linux-kernel - Re: [regression] oops on heavy compilations ("kernel BUG at mm/zswap.c:1005!" and "Oops: invalid opcode: 0000")

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Message-ID: <CAJD7tkaTcnuCFW+dWTzSAuLKBqkkGv9s5uByYm9DaJC=Cp-Xqg@mail.gmail.com>
Date: Sat, 31 Aug 2024 10:23:36 -0700
From: Yosry Ahmed <yosryahmed@...gle.com>
To: Piotr Oniszczuk <piotr.oniszczuk@...il.com>
Cc: Pedro Falcato <pedro.falcato@...il.com>, Nhat Pham <nphamcs@...il.com>, 
	Matthew Wilcox <willy@...radead.org>, 
	Linux regressions mailing list <regressions@...ts.linux.dev>, LKML <linux-kernel@...r.kernel.org>, 
	Johannes Weiner <hannes@...xchg.org>, Linux-MM <linux-mm@...ck.org>
Subject: Re: [regression] oops on heavy compilations ("kernel BUG at
 mm/zswap.c:1005!" and "Oops: invalid opcode: 0000")

On Sat, Aug 31, 2024 at 2:41 AM Piotr Oniszczuk
<piotr.oniszczuk@...il.com> wrote:
>
>
>
> > Wiadomość napisana przez Yosry Ahmed <yosryahmed@...gle.com> w dniu 29.08.2024, o godz. 23:54:
> >
> > I also noticed that you are using z3fold as the zpool. Is the problem
> > reproducible with zsmalloc? I wouldn't be surprised if there's a
> > z3fold bug somewhere.
> >
>
> Hmm - yesterday i recompiled 6.9.12 with zsmalloc and …. after 16h of continuous tests I can’t reproduce issue.
> With zsmalloc 6.9.12 looks to me like stable.

Interesting, and a little bit what I hoped for tbh.

>
> With this - what will be your advice to move forward?

Well, it's possible that some zswap change was not fully compatible
with z3fold, or surfaced a dormant bug in z3fold. Either way, my
recommendation is to use zsmalloc. I have been trying to deprecate
z3fold, and honestly you are the only person I have seen use z3fold in
a while -- which is probably why no one else reported such a problem.

> Is there any possibility/way to avoid bisecting? (due limited time from my side)

So unless you have a reason to specifically use z3fold or avoid
zsmalloc, please use zsmalloc. It should be better for you anyway. I
doubt that you (or anyone) wants to spend time debugging a z3fold
problem :)