On further investigation, the working server had already been rolled back to 4.19.0. Apparently the issue was insurmountable in 5.x. It should be simple enough to set up a test environment out of production for 5.x, if you have any debug tips / would like to see any debug options compiled in. Thanks! ----- Original Message ----- > From: "Timothy Pearson" <tpearson@xxxxxxxxxxxxxxxxxxxxx> > To: "linux-nfs" <linux-nfs@xxxxxxxxxxxxxxx> > Sent: Wednesday, August 4, 2021 7:04:16 PM > Subject: Re: Callback slot table overflowed > 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!
