memory tiering: read last_cpupid correctly in do_huge_pmd_numa_page()

Patch series "Various memory tiering fixes", v3.


This patch (of 3):

last_cpupid is only available when memory tiering is off or the folio is
in toptier node.  Complete the check to read last_cpupid when it is
available.

Before the fix, the default last_cpupid will be used even if memory
tiering mode is turned off at runtime instead of the actual value.  This
can prevent task_numa_fault() from getting right numa fault stats, but
should not cause any crash.  User might see performance changes after the
fix.

Link: https://lkml.kernel.org/r/20240724130115.793641-1-ziy@nvidia.com
Link: https://lkml.kernel.org/r/20240724130115.793641-2-ziy@nvidia.com


Fixes: 33024536 ("memory tiering: hot page selection with hint page fault latency")
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reported-by: David Hildenbrand <david@redhat.com>
Closes: https://lore.kernel.org/linux-mm/9af34a6b-ca56-4a64-8aa6-ade65f109288@redhat.com/


Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>