Re: [RFC PATCH rdma-next 01/10] RDMA: mr: Introduce is_pmem

[Jeff Moyer]

"Li, Zhijian" <lizhijian@xxxxxxxxxxxxxx> writes:

> Copied to nvdimm list
>
> Thanks
>
> Zhijian
>
>
> on 2022/1/6 14:12, Li Zhijian wrote:
>>
>> Add Dan to the party :)
>>
>> May i know whether there is any existing APIs to check whether
>> a va/page backs to a nvdimm/pmem ?

I don't know of one.  You could try walk_system_ram_range looking for
IORES_DESC_PERSISTENT_MEMORY, but that's not very efficient.

>>> You need to get Dan to check this out, but I'm pretty sure this should
>>> be more like this:
>>>
>>> if (is_zone_device_page(page) && page->pgmap->type ==
>>> MEMORY_DEVICE_FS_DAX)

You forgot MEMORY_DEVICE_GENERIC.  However, this doesn't guarantee the
memory belongs to persistent memory, only that it is direct access
capable.

Dan, any ideas?

-Jeff