[yocto] [PATCH][linux-yocto] mount_root: clarify error messages for when no rootfs found (V2)

[Paul Gortmaker]

On 11-11-15 03:19 PM, Darren Hart wrote:
> The following is a modified version the patch at:
> 
> meta/cfg/kernel-cache/patches/boot/mount_root-clarify-error-messages-for-when-no-rootfs.patch
> 
> in the linux-yocto-3.0 git repository. This version adds KERN_EMERG
> so that even using loglevel=1 at boot, the end user will see:
> 
> [    0.217462] VFS: Unable to mount root fs on unknown-block(8,2)
> [    0.223457] User configuration error - no valid root filesystem found
> [    0.230057] Kernel panic - not syncing: Invalid configuration from end user preg
> [    0.238992] Pid: 1, comm: swapper Not tainted 3.0.4-yocto-standard+ #2
> [    0.245691] Call Trace:                                                         
> [    0.248218]  [<c04eddbc>] ? 0xc04eddbc                                          
> [    0.252071]  [<c05549ad>] ? 0xc05549ad                                          
> [    0.255928]  [<c05549fa>] ? 0xc05549fa                                          
> [    0.259790]  [<c0554623>] ? 0xc0554623                                          
> [    0.263650]  [<c0554b1c>] ? 0xc0554b1c                                          
> [    0.267497]  [<c055472a>] ? 0xc055472a                                          
> [    0.271344]  [<c04f0df6>] ? 0xc04f0df6                                          
> 
> Instead of just:
> 
> [    0.230057] Kernel panic - not syncing: Invalid configuration from end user preg
> ...
> 
> Which is arguably no better than what this patch originally attempted to address.
> 
> Paul, has this patch been sent upstream for inclusion? I don't see it in Linus' tree.

No, I never sent it upstream.  It seemed like such a trivial and
cosmetic change.  If you want to put the V2 comment below the ---
and send it upstream, feel free to do so.

P.

> 
> Thanks,
> 
> Darren
> 
> ----------------------
> 
> To an end user who doesn't really know linux that well, a
> message like:
> 
>   Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
> 
> may just look like cryptic computer speak indicating some
> deep and complex problem, instead of the reality that they
> have a simple local configuration problem.  Ideally it would
> be nice to not use the misleading "panic" at all, but since
> various panic notifiers are historically expecting to be
> called when there is no valid rootfs, we can't change that.
> 
> So instead, this tries to make it 100% clear to folks of
> any background that it is an end user configuration issue.
> 
> V2: Use KERN_EMERG so the printk context isn't lost when using loglevel
> 
> Signed-off-by: Paul Gortmaker <paul.gortmaker at windriver.com>
> Signed-off-by: Darren Hart <dvhart at linux.intel.com>
> ---
>  init/do_mounts.c |    8 ++++++--
>  1 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/init/do_mounts.c b/init/do_mounts.c
> index bb008d0..d24b8c7 100644
> --- a/init/do_mounts.c
> +++ b/init/do_mounts.c
> @@ -270,7 +270,9 @@ retry:
>  		printk("DEBUG_BLOCK_EXT_DEVT is enabled, you need to specify "
>  		       "explicit textual name for \"root=\" boot option.\n");
>  #endif
> -		panic("VFS: Unable to mount root fs on %s", b);
> +		printk(KERN_EMERG "VFS: Unable to mount root fs on %s\n", b);
> +		printk(KERN_EMERG "User configuration error - no valid root filesystem found\n");
> +		panic("Invalid configuration from end user prevents continuing");
>  	}
>  
>  	printk("List of all partitions:\n");
> @@ -282,7 +284,9 @@ retry:
>  #ifdef CONFIG_BLOCK
>  	__bdevname(ROOT_DEV, b);
>  #endif
> -	panic("VFS: Unable to mount root fs on %s", b);
> +	printk(KERN_EMERG "VFS: Unable to mount root fs on %s\n", b);
> +	printk(KERN_EMERG "User configuration error - no valid root filesystem found\n");
> +	panic("Invalid configuration from end user prevents continuing");
>  out:
>  	putname(fs_names);
>  }