On Mon, Aug 31, 2015 at 02:24:36PM -0700, Andy Grover wrote:
> 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>]
> +
Hi Andy,
So if I want to change only write_delay and keep read_delay same, how do
I do that. Do I have to keep track of existing delay values in user space
and pass same value in read_delay to achieve this.
Thanks
Vivek
> +'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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> https://www.redhat.com/mailman/listinfo/dm-devel
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