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

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Message-ID: <CA+55aFzSM6qhZpM4CCpRNR_LWNCbLyRtQQ3hnPwnRrBdDkwWUw@mail.gmail.com>
Date:   Fri, 3 Aug 2018 12:22:09 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     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>, wgh@...lan.ru,
        Zdenek Kabelac <zkabelac@...hat.com>
Subject: Re: LVM snapshot broke between 4.14 and 4.16

On Fri, Aug 3, 2018 at 12:06 PM Mike Snitzer <snitzer@...hat.com> wrote:
>
> How does that pass for a fix to this issue?
>
> That'll unilaterally mark all dm device's readonly.

Well, if it wasn't honored before anyway, then...

But yes, a much more targeted patch would be preferred.

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..

                    Linus

View attachment "patch.diff" of type "text/x-patch" (664 bytes)