linux-kernel - Re: [PATCH 1/1 V2] dm raid: fix compat

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Date:   Tue, 11 Oct 2016 18:53:48 +0200
From:   Heinz Mauelshagen <heinzm@...hat.com>
To:     Andy Whitcroft <apw@...onical.com>
Cc:     Mike Snitzer <snitzer@...hat.com>, linux-kernel@...r.kernel.org,
        linux-raid@...r.kernel.org, dm-devel@...hat.com,
        Shaohua Li <shli@...nel.org>, Alasdair Kergon <agk@...hat.com>
Subject: Re: [PATCH 1/1 V2] dm raid: fix compat_features validation


Acked-by: Heinz Mauelshagen <heinzm@...hat.com>

On 10/11/2016 06:21 PM, Andy Whitcroft wrote:
>  From a30fba068e41214cb0ffcb14e68722482765e0c9 Mon Sep 17 00:00:00 2001
> From: Andy Whitcroft <apw@...onical.com>
> Date: Tue, 11 Oct 2016 15:16:57 +0100
>
> In ecbfb9f118bce4 ("dm raid: add raid level takeover support") a new
> compatible feature flag was added.  Validation for these compat_features
> was added but this only passes for new raid mappings with this feature
> flag.  This causes previously created raid mappings to be failed at
> import.

Clarification:
to allow for feature checks, the compat_features member was
in the dm-raid superblock from the beginning (so before ecbfb9f118bce4).
It got renamed from features to compat_features because incompat_features
got introduced with that commit together with the problematic check
of compat_features you thankfully found.


>
> Check compat_features for the only valid combination.
>
> Fixes: ecbfb9f118bce4 ("dm raid: add raid level takeover support")
> Signed-off-by: Andy Whitcroft <apw@...onical.com>
> ---
>   drivers/md/dm-raid.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> V2: simplify checks as per maintainer.
>
> diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
> index 8abde6b..2a39700 100644
> --- a/drivers/md/dm-raid.c
> +++ b/drivers/md/dm-raid.c
> @@ -2258,7 +2258,8 @@ static int super_validate(struct raid_set *rs, struct md_rdev *rdev)
>   	if (!mddev->events && super_init_validation(rs, rdev))
>   		return -EINVAL;
>   
> -	if (le32_to_cpu(sb->compat_features) != FEATURE_FLAG_SUPPORTS_V190) {
> +	if (le32_to_cpu(sb->compat_features) &&
> +	    le32_to_cpu(sb->compat_features) != FEATURE_FLAG_SUPPORTS_V190) {
>   		rs->ti->error = "Unable to assemble array: Unknown flag(s) in compatible feature flags";
>   		return -EINVAL;
>   	}