On Fri, Jul 07, 2017 at 12:13:36PM -0400, Jeff Layton wrote: > On Fri, 2017-07-07 at 11:51 -0400, Theodore Ts'o wrote: > > On Fri, Jul 07, 2017 at 06:51:37AM -0400, Jeff Layton wrote: > > > > > > Right. That's the case today if we don't remove support for old > > > filehandles. If we were to remove them, the clients would get back > > > -ESTALE there if they tried to use the old 2.2-style fh's that they saw > > > before the upgrade. > > > > > > The main takeaway here is that NFS filehandle lifetime is really only > > > bounded by the boot time of the oldest clients. > > > > Well, and how long an NFS server is still up. So one could construct > > a use case where a (hypothetical) system administrator had a RHEL 7.0 > > system with a 2.2.16-22 kernel, and they try to update it to a > > (hypothetical) RHEL 10 kernel in one fell swoop with a 4.13+ kernel > > that no longer supports the 2-2-style fh's. A client that had the > > server mounted when it was running the 2.2 kernel might only be up for > > a few hours, before the upgrade to RHEL 10 happened, and then the > > client would get ESTALE errors. > > > > Of course, I've stopped carrying about enterprise kernel support a > > long time ago, so I just think that scenario is funny. I recognize > > that folks who work at Red Hat have to worry about such things --- and > > I'm sorry. :-) > > > > In reality a server installed with RHEL 7.0 has probably died of old > > age by now --- unless someone crazy is running it in a VMware VM > > because they had some enterprise software package or some bar-code > > printing module for which they don't have source code[1], and so they are > > stuck on RHEL 7.0, even in 2017. Have I mentioned I'm so glad I don't > > have to worry these sorts of things any more? RHEL 7 is current, I think you mean the 17-year-old Red Hat Linux 7. Anyone that far back is on their own as far as any enterprise distro is concerned. There are some exceptions to the "lifetime of a mount" rule, none real issues, I think: - fscache may keep fh's around across client boots, but I suspect you just lose the benefit of the cache until it expires data keyed under old filehandles and repopulates the cache with new ones. - Does the client actually depend on stable filehandles across client reboots if it might cache write data under a persistent delegation? But seeing as we don't even implement persistent delegations, this is a non-issue. - nontraditional NFS clients could do any random thing. NFS is just a protocol, we have no idea how some weird application that talks NFS directly to the server might use filehandles. But this is purely hypothetical, I don't know of one. --b.
