Re: btrfs goes read-only when btrfs-cleaner runs

[Chris Murphy <lists@colorremedies.com>]

On Tue, Jan 15, 2019 at 5:41 PM Chris Murphy <lists@colorremedies.com> wrote:
>
> The relevant error messages are:
>
> unable to find ref byte
> errno=-2 No such entry
>
> Somehow a reference byte has been corrupted and inserted into multiple
> locations in the tree and it's not repairable: i.e. neither a correct
> value can be inferred from other available information, nor do the
> tools have a good way to just trim out the item that contains bad key
> pointers - part of the problem with just cutting out the bad parts is
> it's not clear the problem is made even worse or how far the
> corruption extends.
>
> What's further troubling though is the idea that this corruption might
> have propagated to a separate volume via snapshot send receive. Either
> of the file systems might still be useful for a developer, it seems to
> me important to have some kind of check to make sure it's not possible
> for corruption to propagate in this manner.
>
> In the meantime, I think it's a good idea to do a memory test. There's
> some information in the archives about how to do this in a more
> reliable way than just memtest86 type tests, but if you can run even a
> memtest86 over a weekend it might confirm there's a memory problem.
> Unfortunately a pass doesn't necessarily mean there aren't rare
> transient problems.

Also, this could be related...

[ 4368.361487] CPU: 0 PID: 23915 Comm: kworker/u16:11 Tainted: P
 W  O      4.20.1-gentoo #1

Do you know why it's tainted? Looks like an out of tree proprietary
module. And also there has been a previous kernel warning but that
part of the dmesg isn't included. It's not possible to absolutely
exclude an out of tree kernel from being a source of memory
corruption, but it makes it a possible suspect and therefore it makes
tracking down the source of the problem harder.

-- 
Chris Murphy