[Bug 255473] Infinite writes on UFS with SU+J filesystem

From: <bugzilla-noreply_at_freebsd.org>
Date: Wed, 26 May 2021 04:31:01 UTC
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=255473

sigsys@gmail.com changed:

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                 CC|                            |sigsys@gmail.com

--- Comment #21 from sigsys@gmail.com ---
(In reply to Jack from comment #20)
I think I'm seeing the same problem on 14-CURRENT occasionally and when it
starts doing crazy writes just running "sync" makes it stop.  When running
commands is still possible anyway.

It has gotten rarer for me with recent updates but running chrome and clicking
links really fast would sometimes still trigger the problem (with files from
chrome's cache directory being involved).

In my case it's a VM with the disks on zvols and the pool has sync=disabled. 
Maybe it causes write I/Os to be much faster than what is usual for UFS and
that's what can trigger the problem.  Maybe your NVME disks are way faster than
what it's used to too.  Maybe regular data being written so fast causes more
complex meta-data softupdates structures to be handled together.  I'm really
just guessing here... in case it could give someone an idea.  Maybe running UFS
on virtual disks with ridiculously fast writes could be a good way to try to
reproduce it.

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