linux-kernel - Re: Patch 0727d35de ("Make initramfs honor CONFIG_DEVTMPFS

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Date:   Thu, 25 May 2017 21:44:30 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Leo Yan <leoyan.opensource@...il.com>
Cc:     Yury Norov <ynorov@...iumnetworks.com>,
        Rob Landley <rob@...dley.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Prarit Bhargava <prarit@...hat.com>,
        Yang Shi <yang.shi@...aro.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Kees Cook <keescook@...omium.org>,
        Emese Revfy <re.emese@...il.com>,
        Petr Mladek <pmladek@...e.com>,
        Fabian Frederick <fabf@...net.be>, john.stultz@...aro.org,
        Daniel Thompson <daniel.thompson@...aro.org>
Subject: Re: Patch 0727d35de ("Make initramfs honor CONFIG_DEVTMPFS_MOUNT")
 breaks boot

The previous email was rejected by LKML. So resend again.

On Thu, May 25, 2017 at 09:39:32PM +0800, Leo Yan wrote:
> Hi Rob, Yury,
> 
> On Mon, May 22, 2017 at 8:05 PM, Yury Norov <ynorov@...iumnetworks.com>
> wrote:
> 
> > Hi Rob,
> >
> > I found that next-20170522 fails to boot on arm64 machine with the
> > following log:
> > [...]
> > [4.179509] Freeing unused kernel memory: 1088K
> > Loading, please wait...
> > mount: mounting udev on /dev failed: Device or resource busy
> > W: devtmpfs not available, falling back to tmpfs for /dev
> > Couldn't get a file descriptor referring to the console
> > Begin: Loading essential drivers ... done.
> > Begin: Running /scripts/init-premount ... done.
> > Begin: Mounting root file system ... Begin: Running
> > /scripts/local-top ... done.
> > chvt: can't open console
> > Gave up waiting for root device.  Common problems:
> >  - Boot args (cat /proc/cmdline)
> >    - Check rootdelay= (did the system wait long enough?)
> >    - Check root= (did the system wait for the right device?)
> >  - Missing modules (cat /proc/modules; ls /dev)
> > chvt: can't open console
> > ALERT!  /dev/sda does not exist.  Dropping to a shell!
> > Couldn't get a file descriptor referring to the console
> >
> >
> > BusyBox v1.21.1 (Ubuntu 1:1.21.0-1ubuntu1) built-in shell (ash)
> > Enter 'help' for a list of built-in commands.
> >
> > (initramfs)
> >
> > Bisect points to your patch (attached below). If I revert it, everything
> > becomes fine. If you need to know something more about my environment,
> > feel free to ask me.
> >
> 
> At my side, I also can reproduce this failure on Hikey board with Debian
> rootfs,
> finally the debian rootfs cannot be mounted successfully, the booting log
> is:
> http://termbin.com/akar
> 
> From the log, the failures are exactly same with Yury's reporting:
> mount: mounting udev on /dev failed: Device or resource busy
> ...
> ALERT!  /dev/disk/by-partlabel/system does not exist.  Dropping to a
> shell!
> 
> After applied this patch, the kernel mounts mount devtmpfs on '/dev', then
> later
> udev cannot mount again for devfs. Finally cannot find rootfs path from
> '/dev/disk/by-partlabel/system'. So after I comment out below sentence, the
> rootfs can boot up again.
> 
> diff --git a/init/main.c b/init/main.c
> index 9ec09ff..2ea93d1 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -1050,8 +1050,8 @@ static noinline void __init kernel_init_freeable(void)
>                 ramdisk_execute_command = NULL;
>                 prepare_namespace();
>         } else if (IS_ENABLED(CONFIG_DEVTMPFS_MOUNT)) {
> -               sys_mkdir("/dev", 0755);
> -               devtmpfs_mount("/dev");
> +               //sys_mkdir("/dev", 0755);
> +               //devtmpfs_mount("/dev");
>         }
> 
>         /* Open the /dev/console on the rootfs, this should never fail */
> 
> Thanks,
> Leo Yan