linux-kernel - Re: [next] arm64: allmodconfig: kernel BUG at include/linux/page-flags.h:509

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Message-ID: <20220311183607.291dc950@gandalf.local.home>
Date:   Fri, 11 Mar 2022 18:36:07 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Beau Belgrave <beaub@...ux.microsoft.com>
Cc:     Anders Roxell <anders.roxell@...aro.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-Next Mailing List <linux-next@...r.kernel.org>,
        linux-trace-devel@...r.kernel.org
Subject: Re: [next] arm64: allmodconfig: kernel BUG at
 include/linux/page-flags.h:509

On Fri, 11 Mar 2022 15:28:09 -0800
Beau Belgrave <beaub@...ux.microsoft.com> wrote:

> OK, you know more than I, so hopefully we can land on if we really need
> it or not. For now I've left it in.
> 
> > > 
> > > The other thing is that this patch applied to 5.10.X on ARM64 does not
> > > appear to hit this. Is it some weird interaction with something else or
> > > was 5.10.X just getting lucky?  
> > 
> > Perhaps it's because you allocated the page with kzalloc and not just
> > getting a page directly?

I sent a version that removes it, but I think we can add it back.

> >   
> 
> Yeah, I think so too. I was able to repro locally and validate that using
> alloc_pages directly fixes this by setting DEBUG_VM_PGFLAGS=y.
> 
> I've posted a patch for this:
> https://lore.kernel.org/linux-trace-devel/20220311223028.1865-1-beaub@linux.microsoft.com/

Just saw it (I screwed up my procmail settings getting rid of some more
spam, and ended up sending all my email to a ":" folder :-p)

If you want, I can send another version of my patch that doesn't remove the
reserve. But I like my patch as it sets the MAX_EVENTS based on a order and
not the other way around.

-- Steve