Re: [GIT PULL] bcachefs fixes for 6.12-rc2

Martin Steigerwald
2024-10-07T15:13:11Z

Kent Overstreet - 06.10.24, 19:18:00 MESZ:
> > I still do have a BCacheFS on my laptop for testing, but meanwhile I
> > wonder whether some of the crazy kernel regressions I have seen with
> > the last few kernels where exactly related to having mounted that
> > BCacheFS test filesystem. I am tempted to replace the BCacheFS with a
> > BTRFS just to find out.
>
> I think you should be looking elsewhere - there have been zero reports
> of random crashes or anything like what you're describing. Even in
> syzbot testing we've been pretty free from the kind of memory safety
> issues that would cause random crashes

Okay.

From what I saw of the backtrace I am not sure it is a memory safety bug.
It could be a deadlock thing with work queues. Anyway… as you can read
below it is not BCacheFS related. But I understand too little about all of
this to say for sure.

> The closest bugs to what you're describing would be the
> __wait_on_freeing_inode() deadlock in 6.12-rc1, and the LZ4HC crash that
> I've yet to triage - but you specifically have to be using lz4:15
> compression to hit that path.

Well a crash on reboot happened again, without BCacheFS. I wrote that I
report back, either case.

I think I will wait whether this goes away with a newer kernel as some of
the other regressions I saw before. It was not in all of the 6.11 series
of Debian kernels but just in the most recent one. In case it doesn't I
may open a kernel bug report with Debian directly.

For extra safety I did a memory test with memtest86+ 7.00. Zero errors.

As for one of the other regressions I cannot tell yet, whether they have
gone away. So far they did not occur again.

But so far it looks that replacing BCacheFS with BTRFS does not make a
difference. And I wanted to report that back.

Best,
--
Martin