Re: [PATCH] ndctl: Use the same align value as original namespace on reconfigure

["Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>]

"Verma, Vishal L" <vishal.l.verma@intel.com> writes:

> On Wed, 2019-08-07 at 10:14 +0530, Aneesh Kumar K.V wrote:
>> When using reconfigure command to add a `name` to the namespace we end
>> up updating the align attribute. Avoid this by using the value from
>> the original namespace. Do this only if we are keeping the namespace mode
>> same.
>> 
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
>> ---
>>  ndctl/namespace.c | 16 ++++++++++++++++
>>  1 file changed, 16 insertions(+)
>
> Hi Aneesh,
>
> A few comments below:
>
>> 
>> diff --git a/ndctl/namespace.c b/ndctl/namespace.c
>> index 1f212a2b3a9b..24e51bb35ae1 100644
>> --- a/ndctl/namespace.c
>> +++ b/ndctl/namespace.c
>> @@ -596,6 +596,22 @@ static int validate_namespace_options(struct ndctl_region *region,
>>  			return -ENXIO;
>>  		}
>>  	} else {
>> +
>> +		/*
>> +		 * If we are tryint to reconfigure with the same namespace mode
>
>                              ^trying
>
>> +		 * Use the align details from the origin namespace. Otherwise
>
> s/origin/original/
>
>> +		 * pick the align details from seed namespace
>> +		 */
>> +		if (ndns && p->mode == ndctl_namespace_get_mode(ndns)) {
>
> Do we need to depend on the mode here?
>
> I'm thinking it should be sufficient to do:
>   1. Check We're in 'reconfigure'
>   2. Check param.align was not supplied
>   3. Get alignment from the pfn/dax personality, and just use that.
>
> Does this make sense (Maybe I'm missing something).

We want to use the align value from the seed when we are trying
to reconfigure a namespace with a different mode. ie, if we are moving a
fsdax namespace with align value 64K to a devdax, IMHO we should pick 16M
as alignment for devdax.

>
>> +			struct ndctl_pfn *ns_pfn = ndctl_namespace_get_pfn(ndns);
>> +			struct ndctl_dax *ns_dax = ndctl_namespace_get_dax(ndns);
>> +			if (ns_pfn)
>> +				p->align = ndctl_pfn_get_align(ns_pfn);
>> +			else if (ns_dax)
>> +				p->align = ndctl_dax_get_align(ns_dax);
>> +			else
>> +				p->align = sysconf(_SC_PAGE_SIZE);
>
> Do we need the page size fallback here - there are other checks after
> this point that also do a similar fallback, do they not catch the
> default case?


I did that to simplify the code with that `else if`  

>
>> +		} else
>>  		/*
>>  		 * Use the seed namespace alignment as the default if we need
>>  		 * one. If we don't then use PAGE_SIZE so the size_align

-aneesh

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