Re: [PATCH] Add '--nodes' option in GROW mode

[Jes Sorensen <Jes.Sorensen@redhat.com>]

Guoqing Jiang <gqjiang@suse.com> writes:
> On 03/23/2016 01:56 AM, Jes Sorensen wrote:
>> zhilong <zlliu@suse.com> writes:
>>> Bug description:
>>> # mdadm -Cv /dev/md0 --bitmap=clustered -l1 -n2 /dev/sdd /dev/sdb
>>> --nodes=6 --assume-clean
>>> # mdadm --grow /dev/md0 --bitmap=none
>>> # mdadm --grow /dev/md0 --bitmap=clustered
>>>      -> cluster nodes would be changed to 4, here is my method to
>>> resolve it.
>>> # mdadm --grow /dev/md0 --bitmap=clustered --nodes=6
>>>
>>> Patch:
>>>
>>> Cluster nodes is set 4 as default when switch bitmap from
>>> none to clustered under GROW mode, so add '--nodes'
>>> option in GROW mode.
>>>
>>> Signed-off-by: Zhilong Liu <zlliu@suse.com>
>>> ---
>>>   mdadm.c | 1 +
>>>   1 file changed, 1 insertion(+)
>> Hi,
>>
>> I have a question about this, since I simply do not have the knowledge
>> about clustering to judge this approach.
>>
>> If you remove the bitmap, does that 'uncluster' the array? If not,
>
> Yes, remove the bitmap would 'uncluster' the array since leave()
> will be called in kernel if switch the bitmap from 'clustered' to
> 'none'.
>
>> shouldn't mdadm be fixed to not set #nodes to 4 when adding a clustered
>> bitmap, if a number of cluster nodes is already present?
>
> The nodes is set 4 by default if the 'nodes' parameter is not specified,
> And it could be overwrite if re-create the clustered bitmap.

Thanks for the explanation, in that case I am fine with this. It does
raise the issue whether specifying nodes shouldn't be a required
argument rather than defaulting to a default of 4?

Second, your patch was broken due to bad whitespace formatting, could
you please send me a fresh one.

Thanks,
Jes