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Subject: Re: LVM snapshot broke between 4.14 and 4.16
To:     Linus Torvalds <torvalds@linux-foundation.org>,
        Mike Snitzer <snitzer@redhat.com>
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On 08/03/2018 10:22 PM, Linus Torvalds wrote:
> And in fact, maybe the right thing to do is to not revert the original
> commit entirely, but instead just weaken it a lot. Turn the "you did a
> write request on a RO disk" into a WARN_ON_ONCE() instead of a hard
> error.
>
> Something like the attached patch.
>
> WGH, do you build your own kernels? Does this attached (untested)
> patch make things work for you? It should give a big warning, but let
> the old behavior through..

The patch works for me.

However, there's no text messsage in the kernel log, just a traceback. I
think that's because WARN_ONCE is supposed to take condition as a first
argument.