Re: [PATCH v6] mm/pgmap: Use correct alignment when looking at first pfn from a region

Aneesh Kumar K.V
2019-09-25T03:51:16Z

Andrew Morton <akpm@linux-foundation.org> writes:

> On Tue, 17 Sep 2019 21:01:29 +0530 "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> wrote:
>
>> vmem_altmap_offset() adjust the section aligned base_pfn offset.
>> So we need to make sure we account for the same when computing base_pfn.
>>
>> ie, for altmap_valid case, our pfn_first should be:
>>
>> pfn_first = altmap->base_pfn + vmem_altmap_offset(altmap);
>
> What are the user-visible runtime effects of this change?

This was found by code inspection. If the pmem region is not correctly
section aligned we can skip pfns while iterating device pfn using
for_each_device_pfn(pfn, pgmap)

I still would want Dan to ack the change though.

-aneesh