Re: [dm-devel] [PATCH 1/1] dm raid: fix compat_features validation

From: Andy Whitcroft
Date: Tue Oct 11 2016 - 11:56:04 EST


On Tue, Oct 11, 2016 at 05:04:34PM +0200, Heinz Mauelshagen wrote:
>
> Andy,
>
> good catch.
>
> We should rather check for V190 support only in case any
> compat feature flags are actually set.
>
> {
> + 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;
> }

If the feature flags are single bit combinations then I believe the
below does check exactly that. Checking for no 1s outside of the
expected features, caring not for the value of the valid bits:

+ if (le32_to_cpu(sb->compat_features) & ~(FEATURE_FLAG_SUPPORTS_V190)) {

with the possibilty to or in additional feature bits as they are added.

-apw