unionfs bugs, a partial patch and some comments [Was: Re: 1-BETA3 Panic: __lockmgr_args: downgrade a recursed lockmgr nfs @ /usr/local/share/deploy-tools/RELENG_11/src/sys/fs/unionfs/union_vnops.c:1905]

[Rick Macklem]

Konstantin Belousov wrote:
> I did not touched unionfs, and have no plans to.  It is equally broken in
> all relevant versions of FreeBSD.
Heh, heh. I chuckled when I read this. I think he's trying to say "it probably
won't ever be fixed". My understanding is that it would require a major redesign
of the FreeBSD VFS to make it fully stackable to fix unionfs and that isn't happening
anytime soon...

Harry Schmalzbauer wrote:
> In 2016 I did some tests with 11.0-Beta1, where this thread origins, and
> Rick kindly looked into it and provided the following patch:
> https://lists.freebsd.org/pipermail/freebsd-stable/attachments/20160818/d1d1691d/attachment.obj
> (Explanation:
> https://lists.freebsd.org/pipermail/freebsd-stable/2016-August/085294.html)
Yep, I am guilty of creating this patch. All it tried to do was fix the crash.
I don't know why a debug kernel with the patch crashes, but I might try and
reproduce that.

> Picture has changed, the machine daedlocked over night. So it does have
> a significant influence, but unfortunately isn't the real solution.
So, do you mean there is no longer any unionfs mount on the machine and it
still hangs?
If yes, then this should be looked at.

rick