linux-kernel - Re: [PATCH] use initmpfs even if there's root= cmdline

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Message-ID: <20131212114917.GA2035@darkstar.nay.redhat.com>
Date:	Thu, 12 Dec 2013 19:49:17 +0800
From:	Dave Young <dyoung@...hat.com>
To:	akpm@...ux-foundation.org, rob@...dley.net,
	gregkh@...uxfoundation.org, grant.likely@...retlab.ca,
	sebastian.capella@...aro.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] use initmpfs even if there's root= cmdline

On Thu, Dec 12, 2013 at 05:25:42PM +0800, Dave Young wrote:
> 
> Current code use ramfs instead of tmpfs for stub when root= defined.
> 
> But for real use case with initramfs, usually there's like cmdline like
> root=UUID=$UUID the root dev is the real device. For that case we have
> no way to use initmpfs, thus this patch removes the limitation so tmpfs
> can benefit more people.
> 
> The logic become:
> if CONFIG_TMPFS && rootfstype is not ramfs
>     use tmpfs
> else
>     use ramfs
> 
> Signed-off-by: Dave Young <dyoung@...hat.com>
> ---
>  init/do_mounts.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/init/do_mounts.c b/init/do_mounts.c
> index 8e5addc..6fde471 100644
> --- a/init/do_mounts.c
> +++ b/init/do_mounts.c
> @@ -622,8 +622,8 @@ int __init init_rootfs(void)
>  	if (err)
>  		return err;
>  
> -	if (IS_ENABLED(CONFIG_TMPFS) && !saved_root_name[0] &&
> -		(!root_fs_names || strstr(root_fs_names, "tmpfs"))) {
> +	if (IS_ENABLED(CONFIG_TMPFS) &&
> +		(root_fs_names && !(strstr(root_fs_names, "ramfs")))) {

Oops, I probably mistakenly tested with "rootfstype=tmpfs". Rethinking about
it, below should be what I want:
	if (IS_ENABLED(CONFIG_TMPFS) &&
		(!root_fs_names || strstr(root_fs_names, "tmpfs"))) {

I will retest it tomorrow.

Qeustion to Rob Landley:
Rob, do you remember why you added the checking for root=? git log mentioned
below which is not clear:
use ramfs instead of tmpfs for stub when root= defined (for cosmetic
reasons).

--
Thanks
Dave
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