On 03/09/2018 04:23 PM, Dan Williams wrote:
> On Fri, Mar 9, 2018 at 11:58 AM, Jeff Moyer <[email protected]> wrote:
>> Dan Williams <[email protected]> writes:
>>
>>> On Fri, Mar 9, 2018 at 11:39 AM, Jeff Moyer <[email protected]> wrote:
>>>> Dan Williams <[email protected]> writes:
>>>>
>>>>> Commit a7320456f1bc "ndctl: add sector_size to 'ndctl list' output"
>>>>> mishandles the case where a namespace does not specify a sector_size,
>>>>> but otherwise supports a sector_size selection:
>>>>>
>>>>>     # ndctl list --namespace=namespace1.0
>>>>>     {
>>>>>       "dev":"namespace1.0",
>>>>>       "mode":"memory",
>>>>>       "size":32763805696,
>>>>>       "uuid":"7c985ba5-6d33-48bd-8fde-6c25a520abe0",
>>>>>       "sector_size":-1,
>>>>>       "blockdev":"pmem1",
>>>>>       "numa_node":0
>>>>>     }
>>>>>
>>>>> Fix this and clean up the output to only provide a sector_size in the
>>>>> non-default (i.e. != 512 bytes) case.
>>>>
>>>> That sounds confusing.  Why not just always print out the sector size?
>>>
>>> I'm assuming the users that will go through the hassle of specifying a
>>> non-default sector_size are few and far between. This helps with the
>>> useful information density on a single screen for humans looking at
>>> json output.
>>
>> I think that, to the novice, seeing one namespace print out sector size
>> and another not do the same, that would be confusing.  Also, you'd have
>> to know what the default is.

As a former ndctl user, I'm with Jeff.

> Yes, but personally I think it is only an expert that would care about
> non-512 byte sector sizes. There are no device physics or other
> benefits that require different sector sizes. The only potential
> benefit is amortizing the cost of BTT over larger sectors, but for
> Linux ext4 and xfs should be fine without a BTT. The UEFI spec
> unfortunately requires a default of 4K sector size, but that's only
> for inter-OS compatibility. I'm just finding it hard to justify
> treating sector_size as a first class attribute that the typical user
> would care about.

Since the value can be set, even to the default value, and the kernel default 
doesn't
match the UEFI default, it seems worth including in all cases.

-- ljk

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