Subject: Re: linux-next: Tree for Jan 20 -- Kernel panic - Unable to mount root fs

From: Guenter Roeck <[email-masked]>
Date: Tue, 20 Jan 2015 20:01:26 -0800

On 01/20/2015 07:36 PM, Al Viro wrote:
> On Tue, Jan 20, 2015 at 06:44:34PM -0800, Guenter Roeck wrote:
>>> The shit hits the fan earlier - when we end up missing /dev.  There are
>>> two places where it could've been created (depending on CONFIG_BLK_DEV_INITRD);
>>> 	sys_mkdir(collected, mode);
>>> in init/initramfs.c (line 353 in linux-next) and
>>>          err = sys_mkdir((const char __user __force *) "/dev", 0755);
>>> in init/noinitramfs.c (line 32).  The latter would've screamed on failure;
>>> could you printk of collected (%s), mode (%o) and return value (%d) in the
>>> former and see what happens?
>>>
>>
>> sys_mkdir .:40775 returned -17
>> sys_mkdir usr:40775 returned 0
>> sys_mkdir usr/lib:40775 returned -2
>> sys_mkdir usr/share:40755 returned -2
>> sys_mkdir usr/share/udhcpc:40755 returned -2
>> sys_mkdir usr/bin:40775 returned -2
>> sys_mkdir usr/sbin:40775 returned -2
>> sys_mkdir mnt:40775 returned 0
>> sys_mkdir proc:40775 returned 0
>> sys_mkdir root:40775 returned 0
>> sys_mkdir lib:40775 returned 0
>> sys_mkdir lib/modules:40775 returned -2
>> sys_mkdir lib/modules/3.9.2:40775 returned -2
>> sys_mkdir lib/modules/3.9.2/kernel:40775 returned -2
>>
>> with
>> 	int err = sys_mkdir(collected, mode);
>> 	pr_info("sys_mkdir %s:%o returned %d\n", collected, mode, err);
>> added in init/initramfs.c.
>
> Just what is lib/modules/3.9.2 doing there?  In any case, I think I have at

Artifact from when I created the root file system (which apparently was with
3.9.2). It is irrelevant for my testing, at least so far, so I never
bothered fixing it.

> least a plausible direction for digging.  Look:
>

> diff --git a/fs/namei.c b/fs/namei.c
> index 323957f..c7d107c 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c

With this patch:

sys_mkdir .:40775 returned -17
sys_mkdir usr:40775 returned 0
sys_mkdir usr/lib:40775 returned 0
sys_mkdir usr/share:40755 returned 0
sys_mkdir usr/share/udhcpc:40755 returned 0
sys_mkdir usr/bin:40775 returned 0
sys_mkdir usr/sbin:40775 returned 0
sys_mkdir mnt:40775 returned 0
sys_mkdir proc:40775 returned 0
sys_mkdir root:40775 returned 0
sys_mkdir lib:40775 returned 0
sys_mkdir lib/modules:40775 returned 0
...

and the problem is fixed.

Guenter