On Mon, Aug 31, 2015 at 10:02:33PM -0700, Andy Grover wrote: > On 08/31/2015 07:05 PM, Vivek Goyal wrote: > >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 > > Hi Vivek, > > Yes I suppose userspace would either need to remember read_delay so as to > not change it while setting write_delay, or I guess it could read the > existing values by getting table status before sending the message. Is this > reasonable, or do you think it would be better to, say, have separate > messages for setting the two values, or some other message style? Ideally I think we should have those --key=value type of arguments which we don't have yet. So that option is not feasible I guess. If latest values are readable from status, then I think single message sounds reasoanble to me. Thanks Vivek > > Thanks -- Regards -- Andy -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
