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

[Bruce Ashfield]

On 11-11-15 3:19 PM, Darren Hart wrote:
> The following is a modified version the patch at:

Works for me as well, I'll update the variant in the yocto kernel
trees, while we wait to see if anyone upstream has any interest.

Bruce

>
> 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.
>
> 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);
>   }