Re: [dm-devel] [PATCH 01/26] block: refactor device number setup in __device_add_disk

[Luis Chamberlain <mcgrof@kernel.org>]

On Fri, May 21, 2021 at 07:50:51AM +0200, Christoph Hellwig wrote:
> diff --git a/block/genhd.c b/block/genhd.c
> index 39ca97b0edc6..2c00bc3261d9 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -335,52 +335,22 @@ static int blk_mangle_minor(int minor)

<-- snip -->

> -int blk_alloc_devt(struct block_device *bdev, dev_t *devt)
> +int blk_alloc_ext_minor(void)
>  {
> -	struct gendisk *disk = bdev->bd_disk;
>  	int idx;
>  
> -	/* in consecutive minor range? */
> -	if (bdev->bd_partno < disk->minors) {
> -		*devt = MKDEV(disk->major, disk->first_minor + bdev->bd_partno);
> -		return 0;
> -	}
> -

It is not obviously clear to me, why this was part of add_disk()
path, and ...

> diff --git a/block/partitions/core.c b/block/partitions/core.c
> index dc60ecf46fe6..504297bdc8bf 100644
> --- a/block/partitions/core.c
> +++ b/block/partitions/core.c
> @@ -379,9 +380,15 @@ static struct block_device *add_partition(struct gendisk *disk, int partno,
>  	pdev->type = &part_type;
>  	pdev->parent = ddev;
>  
> -	err = blk_alloc_devt(bdev, &devt);
> -	if (err)
> -		goto out_put;
> +	/* in consecutive minor range? */
> +	if (bdev->bd_partno < disk->minors) {
> +		devt = MKDEV(disk->major, disk->first_minor + bdev->bd_partno);
> +	} else {
> +		err = blk_alloc_ext_minor();
> +		if (err < 0)
> +			goto out_put;
> +		devt = MKDEV(BLOCK_EXT_MAJOR, err);
> +	}
>  	pdev->devt = devt;
>  
>  	/* delay uevent until 'holders' subdir is created */

... and why we only add this here now.

Other than that, this looks like a super nice cleanup!

Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>

  Luis