linux-kernel - Re: "fs/namei.c: keep track of nd->root refcount status" causes boot panic

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Message-ID: <CA+G9fYtQLLTWNNqb289Q+tCLgZ72mXeqmUweTMJF69MBh+8GDA@mail.gmail.com>
Date:   Tue, 3 Sep 2019 19:22:41 +0530
From:   Naresh Kamboju <naresh.kamboju@...aro.org>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Qian Cai <cai@....pw>, linux-fsdevel@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: "fs/namei.c: keep track of nd->root refcount status" causes boot panic

Hi

On Tue, 3 Sep 2019 at 19:01, Al Viro <viro@...iv.linux.org.uk> wrote:
>
> On Tue, Sep 03, 2019 at 01:37:19PM +0100, Al Viro wrote:
> > On Tue, Sep 03, 2019 at 12:21:36AM -0400, Qian Cai wrote:
> > > The linux-next commit "fs/namei.c: keep track of nd->root refcount status” [1] causes boot panic on all
> > > architectures here on today’s linux-next (0902). Reverted it will fix the issue.
> >
> > <swearing>
> >
> > OK, I see what's going on.  Incremental to be folded in:
>
> ... or, better yet,
>
> diff --git a/include/linux/namei.h b/include/linux/namei.h
> index 20ce2f917ef4..397a08ade6a2 100644
> --- a/include/linux/namei.h
> +++ b/include/linux/namei.h
> @@ -37,7 +37,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
>  #define LOOKUP_NO_REVAL                0x0080
>  #define LOOKUP_JUMPED          0x1000
>  #define LOOKUP_ROOT            0x2000
> -#define LOOKUP_ROOT_GRABBED    0x4000
> +#define LOOKUP_ROOT_GRABBED    0x0008
>
>  extern int path_pts(struct path *path);
>

I have applied above patch and tested on arm64 juno-r2 and boot pass [1].
Thanks for the fix patch.

>
> to avoid breaking out-of-tree stuff for now good reason.
> Folded and pushed out.

[1] https://lkft.validation.linaro.org/scheduler/job/898187#L511

- Naresh