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Commit 93b57046 authored by Jens Axboe's avatar Jens Axboe
Browse files

null_blk: add option for managing IO timeouts 



Use the fault injection framework to provide a way for null_blk
to configure timeouts. This only works for queue_mode 1 and 2,
since the bio mode doesn't have code for tracking timeouts.

Let's say you want to have a 10% chance of timing out every
100,000 requests, and for 5 total timeouts, you could do:

modprobe null_blk timeout="100000,10,0,5"

This is useful for adding blktests to test that IO timeouts
are handled appropriately.

Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 8993d445

drivers/block/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ if BLK_DEV 
config BLK_DEV_NULL_BLK

	tristate "Null test block driver"

	select CONFIGFS_FS

	select FAULT_INJECTION



config BLK_DEV_FD

	tristate "Normal floppy disk support"

drivers/block/null_blk.c

+42 −4
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 
#include <linux/hrtimer.h>

#include <linux/configfs.h>

#include <linux/badblocks.h>

#include <linux/fault-inject.h>



#define SECTOR_SHIFT		9

#define PAGE_SECTORS_SHIFT	(PAGE_SHIFT - SECTOR_SHIFT)
@@ -26,6 +27,8 @@ 
#define TICKS_PER_SEC		50ULL

#define TIMER_INTERVAL		(NSEC_PER_SEC / TICKS_PER_SEC)



static DECLARE_FAULT_ATTR(null_timeout_attr);



static inline u64 mb_per_tick(int mbps)

{

	return (1 << 20) / TICKS_PER_SEC * ((u64) mbps);
@@ -162,6 +165,9 @@ static int g_home_node = NUMA_NO_NODE; 
module_param_named(home_node, g_home_node, int, S_IRUGO);

MODULE_PARM_DESC(home_node, "Home node for the device");



static char g_timeout_str[80];

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



static int g_queue_mode = NULL_Q_MQ;



static int null_param_store_val(const char *str, int *val, int min, int max)
@@ -1364,6 +1370,14 @@ static int null_rq_prep_fn(struct request_queue *q, struct request *req) 
	return BLKPREP_DEFER;

}



static bool should_timeout_request(struct request *rq)

{

	if (g_timeout_str[0])

		return should_fail(&null_timeout_attr, 1);



	return false;

}



static void null_request_fn(struct request_queue *q)

{

	struct request *rq;
@@ -1371,11 +1385,13 @@ 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)) {

			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)

{
@@ -1400,7 +1416,10 @@ 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);



	return BLK_STS_OK;

}



static const struct blk_mq_ops null_mq_ops = {
@@ -1634,6 +1653,18 @@ static void null_validate_conf(struct nullb_device *dev) 
		dev->mbps = 0;

}



static bool null_setup_fault(void)

{

	if (!g_timeout_str[0])

		return true;



	if (!setup_fault_attr(&null_timeout_attr, g_timeout_str))

		return false;



	null_timeout_attr.verbose = 0;

	return true;

}



static int null_add_dev(struct nullb_device *dev)

{

	struct nullb *nullb;
@@ -1667,6 +1698,9 @@ static int null_add_dev(struct nullb_device *dev) 
		if (rv)

			goto out_cleanup_queues;



		if (!null_setup_fault())

			goto out_cleanup_queues;



		nullb->tag_set->timeout = 5 * HZ;

		nullb->q = blk_mq_init_queue(nullb->tag_set);

		if (IS_ERR(nullb->q)) {
@@ -1691,6 +1725,10 @@ static int null_add_dev(struct nullb_device *dev) 
			rv = -ENOMEM;

			goto out_cleanup_queues;

		}



		if (!null_setup_fault())

			goto out_cleanup_blk_queue;



		blk_queue_prep_rq(nullb->q, null_rq_prep_fn);

		blk_queue_softirq_done(nullb->q, null_softirq_done_fn);

		blk_queue_rq_timed_out(nullb->q, null_rq_timed_out_fn);