memory tiering: read last_cpupid correctly in do_huge_pmd_numa_page()

JIRA: https://issues.redhat.com/browse/RHEL-84184
Conflicts:
  * context differences from upstream due to RHEL-9 missing the whole
    patch series "mm: convert page cpupid functions to folios", v3;
    starting with commit 1d44f2e ("mm_types: add virtual and
    _last_cpupid into struct folio"), with none of these being relevant
    to this backport

This patch is a backport of the following upstream commit:
commit 3eb2091
Author: Zi Yan <ziy@nvidia.com>
Date:   Wed Jul 24 09:01:13 2024 -0400

    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: 3302453 ("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>

Signed-off-by: Rafael Aquini <raquini@redhat.com>

Author: Rafael Aquini

mm/huge_memory.c

@@ -1544,7 +1544,8 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
 	 * For memory tiering mode, cpupid of slow memory page is used
 	 * to record page access time.  So use default value.
 	 */
-	if (node_is_toptier(nid))
+	if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) ||
+	    node_is_toptier(nid))
 		last_cpupid = page_cpupid_last(&folio->page);
 	target_nid = numa_migrate_prep(folio, vma, haddr, nid, &flags);
 	if (target_nid == NUMA_NO_NODE) {