Commit 24941b90 authored by Jens Axboe's avatar Jens Axboe
Browse files

null_blk: add 'requeue' fault attribute 



Similarly to the support we have for testing/faking timeouts for
null_blk, this adds support for triggering a requeue condition.
Considering the issues around restart we've been seeing, this should be
a useful addition to the testing arsenal to ensure that we are handling
requeue conditions correctly.

This works for queue mode 1 (legacy request_fn based path) and 2 (blk-mq
path), as there's no good way to do requeue with a bio based driver.
This is similar to the timeout path. For the blk-mq path, we alternate
between passing back BLK_STS_RESOURCE and manually calling
blk_mq_requeue_request() in the driver. The former will hit the core
requeue path, while the latter exercises the IO scheduler requeue
path.

Reviewed-by: default avatarBart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: default avatarOmar Sandoval <osandov@fb.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 4ace53f1

drivers/block/null_blk.c

+55 −12
Original line number Diff line number Diff line
@@ -29,6 +29,7 @@ 


#ifdef CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION

static DECLARE_FAULT_ATTR(null_timeout_attr);

static DECLARE_FAULT_ATTR(null_requeue_attr);

#endif



static inline u64 mb_per_tick(int mbps)
@@ -53,6 +54,7 @@ struct nullb_queue { 
	wait_queue_head_t wait;

	unsigned int queue_depth;

	struct nullb_device *dev;

	unsigned int requeue_selection;



	struct nullb_cmd *cmds;

};
@@ -170,6 +172,9 @@ MODULE_PARM_DESC(home_node, "Home node for the device"); 
#ifdef CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION

static char g_timeout_str[80];

module_param_string(timeout, g_timeout_str, sizeof(g_timeout_str), S_IRUGO);



static char g_requeue_str[80];

module_param_string(requeue, g_requeue_str, sizeof(g_requeue_str), S_IRUGO);

#endif



static int g_queue_mode = NULL_Q_MQ;
@@ -1380,7 +1385,15 @@ static bool should_timeout_request(struct request *rq) 
	if (g_timeout_str[0])

		return should_fail(&null_timeout_attr, 1);

#endif

	return false;

}



static bool should_requeue_request(struct request *rq)

{

#ifdef CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION

	if (g_requeue_str[0])

		return should_fail(&null_requeue_attr, 1);

#endif

	return false;

}
@@ -1391,13 +1404,19 @@ static void null_request_fn(struct request_queue *q) 
	while ((rq = blk_fetch_request(q)) != NULL) {

		struct nullb_cmd *cmd = rq->special;



		if (!should_timeout_request(rq)) {

		/* just ignore the request */

		if (should_timeout_request(rq))

			continue;

		if (should_requeue_request(rq)) {

			blk_requeue_request(q, rq);

			continue;

		}



		spin_unlock_irq(q->queue_lock);

		null_handle_cmd(cmd);

		spin_lock_irq(q->queue_lock);

	}

}

}



static enum blk_eh_timer_return null_timeout_rq(struct request *rq, bool res)

{
@@ -1422,11 +1441,24 @@ static blk_status_t null_queue_rq(struct blk_mq_hw_ctx *hctx, 


	blk_mq_start_request(bd->rq);



	if (!should_timeout_request(bd->rq))

		return null_handle_cmd(cmd);



	if (should_requeue_request(bd->rq)) {

		/*

		 * Alternate between hitting the core BUSY path, and the

		 * driver driven requeue path

		 */

		nq->requeue_selection++;

		if (nq->requeue_selection & 1)

			return BLK_STS_RESOURCE;

		else {

			blk_mq_requeue_request(bd->rq, true);

			return BLK_STS_OK;

		}

	}

	if (should_timeout_request(bd->rq))

		return BLK_STS_OK;



	return null_handle_cmd(cmd);

}



static const struct blk_mq_ops null_mq_ops = {

	.queue_rq       = null_queue_rq,
@@ -1659,16 +1691,27 @@ static void null_validate_conf(struct nullb_device *dev) 
		dev->mbps = 0;

}



static bool null_setup_fault(void)

{

#ifdef CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION

	if (!g_timeout_str[0])

static bool __null_setup_fault(struct fault_attr *attr, char *str)

{

	if (!str[0])

		return true;



	if (!setup_fault_attr(&null_timeout_attr, g_timeout_str))

	if (!setup_fault_attr(attr, str))

		return false;



	null_timeout_attr.verbose = 0;

	attr->verbose = 0;

	return true;

}

#endif



static bool null_setup_fault(void)

{

#ifdef CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION

	if (!__null_setup_fault(&null_timeout_attr, g_timeout_str))

		return false;

	if (!__null_setup_fault(&null_requeue_attr, g_requeue_str))

		return false;

#endif

	return true;

}

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