> On Thu, Dec 7, 2017 at 11:58 AM, J. Bruce Fields <bfields@xxxxxxxxxxxx> > wrote: > > On Thu, Dec 07, 2017 at 11:10:16AM -0500, Olga Kornievskaia wrote: > >> Ok. I thought that because RFC1813 covers NLM operations that it is. > > > > Yeah, I don't see a harm to the occasional NLM question on the v4 > > working group list. It's a bit of an orphaned protocol, so there's > > not really any other implementation-independent forum. > > > >> I will extend this question to the Linux NFS mailing list as the > >> client implementation I'm interested is Linux. > > > > But that's fine too. > > > > I thought that LOCK/CANCEL race was one of the motivations for NFSv4, > > so... > > > >> >> Is there a solution or this is broken protocol? > > > > ... I'd always assumed the protocol was impossible to implement 100% > > correctly, though maybe there's some clever solution. > > Is such race still possible with the linux server implementation which is single > threaded and in my testing isn't processing LOCK/CANCEL out-of-order then? > > >> >> Should it be client's responsibility to notice that it received a > >> >> LOCK reply for which it wasn't waiting and always follow up with an > UNLOCK? > > > > That would be tricky and still not handle all cases, I think. > > Yes I'm not sure the client can do it. It will have no info about the lock and not > sure how to create an appropriate UNLOCK reply (unless we keep around > lock info of all cancelled locks). The NLM4_GRANTED call has a response where the client can respond NLM4_DENIED to indicate it is not accepting the lock. The Ganesha NFS server could process out of order, however, if the client responds to the grant with NLM4_DENIED, Ganesha will properly release the lock. The imperfectness of NLM is why I have seen requests for tools to free wedged locks... We haven't managed to write such a tool for Ganesha yet (so either we don't actually have that many NLM clients, or folks are using other mechanisms to deal with the issue - restarting the server and making all the clients reclaim the locks they want is one way to do it...). Frank --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus -- 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
