panic on 4.20 server exporting xfs filesystem

[J. Bruce Fields]

I'm getting mysterious crashes on a server exporting an xfs filesystem.

Strangely, I've reproduced this on

	93aaa830fc17 "Merge tag 'xfs-pnfs-for-linus-3.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/dgc/linux-xfs

but haven't yet managed to reproduce on either of its parents
(24a52e412ef2 or 781355c6e5ae).  That might just be chance, I'll try
again.

I can also try a serial console or something, but for now I'm not
getting a lot of information about the crashes.

The filesystem in question isn't on a block device available to the
client, but I'm still seeing occasional GETLAYOUT and GETDEVICEINFO
calls; I suppose the client's getting that far, finding no devices it
can use, and giving up?

Sorry for the incomplete report, I'll pass along more when I have it.

--b.