Re: linux-next: build failure after merge of the nvdimm tree

Re: linux-next: build failure after merge of the nvdimm tree

[Oliver]

On Mon, Apr 9, 2018 at 1:38 PM, Oliver <oohall@gmail.com> wrote:
> On Mon, Apr 9, 2018 at 1:16 PM, Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>> Hi Dan,
>>
>> After merging the nvdimm tree, today's linux-next build (x86_64
>> allmodconfig) failed like this:
>>
>> ERROR: "of_node_to_nid" [drivers/nvdimm/of_pmem.ko] undefined!
>>
>> Caused by commit
>>
>>   717197608952 ("libnvdimm: Add device-tree based driver")
>>
>> X86 seems to not have a version of of_node_to_nid() even though CONFIG_OF
>> and CONFIG_NUMA are both 'y' in this build.
>
> It's a side effect of a driver selecting CONFIG_OF accidently. There's
> a patch to fix this in the drm-misc-next tree:
>
> https://lkml.org/lkml/2018/4/3/17
>
>> I have used the nvdimm tree from next-20180406 for today.
>
> That works too.

Hmm, on closer inspection this is actually a bug in the of driver. The
patch above fixes the specific problem that we hit on ia64 due to
CONFIG_OF being selected by accident, but the underlying issue will
affect any platform that doesn't provide an implementation of
of_node_to_nid().

The fundamental problem is that the various actual implementations of
of_node_to_nid (ppc, sparc and the generic one in of_numa.c) export
the symbol. While the fallback implementation does not because it is
defined as a weak symbol. As a result we'll get this build failure iff
there's a call to of_node_to_nid() in a module.

The one-line fix is just to delete the call to of_node_to_nid() in
of_pmem.c. I have a patch that adds a Kconfig options and removes the
weak symbol games. That needs Acks from the ppc, sparc and DT
maintainers though so it'll take longer to organise.

Oliver

Re: linux-next: build failure after merge of the nvdimm tree

[Dan Williams]

On Mon, Apr 9, 2018 at 12:34 AM, Oliver <oohall@gmail.com> wrote:
> On Mon, Apr 9, 2018 at 1:38 PM, Oliver <oohall@gmail.com> wrote:
>> On Mon, Apr 9, 2018 at 1:16 PM, Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>>> Hi Dan,
>>>
>>> After merging the nvdimm tree, today's linux-next build (x86_64
>>> allmodconfig) failed like this:
>>>
>>> ERROR: "of_node_to_nid" [drivers/nvdimm/of_pmem.ko] undefined!
>>>
>>> Caused by commit
>>>
>>>   717197608952 ("libnvdimm: Add device-tree based driver")
>>>
>>> X86 seems to not have a version of of_node_to_nid() even though CONFIG_OF
>>> and CONFIG_NUMA are both 'y' in this build.
>>
>> It's a side effect of a driver selecting CONFIG_OF accidently. There's
>> a patch to fix this in the drm-misc-next tree:
>>
>> https://lkml.org/lkml/2018/4/3/17
>>
>>> I have used the nvdimm tree from next-20180406 for today.
>>
>> That works too.
>
> Hmm, on closer inspection this is actually a bug in the of driver. The
> patch above fixes the specific problem that we hit on ia64 due to
> CONFIG_OF being selected by accident, but the underlying issue will
> affect any platform that doesn't provide an implementation of
> of_node_to_nid().
>
> The fundamental problem is that the various actual implementations of
> of_node_to_nid (ppc, sparc and the generic one in of_numa.c) export
> the symbol. While the fallback implementation does not because it is
> defined as a weak symbol. As a result we'll get this build failure iff
> there's a call to of_node_to_nid() in a module.
>
> The one-line fix is just to delete the call to of_node_to_nid() in
> of_pmem.c. I have a patch that adds a Kconfig options and removes the
> weak symbol games. That needs Acks from the ppc, sparc and DT
> maintainers though so it'll take longer to organise.

How about just marking OF_PMEM as bool for the time being until all of
these other reworks land upstream?

Re: linux-next: build failure after merge of the nvdimm tree

[Dan Williams]

On Mon, Apr 9, 2018 at 10:11 AM, Dan Williams <dan.j.williams@intel.com> wrote:
> On Mon, Apr 9, 2018 at 12:34 AM, Oliver <oohall@gmail.com> wrote:
>> On Mon, Apr 9, 2018 at 1:38 PM, Oliver <oohall@gmail.com> wrote:
>>> On Mon, Apr 9, 2018 at 1:16 PM, Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>>>> Hi Dan,
>>>>
>>>> After merging the nvdimm tree, today's linux-next build (x86_64
>>>> allmodconfig) failed like this:
>>>>
>>>> ERROR: "of_node_to_nid" [drivers/nvdimm/of_pmem.ko] undefined!
>>>>
>>>> Caused by commit
>>>>
>>>>   717197608952 ("libnvdimm: Add device-tree based driver")
>>>>
>>>> X86 seems to not have a version of of_node_to_nid() even though CONFIG_OF
>>>> and CONFIG_NUMA are both 'y' in this build.
>>>
>>> It's a side effect of a driver selecting CONFIG_OF accidently. There's
>>> a patch to fix this in the drm-misc-next tree:
>>>
>>> https://lkml.org/lkml/2018/4/3/17
>>>
>>>> I have used the nvdimm tree from next-20180406 for today.
>>>
>>> That works too.
>>
>> Hmm, on closer inspection this is actually a bug in the of driver. The
>> patch above fixes the specific problem that we hit on ia64 due to
>> CONFIG_OF being selected by accident, but the underlying issue will
>> affect any platform that doesn't provide an implementation of
>> of_node_to_nid().
>>
>> The fundamental problem is that the various actual implementations of
>> of_node_to_nid (ppc, sparc and the generic one in of_numa.c) export
>> the symbol. While the fallback implementation does not because it is
>> defined as a weak symbol. As a result we'll get this build failure iff
>> there's a call to of_node_to_nid() in a module.
>>
>> The one-line fix is just to delete the call to of_node_to_nid() in
>> of_pmem.c. I have a patch that adds a Kconfig options and removes the
>> weak symbol games. That needs Acks from the ppc, sparc and DT
>> maintainers though so it'll take longer to organise.
>
> How about just marking OF_PMEM as bool for the time being until all of
> these other reworks land upstream?

I went ahead and just pushed this workaround for now:

https://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm.git/commit/?h=libnvdimm-for-next&id=291717b6fbdb175da88ae2144fc58d63a490128d