Re: [PATCH] dm-cache: document zeroing metadata device step

[Matthew Wilcox]

On Mon, Jul 13, 2020 at 03:40:39AM +0800, Austin Chang wrote:
> +  # When using dmsetup directly instead of volume manager like lvm2,
> +  # the first 4k of the metadata device should be zeroed to indicate
> +  # empty metadata.
> +  dd if=/dev/zero of=/dev/mapper/metadata bs=4k conv=notrunc

... don't you need 'count=1' or you'll zero the entire device?

>    dmsetup create my_cache --table '0 41943040 cache /dev/mapper/metadata \
>  	  /dev/mapper/ssd /dev/mapper/origin 512 1 writeback default 0'
>    dmsetup create my_cache --table '0 41943040 cache /dev/mapper/metadata \
> -- 
> 2.26.2
>