On Jan 7, 2010, at 3:25 PM, Steve Dickson wrote:
On 01/07/2010 01:38 PM, Chuck Lever wrote:
On Jan 7, 2010, at 12:52 PM, Steve Dickson wrote:
On 01/07/2010 11:26 AM, Chuck Lever wrote:
Hi Steve-
As promised, a couple of bug fixes for the recent improvements to
the
showmount command.
---
Chuck Lever (2):
showmount: Use CLNT_CONTROL for version fallback
Why is calling CLNT_CONTROL() verses calling clnt_create again
so much better?? In between failures the server status could
change so why not just ping it again??
The clnt_create(3) library call is quite heavyweight. It does a DNS
lookup via its own transport socket, a GETPORT via its own transport
socket, then creates and connects a socket to do the application's
RPC
work.
Each time showmount calls clnt_create(3), the library will set up a
socket for the DNS lookup (usually but not always UDP), set up a
socket
to do a GETPORT, and then set up a third socket for the
MNTPROC_EXPORT
request. That's three sockets, each time through your retry loop.
When contacting a MNTv1-only server over TCP, the showmount command
can
leave up to six TCP sockets in TIME_WAIT (not counting sockets used
for
DNS) for 120 seconds after the command exits, if it doesn't use
CLNT_CONTROL.
Now really... who do you know that runs an v2 only server...
I would call that badly misconfigured server... and I just
don't think it happens...because if it did, the bug would have
become much more prevalent a long time ago...
If you think v2-only servers are so rare, why even bother downshifting
the protocol version at all? The original showmount command does not
have any problem connecting to a v2-only server, since it used only
MNTv1 to do the EXPORT request.
Most legacy servers are NFSv2 only. I bought a new-in-box ReadyNAS a
year or so ago that ran Linux 2.4, and it's NFS server was, in fact,
v2-only.
/me gives up.
--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com
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