[PATCH] parted: add max option to mkpart <end>

[Sascha Hauer]

Hi Maud,

On Sun, Oct 19, 2025 at 05:07:06PM +0200, Maud Spierings via B4 Relay wrote:
> From: Maud Spierings <maud_spierings at hotmail.com>
> 
> Add the option to specify "max" as the end location, this will fill the
> block device up to the end of its available space.
> 
> A secondary effect is that it is now possible to use two different size
> units for start and end
> 
> mkpart root ext4 66MiB 3866111KiB
> 
> previously it would read 66MiB as 66KiB as it only used the last read
> unit.

Uh, yes, that's a bug. Thanks for fixing this.

> diff --git a/commands/parted.c b/commands/parted.c
> index 7ec56da4c15f..0e858eb881ba 100644
> --- a/commands/parted.c
> +++ b/commands/parted.c
> @@ -138,6 +138,10 @@ static int do_mkpart(struct block_device *blk, int argc, char *argv[])
>  	int ret;
>  	uint64_t mult;
>  
> +	pdesc = pdesc_get(blk);
> +	if (!pdesc)
> +		return -EINVAL;
> +
>  	if (argc < 5) {
>  		printf("Error: Missing required arguments\n");
>  		return -EINVAL;
> @@ -150,40 +154,51 @@ static int do_mkpart(struct block_device *blk, int argc, char *argv[])
>  	if (ret)
>  		return ret;
>  
> -	ret = parted_strtoull(argv[4], &end, &mult);
> -	if (ret)
> -		return ret;
> -
>  	if (!mult)
>  		mult = gunit;
> -
>  	start *= mult;
> -	end *= mult;
>  
> -	/* If not on sector boundaries move start up and end down */
> +	/* If not on sector boundaries round start up */
>  	start = ALIGN(start, SZ_1M);
> -	end = ALIGN_DOWN(end, SZ_1M);

I am not sure we need the alignment of the end at all. I can imagine
that it helps the storage device to align the start of a partition, but
the end shouldn't really matter.

Maybe we should remove the end alignment because with this patch the
ending becomes inconsistent. It will align down to 1MiB boundary when
the size is specified, but will use an unaligned ending with size =
"max".

Better drop the end alignment entirely for more consistency.

>  
>  	/* convert to LBA */
>  	start >>= SECTOR_SHIFT;
> -	end >>= SECTOR_SHIFT;
> +
> +	if (!strcmp(argv[4], "max")) {
> +		/* gpt requires 34 blocks at the end */
> +		if (pdesc->parser->type == filetype_gpt)
> +			end = blk->num_blocks - 35;
> +		else if (pdesc->parser->type == filetype_mbr)
> +			end = blk->num_blocks - 1;
> +		else
> +			return -ENOSYS;
> +	} else if (!(ret = parted_strtoull(argv[4], &end, &mult))) {

Rewrite to:

	} else {
		ret = parted_strtoull(argv[4], &end, &mult);
		if (ret)
			return ret;
		...
	}

It solves the checkpatch warning and is easier to read IMO.

Sascha

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |