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With this, to unmount >>> an exported filesystem is it sufficient to disable export of that >>> filesystem, and then write the path to unlock_filesystem. >>> >>> I've cursed mainly on NFSv4.1 and later for this. I haven't tested >>> yet with NFSv4.0 which has different mechanisms for state management. >>> >>> If this series is seen as a general acceptable approach, I'll look into >>> the NFSv4.0 aspects properly and make sure it works there. >> I've browsed this series and need to think about: >> - whether we want to enable administrative state revocation and >> - whether NFSv4.0 can support that reasonably >> >> In particular, are there security consequences for revoking >> state? What would applications see, and would that depend on >> which minor version is in use? Are there data corruption risks >> if this facility were to be misused? > The expectation is that this would only be used after unexporting the > filesystem. In that case, the client wouldn't notice any difference > from the act of writing to unlock_filesystem, as the entire filesystem > would already be inaccessible. > > If we did unlock_filesystem a filesystem that was still exported, the > client would see similar behaviour to a network partition that was of > longer duration than the lease time. Locks would be lost. > >> Also, Dai's courteous server work is something that potentially >> conflicts with some of this, and I'd like to see that go in >> first. > I'm perfectly happy to wait for the courteous server work to land before > pursuing this. Thank you Chuck and Neil, I'm chasing a couple intermittent share reservation related problems with pynfs test. I hope to have them resolved and submit the v10 patch by end of this week. -Dai > >> Do you have specific user requests for this feature, and if so, >> what are the particular usage scenarios? > It's complicated.... > > The customer has an HA config with multiple filesystem resource which > they want to be able to migrate independently. I don't think we really > support that, but they seem to want to see if they can make it work (and > it should be noted that I talk to an L2 support technician who talks to > the customer representative, so I might be getting the full story). > > Customer reported that even after unexporting a filesystem, they cannot > then unmount it. Whether or not we think that independent filesystem > resources is supportable, I do think that the customer should have a > clear path for unmounting a filesystem without interfering with service > provided from other filesystems. Stopping nfsd would interfere with > that service by forcing a grace-period on all filesystems. > The RFC explicitly supports admin-revocation of state, and that would > address this specific need, so it seemed completely appropriate to > provide it. > > As an aside ... I'd like to be able to suggest that the customer use > network namespaces for the different filesystem resources. Each could > be in its own namespace and managed independently. However I don't > think we have good admin infrastructure for that do we? > > I'd like to be able to say "set up these 2 or 3 config files and run > systemctl start nfs-server@foo and the 'foo' network namespace will be > created, configured, and have an nfs server running". > Do we have anything approaching that? Even a HOWTO ?? > > Thanks, > NeilBrown