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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: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mikulas Patocka 2018-04-17 00:33:14 +02:00 committed by Mike Snitzer
parent 3876ac76f0
commit cda6b5ab7f
2 changed files with 32 additions and 5 deletions
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3
Documentation/device-mapper/delay.txt
View File

@ -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.

34
drivers/md/dm-delay.c
View File

@ -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);
@ -269,7 +285,10 @@ 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) {
c = &dc->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;