This is a revised version of a patch set I sent over a year ago. It now supports v4.0 and has had more testing. There are cirsumstances where an admin might need to unmount a filesystem that is NFS-exported and in active use, but does not want to stop the NFS server completely. These are certainly unusual circumstance and doing this might negatively impact any clients acting on the filesystem, but the admin should be able to do this. Currently this is quite possible for for NFSv3. Unexporting the filesystem will ensure no new opens happen, and writing the path name to /proc/fs/nfsd/unlock_filesystem will ensure anly NLM locks held in the filesystem are released so that NFSD no longer prevents the filesystem from being unlocked. It is not currently possible for NFSv4. Writing to unlock_filesystem does not affect NFSv4, which is arguably a bug. This series fixes the bug. For NFSv4.1 and later code is straight forward. We add new state types for admin-revoked state (open, lock, deleg) and change the type of any state on a filesystem - inavlidating any access and closing files as we go. While there are any revoked states we report this to the client in the response to SEQUENCE requests, and it will check and free any states that need to be freed. For NFSv4.0 it isn't quite so easy as there is no mechanism for the client to explicitly acknowledged admin-revoked states. The approach this patchset takes is to discard NFSv4.0 admin-revoked states one lease-time after they were revoked, or immediately for a state that the client tryies to use and gets an "ADMIN_REVOKED" error for. If the filestystem has been unmounted (as expected), the client will see STATE errors before it has a chance to see ADMIN_REVOKED errors, so most often the timeout will be how states are discarded. NeilBrown [PATCH 1/6] nfsd: prepare for supporting admin-revocation of state [PATCH 2/6] nfsd: allow admin-revoked state to appear in [PATCH 3/6] nfsd: allow admin-revoked NFSv4.0 state to be freed. [PATCH 4/6] nfsd: allow lock state ids to be revoked and then freed [PATCH 5/6] nfsd: allow open state ids to be revoked and then freed [PATCH 6/6] nfsd: allow delegation state ids to be revoked and then
