[PATCH 5/5] loop: add module parameter of 'nr_hw_queues'

[Ming Lei <ming.lei@xxxxxxxxxx>]

Add module parameter of 'nr_hw_queues' so that loop can support MQ,
which may reduce contention in case of too many io jobs.

Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
 drivers/block/loop.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 46be0c8e75a6..6378dfee6681 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -91,6 +91,7 @@ struct loop_cmd {
 
 #define LOOP_IDLE_WORKER_TIMEOUT (60 * HZ)
 #define LOOP_DEFAULT_HW_Q_DEPTH 128
+#define LOOP_DEFAULT_NR_HW_Q 1
 
 static void loop_queue_work(struct loop_device *lo, struct loop_cmd *cmd);
 
@@ -1928,6 +1929,26 @@ static const struct kernel_param_ops loop_hw_qdepth_param_ops = {
 device_param_cb(hw_queue_depth, &loop_hw_qdepth_param_ops, &hw_queue_depth, 0444);
 MODULE_PARM_DESC(hw_queue_depth, "Queue depth for each hardware queue. Default: " __stringify(LOOP_DEFAULT_HW_Q_DEPTH));
 
+static int nr_hw_queues = LOOP_DEFAULT_NR_HW_Q;
+static int loop_set_nr_hw_queues(const char *s, const struct kernel_param *p)
+{
+	int nr, ret;
+
+	ret = kstrtoint(s, 0, &nr);
+	if (ret < 0)
+		return ret;
+	if (nr < 1)
+		return -EINVAL;
+	nr_hw_queues = nr;
+	return 0;
+}
+static const struct kernel_param_ops loop_nr_hw_q_param_ops = {
+	.set	= loop_set_nr_hw_queues,
+	.get	= param_get_int,
+};
+device_param_cb(nr_hw_queues, &loop_nr_hw_q_param_ops, &nr_hw_queues, 0444);
+MODULE_PARM_DESC(nr_hw_queues, "number of hardware queues. Default: " __stringify(LOOP_DEFAULT_NR_HW_Q));
+
 MODULE_DESCRIPTION("Loopback device support");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS_BLOCKDEV_MAJOR(LOOP_MAJOR);
@@ -2112,7 +2133,7 @@ static int loop_add(int i)
 	i = err;
 
 	lo->tag_set.ops = &loop_mq_ops;
-	lo->tag_set.nr_hw_queues = 1;
+	lo->tag_set.nr_hw_queues = nr_hw_queues;
 	lo->tag_set.queue_depth = hw_queue_depth;
 	lo->tag_set.numa_node = NUMA_NO_NODE;
 	lo->tag_set.cmd_size = sizeof(struct loop_cmd);
-- 
2.47.0