[dm-devel] [PATCH] dm-raid: check events in super_validate

[NeilBrown]

On Sat, 1 Feb 2014 09:35:20 -0500 Nate Dailey <nate.dailey at stratus.com> wrote:

> If an LVM raid1 recovery is interrupted by deactivating the LV, when the 
> LV is reactivated it comes up with both members in sync--the recovery 
> never completes.
> 
> I've been trying to figure out how to fix this. Does this approach look 
> okay? I'm not sure what else to use to determine that a member disk is 
> out of sync. It looks like if disk_recovery_offset in the superblock 
> were updated during the recovery, that would also cause it to resume 
> after interruption--but MD skips the recovery target disk when writing 
> superblocks, so this doesn't work.
> 
> Comments?

I know it is confusing, but this should really have gone to dm-devel rather
than linux-raid, to make sure Jon Brassow see it (hi Jon!).

Setting recovery_offset to 0 certainly looks wrong, it should be set to
  sb->disk_recovery_offset
like the code just above your change.
Why does the code there not meet your need.

Jon: can you help?

NeilBrown

> 
> Thanks,
> 
> Nate Dailey
> Stratus Technologies
> 
> 
> 
> diff -Nupr linux-3.12.9.orig/drivers/md/dm-raid.c 
> linux-3.12.9/drivers/md/dm-raid.c
> --- linux-3.12.9.orig/drivers/md/dm-raid.c    2014-02-01 
> 08:46:51.088086299 -0500
> +++ linux-3.12.9/drivers/md/dm-raid.c    2014-02-01 09:02:06.657149550 -0500
> @@ -1042,6 +1042,21 @@ static int super_validate(struct mddev *
>           rdev->recovery_offset = le64_to_cpu(sb->disk_recovery_offset);
>           if (rdev->recovery_offset != MaxSector)
>               clear_bit(In_sync, &rdev->flags);
> +        else if (!test_bit(Faulty, &rdev->flags)) {
> +            uint64_t events_sb;
> +
> +            /*
> +             * Trigger recovery if events is out-of-date.
> +             */
> +            events_sb = le64_to_cpu(sb->events);
> +            if (events_sb < mddev->events) {
> +                DMINFO("Force recovery on out-of-date device #%d.",
> +                       rdev->raid_disk);
> +                clear_bit(In_sync, &rdev->flags);
> +                rdev->saved_raid_disk = rdev->raid_disk;
> +                rdev->recovery_offset = 0;
> +            }
> +        }
>       }
> 
>       /*
> 
> --
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