On Fri, Dec 18 2015, rgoldwyn@suse.de wrote:

> From: Goldwyn Rodrigues <rgoldwyn@suse.com>
>
> Commit 2910ff17d154baa5eb50e362a91104e831eb2bb6
> introduced a regression which would remove a recently added spare via
> slot_store. Revert part of the patch which touches slot_store() and add
> the disk directly using pers->hot_add_disk()
>
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
> Signed-off-by: Pawel Baldysiak <pawel.baldysiak@intel.com>
> ---
>  drivers/md/md.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index a71b36f..0444afa 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -2726,6 +2726,7 @@ slot_store(struct md_rdev *rdev, const char *buf, size_t len)
>  		/* Activating a spare .. or possibly reactivating
>  		 * if we ever get bitmaps working here.
>  		 */
> +		int err;
>  
>  		if (rdev->raid_disk != -1)
>  			return -EBUSY;
> @@ -2747,9 +2748,15 @@ slot_store(struct md_rdev *rdev, const char *buf, size_t len)
>  			rdev->saved_raid_disk = -1;
>  		clear_bit(In_sync, &rdev->flags);
>  		clear_bit(Bitmap_sync, &rdev->flags);
> -		remove_and_add_spares(rdev->mddev, rdev);
> -		if (rdev->raid_disk == -1)
> -			return -EBUSY;
> +		err = rdev->mddev->pers->
> +			hot_add_disk(rdev->mddev, rdev);
> +		if (err) {
> +			rdev->raid_disk = -1;
> +			return err;
> +		} else
> +			sysfs_notify_dirent_safe(rdev->sysfs_state);
> +		if (sysfs_link_rdev(rdev->mddev, rdev))
> +			/* failure here is OK */;
>  		/* don't wakeup anyone, leave that to userspace. */
>  	} else {
>  		if (slot >= rdev->mddev->raid_disks &&
> -- 
> 2.6.2

applied, thanks.

NeilBrown