NFSv3-mounting of BTRFS-FS fails, gives ESTALE

[Ulrich Gemkow <ulrich.gemkow@ikr.uni-stuttgart.de>]

Hello,

[sent this to linux-btrfs mailing list but got no answer,
maybe this is the better list].

we export a BTRFS-filesystem via NFSv3 and tried to mount
this share on a client (also NFSv3). The mount program on the
client hangs and the mount fails.

Server and client use vanilla Linux kernel 4.0.3, the distro
is Ubuntu 14.04.02, btrfs-progs are version 4.0.

Exporting of other filesystems (ext4) and mounting them in
the exactly same setup works, so this seems to be BTRFS-related.

strace-ing the mount-call on the client shows that the mount
syscall returns ESTALE errors and mount enters a loop which
leads to the hang of the mount-program in user land.

I applied the patch of Neil Brown (which should help with
NFS v2) in [1]. The behaviour without and with this patch
is the same.

This seems to be a regression because from the lists I
saw that NFS-exporting of BTRFS is supposed to work
(but NFSv3 is not explicitely mentioned there).

Is this a bug? I am more than willing to help with more
diagnosis.

Thank you and best regards

Ulrich



[1] https://lkml.org/lkml/2015/5/7/1013

-- 
|-----------------------------------------------------------------------
| Ulrich Gemkow
| University of Stuttgart
| Institute of Communication Networks and Computer Engineering (IKR)
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