Commit cda6b5ab authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Mike Snitzer
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dm delay: add flush as a third class of IO 



Add a new class for dm-delay that delays flush requests.  Previously,
flushes were delayed as writes, but it caused problems if the user
needed to create a device with one or a few slow sectors for the purpose
of testing - all flushes would be forwarded to this device and delayed,
and that skews the test results.  Fix this by allowing to select 0 delay
for flushes.

Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 3876ac76

Documentation/device-mapper/delay.txt

+2 −1
Original line number Diff line number Diff line
@@ -5,7 +5,8 @@ Device-Mapper's "delay" target delays reads and/or writes 
and maps them to different devices.



Parameters:

    <device> <offset> <delay> [<write_device> <write_offset> <write_delay>]

    <device> <offset> <delay> [<write_device> <write_offset> <write_delay>

			       [<flush_device> <flush_offset> <flush_delay>]]



With separate write parameters, the first set is only used for reads.

Offsets are specified in sectors.

drivers/md/dm-delay.c

+30 −4
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ struct delay_c { 


	struct delay_class read;

	struct delay_class write;

	struct delay_class flush;



	int argc;

};
@@ -126,6 +127,8 @@ static void delay_dtr(struct dm_target *ti) 
		dm_put_device(ti, dc->read.dev);

	if (dc->write.dev)

		dm_put_device(ti, dc->write.dev);

	if (dc->flush.dev)

		dm_put_device(ti, dc->flush.dev);



	mutex_destroy(&dc->timer_lock);
@@ -171,8 +174,8 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv) 
	struct delay_c *dc;

	int ret;



	if (argc != 3 && argc != 6) {

		ti->error = "Requires exactly 3 or 6 arguments";

	if (argc != 3 && argc != 6 && argc != 9) {

		ti->error = "Requires exactly 3, 6 or 9 arguments";

		return -EINVAL;

	}
@@ -196,6 +199,9 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv) 


	if (argc == 3) {

		ret = delay_class_ctr(ti, &dc->write, argv);

		if (ret)

			goto bad;

		ret = delay_class_ctr(ti, &dc->flush, argv);

		if (ret)

			goto bad;

		goto out;
@@ -204,6 +210,16 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv) 
	ret = delay_class_ctr(ti, &dc->write, argv + 3);

	if (ret)

		goto bad;

	if (argc == 6) {

		ret = delay_class_ctr(ti, &dc->flush, argv + 3);

		if (ret)

			goto bad;

		goto out;

	}



	ret = delay_class_ctr(ti, &dc->flush, argv + 6);

	if (ret)

		goto bad;



out:

	dc->kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0);
@@ -269,6 +285,9 @@ static int delay_map(struct dm_target *ti, struct bio *bio) 
	struct dm_delay_info *delayed = dm_per_bio_data(bio, sizeof(struct dm_delay_info));



	if (bio_data_dir(bio) == WRITE) {

		if (unlikely(bio->bi_opf & REQ_PREFLUSH))

			c = &dc->flush;

		else

			c = &dc->write;

	} else {

		c = &dc->read;
@@ -292,7 +311,7 @@ static void delay_status(struct dm_target *ti, status_type_t type, 


	switch (type) {

	case STATUSTYPE_INFO:

		DMEMIT("%u %u", dc->read.ops, dc->write.ops);

		DMEMIT("%u %u %u", dc->read.ops, dc->write.ops, dc->flush.ops);

		break;



	case STATUSTYPE_TABLE:
@@ -301,6 +320,10 @@ static void delay_status(struct dm_target *ti, status_type_t type, 
			DMEMIT(" ");

			DMEMIT_DELAY_CLASS(&dc->write);

		}

		if (dc->argc >= 9) {

			DMEMIT(" ");

			DMEMIT_DELAY_CLASS(&dc->flush);

		}

		break;

	}

}
@@ -317,6 +340,9 @@ static int delay_iterate_devices(struct dm_target *ti, 
	ret = fn(ti, dc->write.dev, dc->write.start, ti->len, data);

	if (ret)

		goto out;

	ret = fn(ti, dc->flush.dev, dc->flush.start, ti->len, data);

	if (ret)

		goto out;



out:

	return ret;

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