lkml.org 
[lkml]   [2016]   [Oct]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 1/1] dm raid: fix compat_features validation
From
Date


On 10/11/2016 07:44 PM, Mike Snitzer wrote:
> On Tue, Oct 11 2016 at 11:44am -0400,
> Heinz Mauelshagen <heinzm@redhat.com> wrote:
>
>>
>> On 10/11/2016 05:38 PM, Andy Whitcroft wrote:
>>> 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.
>> Thanks,
>> I prefer this to be easier readable.
> Readable or not, the code with the != is _not_ future-proof. Whereas
> Andy's solution is. If/when a new compat feature comes along then
> FEATURE_FLAG_SUPPORTS_V190 would be replaced to be a macro that ORs all
> the new compat features together (e.g. FEATURE_FLAG_COMPAT). E.g. how
> dm-thin-metadata.c:__check_incompat_features() does.

If we'll have to introduce more feature flags in the future (e.g. for
clustered raid1
support), this is going to be based on the test_bit() API for consistency
with any other flag processing we do in the target.

Heinz

> We can go with the != code for now, since any future changes would
> likely cause this test to be changed. Or we could fix it now _for
> real_.
>
> Mike

\
 
 \ /
  Last update: 2016-10-14 19:16    [W:0.073 / U:0.272 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site