On Mon, 11 Apr 2011 15:39:08 +0200 Adam Kwolek <adam.kwolek@xxxxxxxxx> wrote:
> Problem can be obvious visible when to 3-disks raid5 array 2 disks are added.
> (added disks number + parity == old disks number)
> Mdadm generates floating point exception and core file is generated
> due to division by 0 (odata == 0).
>
> During restart for external metadata, getinfo_super() returns
> in mdinfo->array.raid_disks old disks number, that has to be increased
> by delta_disks to receive new value. Function getinfo_super()
> cannot return raid_disks field in different way, as array starting
> geometry information. We are still going to final array geometry.
> This Grow_restart() should have in mind and calculate local variables
> in proper way.
>
> This change makes Grow_restart() to interpret parameters in the same way
> as reshape_array() did during reshape start, and it will do it in the same
> way when it will be called from Continue_reshape().
sorry, but I don't like this change.
I never like having different handling for 'external' and 'non-external'.
Sometimes it is obviously necessary, but we should avoid it if possible.
Once reshape has started, 'raid_disks' is the new number of disks, not the
old number.
So sysfs_set_array should be changed to set raid_disks to
raid_disk - delta_disks
in the first instance, then if reshape is active, to raid_disks.
And getinfo_super should return the 'new' number of disks.
And reshape_array might need to fiddle with raid_disks before calling
analyse_change in the reshape_active case.
So it is more changes, but I think it is a better result.
Thanks,
NeilBrown
>
> Signed-off-by: Adam Kwolek <adam.kwolek@xxxxxxxxx>
> ---
>
> Grow.c | 12 ++++++++----
> 1 files changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/Grow.c b/Grow.c
> index d4308bc..1fdee7e 100644
> --- a/Grow.c
> +++ b/Grow.c
> @@ -3102,13 +3102,17 @@ int Grow_restart(struct supertype *st, struct mdinfo *info, int *fdlist, int cnt
> unsigned long long nstripe, ostripe;
> int ndata, odata;
>
> - odata = info->array.raid_disks - info->delta_disks - 1;
> + if (st->ss->external) {
> + old_disks = info->array.raid_disks;
> + ndata = info->array.raid_disks + info->delta_disks - 1;
> + } else {
> + old_disks = info->array.raid_disks - info->delta_disks;
> + ndata = info->array.raid_disks - 1;
> + }
> + odata = old_disks - 1;
> if (info->array.level == 6) odata--; /* number of data disks */
> - ndata = info->array.raid_disks - 1;
> if (info->new_level == 6) ndata--;
>
> - old_disks = info->array.raid_disks - info->delta_disks;
> -
> if (info->delta_disks <= 0)
> /* Didn't grow, so the backup file must have
> * been used
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