Re: [PATCH v2 1/2] common/dmlogwrites: Extend _log_writes_init() to accept the specified length

["Darrick J. Wong" <djwong@kernel.org>]

On Mon, Nov 14, 2022 at 08:35:02AM +0000, Xiao Yang wrote:
> It is unnecssary to always create a dm-log-writes device
> based on the entire size of the target/underlying device.
> 
> Signed-off-by: Xiao Yang <yangx.jy@fujitsu.com>

Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
>  common/dmlogwrites | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/common/dmlogwrites b/common/dmlogwrites
> index 9fa1c977..c1c85de9 100644
> --- a/common/dmlogwrites
> +++ b/common/dmlogwrites
> @@ -59,14 +59,28 @@ _require_log_writes_dax_mountopt()
>  	fi
>  }
>  
> +# Set up a dm-log-writes device
> +#
> +# blkdev: the specified target device
> +# length(optional): the mapped length in bytes
> +# Note that the entire size of the target device will be used
> +# if length is not specified.
>  _log_writes_init()
>  {
> -	blkdev=$1
> +	local blkdev=$1
> +	local length=$2
> +	local BLK_DEV_SIZE
>  
>  	[ -z "$blkdev" ] && _fail \
>  	"block dev must be specified for _log_writes_init"
>  
> -	local BLK_DEV_SIZE=`blockdev --getsz $blkdev`
> +	if [ -z "$length" ]; then
> +		BLK_DEV_SIZE=`blockdev --getsz $blkdev`
> +	else
> +		local blksz=`blockdev --getss $blkdev`
> +		BLK_DEV_SIZE=$((length / blksz))
> +	fi
> +
>  	LOGWRITES_NAME=logwrites-test
>  	LOGWRITES_DMDEV=/dev/mapper/$LOGWRITES_NAME
>  	LOGWRITES_TABLE="0 $BLK_DEV_SIZE log-writes $blkdev $LOGWRITES_DEV"
> -- 
> 2.34.1
>