linux-kernel - Re: LVM snapshot broke between 4.14 and 4.16

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Date:   Sat, 4 Aug 2018 13:01:32 +0300
From:   WGH <wgh@...lan.ru>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Mike Snitzer <snitzer@...hat.com>
Cc:     Theodore Ts'o <tytso@....edu>, Jens Axboe <axboe@...nel.dk>,
        Sagi Grimberg <sagi@...mberg.me>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-block <linux-block@...r.kernel.org>, dm-devel@...hat.com,
        Ilya Dryomov <idryomov@...il.com>,
        Zdenek Kabelac <zkabelac@...hat.com>
Subject: Re: LVM snapshot broke between 4.14 and 4.16

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.