This patch adds 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 few slow sectors for the
purpose of testing - all flushes would be forwarded to this device and
delayed, and that skews the test results. This patch allows to select 0
delay for flushes.
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
---
Documentation/device-mapper/delay.txt | 2 +-
drivers/md/dm-delay.c | 34 ++++++++++++++++++++++++++++++----
2 files changed, 31 insertions(+), 5 deletions(-)
Index: linux-2.6/drivers/md/dm-delay.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-delay.c 2018-04-17 00:13:44.000000000 +0200
+++ linux-2.6/drivers/md/dm-delay.c 2018-04-17 00:21:11.000000000 +0200
@@ -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 *
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 *t
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;
}
@@ -198,12 +201,25 @@ static int delay_ctr(struct dm_target *t
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;
}
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 *t
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;
}
@@ -289,7 +308,7 @@ static void delay_status(struct dm_targe
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:
@@ -299,6 +318,10 @@ static void delay_status(struct dm_targe
DMEMIT(" ");
EMIT_CLASS(&dc->write);
}
+ if (dc->argc >= 9) {
+ DMEMIT(" ");
+ EMIT_CLASS(&dc->flush);
+ }
#undef EMIT_CLASS
break;
}
@@ -316,6 +339,9 @@ static int delay_iterate_devices(struct
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;
Index: linux-2.6/Documentation/device-mapper/delay.txt
===================================================================
--- linux-2.6.orig/Documentation/device-mapper/delay.txt 2017-06-03 00:22:35.000000000 +0200
+++ linux-2.6/Documentation/device-mapper/delay.txt 2018-04-17 00:24:22.000000000 +0200
@@ -5,7 +5,7 @@ Device-Mapper's "delay" target delays re
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.
--
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