[ceph-users] ln: failed to create hard link 'file name': Read-only file system

Hi all, on an NFS re-export of a ceph-fs (kernel client) I observe a very strange error. I'm un-taring a larger package (1.2G) and after some time I get these errors: ln: failed to create hard link 'file name': Read-only file system The strange thing is that this seems only temporary. When I used "ln src dst" for manual testing, the command failed as above. However, after that I tried "ln -v src dst" and this command created the hard link with exactly the same path arguments. During the period when the error occurs, I can't see any FS in read-only mode, neither on the NFS client nor the NFS server. Funny thing is that file creation and write still works, its only the hard-link creation that fails. For details, the set-up is: file-server: mount ceph-fs at /shares/path, export /shares/path as nfs4 to other server other server: mount /shares/path as NFS More precisely, on the file-server: fstab: MON-IPs:/shares/folder /shares/nfs/folder ceph defaults,noshare,name=NAME,secretfile=sec.file,mds_namespace=FS-NAME,_netdev 0 0 exports: /shares/nfs/folder -no_root_squash,rw,async,mountpoint,no_subtree_check DEST-IP On the host at DEST-IP: fstab: FILE-SERVER-IP:/shares/nfs/folder /mnt/folder nfs defaults,_netdev 0 0 Both, the file server and the client server are virtual machines. The file server is on Centos 8 stream (4.18.0-338.el8.x86_64) and the client machine is on AlmaLinux 8 (4.18.0-425.13.1.el8_7.x86_64). When I change the NFS export from "async" to "sync" everything works. However, that's a rather bad workaround and not a solution. Although this looks like an NFS issue, I'm afraid it is a problem with hard links and ceph-fs. It looks like a race with scheduling and executing operations on the ceph-fs kernel mount. Has anyone seen something like that? Thanks and best regards, ================= Frank Schilder AIT Risø Campus Bygning 109, rum S14