Hi Neil
What is the problem with adding space to the 'far' layout?
I would think you could just create the new array part 1 from the old array part 2, and
then sync the new array part 2 with the new array part 1. (in the case of a far=2 array,
for n>2 similar constructs would apply).
best regards
Keld
On Wed, Mar 14, 2012 at 03:40:41PM +1100, NeilBrown wrote:
> 'resizing' an array in this context means making use of extra
> space that has become available in component devices, not adding new
> devices.
> It also includes shrinking the array to take up less space of
> component devices.
>
> This is not supported for array with a 'far' layout. However
> for 'near' and 'offset' layout arrays, adding and removing space at
> the end of the devices is easy to support, and this patch provides
> that support.
>
> Signed-off-by: NeilBrown <neilb@xxxxxxx>
> ---
>
> drivers/md/raid10.c | 38 ++++++++++++++++++++++++++++++++++++++
> 1 files changed, 38 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index 7b3346a..2f7665c 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -3437,6 +3437,43 @@ static void raid10_quiesce(struct mddev *mddev, int state)
> }
> }
>
> +static int raid10_resize(struct mddev *mddev, sector_t sectors)
> +{
> + /* Resize of 'far' arrays is not supported.
> + * For 'near' and 'offset' arrays we can set the
> + * number of sectors used to be an appropriate multiple
> + * of the chunk size.
> + * For 'offset', this is far_copies*chunksize.
> + * For 'near' the multiplier is the LCM of
> + * near_copies and raid_disks.
> + * So if far_copies > 1 && !far_offset, fail.
> + * Else find LCM(raid_disks, near_copy)*far_copies and
> + * multiply by chunk_size. Then round to this number.
> + * This is mostly done by raid10_size()
> + */
> + struct r10conf *conf = mddev->private;
> + sector_t oldsize, size;
> +
> + if (conf->far_copies > 1 && !conf->far_offset)
> + return -EINVAL;
> +
> + oldsize = raid10_size(mddev, 0, 0);
> + size = raid10_size(mddev, sectors, 0);
> + md_set_array_sectors(mddev, size);
> + if (mddev->array_sectors > size)
> + return -EINVAL;
> + set_capacity(mddev->gendisk, mddev->array_sectors);
> + revalidate_disk(mddev->gendisk);
> + if (sectors > mddev->dev_sectors &&
> + mddev->recovery_cp > oldsize) {
> + mddev->recovery_cp = oldsize;
> + set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
> + }
> + mddev->dev_sectors = sectors;
> + mddev->resync_max_sectors = size;
> + return 0;
> +}
> +
> static void *raid10_takeover_raid0(struct mddev *mddev)
> {
> struct md_rdev *rdev;
> @@ -3506,6 +3543,7 @@ static struct md_personality raid10_personality =
> .sync_request = sync_request,
> .quiesce = raid10_quiesce,
> .size = raid10_size,
> + .resize = raid10_resize,
> .takeover = raid10_takeover,
> };
>
>
>
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