Re: Subject : PATCH [001:001]: raid0 devices size should be aligned to chunk size

[Neil Brown <neilb@suse.de>]

On Monday June 1, raziebe@gmail.com wrote:
> raid devices should be aligned to a chunk size 
> (when this feature will be enabled)  because zones 
> will become un-aligned to chunks and we will traverse
> between zones in a single IO access. 

I'm surprised that you need this as the common code in md is supposed
to round everything th chunk_size...
However I found a bug that it was still assuming power-of-2 for v1.x
metadata.
So I fixed that.
Then I decide that it is best to do the rounding in the personalities
- most of them do already.
So I added rounding code to linear and raid0

http://neil.brown.name/git?p=md;a=commitdiff;h=c9aaceea6015213e571761c0f0899614863c4868

and then removed all the related code from md.c

It is all in my for-next.

thanks,
NeilBrown


> 
>  raid0.c |   22 +++++++++++++++++++++-
>  1 file changed, 21 insertions(+), 1 deletion(-)
> Signed-off-by: raziebe@gmail.com
> ---
> diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
> index 0fcd9b5..987a926 100644
> --- a/drivers/md/raid0.c
> +++ b/drivers/md/raid0.c
> @@ -302,6 +302,26 @@ static sector_t raid0_size(mddev_t *mddev, sector_t sectors, int raid_disks)
>  	return array_sectors;
>  }
>  
> +/*
> + *	Align devices to a chunk size, else zones will not be aligned
> +*/
> +static void align_devices_to_chunk_size(struct list_head *disks,
> +					int chunk_sects)
> +{
> +	sector_t sectors;
> +	mdk_rdev_t *rdev;
> +
> +	list_for_each_entry(rdev, disks, same_set) {
> +		sectors = rdev->sectors;
> +		sector_div(sectors, chunk_sects);
> +		sectors = sectors * chunk_sects;
> +		printk(KERN_INFO "raid0: reduce device size: %lld --> %lld\n",
> +				(unsigned long long)rdev->sectors,
> +				(unsigned long long)sectors);
> +		rdev->sectors = sectors;
> +	}
> +}
> +
>  static int raid0_run(mddev_t *mddev)
>  {
>  	int ret;
> @@ -313,7 +333,7 @@ static int raid0_run(mddev_t *mddev)
>  	}
>  	blk_queue_max_sectors(mddev->queue, mddev->chunk_sectors);
>  	mddev->queue->queue_lock = &mddev->queue->__queue_lock;
> -
> +	align_devices_to_chunk_size(&mddev->disks, mddev->chunk_sectors);
>  	ret = create_strip_zones(mddev);
>  	if (ret < 0)
>  		return ret;
>