Re: [PATCH - v2] DM RAID: Fix for ineffective "sync" directive

[NeilBrown <neilb@suse.de>]

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On Fri, 14 Sep 2012 13:48:03 -0500 Jonathan Brassow <jbrassow@redhat.com>
wrote:

> Neil,
> 
> I've taken your suggestion to not muck around with the BITMAP_STALE, and
> instead simply clear the superblocks as a whole when the "sync"
> directive is given.
> 
>  brassow
> 
> DM RAID: Fix for "sync" directive ineffectiveness
> 
> There are two table arguments that can be given to a DM RAID target that
> control whether the array is forced to (re)synchronize or skip initialization:
> "sync" and "nosync".  When "sync" is given, we set mddev->recovery_cp to 0
> in order to cause the device to resynchronize.  This is insufficient if there
> is a bitmap in use, because the array will simply look at the bitmap and see
> that there is no recovery necessary.
> 
> The fix is to skip over the loading of the superblocks when "sync" is given,
> causing new superblocks to be written that will force the array to go through
> initialization (i.e. synchronization).
> 
> Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
> 
> Index: linux-upstream/drivers/md/dm-raid.c
> ===================================================================
> --- linux-upstream.orig/drivers/md/dm-raid.c
> +++ linux-upstream/drivers/md/dm-raid.c
> @@ -960,6 +960,19 @@ static int analyse_superblocks(struct dm
>  
>  	freshest = NULL;
>  	rdev_for_each_safe(rdev, tmp, mddev) {
> +		/*
> +		 * Skipping super_load due to DMPF_SYNC will cause
> +		 * the array to undergo initialization again as
> +		 * though it were new.  This is the intended effect
> +		 * of the "sync" directive.
> +		 *
> +		 * When reshaping capability is added, we must ensure
> +		 * that the "sync" directive is disallowed during the
> +		 * reshape.
> +		 */
> +		if (rs->print_flags & DMPF_SYNC)
> +			continue;
> +
>  		if (!rdev->meta_bdev)
>  			continue;
>  
> 

OK, applied.

Thanks.
NeilBrown

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