This enables runtime modification of the read and write delay values.
Make sure if the delay time is reduced to flush currently-delayed
bios first, to maintain ordering.
Signed-off-by: Andy Grover <agrover@xxxxxxxxxx>
---
Documentation/device-mapper/delay.txt | 8 +++++++
drivers/md/dm-delay.c | 42 +++++++++++++++++++++++++++++++++++
2 files changed, 50 insertions(+)
diff --git a/Documentation/device-mapper/delay.txt b/Documentation/device-mapper/delay.txt
index 15adc55..9e80751 100644
--- a/Documentation/device-mapper/delay.txt
+++ b/Documentation/device-mapper/delay.txt
@@ -10,6 +10,14 @@ Parameters:
With separate write parameters, the first set is only used for reads.
Delays are specified in milliseconds.
+Message Interface
+-----------------
+The delay target will accept a message of the following format:
+
+set_delay <read_delay> [<write_delay>]
+
+'man dmsetup' for more information on the message interface.
+
Example scripts
===============
[[
diff --git a/drivers/md/dm-delay.c b/drivers/md/dm-delay.c
index 57b6a19..04c2ab0 100644
--- a/drivers/md/dm-delay.c
+++ b/drivers/md/dm-delay.c
@@ -290,6 +290,47 @@ static int delay_map(struct dm_target *ti, struct bio *bio)
return delay_bio(dc, dc->read_delay, bio);
}
+/* Message interface
+ * set_delay <read_delay> [<write_delay>]
+*/
+static int delay_message(struct dm_target *ti, unsigned argc, char **argv)
+{
+ struct delay_c *dc = ti->private;
+ unsigned read_delay = dc->read_delay;
+ unsigned write_delay = dc->write_delay;
+ char dummy;
+
+ if (argc < 2 || argc > 3)
+ goto error;
+
+ if (strcasecmp(argv[0], "set_delay"))
+ goto error;
+
+ if (sscanf(argv[1], "%u%c", &read_delay, &dummy) != 1) {
+ ti->error = "Invalid read delay";
+ goto error;
+ }
+
+ if (argc == 3) {
+ if (sscanf(argv[2], "%u%c", &write_delay, &dummy) != 1) {
+ ti->error = "Invalid write delay";
+ goto error;
+ }
+ }
+
+ if (read_delay < dc->read_delay
+ || write_delay < dc->write_delay)
+ flush_bios(flush_delayed_bios(dc, 1));
+
+ dc->read_delay = read_delay;
+ dc->write_delay = write_delay;
+ return 0;
+
+error:
+ DMWARN("unrecognised message received.");
+ return -EINVAL;
+}
+
static void delay_status(struct dm_target *ti, status_type_t type,
unsigned status_flags, char *result, unsigned maxlen)
{
@@ -339,6 +380,7 @@ static struct target_type delay_target = {
.map = delay_map,
.presuspend = delay_presuspend,
.resume = delay_resume,
+ .message = delay_message,
.status = delay_status,
.iterate_devices = delay_iterate_devices,
};
--
2.4.3
--
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