[PATCH fstools] partname: add "fstools_use_partlabel" option to find part from label

[Daniel Golle]

On Sat, Mar 12, 2022 at 01:05:17PM +0900, INAGAKI Hiroshi wrote:
> This patch adds "fstools_use_partlabel" option to partname driver.
> 
> The Linux Kernel supports "root=PARTLABEL=<label>" syntax, but fstools
> doesn't and fail to parse the path to the root device.
> To use this syntax, add the option and find from all block devices.
> 
> Note:
> This change is required for I-O DATA HDL-A/HDL2-A. On they, kernel and
> rootfs are stored in the storage device connected to SATA, port1 or
> port2 and the path to the partition will be assigned dynamically. So
> "root=PARTLABEL=<label>" syntax is required instead of "/dev/sdXN".
> 
> Signed-off-by: INAGAKI Hiroshi <musashino.open at gmail.com>
> ---
>  libfstools/partname.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/libfstools/partname.c b/libfstools/partname.c
> index f59c52e..7e57311 100644
> --- a/libfstools/partname.c
> +++ b/libfstools/partname.c
> @@ -121,6 +121,7 @@ static struct volume *partname_volume_find(char *name)
>  	char *rootdev = NULL, *devname, *tmp;
>  	int j;
>  	bool found = false;
> +	bool use_label = false;
>  	glob_t gl;
>  
>  	if (get_var_from_file("/proc/cmdline", "fstools_ignore_partname", rootparam, sizeof(rootparam))) {
> @@ -128,12 +129,17 @@ static struct volume *partname_volume_find(char *name)
>  			return NULL;
>  	}
>  
> -	if (get_var_from_file("/proc/cmdline", "root", rootparam, sizeof(rootparam))) {
> +	if (get_var_from_file("/proc/cmdline", "fstools_use_partlabel", rootparam, sizeof(rootparam)))
> +		if (!strcmp("1", rootparam))
> +			use_label = true;
> +
> +	if (get_var_from_file("/proc/cmdline", "root", rootparam, sizeof(rootparam)) &&
> +	    !use_label) {

Wouldn't it be easier to use strncmp() to match the PARTLABEL= prefix
in string stored at rootparam? In that case you won't have to introduce
a new 'fstools_use_partlabel' parameter and achieve the same result.

>  		rootdev = rootdevname(rootparam);
>  		/* find partition on same device as rootfs */
>  		snprintf(ueventgstr, sizeof(ueventgstr), "%s/%s/*/uevent", block_dir_name, rootdev);
>  	} else {
> -		/* no 'root=' kernel cmdline parameter, find on any block device */
> +		/* no 'root=' kernel cmdline parameter or use_label=true, find on any block device */
>  		snprintf(ueventgstr, sizeof(ueventgstr), "%s/*/uevent", block_dir_name);
>  	}
>  
> -- 
> 2.34.1.windows.1
> 
> 
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