Re: [md PATCH 4/5] md: Fix: BIO I/O Error during reshape for external metadata

[Neil Brown <neilb@suse.de>]

On Wed, 9 Jun 2010 15:22:27 +0100
"Kwolek, Adam" <adam.kwolek@intel.com> wrote:

> (md: Online Capacity Expansion for IMSM)
> When sum of added disks and degraded disks is greater than max_degraded number, reshape decides that stripe is broken, so bio i/o error is a result.
> Added disks without data has no impact on volume degradation (contains no data so far), so we have to be sure that all disks used to reshape has In_sync flag set.
> We have to do this for disks without data.

Again, I'm not really following you.
I agree that devices that are added to make up numbers for a shape should be
marked In_sync, but that is already happening, roughly in the middle of
raid5_start_reshape.

Again, can you give me a specific situation where the current code does the
wrong thing?

Thanks,
NeilBrown


> ---
> 
>  drivers/md/raid5.c |   17 ++++++++++++++++-
>  1 files changed, 16 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index dc25a32..cb74045 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -5468,7 +5468,7 @@ static int raid5_start_reshape(mddev_t *mddev)
>  	/* Add some new drives, as many as will fit.
>  	 * We know there are enough to make the newly sized array work.
>  	 */
> -	list_for_each_entry(rdev, &mddev->disks, same_set)
> +	list_for_each_entry(rdev, &mddev->disks, same_set) {
>  		if (rdev->raid_disk < 0 &&
>  		    !test_bit(Faulty, &rdev->flags)) {
>  			if (raid5_add_disk(mddev, rdev) == 0) { @@ -5488,6 +5488,21 @@ static int raid5_start_reshape(mddev_t *mddev)
>  			} else
>  				break;
>  		}
> +		/* if there is Online Capacity Expansion
> +		 * on degraded array for external meta
> +		 */
> +		if (mddev->external &&
> +		    (conf->raid_disks <= (disk_count + conf->max_degraded))) {
> +			/* check if not spare */
> +			if (!(rdev->raid_disk < 0 &&
> +			      !test_bit(Faulty, &rdev->flags)))
> +				/* make sure that all disks,
> +				 * even added previously have
> +				 * in sync flag set
> +				 */
> +				set_bit(In_sync, &rdev->flags);
> +		}
> +	}
>  
>  	/* When a reshape changes the number of devices, ->degraded
>  	 * is measured against the large of the pre and post number of
>