolume_1 /mnt/snapshot_1
     bcachefs subvolume delete /mnt/snapshot_1
 
     umount /mnt
 
-    bcachefs fsck -n /dev/sdb
+    bcachefs fsck -n ${ktest_scratch_dev[0]}
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_subvol_snapshot_delete_create()
 {
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     bcachefs subvolume create /mnt/subvolume_1
     bcachefs subvolume snapshot /mnt/subvolume_1 /mnt/snapshot_1
     bcachefs subvolume delete /mnt/snapshot_1
@@ -327,75 +327,75 @@ test_subvol_snapshot_delete_create()
 
     umount /mnt
 
-    bcachefs fsck -n /dev/sdb
+    bcachefs fsck -n ${ktest_scratch_dev[0]}
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 d_test_subvol_snapshot_rm()
 {
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     bcachefs subvolume create /mnt/subvolume_1
     bcachefs subvolume snapshot /mnt/subvolume_1 /mnt/snapshot_1
     rm -r /mnt/snapshot_1
 
     umount /mnt
 
-    bcachefs fsck -n /dev/sdb
+    bcachefs fsck -n ${ktest_scratch_dev[0]}
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 # Create a subvolume, then snapshot the parent subvolume, then move the child
 # subvolume:
 test_mkdir_mv_snapshot()
 {
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     mkdir /mnt/dir1
     bcachefs subvolume snapshot /mnt/ /mnt/snap1
     mv /mnt/dir1 /mnt/dir2
     umount /mnt
 
-    bcachefs fsck -n /dev/sdb
+    bcachefs fsck -n ${ktest_scratch_dev[0]}
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_subvol_mv_snapshot()
 {
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     bcachefs subvolume create /mnt/sub1
     bcachefs subvolume snapshot /mnt/ /mnt/snap1
     mv /mnt/sub1 /mnt/sub2
     umount /mnt
 
-    bcachefs fsck -n /dev/sdb
+    bcachefs fsck -n ${ktest_scratch_dev[0]}
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 # Test moving a subvol to another subvol
 test_subvol_mv_subvol()
 {
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     bcachefs subvolume create /mnt/sub1
     bcachefs subvolume create /mnt/sub2
     mv /mnt/sub1 /mnt/sub2
     umount /mnt
 
-    bcachefs fsck -n /dev/sdb
+    bcachefs fsck -n ${ktest_scratch_dev[0]}
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_subvol_snapshot_reuse_snapshot_name()
 {
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     bcachefs subvolume create /mnt/subvolume_1
     bcachefs subvolume snapshot /mnt/subvolume_1 /mnt/snapshot_1
     bcachefs subvolume delete /mnt/snapshot_1
@@ -403,15 +403,15 @@ test_subvol_snapshot_reuse_snapshot_name()
 
     umount /mnt
 
-    bcachefs fsck -n /dev/sdb
+    bcachefs fsck -n ${ktest_scratch_dev[0]}
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_subvol_delete_snapshot_of_deleted_subvol()
 {
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     bcachefs subvolume create /mnt/subvolume_1
     bcachefs subvolume snapshot /mnt/subvolume_1 /mnt/snapshot_1
     rm -rf /mnt/subvolume_1
@@ -419,30 +419,30 @@ test_subvol_delete_snapshot_of_deleted_subvol()
 
     umount /mnt
 
-    bcachefs fsck -n /dev/sdb
+    bcachefs fsck -n ${ktest_scratch_dev[0]}
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_subvol_snapshot_delete_repeat()
 {
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     for i in $(seq 1 64); do
         bcachefs subvolume snapshot /mnt/$i
         bcachefs subvolume delete /mnt/$i
     done
     umount /mnt
 
-    bcachefs fsck -n /dev/sdb
+    bcachefs fsck -n ${ktest_scratch_dev[0]}
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_subvol_snapshot_delete_fio()
 {
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     for i in $(seq 1 10); do
 	#run_fio_randrw --filesize=500M --bs=4k
@@ -452,20 +452,20 @@ test_subvol_snapshot_delete_fio()
 
     for i in $(seq 1 10); do
 	umount /mnt
-	bcachefs fsck -n /dev/sdb
-	mount -t bcachefs -o fsck /dev/sdb /mnt
+	bcachefs fsck -n ${ktest_scratch_dev[0]}
+	mount -t bcachefs -o fsck ${ktest_scratch_dev[0]} /mnt
     done
 
     umount /mnt
-    bcachefs fsck -n /dev/sdb
+    bcachefs fsck -n ${ktest_scratch_dev[0]}
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_snapshot_copygc()
 {
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     for i in $(seq 1 4); do
 	run_fio_randrw --filesize=1000M --loops=4 --bs=4k
@@ -475,13 +475,13 @@ test_snapshot_copygc()
     bcachefs fs usage -h /mnt
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_snapshot_many_overwrite()
 {
-    run_quiet "" bcachefs format -f --errors=panic /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     for i in $(seq 1 100); do
 	echo foo > /mnt/test
@@ -491,13 +491,13 @@ test_snapshot_many_overwrite()
     bcachefs fs usage -h /mnt
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_snapshot_prjquota()
 {
-    run_quiet "" bcachefs format -f --errors=panic --prjquota /dev/sdb
-    mount -t bcachefs /dev/sdb /mnt
+    run_quiet "" bcachefs format -f --errors=panic --prjquota ${ktest_scratch_dev[0]}
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
 
     echo foo > /mnt/test
     bcachefs subvolume snapshot /mnt/snap.$i
@@ -505,10 +505,10 @@ test_snapshot_prjquota()
     bcachefs fs usage -h /mnt
     umount /mnt
 
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 main "$@"
diff --git a/tests/bcachefs/tier.ktest b/tests/bcachefs/tier.ktest
index 9f5bcb2..8aa0db4 100755
--- a/tests/bcachefs/tier.ktest
+++ b/tests/bcachefs/tier.ktest
@@ -13,10 +13,10 @@ run_basic_tiering_test()
 	--block_size=4k				\
 	--btree_node_size=32k			\
 	--bucket=256k				\
-	--label=ssd.ssd1 /dev/sdb		\
-	--label=ssd.ssd2 /dev/sdc		\
-	--label=hdd.hdd1 /dev/sdd		\
-	--label=hdd.hdd2 /dev/sde		\
+	--label=ssd.ssd1 ${ktest_scratch_dev[0]}		\
+	--label=ssd.ssd2 ${ktest_scratch_dev[1]}		\
+	--label=hdd.hdd1 ${ktest_scratch_dev[2]}		\
+	--label=hdd.hdd2 ${ktest_scratch_dev[3]}		\
 	--foreground_target=ssd			\
 	--promote_target=ssd			\
 	--background_target=hdd
@@ -27,15 +27,15 @@ test_tiering_torture()
     run_quiet "" bcachefs format		\
 	--block_size=4k				\
 	--bucket=8M				\
-	--label=ssd.ssd1 /dev/sdb		\
-	--label=ssd.ssd2 /dev/sdc		\
-	--label=hdd.hdd1 /dev/sdd		\
-	--label=hdd.hdd2 /dev/sde		\
+	--label=ssd.ssd1 ${ktest_scratch_dev[0]}		\
+	--label=ssd.ssd2 ${ktest_scratch_dev[1]}		\
+	--label=hdd.hdd1 ${ktest_scratch_dev[2]}		\
+	--label=hdd.hdd2 ${ktest_scratch_dev[3]}		\
 	--foreground_target=ssd			\
 	--promote_target=ssd			\
 	--background_target=hdd
 
-    mount -t bcachefs /dev/sdb:/dev/sdc:/dev/sdd:/dev/sde /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]}:${ktest_scratch_dev[1]}:${ktest_scratch_dev[2]}:${ktest_scratch_dev[3]} /mnt
     run_fio_randrw
     mv /mnt/fiotest /mnt/fiotest_old
     run_fio_randrw --loops=50
@@ -43,7 +43,7 @@ test_tiering_torture()
     mount -o remount,ro /mnt
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_tiering()
@@ -57,13 +57,13 @@ test_tiering_drop_alloc()
     # mount dropping all alloc info
 
     echo "dropping alloc:"
-    mount -t bcachefs -o reconstruct_alloc,fsck,fix_errors /dev/sdb:/dev/sdc:/dev/sdd:/dev/sde /mnt
+    mount -t bcachefs -o reconstruct_alloc,fsck,fix_errors "$(join_by : "${ktest_scratch_dev[@]}")" /mnt
     umount /mnt
 
     echo "final fsck:"
-    bcachefs fsck -n /dev/sd[bcde]
+    bcachefs fsck -n "${ktest_scratch_dev[@]}"
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_tiering_buffered()
@@ -72,15 +72,15 @@ test_tiering_buffered()
 
     run_quiet "" bcachefs format		\
 	--block_size=4k				\
-	--label=ssd.ssd1 /dev/sdb		\
-	--label=ssd.ssd2 /dev/sdc		\
-	--label=hdd.hdd1 /dev/sdd		\
-	--label=hdd.hdd2 /dev/sde		\
+	--label=ssd.ssd1 ${ktest_scratch_dev[0]}		\
+	--label=ssd.ssd2 ${ktest_scratch_dev[1]}		\
+	--label=hdd.hdd1 ${ktest_scratch_dev[2]}		\
+	--label=hdd.hdd2 ${ktest_scratch_dev[3]}		\
 	--foreground_target=ssd			\
 	--promote_target=ssd			\
 	--background_target=hdd
 
-    mount -t bcachefs /dev/sdb:/dev/sdc:/dev/sdd:/dev/sde /mnt
+    mount -t bcachefs "$(join_by : "${ktest_scratch_dev[@]}")" /mnt
 
     local loops=$((($ktest_priority + 1) * 4))
 
@@ -99,24 +99,24 @@ test_tiering_buffered()
 	--bsrange=512-16k
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_writethrough()
 {
-    run_basic_fio_test "$@"			\
-	--durability=0 --label=ssd /dev/sd[bc]	\
-	--durability=1 --label=hdd /dev/sd[de]	\
-	--foreground_target=ssd			\
-	--promote_target=ssd			\
+    run_basic_fio_test "$@"								\
+	--durability=0 --label=ssd ${ktest_scratch_dev[0]} ${ktest_scratch_dev[1]}	\
+	--durability=1 --label=hdd ${ktest_scratch_dev[2]} ${ktest_scratch_dev[3]}	\
+	--foreground_target=ssd								\
+	--promote_target=ssd								\
 	--background_target=hdd
 }
 
 test_promote()
 {
     run_basic_fio_test "$@"			\
-	--durability=0 --label=ssd /dev/sdb	\
-	--durability=1 --label=hdd /dev/sdd	\
+	--durability=0 --label=ssd ${ktest_scratch_dev[0]}	\
+	--durability=1 --label=hdd ${ktest_scratch_dev[2]}	\
 	--foreground_target=hdd			\
 	--promote_target=ssd			\
 	--background_target=hdd
@@ -127,21 +127,21 @@ test_setattr()
     setup_tracing 'bcachefs:*'
 
     run_quiet "" bcachefs format		\
-	--durability=0 --label=ssd /dev/sdb	\
-	--durability=1 --label=hdd /dev/sdd	\
+	--durability=0 --label=ssd ${ktest_scratch_dev[0]}	\
+	--durability=1 --label=hdd ${ktest_scratch_dev[2]}	\
 	--background_target=hdd
 
-    mount -t bcachefs /dev/sdb:/dev/sdd /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]}:${ktest_scratch_dev[2]} /mnt
 
     touch /mnt/foo
     touch /mnt/bar
 
-    bcachefs setattr --foreground_target sdb /mnt/
+    bcachefs setattr --foreground_target $(basename ${ktest_scratch_dev[0]}) /mnt/
     bcachefs setattr --promote_target ssd /mnt/
 
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_tiering_no_checksum()
@@ -177,10 +177,10 @@ test_tiering_replication()
 test_tiering_variable_buckets()
 {
     run_basic_fio_test					\
-	--label=ssd --bucket=32k	/dev/sdb	\
-	--label=ssd --bucket=64k	/dev/sdc	\
-	--label=hdd --bucket=128k	/dev/sde	\
-	--label=hdd --bucket=256k	/dev/sdd	\
+	--label=ssd --bucket=32k	${ktest_scratch_dev[0]}	\
+	--label=ssd --bucket=64k	${ktest_scratch_dev[1]}	\
+	--label=hdd --bucket=128k	${ktest_scratch_dev[3]}	\
+	--label=hdd --bucket=256k	${ktest_scratch_dev[2]}	\
 	--foreground_target=ssd				\
 	--promote_target=ssd				\
 	--background_target=hdd
@@ -190,10 +190,10 @@ test_tiering_variable_buckets_replicas()
 {
     run_basic_fio_test					\
 	--replicas=2					\
-	--label=ssd --bucket=32k	/dev/sdb	\
-	--label=ssd --bucket=64k	/dev/sdc	\
-	--label=hdd --bucket=128k	/dev/sde	\
-	--label=hdd --bucket=256k	/dev/sdd	\
+	--label=ssd --bucket=32k	${ktest_scratch_dev[0]}	\
+	--label=ssd --bucket=64k	${ktest_scratch_dev[1]}	\
+	--label=hdd --bucket=128k	${ktest_scratch_dev[3]}	\
+	--label=hdd --bucket=256k	${ktest_scratch_dev[2]}	\
 	--foreground_target=ssd				\
 	--promote_target=ssd				\
 	--background_target=hdd
@@ -202,52 +202,52 @@ test_tiering_variable_buckets_replicas()
 test_device_add()
 {
     set_watchdog 60
-    run_quiet "" bcachefs format		\
-	--label=ssd /dev/sdb			\
-	--label=hdd /dev/sd[de]
+    run_quiet "" bcachefs format					\
+	--label=ssd ${ktest_scratch_dev[0]}				\
+	--label=hdd ${ktest_scratch_dev[2]} ${ktest_scratch_dev[3]}
 
-    mount -t bcachefs /dev/sdb:/dev/sdd:/dev/sde /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]}:${ktest_scratch_dev[2]}:${ktest_scratch_dev[3]} /mnt
 
     run_fio_randrw|tail -n200 &
 
-    bcachefs device add --label=hdd /mnt /dev/sdc
+    bcachefs device add --label=hdd /mnt ${ktest_scratch_dev[1]}
 
     wait
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_mount_umount_torture()
 {
     set_watchdog 60
-    run_quiet "" bcachefs format			\
-	--replicas=2					\
-	--label=ssd /dev/sd[bc]				\
-	--label=hdd /dev/sd[de]				\
-	--foreground_target=ssd				\
-	--promote_target=ssd				\
+    run_quiet "" bcachefs format					\
+	--replicas=2							\
+	--label=ssd ${ktest_scratch_dev[0]} ${ktest_scratch_dev[1]}	\
+	--label=hdd ${ktest_scratch_dev[2]} ${ktest_scratch_dev[3]}	\
+	--foreground_target=ssd						\
+	--promote_target=ssd						\
 	--background_target=hdd
 
     for i in {0..10}; do
-	mount -t bcachefs /dev/sdb:/dev/sdc:/dev/sdd:/dev/sde /mnt
+	mount -t bcachefs "$(join_by : "${ktest_scratch_dev[@]}")" /mnt
 	umount /mnt
     done
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 test_change_replicas()
 {
     set_watchdog 180
-    run_quiet "" bcachefs format			\
-	--label=ssd /dev/sd[bc]				\
-	--label=hdd /dev/sd[de]				\
-	--foreground_target=ssd				\
-	--promote_target=ssd				\
+    run_quiet "" bcachefs format					\
+	--label=ssd ${ktest_scratch_dev[0]} ${ktest_scratch_dev[1]}	\
+	--label=hdd ${ktest_scratch_dev[2]} ${ktest_scratch_dev[3]}	\
+	--foreground_target=ssd						\
+	--promote_target=ssd						\
 	--background_target=hdd
 
-    mount -t bcachefs /dev/sdb:/dev/sdc:/dev/sdd:/dev/sde /mnt
+    mount -t bcachefs "$(join_by : "${ktest_scratch_dev[@]}")" /mnt
 
     (
 	cd /sys/fs/bcachefs/*
@@ -280,7 +280,7 @@ test_change_replicas()
     kill %1
     umount /mnt
 
-    check_counters /dev/sdb
+    check_counters ${ktest_scratch_dev[0]}
 }
 
 main $@
diff --git a/tests/bcachefs/units.ktest b/tests/bcachefs/units.ktest
index df5a2e4..b19f2b0 100755
--- a/tests/bcachefs/units.ktest
+++ b/tests/bcachefs/units.ktest
@@ -24,10 +24,10 @@ run_test()
 
     bcachefs format				\
 	--errors=panic				\
-	/dev/sdb >/dev/null
+	${ktest_scratch_dev[0]} >/dev/null
 	#--bucket=$btree_node_size		\
 	#--btree_node_size=$btree_node_size	\
-    mount -t bcachefs /dev/sdb /mnt
+    mount -t bcachefs ${ktest_scratch_dev[0]} /mnt
     ln -sf /sys/fs/bcachefs/*/perf_test p
 
     for i in $@; do