On Mon, 2012-03-19 at 13:58 -0700, Boaz Harrosh wrote:
> On 03/16/2012 02:40 PM, Myklebust, Trond wrote:
> > On Thu, 2012-03-15 at 23:23 -0700, Boaz Harrosh wrote:
> >> From: Sachin Bhamare <sbhamare@xxxxxxxxxxx>
> >>
> >> The pnfs-objects protocol mandates that we autologin into devices not
> >> present in the system, according to information specified in the
> >> get_device_info returned from the server.
> >>
> >> The Protocol specifies two login hints.
> >> 1. An IP address:port combination
> >> 2. A string URI which is constructed as a URL with a protocol prefix
> >> followed by :// and a string as address. For each protocol prefix
> >> the string-address format might be different.
> >>
> >> We only support the second option. The first option is just redundant
> >> to the second one.
> >> NOTE: The Kernel part of autologin does not parse the URI string. It
> >> just channels it to a user-mode script. So any new login protocols should
> >> only update the user-mode script which is a part of the nfs-utils package,
> >> but the Kernel need not change.
> >>
> >> We implement the autologin by using the call_usermodehelper() API.
> >> (Thanks to Steve Dickson <steved@xxxxxxxxxx> for pointing it out)
> >> So there is no running daemon needed, and or special setup.
> >>
> >> All is needed is that "/sbin/osd_login" script exists.
> >> TODO:
> >> "osd_login" is an hard coded name. If not present we will rate_limit
> >> print to dmsg and keep failing. In such cases we should stop trying
> >> and provide sysfs interface for re-enabling autologin. For example,
> >> we could ZERO out the script name and let user-mode set a new script
> >> name.
> >> [Q] Where in sysfs should a layout-driver put its things?
> >
> > Please see fs/nfs/cache_lib.c, which already does this sort of thing.
> > The right thing to do is not sysfs, but a kernel module parameter.
> >
>
> I have a question about the "kernel module parameter" is that an hot
> affair. I mean if the module is loaded, does it have to be unloaded
> before I can specify a new "module parameter" on load. Or it will
> update globally even if the module is already loaded?
>
> The reason I'm asking is because the layout-driver is referenced
> by nfs-core on mount. And will not release until unmount, of the
> last pnf-objects mount-point.
>
> That's why I thought of a /sys so all mount-points need not be unmounted
> before admin can fix the problem.
Yes. If you design things correctly, you can make the kernel parameter
writeable by setting the mode in the module_param_string(). Again,
please see fs/nfs/cache_lib.c.
The advantage of the kernel parameter here is that you can initialise it
directly in /etc/modprobe.conf using the 'options' command, but you can
later change it dynamically (without removing the module) using the
pseudofile in /sys/module/objlayout-driver/parameters
--
Trond Myklebust
Linux NFS client maintainer
NetApp
Trond.Myklebust@xxxxxxxxxx
www.netapp.com
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