[PATCH blktests v4 3/4] Introduce the function _configure_null_blk()

[Bart Van Assche <bvanassche@xxxxxxx>]

Introduce a function for creating a null_blk device instance through
configfs.

Suggested-by: Chaitanya Kulkarni <Chaitanya.Kulkarni@xxxxxxx>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@xxxxxxx>
Reviewed-by: Daniel Wagner <dwagner@xxxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
 common/multipath-over-rdma | 17 +++++------------
 common/null_blk            | 14 ++++++++++++++
 tests/block/029            | 16 ++--------------
 3 files changed, 21 insertions(+), 26 deletions(-)

diff --git a/common/multipath-over-rdma b/common/multipath-over-rdma
index a56e7a8269db..e689a9633d13 100644
--- a/common/multipath-over-rdma
+++ b/common/multipath-over-rdma
@@ -620,18 +620,11 @@ run_fio() {
 configure_null_blk() {
 	local i
 
-	(
-		cd /sys/kernel/config/nullb || return $?
-		for i in nullb0 nullb1; do (
-			{ mkdir -p $i &&
-				  cd $i &&
-				  echo 0 > completion_nsec &&
-				  echo 512 > blocksize &&
-				  echo $((ramdisk_size>>20)) > size &&
-				  echo 1 > memory_backed &&
-				  echo 1 > power; } || exit $?
-		) done
-	)
+	for i in nullb0 nullb1; do
+		_configure_null_blk $i completion_nsec=0 blocksize=512 \
+				    size=$((ramdisk_size>>20)) memory_backed=1 \
+				    power=1 || return $?
+	done
 	ls -l /dev/nullb* &>>"$FULL"
 }
 
diff --git a/common/null_blk b/common/null_blk
index a4140e365955..6611db03a00e 100644
--- a/common/null_blk
+++ b/common/null_blk
@@ -29,6 +29,20 @@ _init_null_blk() {
 	return 0
 }
 
+# Configure one null_blk instance with name $1 and parameters $2..${$#}.
+_configure_null_blk() {
+	local nullb=/sys/kernel/config/nullb/$1 param val
+
+	shift
+	mkdir "$nullb" || return $?
+	while [[ $# -gt 0 ]]; do
+		param="${1%%=*}"
+		val="${1#*=}"
+		shift
+		echo "$val" > "$nullb/$param" || return $?
+	done
+}
+
 _exit_null_blk() {
 	_remove_null_blk_devices
 	udevadm settle
diff --git a/tests/block/029 b/tests/block/029
index 0d521edb0cf6..dbb582eab473 100755
--- a/tests/block/029
+++ b/tests/block/029
@@ -14,19 +14,6 @@ requires() {
 	_have_null_blk
 }
 
-# Configure one null_blk instance.
-configure_null_blk() {
-	local nullb0="/sys/kernel/config/nullb/nullb0"
-
-	mkdir "$nullb0" &&
-	echo 0 > "$nullb0/completion_nsec" &&
-	echo 512 > "$nullb0/blocksize" &&
-	echo 16 > "$nullb0/size" &&
-	echo 1 > "$nullb0/memory_backed" &&
-	echo 1 > "$nullb0/power" &&
-	ls -l /dev/nullb* &>>"$FULL"
-}
-
 modify_nr_hw_queues() {
 	local deadline num_cpus
 
@@ -45,7 +32,8 @@ test() {
 
 	: "${TIMEOUT:=30}"
 	_init_null_blk nr_devices=0 queue_mode=2 &&
-	configure_null_blk
+	_configure_null_blk nullb0 completion_nsec=0 blocksize=512 \
+			    size=16 memory_backed=1 power=1 &&
 	if { echo 1 >$sq; } 2>/dev/null; then
 		modify_nr_hw_queues &
 		fio --rw=randwrite --bs=4K --loops=$((10**6)) \