Re: NFS lockd patch proposal for user-level control of the grace period

[Juan Gomez <juang@us.ibm.com>]

I think either way we get to the kernel would be ok with me. I picked
sysctl because some comments in the code susggested somebody already though
of supporting a sysctl gate to user land to export
grace period control, also Chrisptop suggested this was the way to go when
I previously proposed using the raw proc filesystem. I think what is nice
about sysctl is that it is extensible, If we use signals and some other
folks keep on using signals for other control purposed then they will
eventually run out and they will have to add sysctl anyway. Said that I
think either way serves the purpose I want.


Juan



|---------+---------------------------------->
|         |           Neil Brown             |
|         |           <neilb@cse.unsw.edu.au>|
|         |           Sent by:               |
|         |           linux-kernel-owner@vger|
|         |           .kernel.org            |
|         |                                  |
|         |                                  |
|         |           09/08/02 05:27 PM      |
|         |                                  |
|---------+---------------------------------->
  >-----------------------------------------------------------------------------------------------------------------------------|
  |                                                                                                                             |
  |       To:       Juan Gomez/Almaden/IBM@IBMUS                                                                                |
  |       cc:       Alan Cox <alan@lxorguk.ukuu.org.uk>, hch@infradead.org, linux-kernel@vger.kernel.org                        |
  |       Subject:  Re: NFS lockd patch proposal for user-level control of the grace period                                     |
  |                                                                                                                             |
  |                                                                                                                             |
  >-----------------------------------------------------------------------------------------------------------------------------|



On Friday September 6, juang@us.ibm.com wrote:
>
>
>
>
> Christoph, Alan, Neil,
>
> Attached you will find the patch with the sysctl implementation of my
> previous patch to enable grace period control from user-land.
> Please let me know if this looks good enough for inclusion in the kernel
> distribution or whether I still need to do something else.
> Note this piece is derived from net/sunrpc/sysctl.c, which by the way I
> think has a problem with the READ/WRITE verifys which seem
>  to be swicthed which I fixed in lockd version but not there, you may
want
> to take a look at net/sunrpc/sysctl.c and fix that although that's a
minor
> thing.
>
> (See attached file: lockd-sysctl.patch)
>

I still haven't managed to find out exactly what you want to do with
this, and hence whether it is appropriate.

You mentioned in another Email that this was for a High Availability
setup where one server might take-over a filesystem that another
server was previously serving.

If this is the case, do you really want to change the grace period, or
do you really want to re-start the grace period.
If that is what you really want, then I think that sysctl is
un-necessary and a simple signal would do the trick.
Currently, SIGKILL will
   1/ drop all locks held for clients
   2/ restart the grace period.

it would probably be quite sensible (and trivial to code) for SIGHUP
(say) to restart the grace period without dropping the locks.

Would this be suitable for you?

NeilBrown
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