On Thu, May 7, 2009 at 1:08 PM, Tom Talpey <tmtalpey@xxxxxxxxx> wrote: > At 12:42 PM 5/7/2009, Chuck Lever wrote: >>It's not portmap... lockd decides which listeners to start. Thanks Chuck and Tom - that clarifies it. Take care, -Aaron > Also, there is an important distinction between NLM and NLM *callbacks*. > The NLM client follows the NFS protocol selection in many client kernels, > i.e. if you mount with proto=tcp, you get both NFS and NLM over TCP. > > The issue is NLM callbacks, which are used only in specific cases where > clients take blocking locks, which actually need to block due to being already > held by another client. The server replies over NLM (e.g. TCP) with an indication > that a callback will arive later. But when the other lock is released, the callback > comes on a second connection, initiated from the server back to the client and > not on the original NLM channel. To make matters worse, some servers only > ever perform the callback on UDP in order to simplify and reduce the overhead > required. > > If this callback doesn't arrive at the client, or arrives in such a way that > it's not recognized (e.g traverses a NAT and therefore changes source IP), > then the client only wakes up on a timer. The long pauses can be a real > problem, and one which only arises occasionally - i.e. very hard to trace down. > > Just something to be aware of... it's a day-one defect in the NLM protocol, > actually. > > Tom. > >> >>> I know there >>> are servers out there that will always speak NLM over UDP >>> (netapp/ontap being the prominent one), and as a result there can be >>> problems without firewalls. If servers are out there that will speak >>> NLM over UDP regardless of the mount itself, shouldn't we be binding >>> NLM/UDP regardless of the mount transport? >>> >>> (Or did I miss this change being reverted a while back?) >> >>This change was reverted upstream; see commit 8c3916f4. >> >>-- >>Chuck Lever >>chuck[dot]lever[at]oracle[dot]com >> > > ------------------------------------------------------------------------------ The NEW KODAK i700 Series Scanners deliver under ANY circumstances! Your production scanning environment may not be a perfect world - but thanks to Kodak, there's a perfect scanner to get the job done! With the NEW KODAK i700 Series Scanner you'll get full speed at 300 dpi even with all image processing features enabled. http://p.sf.net/sfu/kodak-com _______________________________________________ NFS maillist - NFS@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/nfs _______________________________________________ Please note that nfs@xxxxxxxxxxxxxxxxxxxxx is being discontinued. Please subscribe to linux-nfs@xxxxxxxxxxxxxxx instead. http://vger.kernel.org/vger-lists.html#linux-nfs -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
