null_blk: add "no_sched" module parameter

add an option that disable io scheduler for null block device.

Signed-off-by: weiping zhang <zhangweiping@didichuxing.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
index 8042c26ea9e6eb6c6d9558b32c3ac85f20ce909d..bf2c8ca3242aa60749ea03483892526de02a0389 100644 (file)
--- a/drivers/block/null_blk.c
+++ b/drivers/block/null_blk.c
@@ -154,6 +154,10 @@ enum {
        NULL_Q_MQ               = 2,
 };
 
+static int g_no_sched;
+module_param_named(no_sched, g_no_sched, int, S_IRUGO);
+MODULE_PARM_DESC(no_sched, "No io scheduler");
+
 static int g_submit_queues = 1;
 module_param_named(submit_queues, g_submit_queues, int, S_IRUGO);
 MODULE_PARM_DESC(submit_queues, "Number of submission queues");
@@ -1754,6 +1758,8 @@ static int null_init_tag_set(struct nullb *nullb, struct blk_mq_tag_set *set)
        set->numa_node = nullb ? nullb->dev->home_node : g_home_node;
        set->cmd_size   = sizeof(struct nullb_cmd);
        set->flags = BLK_MQ_F_SHOULD_MERGE;
+       if (g_no_sched)
+               set->flags |= BLK_MQ_F_NO_SCHED;
        set->driver_data = NULL;
 
        if ((nullb && nullb->dev->blocking) || g_blocking)