On Thu, 20 Mar 2025, Dai Ngo wrote: > Hi, > > Currently when the local file system needs to be unmounted for maintenance > the admin needs to make sure all the NFS clients have stopped using any files > on the NFS shares before the umount(8) can succeed. This is easily achieved with echo /path/to/filesystem > /proc/fs/nfsd/unlock_filesystem Do this after unexporting and before unmounting. All state for NFSv4 exports, and all NLM locks for NFSv2/3 exports, will be invalidated and files closed. NFSv4 clients will get NFS4ERR_ADMIN_REVOKED when they attempt to use any state that was on that filesystem. (I don't think this flushes the NFSv3 file cache, so a short delay might be needed before the unmount when v3 is used. That should be fixed) NeilBrown > > In an environment where there are thousands of clients this manual process > seems almost impossible or impractical. The only option available now is to > restart the NFS server which would works since the NFS client can recover its > state but it seems like this is a big hammer approach. > > Ideally, when the umount command is run there is a callback from the VFS layer > to notify the upper protocols; NFS and SMB, to release its states on this file > system for the umount to complete. > > Is there any existing mechanism to allow NFSD to release its states automatically > on unmount? > > Unmount is not a frequent operation. Is it justifiable to add a bunch of complex > code for something is not frequently needed? > > I appreciate any opinions on this issue. > > Thanks, > -Dai > > > > > > >
