[PATCH fstools] partname: Correct fstools_partname_fallback_scan comparison

[Brian Norris]

On Tue, Jan 24, 2023 at 10:28:14PM -0800, Brian Norris wrote:
> We want to return NULL if the param does *not* match 1 -- i.e., a
> non-zero strcmp().
> 
> Fixes: 1ea5855e980c ("partname: Introduce fstools_partname_fallback_scan option")

Hmm, sorry for the quick self-reply, but after rereading, I noticed
there's a second reason commit 1ea5855e980c may be incorrect:

This fallback *used* to (pre-1ea5855e980c) be used for any block device
(eMMC, SATA, etc.) where we *didn't* specify root= in the boot args.
This could perhaps happen with initramfs systems? (Sorry, I'm not
extremely familiar with the openwrt ecosystem.)

So do we need to refactor this again, so that we allow the fallback in
either (or both) of these cases:

(1) no root= arg
(2) root=XXXX (where XXX is not a /device/path) +
    fstools_partname_fallback_scan=1

?

Anyway, it's probably at least safe to apply my bugfix, but we might
need more.

Brian

> Signed-off-by: Brian Norris <computersforpeace at gmail.com>
> ---
> 
>  libfstools/partname.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libfstools/partname.c b/libfstools/partname.c
> index f42322a49d5b..82c723c02097 100644
> --- a/libfstools/partname.c
> +++ b/libfstools/partname.c
> @@ -143,7 +143,7 @@ static struct volume *partname_volume_find(char *name)
>  		if (!get_var_from_file("/proc/cmdline", "fstools_partname_fallback_scan", rootparam, sizeof(rootparam)))
>  			return NULL;
>  
> -		if (!strcmp("1", rootparam))
> +		if (strcmp("1", rootparam))
>  			return NULL;
>  
>  		/* no useful 'root=' kernel cmdline parameter, find on any block device */
> -- 
> 2.39.0
>