Other information that may be helpful: All clients are using TCP arm64 clients are unaffected by the bug The armel clients use very small (4k) rsize/wsize buffers Prior to the upgrade from Debian Stretch, everything was working perfectly ----- Original Message ----- > From: "Timothy Pearson" <tpearson@xxxxxxxxxxxxxxxxxxxxx> > To: "linux-nfs" <linux-nfs@xxxxxxxxxxxxxxx> > Sent: Wednesday, August 4, 2021 7:00:20 PM > Subject: Callback slot table overflowed > All, > > We've hit an odd issue after upgrading a main NFS server from Debian Stretch to > Debian Buster. In both cases the 5.13.4 kernel was used, however after the > upgrade none of our ARM thin clients can mount their root filesystems -- early > in the boot process I/O errors are returned immediately following "Callback > slot table overflowed" in the client dmesg. > > I am unable to find any useful information on this "Callback slot table > overflowed" message, and have no idea why it is only impacting our ARM (armel) > clients. Both 4.14 and 5.3 on the client side show the issue, other client > kernel versions were not tested. > > Curiously, increasing the rsize/wsize values to 65536 or higher reduces (but > does not eliminate) the number of callback overflow messages. > > The server is a ppc64el 64k page host, and none of our pcc64el or amd64 thin > clients are experiencing any problems. Nothing of interest appears in the > server message log. > > Any troubleshooting hints would be most welcome. > > Thank you!
