Commit db5bcf87 authored by Jens Axboe's avatar Jens Axboe
Browse files

null_blk: add blocking mode 



This adds a new module parameter to null_blk, blocking. If set, null_blk
will set the BLK_MQ_F_BLOCKING flag, indicating that it sometimes/always
needs to block in its ->queue_rq() function.  The intent is to help find
regressions in blocking drivers, since not many of them exist.

If null_blk is loaded with submit_queues > 1 and blocking=1, this
shows the regression recently fixed by bf4907c0.

Reviewed-by: default avatarBart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent bf4907c0

drivers/block/null_blk.c

+9 −0
Original line number Diff line number Diff line
@@ -117,6 +117,10 @@ static bool use_lightnvm; 
module_param(use_lightnvm, bool, S_IRUGO);

MODULE_PARM_DESC(use_lightnvm, "Register as a LightNVM device");



static bool blocking;

module_param(blocking, bool, S_IRUGO);

MODULE_PARM_DESC(blocking, "Register as a blocking blk-mq driver device");



static int irqmode = NULL_IRQ_SOFTIRQ;



static int null_set_irqmode(const char *str, const struct kernel_param *kp)
@@ -357,6 +361,8 @@ static int null_queue_rq(struct blk_mq_hw_ctx *hctx, 
{

	struct nullb_cmd *cmd = blk_mq_rq_to_pdu(bd->rq);



	might_sleep_if(hctx->flags & BLK_MQ_F_BLOCKING);



	if (irqmode == NULL_IRQ_TIMER) {

		hrtimer_init(&cmd->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);

		cmd->timer.function = null_cmd_timer_expired;
@@ -724,6 +730,9 @@ static int null_add_dev(void) 
		nullb->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;

		nullb->tag_set.driver_data = nullb;



		if (blocking)

			nullb->tag_set.flags |= BLK_MQ_F_BLOCKING;



		rv = blk_mq_alloc_tag_set(&nullb->tag_set);

		if (rv)

			goto out_cleanup_queues;

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