linux-ext4 - Re: [GIT PULL] ext2, quota, and udf fixes for 6.6-rc1

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Message-ID: <20231020110739.qfscu56ekan4wqd2@quack3>
Date:   Fri, 20 Oct 2023 13:07:39 +0200
From:   Jan Kara <jack@...e.cz>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Andy Shevchenko <andriy.shevchenko@...el.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>, Jan Kara <jack@...e.cz>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Ferry Toth <ftoth@...londelft.nl>,
        linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org
Subject: Re: [GIT PULL] ext2, quota, and udf fixes for 6.6-rc1

On Thu 19-10-23 10:51:18, Linus Torvalds wrote:
> On Thu, 19 Oct 2023 at 10:26, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> >
> > That said, the quota dependency is quite odd, since normally I
> > wouldn't expect the quota code to really even trigger much during
> > boot. When it triggers that consistently, and that early during boot,
> > I would expect others to have reported more of this.
> >
> > Strange.
> 
> Hmm. I do think the quota list handling has some odd things going on.
> And it did change with the whole ->dq_free thing.
> 
> Some of it is just bad:
> 
>   #ifdef CONFIG_QUOTA_DEBUG
>           /* sanity check */
>           BUG_ON(!list_empty(&dquot->dq_free));
>   #endif
> 
> is done under a spinlock, and if it ever triggers, the machine is
> dead. Dammit, I *hate* how people use BUG_ON() for assertions. It's a
> disgrace. That should be a WARN_ON_ONCE().

I agree. I should go one day and replace these BUG_ONs. This one is from
2006 when we were more accepting of such checks...

> And it does have quite a bit of list-related changes, with the whole
> series from Baokun Li changing how the ->dq_free list works.
> 
> The fact that it consistently bisects to the merge is still odd.

Yes. Plus Andy said that when he reverts quota changes on top of the merge
commit the resulting kernel still crashes. Really puzzling.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR